Human Sperm Chromosomes: To Form Hairpin-Loops, Or Not to Form Hairpin-Loops, That Is the Question

Abstract

Background: Genomes are non-randomly organized within the interphase nucleus; and spermatozoa are proposed to have a unique hairpin-loop configuration, which has been hypothesized to be critical for the ordered exodus of the paternal genome following fertilization. Recent studies suggest that the hairpin-loop model of sperm chromatin organization is more segmentally organized. The purpose of this study is to examine the 3D organization and hairpin-loop configurations of chromosomes in human spermatozoa. Methods: Three-color sperm-fluorescence in-situ hybridization was utilized against the centromeres, and chromosome p- and q-arms of eight chromosomes from five normozoospermic donors. Wide-field fluorescence microscopy and 3D modelling established the radial organization and hairpin-loop chromosome configurations in spermatozoa. Results: All chromosomes possessed reproducible non-random radial organization (p < 0.05) and formed discrete hairpin-loop configurations. However, chromosomes preferentially formed narrow or wide hairpin-loops. We did not find evidence to support the existence of a centralized chromocenter(s) with centromeres being more peripherally localized than one or both of their respective chromosome arms. Conclusion: This provides further evidence to support a more segmental organization of chromatin in the human sperm nucleus. This may be of significance for fertilization and early embryogenesis as specific genomic regions are likely to be exposed, remodeled, and activated first, following fertilization.

Partial illustration of human sperm DNA via microscopy and quantitative analysis of nucleotides

“…(o) geimsa banding pattern was demonstrated very similar to lymphocytes. These micro photos of human sperm structure approve previous reports based on segmental organization of chromatin as well hairpin structure of DNA 7 .…”

“…While, some obtained data indicate the hair loop and segmental structure of chromosomes in human sperm 7 . Numerous fundamental bio-molecular of sperm have been searched and just a few of these characteristics have been used as tools for medical assessment prior to ART 8, 9 .…”

Cytochalasin D restores nuclear size acting on F-actin and IZUMO1 localization in low-quality spermatozoa

“…Then, we hypothesized that the increase in nuclear volume of pre-B SPZ could be associated with an abnormal chromosomal distribution within nuclei. In sperm, chromosomes are non-randomly positioned within the nuclei and occupy domains with preferential radial and linear positioning called chromosomes territories (CT) 36 , 37 . We randomly chose and investigated six chromosomes in sperm nucleus: chromosomes 9, 11, 17, 21, 22 and X.…”

Form from Function, Order from Chaos in Male Germline Chromatin

“…Four studies examine chromosome organisation in mature sperm. First, Dimitris Ioannou and Helen Tempest show that, while chromosomes in human sperm do indeed to form hairpin loops, as predicted from studies in other species, their centromeres are not organized in the classic "chromocenter" arrangement seen in model species such as mice [3]. Second, Heather Fice and Bernard Robaire confirm that relative sperm telomere length does indeed decrease during ageing in rodents, but, crucially, only in inbred strains [4].…”