Three Novel ARID1B Variations in Coffin-Siris Syndrome Patients

Coffin-Siris syndrome (CSS) (OMIM #135900) involves multiple congenital malformations, including hypotonia, short stature, sparse scalp hair, a coarse face, prominent eyebrows, a wide mouth, delayed bone age, and hypoplastic or absent fifth fingers/toes or nails, together with developmental delay. The cause of CSS is suggested to be related to alterations in the BRG- or HRBM-associated factor (BAF) pathway in humans. In this gene family, pathogenic variations in the AT-rich interactive domain-containing protein 1B (ARID1B) gene are revealed to be a significant element causing neurodevelopmental disability in patients with CSS. Herein, we describe the clinical features and gene variations in four Chinese patients with CSS. All the patients shared common features of short fifth fingers/toes or hypoplastic nails, coarse facial features, thick eyebrows, long cilia, a flat nasal bridge, a broad nose, a wide mouth, a high palate, and hypotonia. Besides, they had an intellectual disability, language, and motor developmental delay. Candidate genes were screened for variations using polymerase chain reaction (PCR) and sequencing. The variations were sequenced by next-generation sequencing and confirmed by first-generation sequencing. Exome sequencing suggested four de novo variations in the ARID1B gene in four unrelated patients. These included two frameshift variations (c.3581delC, c.6661_6662insG) and two nonsense variations (c.1936C>T, c.2248C>T). Of the four variations, three variations were novel. The results in our present study broaden the understanding of the disease and further interpret the molecular genetic mechanism of these rare variations in CSS.