There is a current lack of understanding of differential gene expression within the nervous system. Ideally one would like to know, across all neuron types, exactly how the genome is transcribed and processed into functional RNAs. This information is fundamentally important because differential gene expression defines the form and function of individual neurons, determines how individual neurons contribute to circuit physiology and behavior, and influences how individual neurons are affected by injury and disease. Further, detailed and complete knowledge of differential gene expression within the nervous system would help elucidate the logic and cellular mechanisms that generate neuronal diversity, including regulation of gene expression, alternative splicing, and miRNA function. Yet progress in this area has been limited: For most nervous systems, the exact number of distinct types of neurons is unknown and therefore a global map of neuron-specific gene expression is not achievable. Here we propose to address this problem in a project to discover and analyze the C. elegans Neuronal Gene Expression Map & Network (CeNGEN). The C. elegans nervous system contains precisely 302 total neurons comprising 118 classes of distinct neuronal types. We propose to exploit this unique attribute to analyze gene expression with high accuracy in every individual neuronal type. CeNGEN proceeds in four specific aims.
Aim 1) Establish 118 transgenic strains, each one expressing fluorescent markers that uniquely label a single type of neuron.
Aim 2) Use innovative cell dissociation and FACS methods to isolate each type of neuron from age-matched adults, and use RNA-seq approaches to assess global coding transcript and miRNA expression, as well as splicing diversity.
Aim 3) Utilize single cell sequencing technology to precisely map gene expression over multiple parameter spaces.
Aim 4) Build cell-centered and gene-centered expression maps, and seek connections with other uniquely known features of the C. elegans nervous system including the wiring diagram, the cell lineage, neurotransmitter identity, and function. CeNGEN represents a paradigmatic advance in neurogenetics, and provides a unique opportunity to elucidate the global control of neuron-specific gene expression and to relate gene expression to neuronal wiring and function. Expected significant outcomes include: Identification of conserved regulatory mechanisms that generate neuronal specificity and diversity; Detailed understanding of alternative splicing and miRNA function across the nervous system; Relationship of differential gene expression to neuronal lineage, anatomy, function and connectivity. CeNGEN will also serve as a resource for future studies in C. elegans neuroscience, and will provide a framework for addressing global differential gene expression in more complex nervous systems that are currently not amenable to this comprehensive approach.
Differential gene expression among neuronal types underlies differences in function, structure and disease susceptibility. The proposed research is relevant to public health because it will provide the first complete understanding of neuronal diversity and differential gene expression in any organism. Thus, this study will develop fundamental knowledge that is critical to understanding how differential gene expression is regulated to mediate cellular and functional diversity in the nervous system.