CELL-SPECIFIC NUCLEAR ANTIGENS OF BOAR SPERMATOZOA

Demembranated boar sperm heads were differentially extracted at condit ions involving high salt-urea, proteolysis and DNase I cleavage that m imic the conditions promoting the in vivo decondensation of the fertil izing sperm nucleus in the egg ooplasm. The sperm-unique subset of pro teins was studied which remained bound in the residual salt-resistant nuclear structure operationally defined as sperm nuclear matrix. By me ans of polyvalent antisera the immune specificity of the sperm nucleop rotein complex was estimated using ELISA and microcomplement fixation test as compared to somatic type dehistonized chromatin of boar liver. To define immunologically specific sperm DNA-associated proteins, hyb ridomas were generated by fusing lymphocytes immunized with boar sperm protein/DNA complex. Monoclonal antibodies were selected (Mab 1A8, 1B 3, 2B5, 2H5 and 3A4) which identified protein moieties in the sperm DN A-tight binding proteins complex resistant to cleavage with DNase I an d sensitive upon digestion with high concentration of proteases. No ap preciable reactivity was recorded of the antibodies to somatic chromat in and no significant binding to ssDNA. A polypeptide in the residual sperm nuclear structure of apparent Mr 27 kDa was recognized by Mab 3A 4 as detected by Western blotting. The enhanced reactivity to the DNas e I digested sperm nuclear fraction (except for Mab 2H5) suggests that DNA protected from nuclease digestion by a protein might be essential for immune reactivity and full antigenic integrity as well as the dep endence of the cognate proteins on the binding to DNA for antigenicity and immune specificity. The functioning of the identified putative sp erm specific proteins is anticipated in the structural rearrangement o f chromatin in the zygote. (C) 1997 Elsevier Science B.V.