Characterization of the complexity of V2 neurons in the spinal cord.

• Applicant: Dr. Sepand Rastegar, Ph.D., since 7/2021
• Subject Area: Developmental Neurobiology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449817277

The spinal cord with its rather simple computational functions is an useful model to study development and the structural and functional layout of neuronal motor systems. It is increasingly appreciated that the cellular complexity of the spinal is much bigger than so far assumed. In the V2 domain of the spinal cord of the mouse, for example, at least four major interneuron types are found. In the zebrafish spinal cord whose transparency and simple organization are ideal for such studies, several V2 neuron subtypes with similar developmental specifications were identified. This underscores the overall conservation of the structure of the spinal cord in fish and mammals. We recently discovered the V2s interneurons in the zebrafish spinal cord. This subgroup of V2 domain neurons expresses the highly related HMG-box transcription factors Sox1a and b. In preliminary studies of V2s interneurons, we discovered that not all the V2s neurons follow the same pattern of transcription factor co-expression. This suggests that the V2s neuron class is very likely subdivided in further neuronal sub-identities. Moreover, very little is known about the connectivity and the function of the V2s neurons. They may be equivalent to the mouse V2c neurons, which have been studied very superficially only. The overall objective is to characterize the V2s class of interneurons in the spinal cord of the zebrafish, to evaluate whether there are further neuronal sub-identities within the V2s neuronal group, to assess the morphology of the neuronal processes, their connectivity and function. Specifically, we will build on our previous work and our unpublished preliminary observations, and:- analyze the morphology of the axonal processes and the synaptic connection of V2s neurons in embryos larvae and adults (Task 1, Task 2).- elucidate neuronal diversity by carrying out single cell sequencing with V2 spinal cord neurons using transgenes and marker co-expression as references for bioinformatic analysis (Task 3). - establish the relationship between marker gene expression (outcome of single cell sequencing) and morphology and connectivity of neuronal processes (Task 4).- elucidate the function of sox1a/b expressing cells by ablation or optogenetic manipulation combined with assessment of behavior of animals and physiology of involved neurons (Task 5).We will use existing genetic tools and build new tools to combine the genetic capability of the zebrafish with its transparency and small size allowing quantitative high-resolution life imaging and behavioral analysis. In a multidisciplinary approach, we will utilize technology and genetic tools that are uniquely available to us. The outcome will illuminate the complexity of spinal neuronal circuitry and the role of V2s neurons in this process.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Ravindra Peravali, Ph.D.
• Ehemaliger Antragsteller: Professor Dr. Uwe Strähle, until 7/2021