Michael Nonet Research Abstract
The research in my lab is focused on understanding how synapse development is orchestrated at the molecular level. Our approach is based on combining molecular biology, cell biology, imaging, and genetics to define the role of genes in both orchestrating synapse formation during development and stabilizing them during adult life. We use primarily the mechanosensory neurons of C. elegans as a model, but also perform some studies using zebrafish. Current projects in the lab include:
1) Coordinate regulation of a synaptogenesis transcription program. We have previously demonstrated that the transcriptional co-factor SSDP disrupts a portion of the synaptic development program in mechanosensory neurons resulting in synaptic branches with disorganized presynaptic varicosities that no longer co-localize active zone and synaptic vesicles. One component of this transcriptional program mediated through SSDP is repressing the transcription of the PIM-related kinase PRK-2. Our current work is aimed at defining other targets of SSDP as well as the targets of PRK-2 which are orchestrating presynaptic terminal maturation.
2) Characterization of the molecular mechanisms that initiate collateral branch outgrowth during synapse development. C. elegans PLM mechanosensory neurons form a single collateral branch on which the synapses of this neuron develop. In wild type animals, each PLM neuron forms one, and only one, branch at a precise point in development and at a stereotypic position on the anterior-posterior (A-P) axis. We’ve identified mutants that fail to form these branches, form too many branches, and form branches in ectopic positions on the A-P axis. We aim to understand the molecular mechanisms that initiate branching, limit branch formation to a single branch, and define the positioning of branching through molecular and cell biological characterization of these mutants.
3) Regulation of trafficking of synaptic vesicle precursors to synapses. We have identified components of the BORC complex (biogenesis of lysosomal organelle related complex) that disrupt trafficking of synaptic vesicle precursors from the soma to the synapse without disrupting trafficking of other synaptic components such as mitochondria and active zone proteins. In fibroblasts, the BORC complex regulates recruitment of kinesin molecular motors to lysosomes. In neurons, our studies have demonstrated that some components of the BORC complex also are involved in regulating trafficking of synaptic vesicle precursors. Our current work is aimed at understanding how these proteins regulate movements of distinct organelles in the same cell.