Coffin-Siris syndrome is a SWI/SNF complex disorder.

Coffin-Siris syndrome (CSS) is a congenital disorder characterized by intellectual disability, growth deficiency, microcephaly, coarse facial features, and hypoplastic or absent fifth fingernails and/or toenails. We previously reported that five genes are mutated in CSS, all of which encode subunits of the switch/sucrose non-fermenting (SWI/SNF) ATP-dependent chromatin-remodeling complex: SMARCB1, SMARCA4, SMARCE1, ARID1A, and ARID1B. In this study, we examined 49 newly recruited CSS-suspected patients, and re-examined three patients who did not show any mutations (using high-resolution melting analysis) in the previous study, by whole-exome sequencing or targeted resequencing. We found that SMARCB1, SMARCA4, or ARID1B were mutated in 20 patients. By examining available parental samples, we ascertained that 17 occurred de novo. All mutations in SMARCB1 and SMARCA4 were non-truncating (missense or in-frame deletion) whereas those in ARID1B were all truncating (nonsense or frameshift deletion/insertion) in this study as in our previous study. Our data further support that CSS is a SWI/SNF complex disorder.

Tsurusaki Y ，Okamoto N ，Ohashi H ，Mizuno S ，Matsumoto N ，Makita Y ，Fukuda M ，Isidor B ，Perrier J ，Aggarwal S ，Dalal AB ，Al-Kindy A ，Liebelt J ，Mowat D ，Nakashima M ，Saitsu H ，Miyake N ，Matsumoto N ... -  《-》

Genotype-phenotype correlation of Coffin-Siris syndrome caused by mutations in SMARCB1, SMARCA4, SMARCE1, and ARID1A.

Coffin-Siris syndrome (CSS) is a rare congenital malformation syndrome, recently found to be caused by mutations in several genes encoding components of the BAF complex. To date, 109 patients have been reported with their mutations: SMARCB1 (12%), SMARCA4 (11%), SMARCE1 (2%), ARID1A (7%), ARID1B (65%), and PHF6 (2%). We review genotype-phenotype correlation of all previously reported patients with mutations in SMARCB1, SMARCA4, SMARCE1, and ARID1A through reassessment of their clinical and molecular findings. Cardinal features of CSS included variable degrees of intellectual disability (ID) predominantly affecting speech, sucking/feeding difficulty, and craniofacial (thick eyebrows, long eyelashes), digital (hypoplastic 5th fingers or toes, hypoplastic 5th fingernails or toenails), and other characteristics (hypertrichosis). In addition, patients with SMARCB1 mutations had severe neurodevelopmental deficits including severe ID, seizures, CNS structural abnormalities, and no expressive words as well as scoliosis. Especially, those with a recurrent mutation "p.Lys364del" represented strikingly similar phenotypes including characteristic facial coarseness. Patients with SMARCA4 mutations had less coarse craniofacial appearances and behavioral abnormalities. Patients with SMARCE1 mutations had a wide spectrum of manifestations from severe to moderate ID. Patients with ARID1A also had a wide spectrum of manifestations from severe ID and serous internal complications that could result in early death to mild ID. Mutations in SMARCB1, SMARCA4, and SMARCE1 are expected to exert dominant-negative or gain-of-function effects, whereas those in ARID1A are expected to exert loss-of-function effects.

Kosho T ，Okamoto N ，Coffin-Siris Syndrome International Collaborators 《-》

Coffin-Siris syndrome and the BAF complex: genotype-phenotype study in 63 patients.

De novo germline variants in several components of the SWI/SNF-like BAF complex can cause Coffin-Siris syndrome (CSS), Nicolaides-Baraitser syndrome (NCBRS), and nonsyndromic intellectual disability. We screened 63 patients with a clinical diagnosis of CSS for these genes (ARID1A, ARID1B, SMARCA2, SMARCA4, SMARCB1, and SMARCE1) and identified pathogenic variants in 45 (71%) patients. We found a high proportion of variants in ARID1B (68%). All four pathogenic variants in ARID1A appeared to be mosaic. By using all variants from the Exome Variant Server as test data, we were able to classify variants in ARID1A, ARID1B, and SMARCB1 reliably as being pathogenic or nonpathogenic. For SMARCA2, SMARCA4, and SMARCE1 several variants in the EVS remained unclassified, underlining the importance of parental testing. We have entered all variant and clinical information in LOVD-powered databases to facilitate further genotype-phenotype correlations, as these will become increasingly important because of the uptake of targeted and untargeted next generation sequencing in diagnostics. The emerging phenotype-genotype correlation is that SMARCB1 patients have the most marked physical phenotype and severe cognitive and growth delay. The variability in phenotype seems most marked in ARID1A and ARID1B patients. Distal limbs anomalies are most marked in ARID1A patients and least in SMARCB1 patients. Numbers are small however, and larger series are needed to confirm this correlation.

Santen GW ，Aten E ，Vulto-van Silfhout AT ，Pottinger C ，van Bon BW ，van Minderhout IJ ，Snowdowne R ，van der Lans CA ，Boogaard M ，Linssen MM ，Vijfhuizen L ，van der Wielen MJ ，Vollebregt MJ ，Coffin-Siris consortium ，Breuning MH ，Kriek M ，van Haeringen A ，den Dunnen JT ，Hoischen A ，Clayton-Smith J ，de Vries BB ，Hennekam RC ，van Belzen MJ ... -  《-》

Numerous BAF complex genes are mutated in Coffin-Siris syndrome.

Coffin-Siris syndrome (CSS; OMIM#135900) is a rare congenital anomaly syndrome characterized by intellectual disability, coarse face, hypertrichosis, and absence/hypoplasia of the fifth digits' nails. As the majority of patients are sporadic, an autosomal dominant inheritance model has been postulated. Recently, whole exome sequencing (WES) emerged as a comprehensive analytical method for rare variants. We applied WES on five CSS patients and found two de novo mutations in SMARCB1. SMARCB1 was completely sequenced in 23 CSS patients and the mutations were found in two more patients. As SMARCB1 encodes a subunit of the BAF complex functioning as a chromatin remodeling factor, mutations in 15 other subunit genes may cause CSS and thus were analyzed in 23 CSS patients. We identified heterozygous mutations in either of six genes (SMARCA4, SMARCB1, SMARCA2, SMARCE1, ARID1A, and ARID1B) in 20 out of 23 CSS patients. The patient with a SMARCA2 mutation was re-evaluated and identified as having Nicolaides-Baraitser syndrome (OMIM#601358), which is similar to but different from CSS. Additionally, 49 more CSS patients were analyzed as a second cohort. Together with the first cohort, 37 out of 71 (22 plus 49) patients were found to have a mutation in either one of five BAF complex genes. Furthermore, two CSS patients were reported to have a PHF6 abnormality, which can also cause Borjeson-Forssman-Lehmann syndrome (OMIM#301900), an X-linked intellectual disability syndrome with epilepsy and endocrine abnormalities. The current list of mutated genes in CSS is far from being complete and analysis of more patients is required.

Miyake N ，Tsurusaki Y ，Matsumoto N 《-》

Report of a patient with a constitutional missense mutation in SMARCB1, Coffin-Siris phenotype, and schwannomatosis.

We report a patient with a constitutional missense mutation in SMARCB1, Coffin-Siris Syndrome (CSS), and schwannomatosis. CSS is a rare congenital syndrome with characteristic clinical findings. This thirty-three-year-old man was diagnosed early in life with the constellation of moderate intellectual disability, hypotonia, mild microcephaly, coarse facies, wide mouth with full lips, hypoplasia of the digits, and general hirsutism. At age 26, he was found to have schwannomatosis after presenting with acute spinal cord compression. Blood and tissue analysis of multiple subsequent schwannoma resections revealed a germline missense mutation of SMARCB1, acquired loss of 22q including SMARCB1 and NF2 and mutation of the remaining NF2 wild-type allele-thus completing the four-hit, three-event mechanism associated with schwannomatosis. Variations in five genes have been associated with the Coffin-Siris phenotype: ARID1A, ARID1B, SMARCA4, SMARCB1, and SMARCE1. Of these genes, SMARCB1 has a well-established association with schwannomatosis and malignancy. This is the first report of a patient with a constitutional missense mutation of SMARCB1 resulting in CSS and subsequent development of schwannomatosis. This finding demonstrates that a SMARCB1 mutation may be the initial "hit" (constitutional) for a genetic disorder with subsequent risk of developing schwannomas and other malignancies, and raises the possibility that other patients with switch/sucrose non-fermenting (SWI/SNF) mutations may be at increased risk for tumors.

Gossai N ，Biegel JA ，Messiaen L ，Berry SA ，Moertel CL ... -  《-》