Expression, immunolocalization and sperm-association of a protein derived from 24p3 gene in mouse epididymis

The cDNA sequence for 24p3 protein in ICR mouse epididymal tissue was deter mined by PCR using primers designed according to the cDNA sequence derived from 24p3 protein in mouse uterine tissue. In the present study, 24p3 prote in was immunolocalized in the epithelial cells and lumen of mouse epididymi s. Both immunoblot analysis for protein and northern blot analysis for mRNA level showed a declining gradient of 24p3 expression from the caput to cau dal region of the epididymis. The 24p3 protein was undetectable in the test is. These findings suggest that the 24p3 protein is a caput-initiated secre tory protein in the mouse epididymis. A postnatal study revealed that 24p3 gene expression occurred in mice at the age of 14 days, before the completi on of epididymal differentiation. This expression remained at a constant le vel until epididymal differentiation was completed. We also found that the secreted 24p3 protein interacted predominantly with the acrosome of caudal spermatozoa. Our findings suggest that the epididymal 24p3 protein is a cap ut-initiated and sperm-associated gene product and may be important in the reproductive system. (C) 2000 Wiley-Liss, Inc.