Honors & Awards
NIH K23, NIGMS (2014)
Kozaka research award, International Anesthesia Research Society (2013)
Stanford Society for Physician Scholar's award, SSPS (2011, 2012)
Albert J. Ryan Fellowship, Harvard Medical School (2004)
Carnot Foundation Scholarship, Ecole Polytechnique, Paris, France (2000)
George Lurcy's Fellowship, Harvard University (2000)
Internship:Santa Clara Valley Medical Center Radiology Residency (2010) CA
Board Certification: Anesthesia, American Board of Anesthesiology (2014)
Residency:Stanford University School of Medicine (2013) CA
Medical Education:Harvard Medical School (2009) MA
PhD, Harvard Medical School, Neurobiology (2005)
BS, Ecole Polytechnique, Engineering (2000)
Brice Gaudilliere, Gabriela Fragiadakis, Martin Angst, Garry Nolan. "United States Patent S13-373 Flow cytometry methods for the diagnosis of prolonged convalescence after traumatic injury", Leland Stanford Junior University
Azad Bonni, Aryaman Shalizi, Brice Gaudilliere. "United StatesMethods and compositions for modulating synapse formation", Harvard University
Current Research and Scholarly Interests
The advent of high dimensional flow cytometry has revolutionized our ability to study and visualize the human immune system. Our group combines high parameter mass cytometry (a.k.a Cytometry by Time of Flight Mass Spectrometry, CyTOF), with advanced bio-computational methods to study how the human immune system responds and adapts to acute physiological perturbations. The laboratory currently focuses on two clinical scenarios: surgical trauma and pregnancy.
Deep immune profiling of patients undergoing and recovering from surgery: Using high dimensional mass cytometry, we have recently shown that the signaling behavior of specific innate immune cells measured before surgery in patients blood was strongly associated with surgical recovery. Prospective validation of reported immune correlates of surgical recovery are underway. Ongoing work in humans and animal models focuses on the mechanisms by which pre-operative habilitation interventions may alter a patient’s immune state to improve recovery after surgery.
Deep Immune profiling of normal and preterm pregnancy: Our group is an integral component of a multi-disciplinary effort aiming at understanding the mechanisms of preterm birth, and identifying predictive factors of premature delivery. We have now developed a pipeline and the analytical framework to integrate the single-cell analysis of immune signaling networks by mass cytometry and proteomic profiling of secreted serum factors with the precise phenotyping of pregnancy-related clinical outcomes. In a pilot cross-sectional study of non-pregnant women, we identified candidate immune signatures that differentiated women with a history of preterm or term pregnancies. Longitudinal studies in pregnant patients are ongoing to validate these findings.
Detection of Immune Changes as a Result of Surgical Trauma in Human Subject
Surgical trauma triggers a massive inflammatory response. Over time, both the innate and adaptive branches of the immune system are affected by surgical trauma. The purpose of this study to characterize the cellular and molecular mechanisms immune response to surgical trauma. Additionally, detailed information about patients' recovery profile will be recorded over a period of 6 weeks, with the eventual goal of linking immune responses to recovery profiles.
Immune-modulation Effects of an Arginine Rich Nutritional Supplement in Surgical Patients
The primary objective of this study is to characterize the immune-modulatory effects of arginine-rich nutritional supplements in patients undergoing surgery. Numerical and functional changes of all circulating immune cells will be assessed with mass cytometry.
Stanford is currently not accepting patients for this trial. For more information, please contact Julian Silva, MA, 650-724-9341.
An immune clock of human pregnancy.
2017; 2 (15)
The maintenance of pregnancy relies on finely tuned immune adaptations. We demonstrate that these adaptations are precisely timed, reflecting an immune clock of pregnancy in women delivering at term. Using mass cytometry, the abundance and functional responses of all major immune cell subsets were quantified in serial blood samples collected throughout pregnancy. Cell signaling-based Elastic Net, a regularized regression method adapted from the elastic net algorithm, was developed to infer and prospectively validate a predictive model of interrelated immune events that accurately captures the chronology of pregnancy. Model components highlighted existing knowledge and revealed previously unreported biology, including a critical role for the interleukin-2-dependent STAT5ab signaling pathway in modulating T cell function during pregnancy. These findings unravel the precise timing of immunological events occurring during a term pregnancy and provide the analytical framework to identify immunological deviations implicated in pregnancy-related pathologies.
View details for DOI 10.1126/sciimmunol.aan2946
View details for PubMedID 28864494
Deep Immune Profiling of an Arginine-Enriched Nutritional Intervention in Patients Undergoing Surgery.
Journal of immunology (Baltimore, Md. : 1950)
Application of high-content immune profiling technologies has enormous potential to advance medicine. Whether these technologies reveal pertinent biology when implemented in interventional clinical trials is an important question. The beneficial effects of preoperative arginine-enriched dietary supplements (AES) are highly context specific, as they reduce infection rates in elective surgery, but possibly increase morbidity in critically ill patients. This study combined single-cell mass cytometry with the multiplex analysis of relevant plasma cytokines to comprehensively profile the immune-modifying effects of this much-debated intervention in patients undergoing surgery. An elastic net algorithm applied to the high-dimensional mass cytometry dataset identified a cross-validated model consisting of 20 interrelated immune features that separated patients assigned to AES from controls. The model revealed wide-ranging effects of AES on innate and adaptive immune compartments. Notably, AES increased STAT1 and STAT3 signaling responses in lymphoid cell subsets after surgery, consistent with enhanced adaptive mechanisms that may protect against postsurgical infection. Unexpectedly, AES also increased ERK and P38 MAPK signaling responses in monocytic myeloid-derived suppressor cells, which was paired with their pronounced expansion. These results provide novel mechanistic arguments as to why AES may exert context-specific beneficial or adverse effects in patients with critical illness. This study lays out an analytical framework to distill high-dimensional datasets gathered in an interventional clinical trial into a fairly simple model that converges with known biology and provides insight into novel and clinically relevant cellular mechanisms.
View details for DOI 10.4049/jimmunol.1700421
View details for PubMedID 28794234
Mapping the Fetomaternal Peripheral Immune System at Term Pregnancy.
Journal of immunology
Preterm labor and infections are the leading causes of neonatal deaths worldwide. During pregnancy, immunological cross talk between the mother and her fetus is critical for the maintenance of pregnancy and the delivery of an immunocompetent neonate. A precise understanding of healthy fetomaternal immunity is the important first step to identifying dysregulated immune mechanisms driving adverse maternal or neonatal outcomes. This study combined single-cell mass cytometry of paired peripheral and umbilical cord blood samples from mothers and their neonates with a graphical approach developed for the visualization of high-dimensional data to provide a high-resolution reference map of the cellular composition and functional organization of the healthy fetal and maternal immune systems at birth. The approach enabled mapping of known phenotypical and functional characteristics of fetal immunity (including the functional hyperresponsiveness of CD4(+) and CD8(+) T cells and the global blunting of innate immune responses). It also allowed discovery of new properties that distinguish the fetal and maternal immune systems. For example, examination of paired samples revealed differences in endogenous signaling tone that are unique to a mother and her offspring, including increased ERK1/2, MAPK-activated protein kinase 2, rpS6, and CREB phosphorylation in fetal Tbet(+)CD4(+) T cells, CD8(+) T cells, B cells, and CD56(lo)CD16(+) NK cells and decreased ERK1/2, MAPK-activated protein kinase 2, and STAT1 phosphorylation in fetal intermediate and nonclassical monocytes. This highly interactive functional map of healthy fetomaternal immunity builds the core reference for a growing data repository that will allow inferring deviations from normal associated with adverse maternal and neonatal outcomes.
View details for PubMedID 27793998
View details for PubMedCentralID PMC5125527
Clinical recovery from surgery correlates with single-cell immune signatures.
Science translational medicine
2014; 6 (255): 255ra131-?
Delayed recovery from surgery causes personal suffering and substantial societal and economic costs. Whether immune mechanisms determine recovery after surgical trauma remains ill-defined. Single-cell mass cytometry was applied to serial whole-blood samples from 32 patients undergoing hip replacement to comprehensively characterize the phenotypic and functional immune response to surgical trauma. The simultaneous analysis of 14,000 phosphorylation events in precisely phenotyped immune cell subsets revealed uniform signaling responses among patients, demarcating a surgical immune signature. When regressed against clinical parameters of surgical recovery, including functional impairment and pain, strong correlations were found with STAT3 (signal transducer and activator of transcription), CREB (adenosine 3',5'-monophosphate response element-binding protein), and NF-κB (nuclear factor κB) signaling responses in subsets of CD14(+) monocytes (R = 0.7 to 0.8, false discovery rate <0.01). These sentinel results demonstrate the capacity of mass cytometry to survey the human immune system in a relevant clinical context. The mechanistically derived immune correlates point to diagnostic signatures, and potential therapeutic targets, that could postoperatively improve patient recovery.
View details for DOI 10.1126/scitranslmed.3009701
View details for PubMedID 25253674
Multicenter Systems Analysis of Human Blood Reveals Immature Neutrophils in Males and During Pregnancy.
Journal of immunology
2017; 198 (6): 2479-2488
Despite clear differences in immune system responses and in the prevalence of autoimmune diseases between males and females, there is little understanding of the processes involved. In this study, we identified a gene signature of immature-like neutrophils, characterized by the overexpression of genes encoding for several granule-containing proteins, which was found at higher levels (up to 3-fold) in young (20-30 y old) but not older (60 to >89 y old) males compared with females. Functional and phenotypic characterization of peripheral blood neutrophils revealed more mature and responsive neutrophils in young females, which also exhibited an elevated capacity in neutrophil extracellular trap formation at baseline and upon microbial or sterile autoimmune stimuli. The expression levels of the immature-like neutrophil signature increased linearly with pregnancy, an immune state of increased susceptibility to certain infections. Using mass cytometry, we also find increased frequencies of immature forms of neutrophils in the blood of women during late pregnancy. Thus, our findings show novel sex differences in innate immunity and identify a common neutrophil signature in males and in pregnant women.
View details for DOI 10.4049/jimmunol.1601855
View details for PubMedID 28179497
Expression of specific inflammasome gene modules stratifies older individuals into two extreme clinical and immunological states
2017; 23 (2): 174-184
Low-grade, chronic inflammation has been associated with many diseases of aging, but the mechanisms responsible for producing this inflammation remain unclear. Inflammasomes can drive chronic inflammation in the context of an infectious disease or cellular stress, and they trigger the maturation of interleukin-1β (IL-1β). Here we find that the expression of specific inflammasome gene modules stratifies older individuals into two extremes: those with constitutive expression of IL-1β, nucleotide metabolism dysfunction, elevated oxidative stress, high rates of hypertension and arterial stiffness; and those without constitutive expression of IL-1β, who lack these characteristics. Adenine and N(4)-acetylcytidine, nucleotide-derived metabolites that are detectable in the blood of the former group, prime and activate the NLRC4 inflammasome, induce the production of IL-1β, activate platelets and neutrophils and elevate blood pressure in mice. In individuals over 85 years of age, the elevated expression of inflammasome gene modules was associated with all-cause mortality. Thus, targeting inflammasome components may ameliorate chronic inflammation and various other age-associated conditions.
View details for DOI 10.1038/nm.4267
View details for Web of Science ID 000393729000009
View details for PubMedID 28092664
- The road ahead: Implementing mass cytometry in clinical studies, one cell at a time. Cytometry B Clin Cytom. 2017: 10–11
Mass cytometry: The time to settle down.
View details for DOI 10.1002/cyto.a.23032
- Deep Immune Profiling in Trauma and Sepsis: Flow Is the Way to Go! Critical care medicine 2017; 45 (9): 1577–78
A Proteomic Clock of Human Pregnancy.
American journal of obstetrics and gynecology
Early detection of maladaptive processes underlying pregnancy-related pathologies is desirable, as it will enable targeted interventions ahead of clinical manifestations. The quantitative analysis of plasma proteins features prominently among molecular approaches used to detect deviations from normal pregnancy. However, derivation of proteomic signatures sufficiently predictive of pregnancy-related outcomes has been challenging. An important obstacle hindering such efforts were limitations in assay technology, which prevented the broad examination of the plasma proteome.The recent availability of a highly-multiplexed platform affording the simultaneous measurement of 1,310 plasma proteins opens the door for a more explorative approach. The major aim of this study was to examine whether analysis of plasma collected during gestation of term pregnancy would allow identifying a set of proteins that tightly track gestational age. Establishing precisely-timed plasma proteomic changes during term pregnancy is a critical step in identifying deviations from regular patterns due to fetal and maternal maladaptations. A second aim was to gain insight into functional attributes of identified proteins, and link such attributes to relevant immunological changes.Pregnant women participated in this longitudinal study. In two subsequent subsets of 21 (training cohort) and 10 (validation cohort) women, specific blood specimens were collected during the first (7-14 wks), second (15-20 wks), and third (24-32 wks) trimesters, and 6 wks post-partum for analysis with a highly-multiplexed aptamer-based platform. An elastic net algorithm was applied to infer a proteomic model predicting gestational age. A bootstrapping procedure and piece-wise regression analysis was used to extract the minimum number of proteins required for predicting gestational age without compromising predictive power. Gene ontology analysis was applied to infer enrichment of molecular functions among proteins included in the proteomic model. Changes in abundance of proteins with such functions were linked to immune features predictive of gestational age at the time of sampling in pregnancies delivering at term.An independently validated model consisting of 74 proteins strongly predicted gestational age (p = 3.8x10-14, R = 0.97). The model could be reduced to eight proteins without losing its predictive power (p = 1.7x10-3, R = 0.91). The three top ranked proteins were glypican 3, chorionic somatomammotropin hormone, and granulins. Proteins activating the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway were enriched in the proteomic model, chorionic somatomammotropin hormone being the top ranked protein. Abundance of chorionic somatomammotropin hormone strongly correlated with STAT5 signaling activity in CD4 T cells, the endogenous cell-signaling event most predictive of gestational age.Results indicate that precisely timed changes in the plasma proteome during term pregnancy mirror a "proteomic clock". Importantly, the combined use of several plasma proteins was required for accurate prediction. The exciting promise of such a "clock" is that deviations from its regular chronological profile may assist in the early diagnoses of pregnancy-relate pathologies and point to underlying pathophysiology. Functional analysis of the proteomic model generated the novel hypothesis that somatomammotropin hormone may critically regulate T-cell function during pregnancy.
View details for DOI 10.1016/j.ajog.2017.12.208
View details for PubMedID 29277631
Patient-specific Immune States before Surgery Are Strong Correlates of Surgical Recovery
2015; 123 (6): 1241-1255
Recovery after surgery is highly variable. Risk-stratifying patients based on their predicted recovery profile will afford individualized perioperative management strategies. Recently, application of mass cytometry in patients undergoing hip arthroplasty revealed strong immune correlates of surgical recovery in blood samples collected shortly after surgery. However, the ability to interrogate a patient's immune state before surgery and predict recovery is highly desirable in perioperative medicine.To evaluate a patient's presurgical immune state, cell-type-specific intracellular signaling responses to ex vivo ligands (lipopolysaccharide, interleukin [IL]-6, IL-10, and IL-2/granulocyte macrophage colony-stimulating factor) were quantified by mass cytometry in presurgical blood samples. Selected ligands modulate signaling processes perturbed by surgery. Twenty-three cell surface and 11 intracellular markers were used for the phenotypic and functional characterization of major immune cell subsets. Evoked immune responses were regressed against patient-centered outcomes, contributing to protracted recovery including functional impairment, postoperative pain, and fatigue.Evoked signaling responses varied significantly and defined patient-specific presurgical immune states. Eighteen signaling responses correlated significantly with surgical recovery parameters (|R| = 0.37 to 0.70; false discovery rate < 0.01). Signaling responses downstream of the toll-like receptor 4 in cluster of differentiation (CD) 14 monocytes were particularly strong correlates, accounting for 50% of observed variance. Immune correlates identified in presurgical blood samples mirrored correlates identified in postsurgical blood samples.Convergent findings in pre- and postsurgical analyses provide validation of reported immune correlates and suggest a critical role of the toll-like receptor 4 signaling pathway in monocytes for the clinical recovery process. The comprehensive assessment of patients' preoperative immune state is promising for predicting important recovery parameters and may lead to clinical tests using standard flow cytometry.
View details for DOI 10.1097/ALN.0000000000000887
View details for Web of Science ID 000365483600009
View details for PubMedID 26655308
View details for PubMedCentralID PMC4681408
Implementing Mass Cytometry at the Bedside to Study the Immunological Basis of Human Diseases: Distinctive Immune Features in Patients with a History of Term or Preterm Birth.
Cytometry. Part A : the journal of the International Society for Analytical Cytology
2015; 87 (9): 817-829
Single-cell technologies have immense potential to shed light on molecular and biological processes that drive human diseases. Mass cytometry (or Cytometry by Time Of Flight mass spectrometry, CyTOF) has already been employed in clinical studies to comprehensively survey patients' circulating immune system. As interest in the "bedside" application of mass cytometry is growing, the delineation of relevant methodological issues is called for. This report uses a newly generated dataset to discuss important methodological considerations when mass cytometry is implemented in a clinical study. Specifically, the use of whole blood samples versus peripheral blood mononuclear cells (PBMCs), design of mass-tagged antibody panels, technical and analytical implications of sample barcoding, and application of traditional and unsupervised approaches to analyze high-dimensional mass cytometry datasets are discussed. A mass cytometry assay was implemented in a cross-sectional study of 19 women with a history of term or preterm birth to determine whether immune traits in peripheral blood differentiate the two groups in the absence of pregnancy. Twenty-seven phenotypic and 11 intracellular markers were simultaneously analyzed in whole blood samples stimulated with lipopolysaccharide (LPS at 0, 0.1, 1, 10, and 100 ng mL(-1) ) to examine dose-dependent signaling responses within the toll-like receptor 4 (TLR4) pathway. Complementary analyses, grounded in traditional or unsupervised gating strategies of immune cell subsets, indicated that the prpS6 and pMAPKAPK2 responses in classical monocytes are accentuated in women with a history of preterm birth (FDR<1%). The results suggest that women predisposed to preterm birth may be prone to mount an exacerbated TLR4 response during the course of pregnancy. This important hypothesis-generating finding points to the power of single-cell mass cytometry to detect biologically important differences in a relatively small patient cohort. © 2015 International Society for Advancement of Cytometry.
View details for DOI 10.1002/cyto.a.22720
View details for PubMedID 26190063
Transient partial permeabilization with saponin enables cellular barcoding prior to surface marker staining.
Cytometry. Part A : the journal of the International Society for Analytical Cytology
2014; 85 (12): 1011-1019
Fluorescent cellular barcoding and mass-tag cellular barcoding are cytometric methods that enable high sample throughput, minimize inter-sample variation, and reduce reagent consumption. Previously employed barcoding protocols require that barcoding be performed after surface marker staining, complicating combining the technique with measurement of alcohol-sensitive surface epitopes. This report describes a method of barcoding fixed cells after a transient partial permeabilization with 0.02% saponin that results in efficient and consistent barcode staining with fluorescent or mass-tagged reagents while preserving surface marker staining. This approach simplifies barcoding protocols and allows direct comparison of surface marker staining of multiple samples without concern for variations in the antibody cocktail volume, antigen-antibody ratio, or machine sensitivity. Using this protocol, cellular barcoding can be used to reliably detect subtle differences in surface marker expression. © 2014 International Society for Advancement of Cytometry.
View details for DOI 10.1002/cyto.a.22573
View details for PubMedID 25274027
A FOXO-Pak1 transcriptional pathway controls neuronal polarity
GENES & DEVELOPMENT
2010; 24 (8): 799-813
Neuronal polarity is essential for normal brain development and function. However, cell-intrinsic mechanisms that govern the establishment of neuronal polarity remain to be identified. Here, we report that knockdown of endogenous FOXO proteins in hippocampal and cerebellar granule neurons, including in the rat cerebellar cortex in vivo, reveals a requirement for the FOXO transcription factors in the establishment of neuronal polarity. The FOXO transcription factors, including the brain-enriched protein FOXO6, play a critical role in axo-dendritic polarization of undifferentiated neurites, and hence in a switch from unpolarized to polarized neuronal morphology. We also identify the gene encoding the protein kinase Pak1, which acts locally in neuronal processes to induce polarity, as a critical direct target gene of the FOXO transcription factors. Knockdown of endogenous Pak1 phenocopies the effect of FOXO knockdown on neuronal polarity. Importantly, exogenous expression of Pak1 in the background of FOXO knockdown in both primary neurons and postnatal rat pups in vivo restores the polarized morphology of neurons. These findings define the FOXO proteins and Pak1 as components of a cell-intrinsic transcriptional pathway that orchestrates neuronal polarity, thus identifying a novel function for the FOXO transcription factors in a unique aspect of neural development.
View details for DOI 10.1101/gad.1880510
View details for Web of Science ID 000276730300008
View details for PubMedID 20395366
PIASx is a MEF2 SUMO E3 ligase that promotes postsynaptic dendritic morphogenesis
JOURNAL OF NEUROSCIENCE
2007; 27 (37): 10037-10046
Postsynaptic morphogenesis of dendrites is essential for the establishment of neural connectivity in the brain, but the mechanisms that govern postsynaptic dendritic differentiation remain poorly understood. Sumoylation of the transcription factor myocyte enhancer factor 2A (MEF2A) promotes the differentiation of postsynaptic granule neuron dendritic claws in the cerebellar cortex. Here, we identify the protein PIASx as a MEF2 SUMO E3 ligase that represses MEF2-dependent transcription in neurons. Gain-of-function and genetic knockdown experiments in rat cerebellar slices and in the postnatal cerebellum in vivo reveal that PIASx drives the differentiation of granule neuron dendritic claws in the cerebellar cortex. MEF2A knockdown suppresses PIASx-induced dendritic claw differentiation, and expression of sumoylated MEF2A reverses PIASx knockdown-induced loss of dendritic claws. These findings define the PIASx-MEF2 sumoylation signaling link as a key mechanism that orchestrates postsynaptic dendritic claw morphogenesis in the cerebellar cortex and suggest novel functions for SUMO E3 ligases in brain development and plasticity.
View details for DOI 10.1523/JNEUROSCI.0361-07.2007
View details for Web of Science ID 000249415000024
View details for PubMedID 17855618
Transcription factor Sp4 regulates dendritic patterning during cerebellar maturation
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2007; 104 (23): 9882-9887
Integration of inputs by a neuron depends on dendritic arborization patterns. In mammals, the genetic programs that regulate dynamic remodeling of dendrites during development and in response to activity are incompletely understood. Here we report that knockdown of the transcription factor Sp4 led to an increased number of highly branched dendrites during maturation of cerebellar granule neurons in dissociated cultures and in cerebellar cortex. Time-course analysis revealed that depletion of Sp4 led to persistent generation of dendritic branches and a failure in resorption of transient dendrites. Depolarization induced a reduction in the number of dendrites, and knockdown of Sp4 blocked depolarization-induced remodeling. Furthermore, overexpression of Sp4 wild type, but not a mutant lacking the DNA-binding domain, was sufficient to promote dendritic pruning in nondepolarizing conditions. These findings indicate that the transcription factor Sp4 controls dendritic patterning during cerebellar development by limiting branch formation and promoting activity-dependent pruning.
View details for DOI 10.1073/pnas.0701946104
View details for Web of Science ID 000247114100061
View details for PubMedID 17535924
A calcium-regulated MEF2 surnoylation switch controls postsynaptic differentiation
2006; 311 (5763): 1012-1017
Postsynaptic differentiation of dendrites is an essential step in synapse formation. We report here a requirement for the transcription factor myocyte enhancer factor 2A (MEF2A) in the morphogenesis of postsynaptic granule neuron dendritic claws in the cerebellar cortex. A transcriptional repressor form of MEF2A that is sumoylated at lysine-403 promoted dendritic claw differentiation. Activity-dependent calcium signaling induced a calcineurin-mediated dephosphorylation of MEF2A at serine-408 and, thereby, promoted a switch from sumoylation to acetylation at lysine-403, which led to inhibition of dendritic claw differentiation. Our findings define a mechanism underlying postsynaptic differentiation that may modulate activity-dependent synapse development and plasticity in the brain.
View details for DOI 10.1126/science.1122513
View details for Web of Science ID 000235456900049
A CaMKII-NeuroD signaling pathway specifies dendritic morphogenesis
2004; 41 (2): 229-241
The elaboration of dendrites is fundamental to the establishment of neuronal polarity and connectivity, but the mechanisms that underlie dendritic morphogenesis are poorly understood. We found that the genetic knockdown of the transcription factor NeuroD in primary granule neurons including in organotypic cerebellar slices profoundly impaired the generation and maintenance of dendrites while sparing the development of axons. We also found that NeuroD mediated neuronal activity-dependent dendritogenesis. The activity-induced protein kinase CaMKII catalyzed the phosphorylation of NeuroD at distinct sites, including endogenous NeuroD at Ser336 in primary neurons, and thereby stimulated dendritic growth. These findings uncover an essential function for NeuroD in granule neuron dendritic morphogenesis. Our study also defines the CaMKII-NeuroD signaling pathway as a novel mechanism underlying activity-regulated dendritic growth that may play important roles in the developing and mature brain.
View details for Web of Science ID 000221457800009
View details for PubMedID 14741104
Characterization of a neurotrophin signaling mechanism that mediates neuron survival in a temporally specific pattern
JOURNAL OF NEUROSCIENCE
2003; 23 (19): 7326-7336
The temporally specific nature of neurotrophic factor-induced responses is a general feature of mammalian nervous system development, the mechanisms of which remain to be elucidated. We characterized a mechanism underlying the temporal specificity by which BDNF selectively promotes the survival of newly generated, but not mature, granule neurons of the mammalian cerebellum. We found that BDNF specifically induces the extracellular signal-regulated kinase 5 (ERK5)-myocyte enhancer factor (MEF2) signaling pathway in newly generated granule neurons and thereby induces transcription of neurotrophin-3 (NT-3), a novel gene target of MEF2. Inhibition of endogenous ERK5, MEF2, or NT-3 in neurons by several approaches including disruption of the NT-3 gene in mice revealed a requirement for the ERK5-MEF2-NT-3 signaling pathway in BDNF-induced survival of newly generated granule neurons. These findings define a novel mechanism that underlies the antiapoptotic effect of neurotrophins in a temporally defined pattern in the developing mammalian brain.
View details for Web of Science ID 000184817700011
View details for PubMedID 12917366
RNA interference reveals a requirement for myocyte enhancer factor 2A in activity-dependent neuronal survival
JOURNAL OF BIOLOGICAL CHEMISTRY
2002; 277 (48): 46442-46446
RNA interference (RNAi) provides a powerful method of gene silencing in eukaryotic cells, including proliferating mammalian cells. However, the utility of RNAi as a method of gene knock-down in primary postmitotic mammalian neurons remained unknown. Here, we asked if RNAi might be utilized to allow the assessment of the biological function of a specific gene in the nervous system. We employed a U6 promoter-driven DNA template approach to induce hairpin RNA-triggered RNAi to characterize the role of the transcription factor myocyte enhancer factor 2A (MEF2A) in the neuronal activity-dependent survival of granule neurons of the developing rat cerebellum. We found that the expression of MEF2A hairpin RNAs leads to the efficient and specific inhibition of endogenous MEF2A protein expression in primary cerebellar granule neurons. We also found that RNAi of MEF2A reduces significantly MEF2 response element-mediated transcription in granule neurons and inhibits activity-dependent granule neuron survival. Taken together, our RNAi experiments have revealed that MEF2A plays a critical role in activity-dependent neuronal survival. In addition, our findings indicate that RNAi does operate in postmitotic mammalian neurons and thus offers a rapid genetic method of studying gene function in the development and function of the mammalian nervous system.
View details for DOI 10.1074/jbc.M206653200
View details for Web of Science ID 000179529300096
View details for PubMedID 12235147