The observation that DEAF1 binds to a site within the RAI1 gene and activates RAI1 mRNA expression in vitro suggests that RAI1 may be a downstream effector for DEAF1 and genetic differences in the regulation of RAI1 by DEAF1 may contribute to phenotypic differences observed in SMS and PTLS patients and other common mental disorders. Here, RAI1 is linked to Smith-Magenis syndrome.