Decondensation of sperm nuclei in vitro

Treatment of mouse spermatozoa with dithiothreitol and proteases, particularly trypsin, causes the nucleus to enlarge and decondense, while the acrosomal region remains relatively intact. Dithiothreitol or trypsin alone does not induce swelling, and exposure to the reducing agent is necessary before trypsin can act. Chymotrypsin, promise, and papain will substitute for trypsin, but micrococcal nuclease and pancreatic deoxyribonuclease will not. Similar results were obtained with rat, guinea pig, and rabbit sperm. These results provide the basis for a method of purifying sperm acrosomes and suggest possible mechanisms for decondensation of the sperm nucleus after penetration of the egg.