Immunolocalization of N-cadherin in human sperm and evaluation of its involvement in fertilization

MARÍN BRIGGILER CI; LENTZ EM; VEIGA F; GONZALEZ-ECHEVERRIA F; VAZQUEZ-LEVIN M

Seattle, Washington, USA

Congreso; 30th Annual American Society of Andrology Meeting; 2005

American Society of Andrology

Cadherins are membrane glycoproteins involved in cell-to-cell adhesion. Preliminary evidence suggest the presence of neural cadherin (Ncad) in human sperm (Rufas et al, 2000), and identification of Ncad sperm transcripts (Goodwin et al, 2000). The aim of the study was to describe the localization of Ncad in human sperm and to assess its involvement in fertilization. Western immunobloting of sperm proteins with a specific polyclonal antibody towards Ncad domain 5 (Santa Cruz Biotech) revealed the presence of a 113 KDa Ncad form, resistent to sperm dissociation after cell treatment with a buffer containing 1M NaCl. This protein form was also immunodetected in protein extracts from testis and seminal plasma. Ncad was mainly immunolocalized in the equatorial segment and acrosomal cap of ejaculated (62±7 %; 17±10 %, respectively; mean+SEM) and 18h-capacitated sperm (51±8 %; 30±8 %, respectively) (n=5). In acrosome reacted sperm, Ncad was mainly found in the equatorial segment (84±2 % of sperm) (n=3). In all cases, a specific signal for Ncad on the sperm flagellum was also detected. Sperm preincubation with the antibody towards Ncad (100 mg/ml) did not affect binding to homologous zona pellucida (ZP) (anti Ncad=29±11 vs Control=33±12 bound sperm/hemizona; n=6). However, preincubation of ZP free-hamster eggs with anti Ncad antibody (20 mg/ml) resulted in the decrease of the percentage of sperm penetrations compared to control conditions (anti Ncad=40 % vs Control=100 %; n=2). The studies describe the presence and localization of Ncad in ejaculated, capacitated and acrosome reacted sperm, and suggest its participation in adhesion events during sperm interaction with the oolema.