Comparative genomics on Wnt7a orthologs

WNT and Hedgehog signaling pathways network together during carcinogenesis and embryogenesis. WNT7A mRNA is expressed in human gastric and pancreatic cancer cells. WNT7A mRNA expression is relatively high in the temporal, occipital and parietal lobes, paracentral gyrus of the cerebral cortex, caudate nucleus, hippocampus, medulla oblongata and putamen within the adult human brain. Here, we identified and characterized the rat Wnt7a gene using bioinformatics. The rat Wnt7a gene, consisting of four exons, was located within the AC106100.7 genome sequence. Rat Wnt7a (349 aa) with 24 Cys residues and 3 Asn-linked glycosylation sites showed 99.7, 99.1 and 93.7% total-amino- acid identity with mouse Wnt7a, human WNT7A and chicken wnt7a, respectively. The N-terminal signal peptide was not identified within the Wnt7a orthologs. Exonic regions, except the 3'-UTR, were conserved between the rat Wnt7a and human WNT7A genes; however, the 5'-flanking region was significantly divergent between the rat Wnt7a and human WNT7A genes. Although the COMP1- and ELK1-binding sites within exon 1 were conserved among mammalian Wnt7a promoters, transcriptional regulation of the rodent Wnt7a orthologs was predicted to be distinct from that of human WNT7A based on the divergence within the 5'-flanking promoter region. Therefore, biological functions of rodent Wnt7a are not always consistent with those of human WNT7A due to promoter evolution. This is the first report on the rat Wnt7a gene and comparative genomics for Wnt7a orthologs.