Molecular characteristics

ARID1B encodes a subunit of BAF (SWI/SNF) chromatin remodelling complex. In addition to ARID1B mutations in other genes (ARID1A, SMARCA4, SMARCB1, or SMARCE1) encoding other proteins of this chromatin remodelling complex have been associated with Coffin-Siris Syndrome.

Mutations in ARID1B are rare and usually occur de novo. Autosomal dominant inheritance is possible, one patients has been reported to reproduce (Smith et al., 2016).

All patients with mutations in ARID1B had truncating mutations, indicating that ARID1B haploinsufficiency is responsible for their phenotype. Since only a single de novo missense mutation has been identified in an affected patient, care must be taken when interpreting such variants in absence of inheritance status.

Mutations in ARID1B can be identified using molecular genetic testing, either directly by sequencing and/or MLPA of the ARID1B gene or by exome/genome sequencing.