Evolution, structure, and expression of GNPI/Oscillin orthologous genes.

Oscillin was identified from hamster sperm as a factor responsible for oocyte calcium oscillations. However, its high level of homology with the bacterial glucosamine-6-phosphate isomerase suggests that it may play more fundamental roles. In the current study, we identified Oscillin orthologs from Caenorhabditis elegans, Drosophila melanogaster, mouse, and human. Their amino acid identities with hamster oscillin were 67.0, 72.3, 97.6, and 95.5%, respectively. No Oscillin orthologs were found in Saccharomyces cerevisiae. The human Oscillin gene (HGMW-approved symbol GNPI) spans 12.4 kb and consists of eight exons. The position of the fourth intron was conserved in other species. The human Oscillin promoter has features characteristic of housekeeping genes, including a GC-rich content, multiple SP1 binding sites, and the absence of a TATA motif. Human and mouse Oscillin genes were ubiquitously expressed in all tissues examined. These data showed that Oscillin is a housekeeping gene conserved throughout evolution and do not support the notion that Oscillin is the sperm-specific factor responsible for calcium oscillations.