Identification of an additional gene belonging to the α 2 adrenergic receptor family in the human genome by PCR

We here describe the cloning of an additional gene, called α 2-1.8, which is similar to the previously cloned human α 2-adrenergic receptor located on chromosome 4. The α 2-1.8 gene was identified by using the polymerase chain reaction with primers specific for sequences in transmembrane regions 2 and 5 of the previously isolated human α 2-C4 and α 2-C10 adrenoceptor genes, which are localized on chromosomes 4 and 10, respectively. The new gene was identified by amplifying the 1.8 kb size fractionated region of PstI restriction cut human genomic DNA. The previously cloned α 2-C10 and α 2-C4 genes were recovered at their expected locations, 0.96 and 5.9 kb, respectively. We have identified 387 bases of the new α 2-1.8 gene, and its sequence is identical to the previously described α 2-C4 gene, but is distinct from the α 2-C10 and α 2-C2 genes. Our results demonstrate that the α 2-C4 adrenergic receptor exists in more than one copy in the human genome.