Ryann Fame PhD joined the faculty at Stanford University in 2022. Following her undergraduate degree in Biology and Chemistry at the College of William & Mary, Dr. Fame completed a PhD in Molecular and Cellular Biology at Harvard University. She conducted postdoctoral fellowships at The Whitehead Institute for Biomedical Research at MIT and at Boston Children’s Hospital Pathology Department. Her research program encompasses the early neural stem cell niche, neural tube closure, cerebrospinal fluid (CSF), metabolism, and cortical neuronal development. As a stem cell and developmental molecular biologist, Dr. Fame is dedicated to broad collaboration focused on translating an understanding of neural development and CSF biology into regenerative strategies for the treatment of neurodevelopmental disease.
Honors & Awards
McCormick and Gabilan Faculty Award, Stanford University OFDD (2023-2025)
Research Grant, The Shurl and Kay Curci Foundation (2023-2025)
Hydrocephalus Innovator Award, Hydrocephalus Association (2022-2023)
Office of Faculty Development Career Award, Boston Children’s Hospital (2020-2022)
Balkin-Markell-Weinberg Postdoctoral Fellow, The Whitehead Institute (2015-2016)
NIH NRSA Graduate Research Fellow (F31), National Institutes of Health (NIH) (2010-2012)
NSF Post Graduate Research Fellow, National Science Foundation (NSF) (2007-2010)
Derek Bok Certificate of Distinction in Teaching, Harvard University (2007)
Ashford Fellow, Harvard University (2006-2013)
Vranos Fellow, Harvard University (2006-2007)
Biology Departmental Senior Thesis Award, The College of William and Mary (2006)
International Research Award, The College of William and Mary (2005)
Boards, Advisory Committees, Professional Organizations
Member, Society for Neuroscience (2007 - Present)
Instructor of Pathology, Boston Children's Hospital, Neurodevelopment (2022)
Postdoctoral Fellow, The Whitehead Institutes for Biomedical Research at MIT, Neurodevelopment (2016)
PhD, Harvard University, Stem Cell and Regenerative Biology (2013)
AM, Harvard University, Molecular and Cellular Biology (2008)
AB, The College of William and Mary, Biology and Chemistry (2006)
Ryann Fame, Maria Lehtinen, Cameron Sadegh, Huixin Xu. "United States Patent WO-2022164451-A1 COMPOSITIONS AND METHODS FOR TREATING CEREBROSPINAL FLUID DISORDERS", Boston Children's Hospital, Sep 16, 2022
Current Research and Scholarly Interests
Early neural progenitors respond to extrinsic cues that maintain and support their potency. These stem/ progenitor cells are in direct contact with the cerebrospinal fluid (CSF), which acts as part of their niche. Our research program encompasses the early neural stem cell niche, neural tube closure, CSF, metabolism, and cortical neuronal development. We are dedicated to broad collaboration focused on translating an understanding of neurodevelopment and CSF biology into regenerative strategies.
Doctoral Dissertation Reader (AC)
Postdoctoral Faculty Sponsor
Doctoral Dissertation Advisor (AC)
Arjun Rajan, Blake Zhou
Graduate and Fellowship Programs
Ependymal cells SCOre sweet cerebrospinal fluid.
2023; 21 (9): e3002323
The subcommissural organ (SCO) is a secretory tissue located on the roof of the brain's third ventricle. A new study published in PLOS Biology finds that the SCO responds to glucose by secreting signaling molecules into the cerebrospinal fluid (CSF), thereby decreasing the local ependyma-driven CSF movement.
View details for DOI 10.1371/journal.pbio.3002323
View details for PubMedID 37738230
Defining diurnal fluctuations in mouse choroid plexus and CSF at high molecular, spatial, and temporal resolution.
2023; 14 (1): 3720
Transmission and secretion of signals via the choroid plexus (ChP) brain barrier can modulate brain states via regulation of cerebrospinal fluid (CSF) composition. Here, we developed a platform to analyze diurnal variations in male mouse ChP and CSF. Ribosome profiling of ChP epithelial cells revealed diurnal translatome differences in metabolic machinery, secreted proteins, and barrier components. Using ChP and CSF metabolomics and blood-CSF barrier analyses, we observed diurnal changes in metabolites and cellular junctions. We then focused on transthyretin (TTR), a diurnally regulated thyroid hormone chaperone secreted by the ChP. Diurnal variation in ChP TTR depended on Bmal1 clock gene expression. We achieved real-time tracking of CSF-TTR in awake TtrmNeonGreen mice via multi-day intracerebroventricular fiber photometry. Diurnal changes in ChP and CSF TTR levels correlated with CSF thyroid hormone levels. These datasets highlight an integrated platform for investigating diurnal control of brain states by the ChP and CSF.
View details for DOI 10.1038/s41467-023-39326-3
View details for PubMedID 37349305
Age-appropriate potassium clearance from perinatal cerebrospinal fluid depends on choroid plexus NKCC1.
Fluids and barriers of the CNS
2023; 20 (1): 45
Regulation of the volume and electrolyte composition of the cerebrospinal fluid (CSF) is vital for brain development and function. The Na-K-Cl co-transporter NKCC1 in the choroid plexus (ChP) plays key roles in regulating CSF volume by co-transporting ions and mediating same-direction water movements. Our previous study showed ChP NKCC1 is highly phosphorylated in neonatal mice as the CSF K+ level drastically decreases and that overexpression of NKCC1 in the ChP accelerates CSF K+ clearance and reduces ventricle size . These data suggest that NKCC1 mediates CSF K+ clearance following birth in mice. In this current study, we used CRISPR technology to create a conditional NKCC1 knockout mouse line and evaluated CSF K+ by Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). We demonstrated ChP-specific reduction of total and phosphorylated NKCC1 in neonatal mice following embryonic intraventricular delivery of Cre recombinase using AAV2/5. ChP-NKCC1 knockdown was accompanied by a delayed perinatal clearance of CSF K+. No gross morphological disruptions were observed in the cerebral cortex. We extended our previous results by showing embryonic and perinatal rats shared key characteristics with mice, including decreased ChP NKCC1 expression level, increased ChP NKCC1 phosphorylation state, and increased CSF K+ levels compared to adult. Collectively, these follow up data support ChP NKCC1's role in age-appropriate CSF K+ clearance during neonatal development.
View details for DOI 10.1186/s12987-023-00438-z
View details for PubMedID 37328833
View details for PubMedCentralID 7815709
Choroid plexus-targeted NKCC1 overexpression to treat post-hemorrhagic hydrocephalus.
Post-hemorrhagic hydrocephalus (PHH) refers to a life-threatening accumulation of cerebrospinal fluid (CSF) that occurs following intraventricular hemorrhage (IVH). An incomplete understanding of this variably progressive condition has hampered the development of new therapies beyond serial neurosurgical interventions. Here, we show a key role for the bidirectional Na-K-Cl cotransporter, NKCC1, in the choroid plexus (ChP) to mitigate PHH. Mimicking IVH with intraventricular blood led to increased CSF [K+] and triggered cytosolic calcium activity in ChP epithelial cells, which was followed by NKCC1 activation. ChP-targeted adeno-associated viral (AAV)-NKCC1 prevented blood-induced ventriculomegaly and led to persistently increased CSF clearance capacity. These data demonstrate that intraventricular blood triggered a trans-choroidal, NKCC1-dependent CSF clearance mechanism. Inactive, phosphodeficient AAV-NKCC1-NT51 failed to mitigate ventriculomegaly. Excessive CSF [K+] fluctuations correlated with permanent shunting outcome in humans following hemorrhagic stroke, suggesting targeted gene therapy as a potential treatment to mitigate intracranial fluid accumulation following hemorrhage.
View details for DOI 10.1016/j.neuron.2023.02.020
View details for PubMedID 36893755
Cerebrovasculature pumps up progenitors.
2022; 185 (20): 3645-3647
Fetal human brain stem cell niches that contain multipotent neural progenitors are progressively vascularized during development. Crouch et al. (Crouch et al., 2022) report endothelial and mural lineage trajectories that build developing prenatal vascular in second trimester fetal brain. This cerebral angiogenesis in neural progenitor zones occurs simultaneously with and can promote neurogenesis.
View details for DOI 10.1016/j.cell.2022.09.014
View details for PubMedID 36179664
The choroid plexus: a missing link in our understanding of brain development and function.
Studies of the choroid plexuses lag behind those of, the more widely known, blood brain barrier in spite of a much longer history. This review has two overall aims. The first is to outline longstanding areas of research where there are unanswered questions, such as control of cerebrospinal fluid (CSF) secretion and blood flow. The second part reviews research over the past ten years where the focus has shifted to the idea that the choroid plexuses make specific contributions to brain development and function through molecules they generate and circulate throughout the CSF; these appear to be particularly important for aspects of normal brain growth. Most research in the 20th Century dealt with the choroid plexuses as one of the brain barrier interfaces that make an important contribution to the composition and stability of the internal environment of the brain in the adult and during its development. More recent research has shown the importance of choroid plexus generated CSF in neurogenesis, influence of sex and other hormones on plexus function, and their role in circadian rhythms and sleep. Of clinical importance are attempts to develop methods to deliver brain-specific drugs via the CSF and understanding the implications of drug entry into developing brain when administered to pregnant women.
View details for DOI 10.1152/physrev.00060.2021
View details for PubMedID 36173801
Disruption of GMNC-MCIDAS multiciliogenesis program is critical in choroid plexus carcinoma development.
Cell death and differentiation
2022; 29 (8): 1596-1610
Multiciliated cells (MCCs) in the brain reside in the ependyma and the choroid plexus (CP) epithelia. The CP secretes cerebrospinal fluid that circulates within the ventricular system, driven by ependymal cilia movement. Tumors of the CP are rare primary brain neoplasms mostly found in children. CP tumors exist in three forms: CP papilloma (CPP), atypical CPP, and CP carcinoma (CPC). Though CPP and atypical CPP are generally benign and can be resolved by surgery, CPC is a particularly aggressive and little understood cancer with a poor survival rate and a tendency for recurrence and metastasis. In contrast to MCCs in the CP epithelia, CPCs in humans are characterized by solitary cilia, frequent TP53 mutations, and disturbances to multiciliogenesis program directed by the GMNC-MCIDAS transcriptional network. GMNC and MCIDAS are early transcriptional regulators of MCC fate differentiation in diverse tissues. Consistently, components of the GMNC-MCIDAS transcriptional program are expressed during CP development and required for multiciliation in the CP, while CPC driven by deletion of Trp53 and Rb1 in mice exhibits multiciliation defects consequent to deficiencies in the GMNC-MCIDAS program. Previous studies revealed that abnormal NOTCH pathway activation leads to CPP. Here we show that combined defects in NOTCH and Sonic Hedgehog signaling in mice generates tumors that are similar to CPC in humans. NOTCH-driven CP tumors are monociliated, and disruption of the NOTCH complex restores multiciliation and decreases tumor growth. NOTCH suppresses multiciliation in tumor cells by inhibiting the expression of GMNC and MCIDAS, while Gmnc-Mcidas overexpression rescues multiciliation defects and suppresses tumor cell proliferation. Taken together, these findings indicate that reactivation of the GMNC-MCIDAS multiciliogenesis program is critical for inhibiting tumorigenesis in the CP, and it may have therapeutic implications for the treatment of CPC.
View details for DOI 10.1038/s41418-022-00950-z
View details for PubMedID 35322202
View details for PubMedCentralID PMC9345885
Mitochondria in Early Forebrain Development: From Neurulation to Mid-Corticogenesis.
Frontiers in cell and developmental biology
2021; 9: 780207
Function of the mature central nervous system (CNS) requires a substantial proportion of the body's energy consumption. During development, the CNS anlage must maintain its structure and perform stage-specific functions as it proceeds through discrete developmental stages. While key extrinsic signals and internal transcriptional controls over these processes are well appreciated, metabolic and mitochondrial states are also critical to appropriate forebrain development. Specifically, metabolic state, mitochondrial function, and mitochondrial dynamics/localization play critical roles in neurulation and CNS progenitor specification, progenitor proliferation and survival, neurogenesis, neural migration, and neurite outgrowth and synaptogenesis. With the goal of integrating neurodevelopmental biologists and mitochondrial specialists, this review synthesizes data from disparate models and processes to compile and highlight key roles of mitochondria in the early development of the CNS with specific focus on forebrain development and corticogenesis.
View details for DOI 10.3389/fcell.2021.780207
View details for PubMedID 34888312
View details for PubMedCentralID PMC8650308
MEIS-WNT5A axis regulates development of fourth ventricle choroid plexus.
Development (Cambridge, England)
2021; 148 (10)
The choroid plexus (ChP) produces cerebrospinal fluid and forms an essential brain barrier. ChP tissues form in each brain ventricle, each one adopting a distinct shape, but remarkably little is known about the mechanisms underlying ChP development. Here, we show that epithelial WNT5A is crucial for determining fourth ventricle (4V) ChP morphogenesis and size in mouse. Systemic Wnt5a knockout, or forced Wnt5a overexpression beginning at embryonic day 10.5, profoundly reduced ChP size and development. However, Wnt5a expression was enriched in Foxj1-positive epithelial cells of 4V ChP plexus, and its conditional deletion in these cells affected the branched, villous morphology of the 4V ChP. We found that WNT5A was enriched in epithelial cells localized to the distal tips of 4V ChP villi, where WNT5A acted locally to activate non-canonical WNT signaling via ROR1 and ROR2 receptors. During 4V ChP development, MEIS1 bound to the proximal Wnt5a promoter, and gain- and loss-of-function approaches demonstrated that MEIS1 regulated Wnt5a expression. Collectively, our findings demonstrate a dual function of WNT5A in ChP development and identify MEIS transcription factors as upstream regulators of Wnt5a in the 4V ChP epithelium.
View details for DOI 10.1242/dev.192054
View details for PubMedID 34032267
View details for PubMedCentralID PMC8180257
Choroid plexus NKCC1 mediates cerebrospinal fluid clearance during mouse early postnatal development
2021; 12 (1): 447
Cerebrospinal fluid (CSF) provides vital support for the brain. Abnormal CSF accumulation, such as hydrocephalus, can negatively affect perinatal neurodevelopment. The mechanisms regulating CSF clearance during the postnatal critical period are unclear. Here, we show that CSF K+, accompanied by water, is cleared through the choroid plexus (ChP) during mouse early postnatal development. We report that, at this developmental stage, the ChP showed increased ATP production and increased expression of ATP-dependent K+ transporters, particularly the Na+, K+, Cl-, and water cotransporter NKCC1. Overexpression of NKCC1 in the ChP resulted in increased CSF K+ clearance, increased cerebral compliance, and reduced circulating CSF in the brain without changes in intracranial pressure in mice. Moreover, ChP-specific NKCC1 overexpression in an obstructive hydrocephalus mouse model resulted in reduced ventriculomegaly. Collectively, our results implicate NKCC1 in regulating CSF K+ clearance through the ChP in the critical period during postnatal neurodevelopment in mice.
View details for DOI 10.1038/s41467-020-20666-3
View details for Web of Science ID 000613519600004
View details for PubMedID 33469018
View details for PubMedCentralID PMC7815709
Tracking Calcium Dynamics and Immune Surveillance at the Choroid Plexus Blood-Cerebrospinal Fluid Interface.
2020; 108 (4): 623-639.e10
The choroid plexus (ChP) epithelium is a source of secreted signaling factors in cerebrospinal fluid (CSF) and a key barrier between blood and brain. Here, we develop imaging tools to interrogate these functions in adult lateral ventricle ChP in whole-mount explants and in awake mice. By imaging epithelial cells in intact ChP explants, we observed calcium activity and secretory events that increased in frequency following delivery of serotonergic agonists. Using chronic two-photon imaging in awake mice, we observed spontaneous subcellular calcium events as well as strong agonist-evoked calcium activation and cytoplasmic secretion into CSF. Three-dimensional imaging of motility and mobility of multiple types of ChP immune cells at baseline and following immune challenge or focal injury revealed a range of surveillance and defensive behaviors. Together, these tools should help illuminate the diverse functions of this understudied body-brain interface.
View details for DOI 10.1016/j.neuron.2020.08.024
View details for PubMedID 32961128
View details for PubMedCentralID PMC7847245
Brain Ventricular System and Cerebrospinal Fluid Development and Function: Light at the End of the Tube: A Primer with Latest Insights.
BioEssays : news and reviews in molecular, cellular and developmental biology
2020; 42 (3): e1900186
The brain ventricular system is a series of connected cavities, filled with cerebrospinal fluid (CSF), that forms within the vertebrate central nervous system (CNS). The hollow neural tube is a hallmark of the chordate CNS, and a closed neural tube is essential for normal development. Development and function of the ventricular system is examined, emphasizing three interdigitating components that form a functional system: ventricle walls, CSF fluid properties, and activity of CSF constituent factors. The cellular lining of the ventricle both can produce and is responsive to CSF. Fluid properties and conserved CSF components contribute to normal CNS development. Anomalies of the CSF/ventricular system serve as diagnostics and may cause CNS disorders, further highlighting their importance. This review focuses on the evolution and development of the brain ventricular system, associated function, and connected pathologies. It is geared as an introduction for scholars with little background in the field.
View details for DOI 10.1002/bies.201900186
View details for PubMedID 32078177
Emergence and Developmental Roles of the Cerebrospinal Fluid System.
2020; 52 (3): 261-275
We summarize recent work illuminating how cerebrospinal fluid (CSF) regulates brain function. More than a protective fluid cushion and sink for waste, the CSF is an integral CNS component with dynamic and diverse roles emerging in parallel with the developing CNS. This review examines the current understanding about early CSF and its maturation and roles during CNS development and discusses open questions in the field. We focus on developmental changes in the ventricular system and CSF sources (including neural progenitors and choroid plexus). We also discuss concepts related to the development of fluid dynamics including flow, perivascular transport, drainage, and barriers.
View details for DOI 10.1016/j.devcel.2020.01.027
View details for PubMedID 32049038
A concerted metabolic shift in early forebrain alters the CSF proteome and depends on MYC downregulation for mitochondrial maturation.
Development (Cambridge, England)
2019; 146 (20)
Massive, coordinated cellular changes accompany the transition of central nervous system (CNS) progenitors from forebrain neurectodermal cells to specified neuroepithelial cells. We have previously found that MYC regulates the changing ribosomal and proteostatic landscapes in mouse forebrain precursors at embryonic days E8.5 and E10.5 (before and after neural tube closure; NTC) (Chau et al., 2018). Here, we demonstrate parallel coordinated transcriptional changes in metabolic machinery during this same stage of forebrain specification. Progenitors showed striking mitochondrial structural changes transitioning from glycolytic cristae at E8.5, to more traditional mitochondria at E10.5. Accordingly, glucose use shifted in progenitors such that E8.5 progenitors relied on glycolysis, and after NTC increasingly used oxidative phosphorylation. This metabolic shift was matched by changes in surrounding amniotic and cerebrospinal fluid proteomes. Importantly, these mitochondrial morphological shifts depend on MYC downregulation. Together, our findings demonstrate that metabolic shifting accompanies dynamic organelle and proteostatic remodeling of progenitor cells during the earliest stages of forebrain development.
View details for DOI 10.1242/dev.182857
View details for PubMedID 31575649
View details for PubMedCentralID PMC6826040
Targeting Peripheral Somatosensory Neurons to Improve Tactile-Related Phenotypes in ASD Models.
2019; 178 (4): 867-886.e24
Somatosensory over-reactivity is common among patients with autism spectrum disorders (ASDs) and is hypothesized to contribute to core ASD behaviors. However, effective treatments for sensory over-reactivity and ASDs are lacking. We found distinct somatosensory neuron pathophysiological mechanisms underlie tactile abnormalities in different ASD mouse models and contribute to some ASD-related behaviors. Developmental loss of ASD-associated genes Shank3 or Mecp2 in peripheral mechanosensory neurons leads to region-specific brain abnormalities, revealing links between developmental somatosensory over-reactivity and the genesis of aberrant behaviors. Moreover, acute treatment with a peripherally restricted GABAA receptor agonist that acts directly on mechanosensory neurons reduced tactile over-reactivity in six distinct ASD models. Chronic treatment of Mecp2 and Shank3 mutant mice improved body condition, some brain abnormalities, anxiety-like behaviors, and some social impairments but not memory impairments, motor deficits, or overgrooming. Our findings reveal a potential therapeutic strategy targeting peripheral mechanosensory neurons to treat tactile over-reactivity and select ASD-related behaviors.
View details for DOI 10.1016/j.cell.2019.07.024
View details for PubMedID 31398341
View details for PubMedCentralID PMC6704376
Sister, Sister: Ependymal Cells and Adult Neural Stem Cells Are Separated at Birth by Geminin Family Members.
2019; 102 (2): 278-279
The adult subventricular zone (SVZ) stem cell niche is comprised of multi-ciliated ependymal cells that line the brain ventricular system and adult stem cells. Papers in Neuron (Ortiz-Álvarez et al., 2019) and Cell Reports (Redmond et al., 2019) report that these cell types share a common precursor. Ortiz-Álvarez et al. further show that Geminin family members modulate the fate of daughter cells.
View details for DOI 10.1016/j.neuron.2019.02.040
View details for PubMedID 30998898
Mice Expressing Myc in Neural Precursors Develop Choroid Plexus and Ciliary Body Tumors.
The American journal of pathology
2018; 188 (6): 1334-1344
Choroid plexus tumors and ciliary body medulloepithelioma are predominantly pediatric neoplasms. Progress in understanding the pathogenesis of these tumors has been hindered by their rarity and lack of models that faithfully recapitulate the disease. Here, we find that endogenous Myc proto-oncogene protein is down-regulated in the forebrain neuroepithelium, whose neural plate border domains give rise to the anterior choroid plexus and ciliary body. To uncover the consequences of persistent Myc expression, MYC expression was forced in multipotent neural precursors (nestin-Cre:Myc), which produced fully penetrant models of choroid plexus carcinoma and ciliary body medulloepithelioma. Nestin-mediated MYC expression in the epithelial cells of choroid plexus leads to the regionalized formation of choroid plexus carcinoma in the posterior domain of the lateral ventricle choroid plexus and the fourth ventricle choroid plexus that is accompanied by loss of multiple cilia, up-regulation of protein biosynthetic machinery, and hydrocephalus. Parallel MYC expression in the ciliary body leads also to up-regulation of protein biosynthetic machinery. Additionally, Myc expression in human choroid plexus tumors increases with aggressiveness of disease. Collectively, our findings expose a select vulnerability of the neuroepithelial lineage to postnatal tumorigenesis and provide a new mouse model for investigating the pathogenesis of these rare pediatric neoplasms.
View details for DOI 10.1016/j.ajpath.2018.02.009
View details for PubMedID 29545198
View details for PubMedCentralID PMC5971223
Downregulation of ribosome biogenesis during early forebrain development.
Forebrain precursor cells are dynamic during early brain development, yet the underlying molecular changes remain elusive. We observed major differences in transcriptional signatures of precursor cells from mouse forebrain at embryonic days E8.5 vs. E10.5 (before vs. after neural tube closure). Genes encoding protein biosynthetic machinery were strongly downregulated at E10.5. This was matched by decreases in ribosome biogenesis and protein synthesis, together with age-related changes in proteomic content of the adjacent fluids. Notably, c-MYC expression and mTOR pathway signaling were also decreased at E10.5, providing potential drivers for the effects on ribosome biogenesis and protein synthesis. Interference with c-MYC at E8.5 prematurely decreased ribosome biogenesis, while persistent c-MYC expression in cortical progenitors increased transcription of protein biosynthetic machinery and enhanced ribosome biogenesis, as well as enhanced progenitor proliferation leading to subsequent macrocephaly. These findings indicate large, coordinated changes in molecular machinery of forebrain precursors during early brain development.
View details for DOI 10.7554/eLife.36998
View details for PubMedID 29745900
View details for PubMedCentralID PMC5984036
Caveolin1 Identifies a Specific Subpopulation of Cerebral Cortex Callosal Projection Neurons (CPN) Including Dual Projecting Cortical Callosal/Frontal Projection Neurons (CPN/FPN).
2018; 5 (1)
The neocortex is composed of many distinct subtypes of neurons that must form precise subtype-specific connections to enable the cortex to perform complex functions. Callosal projection neurons (CPN) are the broad population of commissural neurons that connect the cerebral hemispheres via the corpus callosum (CC). Currently, how the remarkable diversity of CPN subtypes and connectivity is specified, and how they differentiate to form highly precise and specific circuits, are largely unknown. We identify in mouse that the lipid-bound scaffolding domain protein Caveolin 1 (CAV1) is specifically expressed by a unique subpopulation of Layer V CPN that maintain dual ipsilateral frontal projections to premotor cortex. CAV1 is expressed by over 80% of these dual projecting callosal/frontal projection neurons (CPN/FPN), with expression peaking early postnatally as axonal and dendritic targets are being reached and refined. CAV1 is localized to the soma and dendrites of CPN/FPN, a unique population of neurons that shares information both between hemispheres and with premotor cortex, suggesting function during postmitotic development and refinement of these neurons, rather than in their specification. Consistent with this, we find that Cav1 function is not necessary for the early specification of CPN/FPN, or for projecting to their dual axonal targets. CPN subtype-specific expression of Cav1 identifies and characterizes a first molecular component that distinguishes this functionally unique projection neuron population, a population that expands in primates, and is prototypical of additional dual and higher-order projection neuron subtypes.
View details for DOI 10.1523/ENEURO.0234-17.2017
View details for PubMedID 29379878
View details for PubMedCentralID PMC5780842
Subtype-Specific Genes that Characterize Subpopulations of Callosal Projection Neurons in Mouse Identify Molecularly Homologous Populations in Macaque Cortex.
Cerebral cortex (New York, N.Y. : 1991)
2017; 27 (3): 1817-1830
Callosal projection neurons (CPN) interconnect the neocortical hemispheres via the corpus callosum and are implicated in associative integration of multimodal information. CPN have undergone differential evolutionary elaboration, leading to increased diversity of cortical neurons-and more extensive and varied connections in neocortical gray and white matter-in primates compared with rodents. In mouse, distinct sets of genes are enriched in discrete subpopulations of CPN, indicating the molecular diversity of rodent CPN. Elements of rodent CPN functional and organizational diversity might thus be present in the further elaborated primate cortex. We address the hypothesis that genes controlling mouse CPN subtype diversity might reflect molecular patterns shared among mammals that arose prior to the divergence of rodents and primates. We find that, while early expression of the examined CPN-enriched genes, and postmigratory expression of these CPN-enriched genes in deep layers are highly conserved (e.g., Ptn, Nnmt, Cited2, Dkk3), in contrast, the examined genes expressed by superficial layer CPN show more variable levels of conservation (e.g., EphA3, Chn2). These results suggest that there has been evolutionarily differential retraction and elaboration of superficial layer CPN subpopulations between mouse and macaque, with independent derivation of novel populations in primates. Together, these data inform future studies regarding CPN subpopulations that are unique to primates and rodents, and indicate putative evolutionary relationships.
View details for DOI 10.1093/cercor/bhw023
View details for PubMedID 26874185
View details for PubMedCentralID PMC6317451
Directional cerebrospinal fluid movement between brain ventricles in larval zebrafish.
Fluids and barriers of the CNS
2016; 13 (1): 11
Cerebrospinal fluid (CSF) contained within the brain ventricles contacts neuroepithelial progenitor cells during brain development. Dynamic properties of CSF movement may limit locally produced factors to specific regions of the developing brain. However, there is no study of in vivo CSF dynamics between ventricles in the embryonic brain. We address CSF movement using the zebrafish larva, during the major period of developmental neurogenesis.CSF movement was monitored at two stages of zebrafish development: early larva [pharyngula stage; 27-30 h post-fertilization (hpf)] and late larva (hatching period; 51-54 hpf) using photoactivatable Kaede protein to calculate average maximum CSF velocity between ventricles. Potential roles for heartbeat in early CSF movement were investigated using tnnt2a mutant fish (tnnt2a (-/-)) and chemical [2,3 butanedione monoxime (BDM)] treatment. Cilia motility was monitored at these stages using the Tg(βact:Arl13b-GFP) transgenic fish line.In wild-type early larva there is net CSF movement from the telencephalon to the combined diencephalic/mesencephalic superventricle. This movement directionality reverses at late larval stage. CSF moves directionally from diencephalic to rhombencephalic ventricles at both stages examined, with minimal movement from rhombencephalon to diencephalon. Directional movement is partially dependent on heartbeat, as indicated in assays of tnnt2a (-/-) fish and after BDM treatment. Brain cilia are immotile at the early larval stage.These data demonstrate directional movement of the embryonic CSF in the zebrafish model during the major period of developmental neurogenesis. A key conclusion is that CSF moves preferentially from the diencephalic into the rhombencephalic ventricle. In addition, the direction of CSF movement between telencephalic and diencephalic ventricles reverses between the early and late larval stages. CSF movement is partially dependent on heartbeat. At early larval stage, the absence of motile cilia indicates that cilia likely do not direct CSF movement. These data suggest that CSF components may be compartmentalized and could contribute to specialization of the early brain. In addition, CSF movement may also provide directional mechanical signaling.
View details for DOI 10.1186/s12987-016-0036-z
View details for PubMedID 27329482
View details for PubMedCentralID PMC4915066
Cited2 Regulates Neocortical Layer II/III Generation and Somatosensory Callosal Projection Neuron Development and Connectivity.
The Journal of neuroscience : the official journal of the Society for Neuroscience
2016; 36 (24): 6403-19
The neocortex contains hundreds to thousands of distinct subtypes of precisely connected neurons, allowing it to perform remarkably complex tasks of high-level cognition. Callosal projection neurons (CPN) connect the cerebral hemispheres via the corpus callosum, integrating cortical information and playing key roles in associative cognition. CPN are a strikingly diverse set of neuronal subpopulations, and development of this diversity requires precise control by a complex, interactive set of molecular effectors. We have found that the transcriptional coregulator Cited2 regulates and refines two stages of CPN development. Cited2 is expressed broadly by progenitors in the embryonic day 15.5 subventricular zone, during the peak of superficial layer CPN birth, with a progressive postmitotic refinement in expression, becoming restricted to CPN of the somatosensory cortex postnatally. We generated progenitor-stage and postmitotic forebrain-specific Cited2 conditional knock-out mice, using the Emx1-Cre and NEX-Cre mouse lines, respectively. We demonstrate that Cited2 functions in progenitors, but is not necessary postmitotically, to regulate both (1) broad generation of layer II/III CPN and (2) acquisition of precise area-specific molecular identity and axonal/dendritic connectivity of somatosensory CPN. This novel CPN subtype-specific and area-specific control from progenitor action of Cited2 adds yet another layer of complexity to the multistage developmental regulation of neocortical development.This study identifies Cited2 as a novel subtype-specific and area-specific control over development of distinct subpopulations within the broad population of callosal projection neurons (CPN), whose axons connect the two cerebral hemispheres via the corpus callosum (CC). Currently, how the remarkable diversity of CPN subtypes is specified, and how they differentiate to form highly precise and specific circuits, are largely unknown. We found that Cited2 functions within subventricular zone progenitors to both broadly regulate generation of superficial layer CPN throughout the neocortex, and to refine precise area-specific development and connectivity of somatosensory CPN. Gaining insight into molecular development and heterogeneity of CPN will advance understanding of both diverse functions of CPN and of the remarkable range of neurodevelopmental deficits correlated with CPN/CC development.
View details for DOI 10.1523/JNEUROSCI.4067-15.2016
View details for PubMedID 27307230
View details for PubMedCentralID PMC5015778
Development, specification, and diversity of callosal projection neurons.
Trends in neurosciences
2011; 34 (1): 41-50
Callosal projection neurons (CPN) are a diverse population of neocortical projection neurons that connect the two hemispheres of the cerebral cortex via the corpus callosum. They play key roles in high-level associative connectivity, and have been implicated in cognitive syndromes of high-level associative dysfunction, such as autism spectrum disorders. CPN evolved relatively recently compared to other cortical neuron populations, and have undergone disproportionately large expansion from mouse to human. While much is known about the anatomical trajectory of developing CPN axons, and progress has been made in identifying cellular and molecular controls over midline crossing, only recently have molecular-genetic controls been identified that specify CPN populations, and help define CPN subpopulations. In this review, we discuss the development, diversity and evolution of CPN.
View details for DOI 10.1016/j.tins.2010.10.002
View details for PubMedID 21129791
View details for PubMedCentralID PMC3053014
SOX6 controls dorsal progenitor identity and interneuron diversity during neocortical development.
2009; 12 (10): 1238-47
The neuronal diversity of the CNS emerges largely from controlled spatial and temporal segregation of cell type-specific molecular regulators. We found that the transcription factor SOX6 controls the molecular segregation of dorsal (pallial) from ventral (subpallial) telencephalic progenitors and the differentiation of cortical interneurons, regulating forebrain progenitor and interneuron heterogeneity. During corticogenesis in mice, SOX6 and SOX5 were largely mutually exclusively expressed in pallial and subpallial progenitors, respectively, and remained mutually exclusive in a reverse pattern in postmitotic neuronal progeny. Loss of SOX6 from pallial progenitors caused their inappropriate expression of normally subpallium-restricted developmental controls, conferring mixed dorsal-ventral identity. In postmitotic cortical interneurons, loss of SOX6 disrupted the differentiation and diversity of cortical interneuron subtypes, analogous to SOX5 control over cortical projection neuron development. These data indicate that SOX6 is a central regulator of both progenitor and cortical interneuron diversity during neocortical development.
View details for DOI 10.1038/nn.2387
View details for PubMedID 19657336
View details for PubMedCentralID PMC2903203
Novel subtype-specific genes identify distinct subpopulations of callosal projection neurons.
The Journal of neuroscience : the official journal of the Society for Neuroscience
2009; 29 (39): 12343-54
Little is known about the molecular development and heterogeneity of callosal projection neurons (CPN), cortical commissural neurons that connect homotopic regions of the two cerebral hemispheres via the corpus callosum and that are critical for bilateral integration of cortical information. Here we report on the identification of a series of genes that individually and in combination define CPN and novel CPN subpopulations during embryonic and postnatal development. We used in situ hybridization analysis, immunocytochemistry, and retrograde labeling to define the layer-specific and neuron-type-specific distribution of these newly identified CPN genes across different stages of maturation. We demonstrate that a subset of these genes (e.g., Hspb3 and Lpl) appear specific to all CPN (in layers II/III and V-VI), whereas others (e.g., Nectin-3, Plexin-D1, and Dkk3) discriminate between CPN of the deep layers and those of the upper layers. Furthermore, the data show that several genes finely subdivide CPN within individual layers and appear to label CPN subpopulations that have not been described previously using anatomical or morphological criteria. The genes identified here likely reflect the existence of distinct programs of gene expression governing the development, maturation, and function of the newly identified subpopulations of CPN. Together, these data define the first set of genes that identify and molecularly subcategorize distinct populations of callosal projection neurons, often located in distinct subdivisions of the canonical cortical laminae.
View details for DOI 10.1523/JNEUROSCI.6108-08.2009
View details for PubMedID 19793993
View details for PubMedCentralID PMC2776075
Second-order projection from the posterior lateral line in the early zebrafish brain.
2006; 1: 4
Mechanosensory information gathered by hair cells of the fish lateral-line system is collected by sensory neurons and sent to the ipsilateral hindbrain. The information is then conveyed to other brain structures through a second-order projection. In the adult, part of the second-order projection extends to the contralateral hindbrain, while another part connects to a midbrain structure, the torus semicircularis.In this paper we examine the second-order projection from the posterior lateral-line system in late embryonic/early larval zebrafish. At four days after fertilization the synaptic field of the sensory neurons can be accurately targeted, allowing a very reproducible labeling of second-order neurons. We show that second-order projections are highly stereotyped, that they vary according to rhombomeric identity, and that they are almost completely lateralized. We also show that the projections extend not only to the contralateral hindbrain and torus semicircularis but to many other brain centers as well, including gaze- and posture-controlling nuclei in the midbrain, and presumptive thalamic nuclei.We propose that the extensive connectivity observed in early brain development reveals a basic scaffold common to most vertebrates, from which different subsets are later reinforced in various vertebrate groups. The large repertoire of projection targets provides a promising system to study the genetic encoding of this differential projection capacity.
View details for DOI 10.1186/1749-8104-1-4
View details for PubMedID 17147780
View details for PubMedCentralID PMC1693910
- Specification of neurotransmitter phenotypes in Xenopus laevis ACADEMIC PRESS INC ELSEVIER SCIENCE. 2006: 409