CHARACTERIZATION OF 2 NOVEL PROTOCADHERINS (PCDH8 AND PCDH9) LOCALIZED ON HUMAN-CHROMOSOME-13 AND MOUSE-CHROMOSOME-14

The protocadherins are a subfamily of the calcium-dependent cell-cell adhesion and recognition proteins of the cadherin superfamily. In this study we describe the isolation and characterization of two novel pro tocadherins, PCDH8 and PCDH9, that constitute a new linkage group on h uman chromosome 13 and mouse chromosome 14. Like other protocadherins both genes are predominantly expressed in brain, but PCDH9 is also exp ressed in a broader variety of tissues, and the expression patterns ap pear to be developmentally regulated. We have determined the genomic o rganization of PCDH8, which differs significantly from that of the oth er cadherin subfamilies. In contrast to the classical and desmosomal c adherins, which in general consist of 15-17 exons and share a remarkab le degree of conservation in intron position, PCDH8 consists of only t hree exons and lacks introns in the extracellular domain. The first ex on encodes the extracellular domain, the transmembrane region, and par t of the cytoplasmic tail. The second exon encodes the remainder of th e cytoplasmic region and is partially untranslated. The differences in the genomic structure of cadherin subfamilies will be discussed in th e context of the evolution of the cadherin superfamily. (C) 1998 Acade mic Press.