Sequence analysis of PG10.2, a gene expressed in the pineal gland and the outer nuclear layer of the retina.

A cDNA (PG10.2) was cloned from rat using RNA fingerprinting by arbitrarily primed PCR (AP-PCR). Initially, a 145-bp DNA fragment was isolated from a pineal-specific band revealed on a sequencing gel. Riboprobes generated from the DNA fragment were used for hybridization histochemical and Northern analyses. Both techniques indicate a gene (8 kb mRNA) expressed only in the pineal gland and the outer nuclear layer of the retina. Two 4-kb cDNA fragments generated by 5'-RACE (rapid amplification of cDNA ends) and 3'-RACE were obtained using a long template PCR-based RACE technique. DNA sequencing revealed a single long open reading frame (ORF) encoding a predicted protein of 1239 amino acids, containing multiple motifs: a typical signal sequence of 20 amino acids at the NH2-terminus, a long extracellular domain with multiple potential glycosylation sites, a 31-amino-acid transmembrane domain near the COOH-terminus and a 109-amino-acid cytoplasmic tail. There are also two domains similar, but not identical, to EGF-like (epidermal growth factor-like) domains located just upstream of the transmembrane domain. These features suggest that this gene may encode a glycoprotein involved in cell adhesion, growth, and differentiation of pineal and retinal photoreceptor cells.