Microtubule-associated proteins during mouse spermatogenesis: localization of a protein immunologically related to brain MAP1B protein in the synaptonemal complex.

Monospecific polyclonal antibodies against MAP1A protein and an immunologically related brain MAP1B polypeptide were used to visualize mouse synaptonemal complexes (SCs) with immunofluorescence microscopy. Anti-MAP1A antibody recognized SCs uniformly. However, when anti-MAP1B antibody was used, a dashed pattern of staining was observed along the SCs in both autosomes and pachytene XY bivalents. After purification of SCs, immunoblots of the electrophoresed proteins revealed a polypeptide of 220 kDal, which was recognized by anti-MAP1B antibody, and two proteins of 180 kDal and 160 kDal, which were recognized by anti-MAP1A antibody. High-molecular-weight polypeptides immunologically related to microtubule-associated proteins were localized in the cell nucleus. The function of these nuclear proteins is unknown. The distribution of fluorescent signal corresponding to the 220-kDal protein during meiosis and spermiogenesis and its localization in the nuclear matrix suggest the participation of preexisting nucleoskeletal proteins in the molecular organization of the SC and its dynamics during meiotic prophase.