Abstract

Down syndrome is the most common birth defect, and is caused by trisomy 21. We identified a novel gene in the so-called Down syndrome critical region by means of computer-aided exon prediction and subsequent cDNA cloning. The gene, designated as DCRA (Down syndrome Critical Region gene A), consists of eight exons of 3,252 bp in total and encodes a large open reading frame of 297 amino acid residues. The open reading frame shows significant homology to Hbeta58, a mouse gene essential for embryogenesis, PEP8, a yeast homologue of Hbeta58, and an expressed sequence tag of Arabidopsis thariana, suggesting that DCRA has some important function that has been conserved during the course of evolution. DCRA is expressed in most tissues examined, including fetal and adult brain, heart, lung, liver, and kidney. The cDNA of the DCRA mouse homologue, Dcra, was also cloned. It is 2,157 bp long and has an open reading frame of 297 amino acid residues, which shows 92% identity to human DCRA. Dcra is expressed in all the embryo and adult tissues examined.