Genome-wide CRISPR-Cas9 interrogation of splicing networks reveals a mechanism for recognition of autism-misregulated neuronal microexons [CLIP-seq]

Alternative splicing has critical roles in diverse cellular, developmental and pathological processes. However, the full repertoires of factors that control individual splicing events are not known. We describe a CRISPR-based screening strategy for the systematic identification of genes that control 3-27 nt microexons with functions in nervous system development and that are commonly disrupted in autism. Besides known regulators including nSR100/Srrm4, Rbfox and Ptbp1, approximately 200 additional genes impact microexon splicing. These genes are enriched in genetic links to autism. Two of the screen hits, Srsf11 and Rnps1, preferentially regulate Srrm4-dependent microexons relative to other exons. These factors form mutually stabilizing interactions with Srrm4 that bridge upstream intronic enhancer elements and exonic sequences to activate microexon splicing. Our study thus presents a system for the genome-wide definition of splicing regulatory networks and further reveals a mechanism for the recognition of microexons with critical roles in nervous system development and disorders. iCLIP-seq of Rnps1, Srsf11, or GFP in N2A cells, as well as Srrm4 and GFP in in-vitro differentiated neurons.