Aberrant recursive splicing in a human disease locus.

Recursive splice sites are rare motifs postulated to facilitate splicing across massive introns and shape isoform diversity. The necessity of recursive splicing (RS) and its role in human disease are unsubstantiated. Here, we use CRISPR to model intronic deletions eliminating an RS site (RS1) in CADM2 and conferring risk for attention deficit hyperactivity disorder and other neurobehavioral traits. Ablating RS1 in human induced neurons alters the gradient of RNA abundance across CADM2's first intron, decreases CADM2 expression, and impacts transcript usage. Decreased CADM2 expression is reflected in reduced exon usage downstream of RS1 and global alteration to genes involved in neuronal processes. In vivo rodent models harboring Cadm2 RS1 deletions exhibit an attenuated effect on Cadm2 expression and modest changes in behavior and functional brain connectivity. This study demonstrates RS as a noncoding regulatory mechanism in a gene associated with a spectrum of neuropsychiatric and behavioral traits.