Identification and molecolar cloning of Xenopus laevis SP22, a protein associated with fertilization in mammals

SP22 is a novel sperm protein that has been shown to be highly correlated with fertility in rats. SP22 homologues have been studied in mouse and man but a definitive role for the protein has not yet been established. Using a polyclonal IgG to recombinant rat SP22, we detected the presence of this protein in Xenopus laevis tissues. Moreover, a Xenopus EST was found that shares a high degree of similarity with rat SP22 and the derived sequence codes for an 189 aa protein that is very similar to rat SP22. Finally, using Western blotting and RT-PCR analyses, we investigated the expression of Xenopus SP22 both in adult tissues and during embyronic development. SP22 protein expression predominated in the adult testis, and both mRNA and protein levels diminished subsequent to the initial day following fertilization. © 2002 Elsevier Science Inc. All rights reserved.