EWS splicing regulation contributes to balancing Foxp1 isoforms required for neuronal differentiation

Alternative splicing is a key regulatory process underlying the amplification of genomic information and the expansion of proteomic diversity, particularly in brain. Here, we identify the Ewing sarcoma protein (EWS) as a new player of alternative splicing regulation during neuronal differentiation. Knockdown of EWS in neuronal progenitor cells leads to premature differentiation. Transcriptome profiling of EWS-depleted cells revealed global changes in splicing regulation. Bioinformatic analyses and biochemical experiments demonstrated that EWS regulates alternative exons in a position-dependent fashion. Notably, several EWS-regulated splicing events are physiologically modulated during neuronal differentiation and EWS depletion in neuronal precursors anticipates the splicing-pattern of mature neurons. Among other targets, we found that EWS controls the alternative splicing of the forkhead family transcription factor FOXP1, a pivotal transcriptional regulator of neuronal differentiation, possibly contributing to the switch of gene expression underlying the neuronal differentiation program.