Among these are classic disorders such as Angelman syndrome and MECP2-related disorder (formerly Rett syndrome), as well as more recently described clinical entities associated with mutations in CASK, CDKL5, CREBBP, and EP300 (Rubinstein-Taybi syndrome), FOXG1, SLC9A6 (Christianson syndrome), and TCF4 (Pitt-Hopkins syndrome).
The patient with the SLC9A6 mutation showed the typical AS phenotype, further demonstrating the similarity between patients with AS and those with SLC9A6 mutations.
Our results suggest that NHE6 participates in regulation of endosomal pH and provides a cellular basis for understanding the loss of NHE6 function leading to a neurological phenotype resembling Angelman syndrome.