Identification and characterization of human MPP7 gene and mouse Mpp7 gene in silico

Drosophila Crumbs (Crb), Stardust (Sdt), Discs large (Dlg), Scribble (Scrib) and Lethal giant larvae (Lgl) are involved in the establishment and the maintenance of apico-basal polarity in epithelial tissues. Because epithelial polarity is disrupted in tumors, human homologs of Drosophila crb, sdt, dlg, scrib, and lgl are potential cancer-associated genes. MPP1/EMP55, MPP2, MPP3, MPP4, MPP5/PALS1 and MPP6/PALS2 genes are human homologs of Drosoplila sdt. Here, we identified and characterized a novel member of MPP gene family, MPP7, by using bioinformatics. Uncharacterized FLJ32798 cDNAs (BC038105 and AK057360) were derived from human MPP7 gene. BC038105 was a representative MPP7 cDNA, while AK057360 was an aberrant MPP7 cDNA with a frame shift. Human MPP7 mRNA was expressed in placenta, brain, testis as well as in uterus tumor, bladder tumor, and lymphoma. Microsatellite marker D10S588, linked to IDDM and hereditary thrombocytopenia, was located within the MPP7 gene at human chromosome 10p12.1. Nucleotide sequence of mouse Mpp7 cDNA was determined in silico by assembling 3'-truncated cDNA AK078849, genome clone RP24-255J24, and EST AV260217. Human MPP7 showed 92.9% total-amino-acid identity with mouse Mpp7, and 75.7% total-amino-acid identity with zebrafish humpback. MPP7 orthologs were MAGUK proteins with two L27 domains, PDZ domain, SH3 domain, and GuKc domain. MPP7 was most related to MPP3 among MPP family members, functioning as adopter molecules assembling Crb homologs (CRB1, CRB3), Dlt homologs (INADL/PATJ, MPDZ/MUPP1), and Lin-7 homologs (LIN7A, LIN7B, LIN7C). This is the first report on identification and characterization of human MPP7 and mouse Mpp7 genes.