Isolation and analysis of chromosome 21 genes potentially involved in Down Syndrome

Abstract

Down syndrome is the most common birth defect (1 in 700 newborns) and the most important cause of mental retardation. This disease is characterized by a complex phenotype, mainly including morphological abnormalities of the head and limbs, short stature, hypotonia, hyperlaxity of ligaments, visceral malformations (particularly heart defects), and a constant mental retardation. In most cases, it results from the presence of an entire chromosome 21 in excess in all cells of the afflicted individuals. Phenotype-genotype correlation of rare patients with partial trisomy 21 identified a small region of chromosome 21 on 21q22.2, duplication of which is associated with many features of the syndrome. This region, named Down syndrome Chromosome Region 1 or DCR1, is associated with short stature, hypotonia, joint hyperlaxity, face and limbs dysmorphy, and mental retardation. In order to identify genes potentially involved in the Down syndrome phenotype and particularly in mental retardation. DNA clones overlapping this region were isolated and used to search for transcribed sequences by different methods.