Abstract
Despite progress in understanding pre-mRNA splicing, the regulatory mechanisms controlling most alternative splicing events remain unclear. We developed CRASP-seq (CRISPR-based identification of regulators of alternative splicing with phenotypic sequencing), a method that integrates pooled CRISPR-based genetic perturbations with deep sequencing of splicing reporters, to quantitatively assess the impact of all human genes on alternative splicing from a single RNA sample. CRASP-seq identified both known and untested regulators, enriched for proteins involved in RNA splicing and metabolism. As a proof-of-concept, CRASP-seq analysis of the LMNA cryptic splicing event linked to progeria uncovered ZNF207, primarily known for mitotic spindle assembly, as a regulator of progerin splicing. ZNF207 depletion enhances canonical LMNA splicing and decreases progerin protein levels in patient-derived cells. We further show that ZNF207's zinc-finger domain broadly impacts alternative splicing through direct interactions with U1 small nuclear ribonucleoprotein (snRNP) components. These findings position ZNF207 as a U1 snRNP auxiliary factor and demonstrate the power of CRASP-seq to uncover key regulators and domains of alternative splicing.