Parental Origin of the Deletion 22q11.2 and Brain Development in Velocardiofacial Syndrome

Abstract
VELOCARDIOFACIAL syndrome (VCFS) is a common genetic condition associated with physical features, including heart malformations, palatal abnormalities, and characteristic facial dysmorphism.1 The high frequency of VCFS (1 in 2000-4000 live births)2 ranks this condition as one of the most common genetic causes of learning disabilities and mild mental retardation. In most diagnosed cases, the syndrome is due to a 3 megabase (Mb) de novo deletion on chromosome 22q11.2,3 and can occur on either parental chromosome. At least 30 genes are encoded in the common deleted segment.4 Among these, a few are expressed in brain tissue, and some are likely to be essential for normal brain development.5-7