A combinatorial regulatory signature controls terminal differentiation of the dopaminergic nervous system in C. elegans

15 páginas, 7 figuras, 3 tablas.Terminal differentiation programs in the nervous system are encoded by cis-regulatory elements that control the expression of terminal features of individual neuron types. We decoded the regulatory information that controls the expression of five enzymes and transporters that define the terminal identity of all eight dopaminergic neurons in the nervous system of the Caenorhabditis elegans hermaphrodite. We show that the tightly coordinated, robust expression of these dopaminergic enzymes and transporters ("dopamine pathway") is ensured through a combinatorial cis-regulatory signature that is shared by all dopamine pathway genes. This signature is composed of an Ets domain-binding site, recognized by the previously described AST-1 Ets domain factor, and two distinct types of homeodomain-binding sites that act in a partially redundant manner. Through genetic screens, we identified the sole C. elegans Distalless/Dlx ortholog, ceh-43, as a factor that acts through one of the homeodomain sites to control both induction and maintenance of terminal dopaminergic fate. The second type of homeodomain site is a Pbx-type site, which is recognized in a partially redundant and neuron subtype-specific manner by two Pbx factors, ceh-20 and ceh-40, revealing novel roles of Pbx factors in the context of terminal neuron differentiation. Taken together, we revealed a specific regulatory signature and cognate, terminal selector-type transcription factors that define the entire dopaminergic nervous system of an animal. Dopaminergic neurons in the mouse olfactory bulb express a similar combinatorial transcription factor collective of Ets/Dlx/Pbx factors, suggesting deep phylogenetic conservation of dopaminergic regulatory programs.This work was funded by EMBO post-doctoral fellowships and Marie Curie Funds (to M.D. and N.F.), the New York Stem Cell Foundation Fellowships and the Spanish Government (SAF2011-26273) (to N.F), the NIH (R01NS039996-05; R01NS050266-03 to O.H.; R01GM30997 to M.C.; R01GM054510 to R.S.M.; and F32GM099160 to N.A.), and the Stavanger University Hospital (to M.D.). N.F is a NARSAD Young Investigator. O.H. is an Investigator of the Howard Hughes Medical Institute.Peer reviewe

Mechanisms of TRP-channel mediated dopaminergic degeneration in C. elegans

Master's thesis in Biological chemistryOne of the most common manifestations of dopaminergic degeneration in humans is in Parkinson’s Disease (PD). Although dopaminergic degeneration affects a significant portion of the aging population, the pathways and mechanisms underlying it have not yet been elucidated. The Doitsidou lab has recently established a model of dopaminergic degeneration in Caenorhabditis elegans. In this model, a Transient Receptor Potential (TRP) channel (TRP-4) has mutated and results in a gain of function. Based on the morphology of the dopaminergic neurons, the overactive channel is believed to be activating a necrotic cell death pathway. This thesis aims to identify the pathways relevant to TRP-4 mediated dopaminergic de-generation in Caenorhabditis elegans. It takes a two-pronged approach, comparing TRP-4 degeneration to other models of neurodegeneration and conducting a forward genetic screen to identify novel candidates. Through these approaches, the nature of TRP-4 degeneration has been further eluci-dated. The results gathered in this thesis explore the involvement of lysosomal acidifica-tion through the V-ATPase pump in dopaminergic cell death and are not conclusive as to whether or not the V-ATPase pump plays a role in TRP-4 induced degeneration. The lysosomal biogenesis pathway is implicated in dopaminergic degeneration in the TRP-4 model. Differences in lysosomal morphology in dopaminergic neurons are established between the wild type and degenerating states. Finally, three full and three partial sup-pressors of degeneration were discovered through the automated forward genetic screen. Together, this thesis brings insight into intracellular the mechanisms underlying a novel, TRP-channel based model of dopaminergic degeneration.

Transcriptional and Post-Transcriptional Mechanisms of the Development of Neocortical Lamination

The neocortex is a laminated brain structure that is the seat of higher cognitive capacity and responses, long-term memory, sensory and emotional functions, and voluntary motor behavior. Proper lamination requires that progenitor cells give rise to a neuron, that the immature neuron can migrate away from its mother cell and past other cells, and finally that the immature neuron can take its place and adopt a mature identity characterized by connectivity and gene expression; thus lamination proceeds through three steps: genesis, migration, and maturation. Each neocortical layer contains pyramidal neurons that share specific morphological and molecular characteristics that stem from their prenatal birth date. Transcription factors are dynamic proteins because of the cohort of downstream factors that they regulate. RNA-binding proteins are no less dynamic, and play important roles in every step of mRNA processing. Indeed, recent screens have uncovered post-transcriptional mechanisms as being integral regulatory mechanisms to neocortical development. Here, we summarize major aspects of neocortical laminar development, emphasizing transcriptional and post-transcriptional mechanisms, with the aim of spurring increased understanding and study of its intricacies

Translational derepression of Elavl4 isoforms at their alternative 5' UTRs determines neuronal development

International audienceNeurodevelopment requires precise regulation of gene expression, including post-transcriptional regulatory events such as alternative splicing and mRNA translation. However, translational regulation of specific isoforms during neurodevelopment and the mechanisms behind it remain unknown. Using RNA-seq analysis of mouse neocortical polysomes, here we report translationally repressed and derepressed mRNA isoforms during neocortical neurogenesis whose orthologs include risk genes for neurodevelopmental disorders. We demonstrate that the translation of distinct mRNA isoforms of the RNA binding protein (RBP), Elavl4, in radial glia progenitors and early neurons depends on its alternative 5' UTRs. Furthermore, 5' UTR-driven Elavl4 isoform-specific translation depends on upstream control by another RBP, Celf1. Celf1 regulation of Elavl4 translation dictates development of glutamatergic neurons. Our findings reveal a dynamic interplay between distinct RBPs and alternative 5' UTRs in neuronal development and underscore the risk of post-transcriptional dysregulation in co-occurring neurodevelopmental disorders