NRXN1 and autism: Even well-established risk loci for autism, ID, schizophrenia and other neurodevelopmental syndromes provide examples of imperfect segregation, as shown by exonic CNVs in NRXN1,35 missense mutations in SHANK2,36 rare sequence and structural variants in CNTNAP2,37, 38 microdeletions and microduplications at 16p11.2.39, 40, 41