Divergent human and mouse orthologs of a novel gene (WBSCR15/Wbscr15) reside within the genomic interval commonly deleted in Williams syndrome.

Williams syndrome (WS) is a contiguous gene deletion disorder resulting in complex and intriguing clinical features. Detailed molecular characterization studies of the genomic segment on human chromosome 7q11.23 commonly deleted in WS have uncovered numerous genes, each of which is being actively studied for its possible role in the etiology of the syndrome. Our efforts have focused on the comparative mapping and sequencing of the WS region in human and mouse. In previous studies, we uncovered important differences in the long-range organization of these human and mouse genomic regions; in particular, the notable absence of large duplicated blocks of DNA in mouse that are present in human. Aided by available genomic sequence data, we have used a combination of gene-prediction programs and cDNA isolation to identify the human and mouse orthologs of a novel gene (WBSCR15 and Wbscr15, respectively) residing within the genomic segment commonly deleted in WS. Unlike the flanking genes, which are closely related in human and mouse, WBSCR15 and Wbscr15 are strikingly different with respect to their cDNA and corresponding protein sequences as well as tissue-expression pattern. Neither the WBSCR15- nor Wbscr15-encoded amino acid sequence shows a statistically significant similarity to any characterized protein. These findings reveal another interesting evolutionary difference between the human and mouse WS regions and provide an additional candidate gene to evaluate with respect to its possible role in the pathogenesis of WS.