SLC9A6 and Christianson syndrome: This study delineates postnatal neurodevelopmental changes (from 1 month to 2 years) in the gross morphology and histopathology of the brains of mice containing a null mutation of the endosomal Na+/H+ exchanger 6 gene (NHE6/SLC9A6), an established animal model of Christianson Syndrome (generated by transgene lacZ/Neo insertion into exon 6).