The role of MCT8 at the differentiation stage of neurogenesis is of particular relevance to the pathophysiology of Allan-Herndon-Dudley syndrome (AHDS), a severe form of psychomotor retardation caused by inactivating mutations in MCT8 (Dumitrescu et al., 2004, Friesema et al., 2004, Schwartz et al., 2005). Here, SLC16A2 is linked to Allan-Herndon-Dudley syndrome.