Article

DNA organization in human spermatozoa

Division of Urology, Robert Wood Johnson University Medical School, New Brunswick, New Jersey 08903-0019.
Journal of Andrology (Impact Factor: 1.69). 03/1994; 15(2):139-44. DOI: 10.1002/j.1939-4640.1994.tb00419.x
Source: PubMed

ABSTRACT Previous studies from this laboratory on hamster spermatozoa have demonstrated 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 matrix, the skeletal structure of the nucleus. When nuclei are completely decondensed, the nuclear matrix dissipates, and the entire genome remains anchored to a single structure located at the base of the tail, termed the nuclear annulus. Here, we have extended these studies to human sperm nuclei, which were found to be similar to hamster. Human sperm DNA was found to be organized into loop domains attached at their bases to a nuclear matrix. The average size of the human sperm halo of DNA 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 tail 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 its structural instability when separated from the tail. Using human centromere 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 nuclear structures.

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    • "These processes are associated with marked changes in the structure of the sperm chromatin (D'Occhio et al., 2007). As spermatogenesis proceeds, 85% of the histone nucleoproteins are replaced by transition proteins, which are subsequently replaced by small, arginine-rich proteins known as protamines (Oliva and Dixon, 1990; Barone et al., 1994; Balhorn et al., 2000). These changes give a compact, denaturating-resistant structure to the chromatin. "
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    • "The chromatin structure of mammalian sperm nuclei differs significantly from that of somatic cells (Barone et al. 1994; Churikov et al. 2004; Steger et al. 1998). In the course of spermiogenesis, the extremely compact chromatin structure of mature spermatozoa (Poccia 1986) is formed by the replacement of histones by the transition proteins TP1 and TP2, which themselves are in turn replaced by protamines (Steger et al. 1998; Wouters-Tyrou et al. 1998). "
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    • "When the human sperm undergoes decondensation, the DNA remains anchored to the base of the tail. This fact suggests the presence of a nuclear annulus-like structure in human sperm (Barone et al., 1994). This DNA organization not only permits the very tightly packaged genetic information to be transferred to the egg, but also ensures that the DNA is delivered in a physical and chemical form that allows the developing embryo to access the genetic information (Sakkas et al., 1999a). "
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