SHANK3 as an autism spectrum disorder-associated gene

SHANK3 is a synaptic scaffolding protein enriched in the postsynaptic density of excitatory synapses, and plays important roles in the formation, maturation, and maintenance of synapses. Haploinsufficiency of the SHANK3 gene causes a developmental disorder, 22q13.3 deletion syndrome (known as Phelan-McDermid syndrome), that is characterized by severe expressive language and speech delay, hypotonia, global developmental delay, and autistic behavior. Since several SHANK3 mutations have been identified in a particular phenotypic group in patients with autism spectrum disorder (ASD), the SHANK3 is strongly suspected of being involved in the pathogenesis and neuropathology of ASD. Five CpG-islands have been identified in the SHANK3 gene, and tissue-specific expression of SHANK3 is regulated by DNA methylation in an epigenetic manner. Cumulative evidence has shown that several SHANK3 variants are expressed in the developing rodent brain and that their expression is regulated by DNA methylation of intragenic promoters. We identified novel SHANK3 transcripts whose transcription started at the vicinity of the CpG-island 2 in the mouse brain. Shank3 mutant mice exhibit autistic-like behaviors, including impaired social interaction and repetitive behaviors. In this article we review recent findings in regard to higher brain functions of SHANK3, epigenetic regulation of SHANK3 expression, and SHANK3-related ASD that were obtained from genetic analyses in ASD patients, molecular biological studies using developing mouse brains, and studies of Shank3 mutant mice.