DNA ORGANIZATION IN HUMAN SPERMATOZOA

Previous studies from this laboratory on hamster spermatozoa have demo nstrated that rodent sperm DNA is packaged into the sperm nucleus in a specific manner by nuclear structures. The entire genome is organized into DNA loop domains attached at their bases to a sperm nuclear matr ix, the skeletal structure of the nucleus. When nuclei are completely decondensed, the nuclear matrix dissipates, and the entire genome rema ins anchored to a single structure located at the base of the tail, te rmed the nuclear annulus. Here, we have extended these studies to huma n sperm nuclei, which were found to be similar to hamster. Human sperm DNA was found to be organized into loop domains attached at their bas es to a nuclear matrix. The average size of the human sperm halo of DN A surrounding the extracted sperm nucleus (made up of DNA loop domains ) was about 50% smaller than those that have been reported for somatic cells (this corresponds to an approximate loop domain size of 26.8 +/ - 2.1 kb). Human sperm DNA also remained anchored to the base of the t ail when completely decondensed, indicating the existence of a nuclear annulus-like structure in human spermatozoa; but, unlike the hamster nuclear annulus, the human annulus could not be isolated because of it s structural instability when separated from the tail. Using human cen tromere repeats as a probe for in situ hybridization, we examined the packaging of individual DNA sequences within the sperm nucleus. These studies demonstrate that human sperm DNA is highly organized by nuclea r structures.