Actin, myosin, cytokeratins and spectrin are components of the guinea pig sperm nuclear matrix.

The nuclear matrix (NM) of somatic cells is an internal nuclear framework structure, with a structural function and participation in DNA replication and transcription. The NM has been described in mouse, hamster and human spermatozoa. In this study, an NM structural component of the guinea pig sperm nucleus was obtained by removing nuclear proteins and DNA from DTT-CTAB nuclei. Removal was achieved with high ionic strength salt and microccocal nuclease treatments including a heparin treatment to cause a slight swelling of the nucleus and facilitate material extraction. Actin, myosin, cytokeratins and spectrin were detected associated to NM by indirect immunofluorescence, immunogold staining and Western blotting analysis using specific antibodies. The presence of NM in guinea pig sperm nucleus is shown for the first time and some of its components are identified. This is also the first report on cytokeratins and myosin presence in guinea pig sperm. A retarding effect of nuclear decondensation caused by heparin is induced after phalloidin and/or diacetyl-monoxime (a myosin ATPase activity inhibitor) treatment, suggesting a role for F-actin and myosin in the maintenance of nuclear stability in sperm. The actin role was supported by the decondensing effect that citochalasin D and gelsolin had on sperm nuclei.