the unaffected mother and shared with an unaffected sister (see Supplementary Materials). In Family 10, which shows the V195I substitution in PTCHD1, we have previously reported a 66 Kb de novo loss at 7q36.2 that results in deletion of the third exon of DPP6 (MIM 126141) – previously reported as a positional and functional candidate gene for autism (3). In ID Family 8, we have identified a H359R substitution in PTCHD1 and a 2 Kb deletion spanning the last exon of SLC16A2, both variants are maternally inherited. The phenotype in this family was severe ID compatible with Allan-Herndon-Dudley syndrome (MIM 300523) (28,29), for which mutations in SLC16A2 have previously been reported.
