Two other genes, PIGW and PCGF2, are also hypothesized to be candidates for NDDs (55, 60) as genetic variations of those two genes have been linked with developmental delay and/or epilepsy (68–70) In addition, Laffargue et al. (27) suggested that an interaction between HNF1B and other transcription factors like homeobox protein Hox-A1 could cause NDD, as an interaction of those two transcription factors has been found during mural hindbrain development (71). Here, PCGF2 is linked to Global developmental delay.