The role of SYNGAP1 isoforms in brain development

Synaptic Ras GTPase activating protein (SynGAP) is crucial for neuronal communication and is highly concentrated in excitatory synapses. Mutations in the SYNGAP1 gene cause SYNGAP1-related intellectual disability (SRID), a neurodevelopmental disorder characterized by epilepsy, developmental delay, and autism. As there is no cure for SRID, this proposal will elucidate SYNGAP1 expression and function during development. In the adult brain, SynGAP regulates synaptic plasticity by interacting with other proteins to modulate synaptic strength. Recent studies suggest non-synaptic functions for SynGAP during neurodevelopment, regulating cell type specification in early cortical formation. This study will pioneer the investigation of SYNGAP1 isoform function and regulation across brain development.SYNGAP1 encodes for multiple N- and C-terminal isoforms with unique roles in synaptic function. Mouse models revealed that SynGAP-α1 affects synaptic plasticity, while SynGAP-β influences dendritic growth. Despite this, the regulation of the gene and its mRNA and isoform expression, especially during neurodevelopment, remains poorly understood. Preliminary analysis shows differential SYNGAP1 N-terminal isoform expression prenatally compared to adult brain. We hypothesize that (i) SYNGAP1 isoform expression is transcriptionally regulated in neurodevelopment with differential isoform usage between pre- and postnatal stages, and (ii) these isoforms have unique functions. We find that CRISPR activation (CRISPRa) upregulates Syngap1 in adult mouse hippocampus, offering a promising approach for modulating isoform expression. To test these hypotheses, we aim to employ cutting-edge techniques in mouse and human SRID models. Approaches include targeted long-read sequencing, intrahippocampal CRISPRa, behavioral phenotyping, and human cortical organoids. The goal is to uncover mechanisms of isoform-specific functions and their impact on SRID, potentially informing new therapies.