What are the molecular and cellular steps that govern presynaptic assembly and determine presynaptic function?
WHAT IS THE ROLE OF CELL ADHESION MOLECULES SUCH AS NEUREXIN IN PRESYNAPTIC ASSEMBLY?
We have found that a recently-identified, conserved short isoform of neurexin, called gamma-neurexin, which does not contain any of the canonical extracellular binding domains, can nonetheless mediate presynaptic assembly and maturation. Our current studies are focused on elucidating the role of this short but seemingly redundant isoform in synapse development.
Moreover, we have found that the intracellular domain of neurexin alone is sufficient for presynaptic assembly. To understand the contribution of neurexin’s intracellular domain to presynaptic organization, we are undertaking proximity labeling approaches to identify neurexin’s intracellular binding partners.
SYNAPSE ASSEMBLY AT DISTINCT STAGES OF NEURONAL DEVELOPMENT
HOW IS THE ASSEMBLY OF PRESYNAPTIC SPECIALIZATIONS REGULATED?
MODELING HUMAN PATIENT CALCIUM CHANNEL MUTATIONS IN C. ELEGANS
Using C. elegans to understand how patient mutations in calcium channels affect their localization and function. A. Secondary structure of UNC-2/CaV2α. Adapted from Huang et al., 2019, eLife. B. A novel patient mutation in a highly homologous region confers developmental abnormalities. We have used Crispr/Cas9 to create worm models of this mutation. C. Worm locomotion is quantified using worm tracking software and analyzed to reveal behavioral defects. D. Reduced speed of locomotion in worms harboring the patient mutation mirrors mouse and human ataxia. We are using these models to delve deeper into potential defects in synapse structure and function resulting from patient mutations.
DEVELOPING A SINGLE-SYNAPSE OPTICAL READOUT FOR SYNAPSE FUNCTION
We are developing an optical physiology assay to look at synaptic function with single-synapse resolution. A-B. Using postsynaptically targeted GCaMP6 we can measure calcium transients opposite individual presynaptic release sites. C. We have developed an analysis pipeline to automatically detect regions of interest (ROIs) that correspond to individual synapses. D. Calcium transients at nearby ROIs are correlated but not identical to one another (and offset in time). E. ROIs form functional clusters.
THE WNT RECEPTOR FRIZZLED MEDIATES BOTH SYNAPSE ASSEMBLY AND SYNAPSE ELIMINATION THROUGH UNKNOWN PATHWAYS
Wnt, binding to the Frizzled (Fz) receptor, leads to Fz endocytosis and subsequent synapse elimination. To understand how this process works, we have undertaken forward genetic modifier screens and isolated suppressors of the Fz phenotype.