Cells, like whole organisms, have an incredible diversity of form which enables diverse functions. In the Feldman Lab, we are interested in understanding the mechanisms underlying cell patterning during multicellular development. In particular, we are currently focused on understanding how microtubules become spatially organized, a key aspect of differentiation across different tissues and organisms. In addition, we study fundamental aspects of cell polarization, focusing on symmetry breaking cues that establish polarity in epithelia. We generally ask mechanistic cell biological questions in a living, developing organism using a genetic, biochemical, and live imaging approach in the nematode C. elegans.

This research program was shaped by my previous training. As a graduate student at University of California, San Francisco, I studied the genetic regulation of centrosome structure, function, and positioning and the mechanisms dictating internal cellular organization using the unicellular alga Chlamydomonas. I went on to characterize the role of the centrosome during epithelial polarization in C. elegans, working as a postdoctoral fellow at the Fred Hutchinson Cancer Research Center. I started my lab in the Biology Department in 2014 and aim to maintain a fun, supportive, and inclusive research group.

Academic Appointments

Honors & Awards

  • Dean’s Award for Distinguished Teaching in the School of Humanities and Sciences, Stanford University (2021)
  • Stanford Chambers Fellow, Stanford University (2021)
  • Terman Fellowship, Stanford University (2017)
  • David Huntington Dean’s Faculty Scholar Award, Stanford University (2015)
  • New Innovator Award, NIH (2015-2020)
  • Basil O’Connor Starter Scholar Research Award, March of Dimes Foundation (2015-2017)
  • Postdoctoral Fellowship, American Heart Association (2013)
  • Postdoctoral Fellowship, Helen Hay Whitney Foundation (2010-2013)
  • Predoctoral Fellowship, National Science Foundation (2003-2006)

Boards, Advisory Committees, Professional Organizations

  • Board of Directors, West Coast Representative (re-elected), Society for Developmental Biology (2022 - Present)
  • Board of Directors, West Coast Representative, Society for Developmental Biology (2019 - 2022)
  • Women in Cell Biology Committee, Associate Member, American Society for Cell Biology (2018 - 2021)

Professional Education

  • Postdoc, Fred Hutchinson Cancer Research Center, Cell and Developmental Biology (2013)
  • Ph.D., University of California, San Francisco, Cell Biology (2008)
  • B.A., Columbia University, Biology (2000)

Current Research and Scholarly Interests

Cell differentiation requires cells to polarize, translating developmental information into cell-type specific arrangements of intracellular structures. The major goal of the research in my laboratory is to understand how cells build these functional intracellular patterns during development, specifically focusing on the molecules and mechanisms that build microtubules at cell-type specific locations and the polarity cues that guide this patterning in epithelial cells.

2023-24 Courses

Stanford Advisees

Graduate and Fellowship Programs

  • Biology (School of Humanities and Sciences) (Phd Program)

All Publications

  • MAP9/MAPH-9 supports axonemal microtubule doublets and modulates motor movement. Developmental cell Tran, M. V., Khuntsariya, D., Fetter, R. D., Ferguson, J. W., Wang, J. T., Long, A. F., Cote, L. E., Wellard, S. R., Vazquez-Martinez, N., Sallee, M. D., Genova, M., Magiera, M. M., Eskinazi, S., Lee, J. D., Peel, N., Janke, C., Stearns, T., Shen, K., Lansky, Z., Magescas, J., Feldman, J. L. 2023


    Microtubule doublets (MTDs) comprise an incomplete microtubule (B-tubule) attached to the side of a complete cylindrical microtubule. These compound microtubules are conserved in cilia across the tree of life; however, the mechanisms by which MTDs form and are maintained invivo remain poorly understood. Here, we identify microtubule-associated protein 9 (MAP9) as an MTD-associated protein. We demonstrate that C.elegans MAPH-9, a MAP9 homolog, is present during MTD assembly and localizes exclusively to MTDs, a preference that is in part mediated by tubulin polyglutamylation. We find that loss of MAPH-9 causes ultrastructural MTD defects, including shortened and/or squashed B-tubules with reduced numbers of protofilaments, dysregulated axonemal motor velocity, and perturbed cilia function. Because we find that the mammalian ortholog MAP9 localizes to axonemes in cultured mammalian cells and mouse tissues, we propose that MAP9/MAPH-9 plays a conserved role in regulating ciliary motors and supporting the structure of axonemal MTDs.

    View details for DOI 10.1016/j.devcel.2023.12.001

    View details for PubMedID 38159567

  • Persistent cell contacts enable E-cadherin/HMR-1- and PAR-3-based symmetry breaking within a developing C. elegans epithelium. Developmental cell Naturale, V. F., Pickett, M. A., Feldman, J. L. 2023


    Tissue-wide patterning is essential to multicellular development, requiring cells to individually generate polarity axes and coordinate them in space and time with neighbors. Using the C. elegans intestinal epithelium, we identified a patterning mechanism that is informed by cell contact lifetime asymmetry and executed via the scaffolding protein PAR-3 and the transmembrane protein E-cadherin/HMR-1. Intestinal cells break symmetry as PAR-3 and HMR-1 recruit apical determinants into punctate "local polarity complexes" (LPCs) at homotypic contacts. LPCs undergo an HMR-1-based migration to a common midline, thereby establishing tissue-wide polarity. Thus, symmetry breaking results from PAR-3-dependent intracellular polarization coupled to HMR-1-based tissue-level communication, which occurs through a non-adhesive signaling role for HMR-1. Differential lifetimes between homotypic and heterotypic cell contacts are created by neighbor exchanges and oriented divisions, patterning where LPCs perdure and thereby breaking symmetry. These cues offer a logical and likely conserved framework for how epithelia without obvious molecular asymmetries can polarize.

    View details for DOI 10.1016/j.devcel.2023.07.008

    View details for PubMedID 37552986

  • Context matters: Lessons in epithelial polarity from the Caenorhabditis elegans intestine and other tissues. Current topics in developmental biology Naturale, V. F., Pickett, M. A., Feldman, J. L. 2023; 154: 37-71


    Epithelia are tissues with diverse morphologies and functions across metazoans, ranging from vast cell sheets encasing internal organs to internal tubes facilitating nutrient uptake, all of which require establishment of apical-basolateral polarity axes. While all epithelia tend to polarize the same components, how these components are deployed to drive polarization is largely context-dependent and likely shaped by tissue-specific differences in development and ultimate functions of polarizing primordia. The nematode Caenorhabditis elegans (C. elegans) offers exceptional imaging and genetic tools and possesses unique epithelia with well-described origins and roles, making it an excellent model to investigate polarity mechanisms. In this review, we highlight the interplay between epithelial polarization, development, and function by describing symmetry breaking and polarity establishment in a particularly well-characterized epithelium, the C. elegans intestine. We compare intestinal polarization to polarity programs in two other C. elegans epithelia, the pharynx and epidermis, correlating divergent mechanisms with tissue-specific differences in geometry, embryonic environment, and function. Together, we emphasize the importance of investigating polarization mechanisms against the backdrop of tissue-specific contexts, while also underscoring the benefits of cross-tissue comparisons of polarity.

    View details for DOI 10.1016/bs.ctdb.2023.02.007

    View details for PubMedID 37100523

  • Separable mechanisms drive local and global polarity establishment in the C. elegans intestinal epithelium. Development (Cambridge, England) Pickett, M. A., Sallee, M. D., Cote, L., Naturale, V. F., Akpinaroglu, D., Lee, J., Shen, K., Feldman, J. L. 2022


    Apico-basolateral polarization is essential for epithelial cells to function as selective barriers and transporters, and to provide mechanical resiliency to organs. Epithelial polarity is established locally, within individual cells to establish distinct apical, junctional, and basolateral domains, and globally, within a tissue where cells coordinately orient their apico-basolateral axes. Using live imaging of endogenously tagged proteins and tissue specific protein depletion in the C. elegans embryonic intestine, we found that local and global polarity establishment are temporally and genetically separable. Local polarity is initiated prior to global polarity and is robust to perturbation. PAR-3 is required for global polarization across the intestine but is not required for establishment of local polarity as small groups of cells are able to establish polarized domains in PAR-3 depleted intestines in an HMR-1/E-cadherin dependent manner. Despite the role of PAR-3 in localizing PKC-3 to the apical surface, we additionally find that PAR-3 and PKC-3/aPKC have distinct roles in the establishment and maintenance of local and global polarity. Together, our results indicate that different mechanisms are required for local and global polarity establishment in vivo.

    View details for DOI 10.1242/dev.200325

    View details for PubMedID 36264257

  • Won't You be My Neighbor: How Epithelial Cells Connect Together to Build Global Tissue Polarity. Frontiers in cell and developmental biology Cote, L. E., Feldman, J. L. 2022; 10: 887107


    Epithelial tissues form continuous barriers to protect against external environments. Within these tissues, epithelial cells build environment-facing apical membranes, junction complexes that anchor neighbors together, and basolateral surfaces that face other cells. Critically, to form a continuous apical barrier, neighboring epithelial cells must align their apico-basolateral axes to create global polarity along the entire tissue. Here, we will review mechanisms of global tissue-level polarity establishment, with a focus on how neighboring epithelial cells of different origins align their apical surfaces. Epithelial cells with different developmental origins and/or that polarize at different times and places must align their respective apico-basolateral axes. Connecting different epithelial tissues into continuous sheets or tubes, termed epithelial fusion, has been most extensively studied in cases where neighboring cells initially dock at an apical-to-apical interface. However, epithelial cells can also meet basal-to-basal, posing several challenges for apical continuity. Pre-existing basement membrane between the tissues must be remodeled and/or removed, the cells involved in docking are specialized, and new cell-cell adhesions are formed. Each of these challenges can involve changes to apico-basolateral polarity of epithelial cells. This minireview highlights several in vivo examples of basal docking and how apico-basolateral polarity changes during epithelial fusion. Understanding the specific molecular mechanisms of basal docking is an area ripe for further exploration that will shed light on complex morphogenetic events that sculpt developing organisms and on the cellular mechanisms that can go awry during diseases involving the formation of cysts, fistulas, atresias, and metastases.

    View details for DOI 10.3389/fcell.2022.887107

    View details for PubMedID 35800889

  • A proximity labeling protocol to probe proximity interactions in C.elegans. STAR protocols Sanchez, A. D., Feldman, J. L. 1800; 2 (4): 100986


    Enzyme-catalyzed proximity labeling (PL) has emerged as a critical approach for identifying protein-protein proximity interactions in cells; however, PL techniques were not historically practical in living multicellular organisms due to technical limitations. Here, we present a protocol for applying PL to living C.elegans using the biotin ligase mutant enzyme TurboID. We demonstrated PL in a tissue-specific and region-specific manner by focusing on non-centrosomal MTOCs (ncMTOCs) of intestinal cells. This protocol is useful for targeted in vivo protein network profiling. For complete details on the use and execution of this protocol, please refer to Sanchez et al. (2021).

    View details for DOI 10.1016/j.xpro.2021.100986

    View details for PubMedID 34927095

  • Proximity labeling reveals non-centrosomal microtubule-organizing center components required for microtubule growth and localization. Current biology : CB Sanchez, A. D., Branon, T. C., Cote, L. E., Papagiannakis, A., Liang, X., Pickett, M. A., Shen, K., Jacobs-Wagner, C., Ting, A. Y., Feldman, J. L. 2021


    Microtubules are polarized intracellular polymers that play key roles in the cell, including in transport, polarity, and cell division. Across eukaryotic cell types, microtubules adopt diverse intracellular organization to accommodate these distinct functions coordinated by specific cellular sites called microtubule-organizing centers (MTOCs). Over 50 years of research on MTOC biology has focused mainly on the centrosome; however, most differentiated cells employ non-centrosomal MTOCs (ncMTOCs) to organize their microtubules into diverse arrays, which are critical to cell function. To identify essential ncMTOC components, we developed the biotin ligase-based, proximity-labeling approach TurboID for use in C.elegans. We identified proteins proximal to the microtubule minus end protein PTRN-1/Patronin at the apical ncMTOC of intestinal epithelial cells, focusing on two conserved proteins: spectraplakin protein VAB-10B/MACF1 and WDR-62, a protein we identify as homologous to vertebrate primary microcephaly disease protein WDR62. VAB-10B and WDR-62 do not associate with the centrosome and instead specifically regulate non-centrosomal microtubules and the apical targeting of microtubule minus-end proteins. Depletion of VAB-10B resulted in microtubule mislocalization and delayed localization of a microtubule nucleation complex ɣ-tubulin ring complex (gamma-TuRC), while loss of WDR-62 decreased the number of dynamic microtubules and abolished gamma-TuRC localization. This regulation occurs downstream of cell polarity and in conjunction with actin. As this is the first report for non-centrosomal roles of WDR62 family proteins, we expand the basic cell biological roles of this important disease protein. Our studies identify essential ncMTOC components and suggest a division of labor where microtubule growth and localization are distinctly regulated.

    View details for DOI 10.1016/j.cub.2021.06.021

    View details for PubMedID 34242576

  • Apical PAR complex proteins protect against programmed epithelial assaults to create a continuous and functional intestinal lumen. eLife Sallee, M. D., Pickett, M. A., Feldman, J. L. 2021; 10


    Sustained polarity and adhesion of epithelial cells is essential for the protection of our organs and bodies, and this epithelial integrity emerges during organ development amidst numerous programmed morphogenetic assaults. Using the developing C. elegans intestine as an in vivo model, we investigated how epithelia maintain their integrity through cell division and elongation to build a functional tube. Live-imaging revealed that apical PAR complex proteins PAR-6/Par6 and PKC-3/aPkc remained apical during mitosis while apical microtubules and microtubule-organizing center (MTOC) proteins were transiently removed. Intestine-specific depletion of PAR-6, PKC-3, and the aPkc regulator CDC-42/Cdc42 caused persistent gaps in the apical MTOC as well as in other apical and junctional proteins after cell division and in non-dividing cells that elongated. Upon hatching, gaps coincided with luminal constrictions that blocked food, and larvae arrested and died. Thus, the apical PAR complex maintains apical and junctional continuity to construct a functional intestinal tube.

    View details for DOI 10.7554/eLife.64437

    View details for PubMedID 34137371

  • Microtubule organization across cell types and states CURRENT BIOLOGY Sallee, M. D., Feldman, J. L. 2021; 31 (10): R506-R511
  • Microtubule organization across cell types and states. Current biology : CB Sallee, M. D., Feldman, J. L. 2021; 31 (10): R506-R511


    Encircling and traversing the cell are architectural struts and dynamic intracellular highways made of cylindrical polymers called microtubules. Built from structurally asymmetric subunits of alphabeta-tubulin heterodimers, microtubules have an inherent structural polarity with a slow-growing minus end and a comparatively dynamic plus end that grows and shrinks. Thus, a key feature of microtubules is that each polymer is polarized, allowing for the execution of cellular tasks that are directional in nature. For example, microtubules build polarized highways allowing directional intracellular transport, generate directional force such as in chromosome alignment and segregation, provide structural support for cell shape, and assemble into highly ordered polar structures like centrioles and cilia. The output of these microtubule-based functions is the performance of different tasks, including establishment and maintenance of cellular polarity, secretion and absorption, cell-cell communication, migration, mechanical resiliency, and mitosis. Different cells accomplish these functions by using distinct sites within the cell called microtubule-organizing centers (MTOCs) to build cell-specific microtubule arrangements. While the specific requirement for microtubules in many in vivo cell types is unknown, disrupting even a subset of microtubule-supported functions is often lethal and is associated with many diseases (e.g., cancer and neuropathies), suggesting that specific patterns of microtubule organization are likely important for cellular function in vivo. This Primer focuses on how differentiated animal and plant cells use distinct MTOCs to generate specific microtubule arrangements, how those arrangements support cellular functions, and how cells rearrange their microtubules to accommodate changing cellular tasks.

    View details for DOI 10.1016/j.cub.2021.01.042

    View details for PubMedID 34033781

  • Centriole-less pericentriolar material serves as a microtubule organizing center at the base of C.elegans sensory cilia. Current biology : CB Magescas, J., Eskinazi, S., Tran, M. V., Feldman, J. L. 2021


    During mitosis in animal cells, the centrosome acts as a microtubule organizing center (MTOC) to assemble the mitotic spindle. MTOC function at the centrosome is driven by proteins within the pericentriolar material (PCM), however the molecular complexity of the PCM makes it difficult to differentiate the proteins required for MTOC activity from other centrosomal functions. We used the natural spatial separation of PCM proteins during mitotic exit to identify a minimal module of proteins required for centrosomal MTOC function in C.elegans. Using tissue-specific degradation, we show that SPD-5, the functional homolog of CDK5RAP2, is essential for embryonic mitosis, while SPD-2/CEP192 and PCMD-1, which are essential in the one-cell embryo, are dispensable. Surprisingly, although the centriole is known to be degraded in the ciliated sensory neurons in C.elegans,1-3 we find evidence for "centriole-less PCM" at the base of cilia and use this structure as a minimal testbed to dissect centrosomal MTOC function. Super-resolution imaging revealed that this PCM inserts inside the lumen of the ciliary axoneme and directly nucleates the assembly of dendritic microtubules toward the cell body. Tissue-specific degradation in ciliated sensory neurons revealed a role for SPD-5 and the conserved microtubule nucleator gamma-TuRC, but not SPD-2 or PCMD-1, in MTOC function at centriole-less PCM. This MTOC function was in the absence of regulation by mitotic kinases, highlighting the intrinsic ability of these proteins to drive microtubule growth and organization and further supporting a model that SPD-5 is the primary driver of MTOC function at the PCM.

    View details for DOI 10.1016/j.cub.2021.03.022

    View details for PubMedID 33798428

  • Inherited apicobasal polarity defines the key features of axon-dendrite polarity in a sensory neuron. Current biology : CB Lee, J., Magescas, J., Fetter, R. D., Feldman, J. L., Shen, K. 2021


    Neurons are highly polarized cells with morphologically and functionally distinct dendritic and axonal processes. The molecular mechanisms that establish axon-dendrite polarity in vivo are poorly understood. Here, we describe the initial polarization of posterior deirid (PDE), a ciliated mechanosensory neuron, during development in vivo through 4D live imaging with endogenously tagged proteins. PDE inherits and maintains apicobasal polarity from its epithelial precursor. Its apical domain is directly transformed into the ciliated dendritic tip through apical constriction, which is followed by axonal outgrowth from the opposite basal side of the cell. The apical Par complex and junctional proteins persistently localize at the developing dendritic domain throughout this transition. Consistent with their instructive role in axon-dendrite polarization, conditional depletion of the Par complex and junctional proteins results in robust defects in dendrite and axon formation. During apical constriction, a microtubule-organizing center (MTOC) containing the microtubule nucleator γ-tubulin ring complex (γ-TuRC) forms along the apical junction between PDE and its sister cell in a manner dependent on the Par complex and junctional proteins. This junctional MTOC patterns neuronal microtubule polarity and facilitate the dynein-dependent recruitment of the basal body for ciliogenesis. When non-ciliated neurons are genetically manipulated to obtain ciliated neuronal fate, inherited apicobasal polarity is required for generating ciliated dendritic tips. We propose that inherited apicobasal polarity, together with apical cell-cell interactions drive the morphological and cytoskeletal polarity in early neuronal differentiation.

    View details for DOI 10.1016/j.cub.2021.06.039

    View details for PubMedID 34270949

  • Visualizing the metazoan proliferation-quiescence decision in vivo. eLife Adikes, R. C., Kohrman, A. Q., Martinez, M. A., Palmisano, N. J., Smith, J. J., Medwig-Kinney, T. N., Min, M., Sallee, M. D., Ahmed, O. B., Kim, N., Liu, S., Morabito, R. D., Weeks, N., Zhao, Q., Zhang, W., Feldman, J. L., Barkoulas, M., Pani, A. M., Spencer, S. L., Martin, B. L., Matus, D. Q. 2020; 9


    Cell proliferation and quiescence are intimately coordinated during metazoan development. Here, we adapt a cyclin-dependent kinase (CDK) sensor to uncouple these key events of the cell cycle in C. elegans and zebrafish through live-cell imaging. The CDK sensor consists of a fluorescently tagged CDK substrate that steadily translocates from the nucleus to the cytoplasm in response to increasing CDK activity and consequent sensor phosphorylation. We show that the CDK sensor can distinguish cycling cells in G1 from quiescent cells in G0, revealing a possible commitment point and a cryptic stochasticity in an otherwise invariant C. elegans cell lineage. Finally, we derive a predictive model of future proliferation behavior in C. elegans based on a snapshot of CDK activity in newly born cells. Thus, we introduce a live-cell imaging tool to facilitate in vivo studies of cell cycle control in a wide-range of developmental contexts.

    View details for DOI 10.7554/eLife.63265

    View details for PubMedID 33350383

  • Visualizing the metazoan proliferation-quiescence decision in vivo ELIFE Adikes, R. C., Kohrman, A. Q., Martinez, M. Q., Palmisano, N. J., Smith, J. J., Medwig-Kinney, T. N., Min, M., Sallee, M. D., Ahmed, O. B., Kim, N., Liu, S., Morabito, R. D., Weeks, N., Zhao, Q., Zhang, W., Feldman, J. L., Barkoulas, M., Pani, A. M., Spencer, S. L., Martin, B. L., Matus, D. Q. 2020; 9
  • Growth cone-localized microtubule organizing center establishes microtubule orientation in dendrites. eLife Liang, X., Kokes, M., Fetter, R. D., Sallee, M. D., Moore, A. W., Feldman, J. L., Shen, K. 2020; 9


    A polarized arrangement of neuronal microtubule arrays is the foundation of membrane trafficking and subcellular compartmentalization. Conserved among both invertebrates and vertebrates, axons contain exclusively 'plus-end-out' microtubules while dendrites contain a high percentage of 'minus-end-out' microtubules, the origins of which have been a mystery. Here we show that in Caenorhabditis elegans the dendritic growth cone contains a non-centrosomal microtubule organizing center, which generates minus-end-out microtubules along outgrowing dendrites and plus-end-out microtubules in the growth cone. RAB-11-positive endosomes accumulate in this region and co-migrate with the microtubule nucleation complex gamma-TuRC. The MTOC tracks the extending growth cone by kinesin-1/UNC-116-mediated endosome movements on distal plus-end-out microtubules and dynein clusters this advancing MTOC. Critically, perturbation of the function or localization of the MTOC causes reversed microtubule polarity in dendrites. These findings unveil the endosome-localized dendritic MTOC as a critical organelle for establishing axon-dendrite polarity.

    View details for DOI 10.7554/eLife.56547

    View details for PubMedID 32657271

  • Higher order cytoskeletal structures. Molecular biology of the cell Avasthi, P. n., Feldman, J. L. 2020; 31 (6): 398

    View details for DOI 10.1091/mbc.E19-12-0679

    View details for PubMedID 32163347

  • A two-step mechanism for the inactivation of microtubule organizing center function at the centrosome. eLife Magescas, J., Zonka, J. C., Feldman, J. L. 2019; 8


    The centrosome acts as a microtubule organizing center (MTOC), orchestrating microtubules into the mitotic spindle through its pericentriolar material (PCM). This activity is biphasic, cycling through assembly and disassembly during the cell cycle. Although hyperactive centrosomal MTOC activity is a hallmark of some cancers, little is known about how the centrosome is inactivated as an MTOC. Analysis of endogenous PCM proteins in C. elegans revealed that the PCM is composed of partially overlapping territories organized into an inner and outer sphere that are removed from the centrosome at different rates and using different behaviors. We found that phosphatases oppose the addition of PCM by mitotic kinases, ultimately catalyzing the dissolution of inner sphere PCM proteins at the end of mitosis. The nature of the PCM appears to change such that the remaining aging PCM outer sphere is mechanically ruptured by cortical pulling forces, ultimately inactivating MTOC function at the centrosome.

    View details for DOI 10.7554/eLife.47867

    View details for PubMedID 31246171

  • A Polarizing Issue: Diversity in the Mechanisms Underlying Apico-Basolateral Polarization In Vivo. Annual review of cell and developmental biology Pickett, M. A., Naturale, V. F., Feldman, J. L. 2019


    Polarization along an apico-basolateral axis is a hallmark of epithelial cells and is essential for their selective barrier and transporter functions, as well as for their ability to provide mechanical resiliency to organs. Loss of polarity along this axis perturbs development and is associated with a wide number of diseases. We describe three steps involved in polarization: symmetry breaking, polarity establishment, and polarity maintenance. While the proteins involved in these processes are highly conserved among epithelial tissues and species, the execution of these steps varies widely and is context dependent. We review both theoretical principles underlying these steps and recent work demonstrating how apico-basolateral polarity is established in vivo in different tissues, highlighting how developmental and physiological contexts play major roles in the execution of the epithelial polarity program. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 35 is October 7, 2019. Please see for revised estimates.

    View details for DOI 10.1146/annurev-cellbio-100818-125134

    View details for PubMedID 31461314

  • Efficient proximity labeling in living cells and organisms with TurboID NATURE BIOTECHNOLOGY Branon, T. C., Bosch, J. A., Sanchez, A. D., Udeshi, N. D., Svinkina, T., Carr, S. A., Feldman, J. L., Perrimon, N., Ting, A. Y. 2018; 36 (9): 880-+


    Protein interaction networks and protein compartmentalization underlie all signaling and regulatory processes in cells. Enzyme-catalyzed proximity labeling (PL) has emerged as a new approach to study the spatial and interaction characteristics of proteins in living cells. However, current PL methods require over 18 h of labeling time or utilize chemicals with limited cell permeability or high toxicity. We used yeast display-based directed evolution to engineer two promiscuous mutants of biotin ligase, TurboID and miniTurbo, which catalyze PL with much greater efficiency than BioID or BioID2, and enable 10-min PL in cells with non-toxic and easily deliverable biotin. Furthermore, TurboID extends biotin-based PL to flies and worms.

    View details for PubMedID 30125270

    View details for PubMedCentralID PMC6126969

  • Tissue-specific degradation of essential centrosome components reveals distinct microtubule populations at microtubule organizing centers. PLoS biology Sallee, M. D., Zonka, J. C., Skokan, T. D., Raftrey, B. C., Feldman, J. L. 2018; 16 (8): e2005189


    Non-centrosomal microtubule organizing centers (ncMTOCs) are found in most differentiated cells, but how these structures regulate microtubule organization and dynamics is largely unknown. We optimized a tissue-specific degradation system to test the role of the essential centrosomal microtubule nucleators gamma-tubulin ring complex (gamma-TuRC) and AIR-1/Aurora A at the apical ncMTOC, where they both localize in Caenorhabditis elegans embryonic intestinal epithelial cells. As at the centrosome, the core gamma-TuRC component GIP-1/GCP3 is required to recruit other gamma-TuRC components to the apical ncMTOC, including MZT-1/MZT1, characterized here for the first time in animal development. In contrast, AIR-1 and MZT-1 were specifically required to recruit gamma-TuRC to the centrosome, but not to centrioles or to the apical ncMTOC. Surprisingly, microtubules remain robustly organized at the apical ncMTOC upon gamma-TuRC and AIR-1 co-depletion, and upon depletion of other known microtubule regulators, including TPXL-1/TPX2, ZYG-9/ch-TOG, PTRN-1/CAMSAP, and NOCA-1/Ninein. However, loss of GIP-1 removed a subset of dynamic EBP-2/EB1-marked microtubules, and the remaining dynamic microtubules grew faster. Together, these results suggest that different microtubule organizing centers (MTOCs) use discrete proteins for their function, and that the apical ncMTOC is composed of distinct populations of gamma-TuRC-dependent and -independent microtubules that compete for a limited pool of resources.

    View details for PubMedID 30080857

  • Cytoskeletal variations in an asymmetric cell division support diversity in nematode sperm size and sex ratios DEVELOPMENT Winter, E. S., Schwarz, A., Fabig, G., Feldman, J. L., Pires-daSilva, A., Mueller-Reichert, T., Sadler, P. L., Shakes, D. C. 2017; 144 (18): 3253–63


    Asymmetric partitioning is an essential component of many developmental processes. As spermatogenesis concludes, sperm are streamlined by discarding unnecessary cellular components into cellular wastebags called residual bodies (RBs). During nematode spermatogenesis, this asymmetric partitioning event occurs shortly after anaphase II, and both microtubules and actin partition into a central RB. Here, we use fluorescence and transmission electron microscopy to elucidate and compare the intermediate steps of RB formation in Caenorhabditis elegans, Rhabditis sp. SB347 (recently named Auanema rhodensis) and related nematodes. In all cases, intact microtubules reorganize and move from centrosomal to non-centrosomal sites at the RB-sperm boundary whereas actin reorganizes through cortical ring expansion and clearance from the poles. However, in species with tiny spermatocytes, these cytoskeletal changes are restricted to one pole. Consequently, partitioning yields one functional sperm with the X-bearing chromosome complement and an RB with the other chromosome set. Unipolar partitioning may not require an unpaired X, as it also occurs in XX spermatocytes. Instead, constraints related to spermatocyte downsizing may have contributed to the evolution of a sperm cell equivalent to female polar bodies.

    View details for PubMedID 28827395

    View details for PubMedCentralID PMC5612256

  • Microtubule-organizing centers: from the centrosome to non-centrosomal sites CURRENT OPINION IN CELL BIOLOGY Sanchez, A. D., Feldman, J. L. 2017; 44: 93-101


    The process of cellular differentiation requires the distinct spatial organization of the microtubule cytoskeleton, the arrangement of which is specific to cell type. Microtubule patterning does not occur randomly, but is imparted by distinct subcellular sites called microtubule-organizing centers (MTOCs). Since the discovery of MTOCs fifty years ago, their study has largely focused on the centrosome. All animal cells use centrosomes as MTOCs during mitosis. However in many differentiated cells, MTOC function is reassigned to non-centrosomal sites to generate non-radial microtubule organization better suited for new cell functions, such as mechanical support or intracellular transport. Here, we review the current understanding of non-centrosomal MTOCs (ncMTOCs) and the mechanisms by which they form in differentiating animal cells.

    View details for DOI 10.1016/

    View details for Web of Science ID 000400022400014

    View details for PubMedCentralID PMC5362366

  • Microtubule-organizing centers: from the centrosome to non-centrosomal sites. Current opinion in cell biology Sanchez, A. D., Feldman, J. L. 2016


    The process of cellular differentiation requires the distinct spatial organization of the microtubule cytoskeleton, the arrangement of which is specific to cell type. Microtubule patterning does not occur randomly, but is imparted by distinct subcellular sites called microtubule-organizing centers (MTOCs). Since the discovery of MTOCs fifty years ago, their study has largely focused on the centrosome. All animal cells use centrosomes as MTOCs during mitosis. However in many differentiated cells, MTOC function is reassigned to non-centrosomal sites to generate non-radial microtubule organization better suited for new cell functions, such as mechanical support or intracellular transport. Here, we review the current understanding of non-centrosomal MTOCs (ncMTOCs) and the mechanisms by which they form in differentiating animal cells.

    View details for DOI 10.1016/

    View details for PubMedID 27666167

    View details for PubMedCentralID PMC5362366

  • Flipping the switch: regulating MTOC location. Cell cycle (Georgetown, Tex.) Sallee, M. D., Feldman, J. L. 2015; 14 (22): 3519-20

    View details for DOI 10.1080/15384101.2015.1093450

    View details for PubMedID 26375186

    View details for PubMedCentralID PMC4825708

  • SPD-2/CEP192 and CDK Are Limiting for Microtubule-Organizing Center Function at the Centrosome CURRENT BIOLOGY Yang, R., Feldman, J. L. 2015; 25 (14): 1924-1931


    The centrosome acts as the microtubule-organizing center (MTOC) during mitosis in animal cells. Microtubules are nucleated and anchored by γ-tubulin ring complexes (γ-TuRCs) embedded within the centrosome's pericentriolar material (PCM). The PCM is required for the localization of γ-TuRCs, and both are steadily recruited to the centrosome, culminating in a peak in MTOC function in metaphase. In differentiated cells, the centrosome is often attenuated as an MTOC and MTOC function is reassigned to non-centrosomal sites such as the apical membrane in epithelial cells, the nuclear envelope in skeletal muscle, and down the lengths of axons and dendrites in neurons. Hyperactive MTOC function at the centrosome is associated with epithelial cancers and with invasive behavior in tumor cells. Little is known about the mechanisms that limit MTOC activation at the centrosome. Here, we find that MTOC function at the centrosome is completely inactivated during cell differentiation in C. elegans embryonic intestinal cells and MTOC function is reassigned to the apical membrane. In cells that divide after differentiation, the cellular MTOC state switches between the membrane and the centrosome. Using cell fusion experiments in live embryos, we find that the centrosome MTOC state is dominant and that the inactive MTOC state of the centrosome is malleable; fusion of a mitotic cell to a differentiated or interphase cell results in rapid reactivation of the centrosome MTOC. We show that conversion of MTOC state involves the conserved centrosome protein SPD-2/CEP192 and CDK activity from the mitotic cell.

    View details for DOI 10.1016/j.cub.2015.06.001

    View details for Web of Science ID 000358465600033

  • SPD-2/CEP192 and CDK Are Limiting for Microtubule-Organizing Center Function at the Centrosome. Current biology : CB Yang, R., Feldman, J. L. 2015; 25 (14): 1924-31


    The centrosome acts as the microtubule-organizing center (MTOC) during mitosis in animal cells. Microtubules are nucleated and anchored by γ-tubulin ring complexes (γ-TuRCs) embedded within the centrosome's pericentriolar material (PCM). The PCM is required for the localization of γ-TuRCs, and both are steadily recruited to the centrosome, culminating in a peak in MTOC function in metaphase. In differentiated cells, the centrosome is often attenuated as an MTOC and MTOC function is reassigned to non-centrosomal sites such as the apical membrane in epithelial cells, the nuclear envelope in skeletal muscle, and down the lengths of axons and dendrites in neurons. Hyperactive MTOC function at the centrosome is associated with epithelial cancers and with invasive behavior in tumor cells. Little is known about the mechanisms that limit MTOC activation at the centrosome. Here, we find that MTOC function at the centrosome is completely inactivated during cell differentiation in C. elegans embryonic intestinal cells and MTOC function is reassigned to the apical membrane. In cells that divide after differentiation, the cellular MTOC state switches between the membrane and the centrosome. Using cell fusion experiments in live embryos, we find that the centrosome MTOC state is dominant and that the inactive MTOC state of the centrosome is malleable; fusion of a mitotic cell to a differentiated or interphase cell results in rapid reactivation of the centrosome MTOC. We show that conversion of MTOC state involves the conserved centrosome protein SPD-2/CEP192 and CDK activity from the mitotic cell.

    View details for DOI 10.1016/j.cub.2015.06.001

    View details for PubMedID 26119750

  • Quantitative analysis and modeling of katanin function in flagellar length control MOLECULAR BIOLOGY OF THE CELL Kannegaard, E., Rego, E. H., Schuck, S., Feldman, J. L., Marshall, W. F. 2014; 25 (22): 3686-3698


    Flagellar length control in Chlamydomonas reinhardtii provides a simple model system in which to investigate the general question of how cells regulate organelle size. Previous work demonstrated that Chlamydomonas cytoplasm contains a pool of flagellar precursor proteins sufficient to assemble a half-length flagellum and that assembly of full-length flagella requires synthesis of additional precursors to augment the preexisting pool. The regulatory systems that control the synthesis and regeneration of this pool are not known, although transcriptional regulation clearly plays a role. We used quantitative analysis of length distributions to identify candidate genes controlling pool regeneration and found that a mutation in the p80 regulatory subunit of katanin, encoded by the PF15 gene in Chlamydomonas, alters flagellar length by changing the kinetics of precursor pool utilization. This finding suggests a model in which flagella compete with cytoplasmic microtubules for a fixed pool of tubulin, with katanin-mediated severing allowing easier access to this pool during flagellar assembly. We tested this model using a stochastic simulation that confirms that cytoplasmic microtubules can compete with flagella for a limited tubulin pool, showing that alteration of cytoplasmic microtubule severing could be sufficient to explain the effect of the pf15 mutations on flagellar length.

    View details for DOI 10.1091/mbc.E14-06-1116

    View details for Web of Science ID 000344236800030

    View details for PubMedID 25143397

  • The Kinase Regulator Mob1 Acts as a Patterning Protein for Stentor Morphogenesis PLOS BIOLOGY Slabodnick, M. M., Ruby, J. G., Dunn, J. G., Feldman, J. L., DeRisi, J. L., Marshall, W. F. 2014; 12 (5)


    Morphogenesis and pattern formation are vital processes in any organism, whether unicellular or multicellular. But in contrast to the developmental biology of plants and animals, the principles of morphogenesis and pattern formation in single cells remain largely unknown. Although all cells develop patterns, they are most obvious in ciliates; hence, we have turned to a classical unicellular model system, the giant ciliate Stentor coeruleus. Here we show that the RNA interference (RNAi) machinery is conserved in Stentor. Using RNAi, we identify the kinase coactivator Mob1--with conserved functions in cell division and morphogenesis from plants to humans-as an asymmetrically localized patterning protein required for global patterning during development and regeneration in Stentor. Our studies reopen the door for Stentor as a model regeneration system.

    View details for DOI 10.1371/journal.pbio.1001861

    View details for Web of Science ID 000336969200011

    View details for PubMedID 24823688

  • Cell Interactions and Patterned Intercalations Shape and Link Epithelial Tubes in C. elegans PLOS GENETICS Rasmussen, J. P., Feldman, J. L., Reddy, S. S., Priess, J. R. 2013; 9 (9)


    Many animal organs are composed largely or entirely of polarized epithelial tubes, and the formation of complex organ systems, such as the digestive or vascular systems, requires that separate tubes link with a common polarity. The Caenorhabditis elegans digestive tract consists primarily of three interconnected tubes-the pharynx, valve, and intestine-and provides a simple model for understanding the cellular and molecular mechanisms used to form and connect epithelial tubes. Here, we use live imaging and 3D reconstructions of developing cells to examine tube formation. The three tubes develop from a pharynx/valve primordium and a separate intestine primordium. Cells in the pharynx/valve primordium polarize and become wedge-shaped, transforming the primordium into a cylindrical cyst centered on the future lumenal axis. For continuity of the digestive tract, valve cells must have the same, radial axis of apicobasal polarity as adjacent intestinal cells. We show that intestinal cells contribute to valve cell polarity by restricting the distribution of a polarizing cue, laminin. After developing apicobasal polarity, many pharyngeal and valve cells appear to explore their neighborhoods through lateral, actin-rich lamellipodia. For a subset of cells, these lamellipodia precede more extensive intercalations that create the valve. Formation of the valve tube begins when two valve cells become embedded at the left-right boundary of the intestinal primordium. Other valve cells organize symmetrically around these two cells, and wrap partially or completely around the orthogonal, lumenal axis, thus extruding a small valve tube from the larger cyst. We show that the transcription factors DIE-1 and EGL-43/EVI1 regulate cell intercalations and cell fates during valve formation, and that the Notch pathway is required to establish the proper boundary between the pharyngeal and valve tubes.

    View details for DOI 10.1371/journal.pgen.1003772

    View details for Web of Science ID 000325076600033

    View details for PubMedID 24039608

  • A Role for the Centrosome and PAR-3 in the Hand-Off of MTOC Function during Epithelial Polarization CURRENT BIOLOGY Feldman, J. L., Priess, J. R. 2012; 22 (7): 575-582


    The centrosome is the major microtubule organizing center (MTOC) in dividing cells and in many postmitotic, differentiated cells. In other cell types, however, MTOC function is reassigned from the centrosome to noncentrosomal sites. Here, we analyze how MTOC function is reassigned to the apical membrane of C. elegans intestinal cells.After the terminal intestinal cell division, the centrosomes and nuclei move near the future apical membranes, and the postmitotic centrosomes lose all, or nearly all, of their associated microtubules. We show that microtubule-nucleating proteins such as γ-tubulin and CeGrip-1 that are centrosome components in dividing cells become localized to the apical membrane, which becomes highly enriched in microtubules. Our results suggest that centrosomes are critical to specify the apical membrane as the new MTOC. First, γ-tubulin appears to redistribute directly from the migrating centrosome onto the lateral then apical membrane. Second, γ-tubulin fails to accumulate apically in wild-type cells following laser ablation of the centrosome. We show that centrosomes localize apically by first moving toward lateral foci of the conserved polarity proteins PAR-3 and PAR-6 and then move together with these foci toward the future apical surface. Embryos lacking PAR-3 fail to localize their centrosomes apically and have aberrant localization of γ-tubulin and CeGrip-1.These data suggest that PAR proteins contribute to apical polarity in part by determining centrosome position and that the reassignment of MTOC function from centrosomes to the apical membrane is associated with a physical hand-off of nucleators of microtubule assembly.

    View details for DOI 10.1016/j.cub.2012.02.044

    View details for Web of Science ID 000302844900018

    View details for PubMedID 22425160

  • C. elegans Germ Cells Show Temperature and Age-Dependent Expression of Cer1, a Gypsy/Ty3-Related Retrotransposon PLOS PATHOGENS Dennis, S., Sheth, U., Feldman, J. L., English, K. A., Priess, J. R. 2012; 8 (3)


    Virus-like particles (VLPs) have not been observed in Caenorhabditis germ cells, although nematode genomes contain low numbers of retrotransposon and retroviral sequences. We used electron microscopy to search for VLPs in various wild strains of Caenorhabditis, and observed very rare candidate VLPs in some strains, including the standard laboratory strain of C. elegans, N2. We identified the N2 VLPs as capsids produced by Cer1, a retrotransposon in the Gypsy/Ty3 family of retroviruses/retrotransposons. Cer1 expression is age and temperature dependent, with abundant expression at 15°C and no detectable expression at 25°C, explaining how VLPs escaped detection in previous studies. Similar age and temperature-dependent expression of Cer1 retrotransposons was observed for several other wild strains, indicating that these properties are common, if not integral, features of this retroelement. Retrotransposons, in contrast to DNA transposons, have a cytoplasmic stage in replication, and those that infect non-dividing cells must pass their genomic material through nuclear pores. In most C. elegans germ cells, nuclear pores are largely covered by germline-specific organelles called P granules. Our results suggest that Cer1 capsids target meiotic germ cells exiting pachytene, when free nuclear pores are added to the nuclear envelope and existing P granules begin to be removed. In pachytene germ cells, Cer1 capsids concentrate away from nuclei on a subset of microtubules that are exceptionally resistant to microtubule inhibitors; the capsids can aggregate these stable microtubules in older adults, which exhibit a temperature-dependent decrease in egg viability. When germ cells exit pachytene, the stable microtubules disappear and capsids redistribute close to nuclei that have P granule-free nuclear pores. This redistribution is microtubule dependent, suggesting that capsids that are released from stable microtubules transfer onto new, dynamic microtubules to track toward nuclei. These studies introduce C. elegans as a model to study the interplay between retroelements and germ cell biology.

    View details for DOI 10.1371/journal.ppat.1002591

    View details for Web of Science ID 000302225600040

    View details for PubMedID 22479180

  • A Cell-Based Screen for Inhibitors of Flagella-Driven Motility in Chlamydomonas Reveals a Novel Modulator of Ciliary Length and Retrograde Actin Flow CYTOSKELETON Engel, B. D., Ishikawa, H., Feldman, J. L., Wilson, C. W., Chuang, P., Snedecor, J., Williams, J., Sun, Z., Marshall, W. F. 2011; 68 (3): 188-203


    Cilia are motile and sensory organelles with critical roles in physiology. Ciliary defects can cause numerous human disease symptoms including polycystic kidneys, hydrocephalus, and retinal degeneration. Despite the importance of these organelles, their assembly and function is not fully understood. The unicellular green alga Chlamydomonas reinhardtii has many advantages as a model system for studies of ciliary assembly and function. Here we describe our initial efforts to build a chemical-biology toolkit to augment the genetic tools available for studying cilia in this organism, with the goal of being able to reversibly perturb ciliary function on a rapid time-scale compared to that available with traditional genetic methods. We screened a set of 5520 compounds from which we identified four candidate compounds with reproducible effects on flagella at nontoxic doses. Three of these compounds resulted in flagellar paralysis and one induced flagellar shortening in a reversible and dose-dependent fashion, accompanied by a reduction in the speed of intraflagellar transport. This latter compound also reduced the length of cilia in mammalian cells, hence we named the compound "ciliabrevin" due to its ability to shorten cilia. This compound also robustly and reversibly inhibited microtubule movement and retrograde actin flow in Drosophila S2 cells. Ciliabrevin may prove especially useful for the study of retrograde actin flow at the leading edge of cells, as it slows the retrograde flow in a tunable dose-dependent fashion until flow completely stops at high concentrations, and these effects are quickly reversed upon washout of the drug.

    View details for DOI 10.1002/cm.20504

    View details for Web of Science ID 000288180600005

    View details for PubMedID 21360831

  • ASQ2 Encodes a TBCC-like Protein Required for Mother-Daughter Centriole Linkage and Mitotic Spindle Orientation CURRENT BIOLOGY Feldman, J. L., Marshall, W. F. 2009; 19 (14): 1238-1243


    An intriguing feature of centrioles is that these highly complicated microtubule-based structures duplicate once per cell cycle, affording the cell precise control over their number. Each cell contains exactly two centrioles, linked together as a pair, one of which is a mother centriole formed in a previous cell cycle and the other of which is a daughter centriole whose assembly is templated by the mother. Neither the molecular basis nor the functional role of mother-daughter centriole linkage is understood. We have identified a mutant, asq2, with defects in centriole linkage. asq2 mutant cells have variable numbers of centrioles and centriole positioning defects. Here, we show that ASQ2 encodes the conserved protein Tbccd1, a member of a protein family including a tubulin folding cochaperone and the retinitis pigmentosa protein RP2, involved in tubulin quality control during ciliogenesis. We characterize mitosis in asq2 cells and show that the majority of cells establish a bipolar spindle but have defects in spindle orientation. Few asq2 cells have centrioles at both poles, and these cells have properly positioned spindles, indicating that centrioles at the poles might be important for spindle orientation. The defects in centriole number control, centriole positioning, and spindle orientation appear to arise from perturbation of centriole linkage mediated by Tbccd1/Asq2p.

    View details for DOI 10.1016/j.cub.2009.05.071

    View details for Web of Science ID 000268530200034

    View details for PubMedID 19631545

  • Katanin Knockdown Supports a Role for Microtubule Severing in Release of Basal Bodies before Mitosis in Chlamydomonas MOLECULAR BIOLOGY OF THE CELL Rasi, M. Q., Parker, J. D., Feldman, J. L., Marshall, W. F., Quarmby, L. M. 2009; 20 (1): 379-388


    Katanin is a microtubule-severing protein that participates in the regulation of cell cycle progression and in ciliary disassembly, but its precise role is not known for either activity. Our data suggest that in Chlamydomonas, katanin severs doublet microtubules at the proximal end of the flagellar transition zone, allowing disengagement of the basal body from the flagellum before mitosis. Using an RNA interference approach we have discovered that severe knockdown of the p60 subunit of katanin, KAT1, is achieved only in cells that also carry secondary mutations that disrupt ciliogenesis. Importantly, we observed that cells in the process of cell cycle-induced flagellar resorption sever the flagella from the basal bodies before resorption is complete, and we find that this process is defective in KAT1 knockdown cells.

    View details for DOI 10.1091/mbc.E07-10-1007

    View details for Web of Science ID 000262134800035

    View details for PubMedID 19005222

  • The mother centriole plays an instructive role in defining cell geometry PLOS BIOLOGY Feldman, J. L., Geimer, S., Marshall, W. F. 2007; 5 (6): 1284-1297


    Centriole positioning is a key step in establishment and propagation of cell geometry, but the mechanism of this positioning is unknown. The ability of pre-existing centrioles to induce formation of new centrioles at a defined angle relative to themselves suggests they may have the capacity to transmit spatial information to their daughters. Using three-dimensional computer-aided analysis of cell morphology in Chlamydomonas, we identify six genes required for centriole positioning relative to overall cell polarity, four of which have known sequences. We show that the distal portion of the centriole is critical for positioning, and that the centriole positions the nucleus rather than vice versa. We obtain evidence that the daughter centriole is unable to respond to normal positioning cues and relies on the mother for positional information. Our results represent a clear example of "cytotaxis" as defined by Sonneborn, and suggest that centrioles can play a key function in propagation of cellular geometry from one generation to the next. The genes documented here that are required for proper centriole positioning may represent a new class of ciliary disease genes, defects in which would be expected to cause disorganized ciliary position and impaired function.

    View details for DOI 10.1371/journal.pbio.0050149

    View details for Web of Science ID 000247173200013

    View details for PubMedID 17518519

  • Retinoic acid signaling restricts the cardiac progenitor pool SCIENCE Keegan, B. R., Feldman, J. L., Begemann, G., Ingham, P. W., Yelon, D. 2005; 307 (5707): 247-249


    Organogenesis begins with specification of a progenitor cell population, the size of which provides a foundation for the organ's final dimensions. Here, we present a new mechanism for regulating the number of progenitor cells by limiting their density within a competent region. We demonstrate that retinoic acid signaling restricts cardiac specification in the zebrafish embryo. Reduction of retinoic acid signaling causes formation of an excess of cardiomyocytes, via fate transformations that increase cardiac progenitor density within a multipotential zone. Thus, retinoic acid signaling creates a balance between cardiac and noncardiac identities, thereby refining the dimensions of the cardiac progenitor pool.

    View details for DOI 10.1126/science.1101573

    View details for Web of Science ID 000226361900040

    View details for PubMedID 15653502

  • PCR-based assay for mating type and diploidy in Chlamydomonas BIOTECHNIQUES Zamora, I., Feldman, J. L., Marshall, W. F. 2004; 37 (4): 534-536

    View details for Web of Science ID 000224539400004

    View details for PubMedID 15517961

  • Centrioles: Bad to be bald? CURRENT BIOLOGY Feldman, J. L., Marshall, W. F. 2004; 14 (16): R659-R660


    In the alga Chlamydomonas, mutation of the gene encoding the novel centriolar component Bld10p results in seemingly acentriolar cells. Remarkably, bld10 cells are viable, highlighting the question of whether or not centrioles are essential.

    View details for Web of Science ID 000223586900012

    View details for PubMedID 15324683

  • The elongation factors Pandora/Spt6 and Foggy/Spt5 promote transcription in the zebrafish embryo DEVELOPMENT Keegan, B. R., Feldman, J. L., Lee, D. H., Koos, D. S., Ho, R. K., Stainier, D. Y., Yelon, D. 2002; 129 (7): 1623-1632


    Precise temporal and spatial control of transcription is a fundamental component of embryonic development. Regulation of transcription elongation can act as a rate-limiting step during mRNA synthesis. The mechanisms of stimulation and repression of transcription elongation during development are not yet understood. We have identified a class of zebrafish mutations (pandora, sk8 and s30) that cause multiple developmental defects, including discrete problems with pigmentation, tail outgrowth, ear formation and cardiac differentiation. We demonstrate that the pandora gene encodes a protein similar to Spt6, a proposed transcription elongation factor. Additionally, the sk8 and s30 mutations are null alleles of the foggy/spt5 locus, which encodes another transcription elongation factor. Through real-time RT-PCR analysis, we demonstrate that Spt6 and Spt5 are both required for efficient kinetics of hsp70 transcription in vivo. Altogether, our results suggest that Spt6 and Spt5 play essential roles of comparable importance for promoting transcription during embryogenesis. This study provides the first genetic evidence for parallel functions of Spt6 and Spt5 in metazoans and establishes a system for the future analysis of transcription elongation during development.

    View details for Web of Science ID 000175112300007

    View details for PubMedID 11923199

  • Genetic regulation of cardiac patterning in zebrafish Cold Spring Harbor Symposium on Quantitative Biology Yelon, D., Feldman, J. L., Keegan, B. R. COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT. 2002: 19–25

    View details for Web of Science ID 000183780700004

    View details for PubMedID 12858519