KIF1B and neurodevelopmental disorder: We identified 73 highly variable switch-like exons, such as exon 15 in ADD1, which were included in neurons but skipped in progenitors (Figure 2I).40 Among the 68 genes with highly variable exons, nine (DYNC1I2, NRCAM, KIF1B, ADD1, DNM1, DLG3, VPS13C, KAT6A, and DTYMK) were identified as causal for neurodevelopmental disorders, as indicated in OMIM.41 Clustering analysis based on the PSI values of these exons distinguished neurons from progenitors (Figure 2J).