The absence of lissencephaly and major brain malformations often associated with 17p terminal deletions could be attributed to the retention of PAFAH1B1, YWHAE and CRK genes.
Point mutations or deletion copy number variants of the PAFAH1B1 gene in this genomic region cause lissencephaly, whereas extended deletions involving both PAFAH1B1 and YWHAE result in Miller-Dieker syndrome characterised by facial dysmorphisms and a more severe grade of lissencephaly.
PAFAH1B1/LIS1 and YWHAE, which were deleted in isolated lissencephaly (PAFAH1B1/LIS1 alone) and Miller-Dieker syndrome (both genes), were found to be duplicated in patients with developmental delay.