Transcriptional And Network Regulators Of Neuronal Identity Specification And Synaptic Maturation

To enact its many behaviors, an organism relies on a highly diverse network of neuronal subtypes. During development, it is therefore imperative that the identity of each subtype be correctly specified and that each of these neurons then wires with precise connectivity. The process of identity specification results from a delicate interplay between intrinsic and extrinsic influences during neuronal development. Intrinsically, a critical event in neuronal development is the expression of potent transcription factors that regulate the induction of a subtype-specific neuronal identity. One capability of such factors is to prime a neuron's connectivity by controlling features such as dendritic morphology, axonal targeting, or synaptic specificity. Once incorporated into the circuitry, the neuron relies on extrinsic signals from both its pre-and postsynaptic binding partners to further refine its identity. In this dissertation, I first examine intrinsic regulation of neuronal identity by studying the cell-autonomous capabilities of the subtype-specifying transcription factor Ptfl a to transform the development of cortical pyramidal cells. Ptfl a is primarily necessary for the identity specification of interneurons in the spinal cord, cerebellum, and retina, but its sufficiency to dictate neuronal identity outside its endogenous environment has yet to be fully explored. Using in utero electroporation to misexpress Ptfl a in the developing cortex, 1 demonstrate its ability to override the pyramidal cell transcriptome, upregulating Ptfl a-dependent markers of inhibitory interneurons and inducing a peptidergic neurotransmitter status. Concurrently, misexpression of Ptfl a also transforms the stereotypical pyramidal cell morphology to a more branched, radial morphology. To next explore the extrinsic regulation of neuronal identity, I examine the ability of the developing network to impact the characteristic synaptic protein profile of a population of spinal inhibitory interneurons, called GABApre neurons. I first show that putative GABApre neurons receive descending input from the cortex, via the corticospinal tract. I then use a mouse model of perinatal stroke to investigate how developmental disruption of corticospinal tract input in turn impacts GABApre synaptic expression. I observe a specific upregulation of the hallmark GABApre marker GAD65 contralateral to the cortical injury, implying that this effect is the result of lost input from the cortex.

The nervous system is highly complex both in its structural order and in its ability to perform the many functions required for survival and interaction with the environment; understanding how it develops has proven to be one of the greatest challenges in biology. Such precision demands that key events at every developmental stage are executed properly and are coordinated to produce the circuitry underlying each of the adult nervous system's functions. This volume describes the latest research on the cellular and molecular mechanisms of neural circuitry development, while providing researchers with a one-stop overview and synthesis of contemporary thought in the area. Reviews current research findings on the development of neural circuitry, providing researchers with an overview and synthesis of the latest contemporary thought in the cellular and molecular mechanisms that underlie the development of neural circuitry Includes chapters discussing topics such as the guidance of nerve growth and the formation of plasticity of synapses, helping researchers better understand underlying mechanisms of neural circuit development and maintenance that may play a role in such human diseases/conditions as depression, anxiety, and pain Chapters make use of a variety of human and animal models, allowing researchers to compare and contrast neural circuitry development across a wide spectrum of models

Determinants of Neuronal Identity brings together studies of a wide range of vertebrate and invertebrate organisms that highlight the determinants of neuronal identity. Emphasis of this book is on how neurons are generated; how their developmental identities are specified; and to what degree those identities can be subsequently modified to meet the changing needs of the organism. This book also considers various techniques used in the analysis of different organisms. This volume is comprised of 15 chapters; the first of which introduces the reader to the specification of neuronal identity in C ...

The tremendous diversity of neuronal cell types enables the assembly of neural circuitry that generates and shapes complex behaviors. In contrast to the intense focus on understanding the gene regulatory programs that specify different neuron types, the programs that guide their maturation have received far less attention. Here we show the embryonic maturation of serotonergic (5-HT) neurons, and the role of the transcription factor, PET-1 in driving this maturational program. Initally we undertook a series of experiments to define PET-1’s function in development and the early postnatal period. To this end, we used RNA-Seq in flow sorted fetal YFP+ 5-HT neurons obtained from the rostral hindbrain to identify specific temporal gene expression patterns found in maturing 5-HT neurons from E11.5 to shortly after birth (P1-P3). We found that genes downregulated from E11.5 to birth were genes associated with basic cellular processes, while genes upregulated were associated with maturing neural identity and function. Next we compared the expression profile of E15.5 +/+ and Pet-1-/- 5-HT neurons. Expression of over 800 genes was diminished 1.5-40 fold, and greater than 1000 genes were derepressed 1.5-13 fold in Pet-1-/- 5-HT neurons. Gene ontology shows that PET-1 is a regulator of diverse pathways including cell synaptic development and function, axon and dendrite development, and neural transmission. The role of PET-1’s in driving maturation of genes involved in neuronal excitability was verified by single cell recording of 5-HT neurons. Aditionally, PET-1 was found to regulate the glutamatergic AMPA receptor subunit Gria4, the alpha adrenergic receptor 1b, Adra1b, and the lysophosphtidic acid receptor 1, Lpar1. This was verified by in situ hybridization, immunohistochemistry, and electorphysiological recordings. Finally, to ascertain PET-1’s postnatal function, we deleted Pet-1 in the early postnatal period using the Cre/loxP system. This revealed PET-1 switches its focus on regulating genes needed for 5-HT synthesis to those needed for neuronal activity. Finally, we used ChIP-seq to identify PET-1 direct targets. We found PET-1 binds within or proximal to 25-30% of PET-1 upregulated and down regulated genes, suggesting direct transcriptional activation and repression of PET-1 is required for correct 5-HT development.

The interaction between biology and evolution has been the subject of great interest in recent years. Because evolution is such a highly debated topic, a biologically oriented discussion will appeal not only to scientists and biologists but also to the interested lay person. This topic will always be a subject of controversy and therefore any breaking information regarding it is of great interest.The author is a recognized expert in the field of developmental biology and has been instrumental in elucidating the relationship between biology and evolution. The study of evolution is of interest to many different kinds of people and Genomic Regulatory Systems: In Development and Evolution is written at a level that is very easy to read and understand even for the nonscientist. * Contents Include* Regulatory Hardwiring: A Brief Overview of the Genomic Control Apparatus and Its Causal Role in Development and Evolution * Inside the Cis-Regulatory Module: Control Logic and How the Regulatory Environment Is Transduced into Spatial Patterns of Gene Expression* Regulation of Direct Cell-Type Specification in Early Development* The Secret of the Bilaterians: Abstract Regulatory Design in Building Adult Body Parts* Changes That Make New Forms: Gene Regulatory Systems and the Evolution of Body Plans

Synapse Development and Maturation, the latest release in the Comprehensive Developmental Neuroscience series, presents the latest information on the genetic, molecular and cellular mechanisms of neural development. The book provides a much-needed update that underscores the latest research in this rapidly evolving field, with new section editors discussing the technological advances that are enabling the pursuit of new research on brain development. This volume focuses on the synaptogenesis and developmental sequences in the maturation of intrinsic and synapse-driven patterns. Features leading experts in various subfields as section editors and article authors Presents articles that have been peer reviewed to ensure accuracy, thoroughness and scholarship Includes coverage of mechanisms which regulate synapse formation and maintenance during development Covers neural activity, from cell-intrinsic maturation, to early correlated patterns of activity

Neurons have the difficult task of persisting throughout the life of the animal. This requires a rigid adherence to their highly specialized identity. Paradoxically, they must be flexible, able to modulate their properties in the face of a constantly shifting activity landscape. The work presented here suggests that these two critical processes depend (at least partially) on regulation through microRNAs. I have shown that proprioceptive sensory neurons display a decline in celltype specific gene expression as well as a loss of their specialized muscle afferents upon conditional ablation of the microRNA biogenesis enzyme Dicer. Also, demonstrated here is the fact that parvalbumin-positive fast-spiking cells employ mir-7 to modulate their intrinsic excitability during activity deprivation in culture, as well as sensory deprivation in vivo. These studies support a role for microRNAs in the maintenance of neuronal identity and the regulation of plasticity.

The genetic, molecular, and cellular mechanisms of neural development are essential for understanding evolution and disorders of neural systems. Recent advances in genetic, molecular, and cell biological methods have generated a massive increase in new information, but there is a paucity of comprehensive and up-to-date syntheses, references, and historical perspectives on this important subject. The Comprehensive Developmental Neuroscience series is designed to fill this gap, offering the most thorough coverage of this field on the market today and addressing all aspects of how the nervous system and its components develop. Particular attention is paid to the effects of abnormal development and on new psychiatric/neurological treatments being developed based on our increased understanding of developmental mechanisms. Each volume in the series consists of review style articles that average 15-20pp and feature numerous illustrations and full references. Volume 1 offers 48 high level articles devoted mainly to patterning and cell type specification in the developing central and peripheral nervous systems. Series offers 144 articles for 2904 full color pages addressing ways in which the nervous system and its components develop Features leading experts in various subfields as Section Editors and article Authors All articles peer reviewed by Section Editors to ensure accuracy, thoroughness, and scholarship Volume 1 sections include coverage of mechanisms which: control regional specification, regulate proliferation of neuronal progenitors and control differentiation and survival of specific neuronal subtypes, and controlling development of non-neural cells

Despite substantial progress, however, the basic framework of transcriptional controls over neocortical projection neuron development has not been fully defined. The precise molecular mechanisms by which recently identified regulators act in parallel, synergistically, or cross-repressively to progressively delineate subtype and area identity are not well understood. Moreover, very few downstream-regulated genes responsible for executing specific aspects of neuronal differentiation have been identified.