HSP70-2 IS PART OF THE SYNAPTONEMAL COMPLEX IN MOUSE AND HAMSTER SPERMATOCYTES

Mouse spermatogenic cells are known to express HSP70-2, a member of th e HSP70 family of heat-shock proteins. The purpose of the present stud y was to characterize further the expression and localization of HSP70 -2 in meiotic cells of mice and hamsters. After separating mouse sperm atogenic cells into cytoplasmic and nuclear fractions, proteins were s eparated by two-dimensional gel electrophoresis and detected with HSP- specific antibodies. Of several HSP70 proteins identified in the cytop lasm, only HSC70 and HSP70-2 were also detected in the nucleus. Immuno cytological analyses of spermatocyte prophase cells revealed that HSP7 0-2 was associated with the synaptonemal complex. Surface-spread synap tonemal complexes at pachytene and diplotene stages labeled distinctly with the antiserum to HSP70-2. Synaptonemal complexes from fetal mous e oocytes failed to show any evidence of HSP70-2. Reverse-transcriptas e-polymerase chain reaction (RT-PCR) analyses of gene expression confi rmed this sex specificity; Hsp70-2 mRNA was detected in mouse testes, but not ovaries. These findings are suggestive of a previously unsuspe cted sexual dimorphism in structure and/or function of the synaptonema l complex.