Mental Retardation, Autosomal Dominant 21

A number sign (#) is used with this entry because of evidence that mental retardation-21 (MRD21) is caused by heterozygous mutation in the CTCF gene (604167) on chromosome 16q22.

Molecular Genetics

By trio exome sequencing in a 9.5-year-old boy with mild intellectual disability, short stature, microcephaly, cleft palate, and congenital heart defects, Gregor et al. (2013) identified a de novo frameshift mutation in the CTCF gene (604167.0001). Screening of the CTCF gene in 399 individuals with intellectual disability revealed 2 more de novo mutations in 2 boys: another frameshift mutation (604167.0002) and a missense mutation (R567W; 604167.0003). The patient with the second frameshift mutation was a 9-year-old boy who had had borderline intelligence but developmental delay, pronounced learning difficulties, and behavioral problems, as well as microcephaly. The patient with the missense mutation was a 4-year-old boy who had microcephaly, severe intellectual disability with autistic features, and severe feeding difficulties that necessitated tube feeding. A search of the Decipher database yielded a 15-year-old girl with intellectual disability and a de novo deletion on chromosome 16 involving 8 genes, including CTCF.