Presence of N-cadherin transcripts in mature spermatozoa

The essential mechanism involved in sperm-oolemma fusion has yet to be eluc idated. Recognition and binding is initiated by specific cell surface recep tor engagement between gametes. Fusion between hamster oolemma and spermato zoa is prevented in the presence of trypsin in Ca2+-free media, as is oocyt e activation, implicating a cadherin-like adhesion. Cadherins are a family of Ca2+-dependent adhesion molecules that bind homotypically with their tar get, are morphoregulatory and function eptopically to affect tissue form an d function. Cadherins and cadherin-associated molecules have been identifie d in testes and germinal cells, as well as ejaculated spermatozoa. Moreover , cadherins are also present in oocytes and may suggest a cadherin-mediated adhesion in sperm-oocyte interaction, We have detected antigenic epitopes recognized by N-cadherin monoclonal antibodies diffusely distributed over t he entire sperm head. In addition, Western blot analysis confirmed the pres ence of an antibody reactive peptide in spermatozoa, testis and ovary prote in extracts at the expected molecular weight for authentic N-cadherin. Tota l RNA was isolated from mature motile spermatozoa, as well as ovary and tes tis tissue, and served as template for reverse transcription-polymerase cha in reaction (RT-PCR) with N-cadherin specific primers. Alignment of sequenc es from PCR products of testis, ovary and spermatozoa with published N-cadh erin sequence was identical except for occasional base changes. We intend t o develop methods to analyse this transcript from smalt numbers of spermato zoa from a variety of donors to determine if defects in cadherin distributi on or structure may predict reduced male fertility.