Missense variant in CCDC22 causes X-linked recessive intellectual disability with features of Ritscher-Schinzel/3C syndrome

Eur J Hum Genet. 2015 May;23(5):633-8. doi: 10.1038/ejhg.2014.109. Epub 2014 Jun 11.


Ritscher-Schinzel syndrome (RSS)/3C (cranio-cerebro-cardiac) syndrome (OMIM#220210) is a rare and clinically heterogeneous developmental disorder characterized by intellectual disability, cerebellar brain malformations, congenital heart defects, and craniofacial abnormalities. A recent study of a Canadian cohort identified homozygous sequence variants in the KIAA0196 gene, which encodes the WASH complex subunit strumpellin, as a cause for a form of RSS/3C syndrome. We have searched for genetic causes of a phenotype similar to RSS/3C syndrome in an Austrian family with two affected sons. To search for disease-causing variants, whole-exome sequencing (WES) was performed on samples from two affected male children and their parents. Before WES, CGH array comparative genomic hybridization was applied. Validation of WES and segregation studies was done using routine Sanger sequencing. Exome sequencing detected a missense variant (c.1670A>G; p.(Tyr557Cys)) in exon 15 of the CCDC22 gene, which maps to chromosome Xp11.23. Western blots of immortalized lymphoblastoid cell lines (LCLs) from the affected individual showed decreased expression of CCDC22 and an increased expression of WASH1 but a normal expression of strumpellin and FAM21 in the patients cells. We identified a variant in CCDC22 gene as the cause of an X-linked phenotype similar to RSS/3C syndrome in the family described here. A hypomorphic variant in CCDC22 was previously reported in association with a familial case of syndromic X-linked intellectual disability, which shows phenotypic overlap with RSS/3C syndrome. Thus, different inactivating variants affecting CCDC22 are associated with a phenotype similar to RSS/3C syndrome.

Publication types

  • Case Reports

MeSH terms

  • Abnormalities, Multiple / diagnosis*
  • Abnormalities, Multiple / genetics*
  • Adolescent
  • Amino Acid Sequence
  • Cell Line
  • Child
  • Comparative Genomic Hybridization
  • Craniofacial Abnormalities / diagnosis*
  • Craniofacial Abnormalities / genetics*
  • Dandy-Walker Syndrome / diagnosis*
  • Dandy-Walker Syndrome / genetics*
  • Exome
  • Gene Expression
  • Genes, X-Linked*
  • Genetic Association Studies
  • Heart Septal Defects, Atrial / diagnosis*
  • Heart Septal Defects, Atrial / genetics*
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Intellectual Disability / diagnosis*
  • Intellectual Disability / genetics*
  • Male
  • Molecular Sequence Data
  • Mutation, Missense*
  • Pedigree
  • Phenotype
  • Proteins / chemistry
  • Proteins / genetics*
  • Sequence Alignment


  • CCDC22 protein, human
  • Proteins

Supplementary concepts

  • 3C syndrome