We characterized the precise breakpoints of the 167 Kb deletion at PTCHD1 identified in the male proband from Family 1. This CNV also disrupts long, spliced non-coding RNAs (ncRNAs) on the opposite strand, but no other coding genes were interrupted (Fig. 1). The deletion was validated in the family using both PCR and SYBR-Green I-based real-time quantitative PCR (qPCR) and was found to be transmitted from a heterozygous unaffected mother to two affected dizygotic twin sons, also to an unaffected daughter (Fig. 2). X-chromosome inactivation (XCI) analysis of the mother, carrier of the PTCHD1 deletion, revealed a highly skewed allelic ratio of 94:6.
