Nature and origin of transient DNA strand breaks during spermiogenesis

• DOI: 10.1016/j.ics.2004.05.082
• Publication Date: 2005-02-16T22:36:05Z
• Authors: Rémi-Martin Laberge; Guylain Boissonne...
• Keywords: Spermiogenesis

Abstract During mid-spermiogenesis steps, transient DNA strand breaks appear in the whole population of elongating spermatids. This would be necessary to relieve the free DNA supercoils remaining after histones displacement since the DNA is no longer supercoiled in the mature spermatozoa. Histones hyperacetylation is coincident with the chromatin remodelling steps. This post-translational modification appears to be essential for histones displacement and is found to co-localize with the transient DNA strand breaks suggesting that it may represent a prerequisite to allow strand breakages to form. The negative supercoils resulting from DNA wrapping around the nucleosome could be eliminated by the enzymatic action of topoisomerases known to relax negative supercoils. The transition proteins (TPs) and protamines, which sequentially bind DNA after histones removal, could provide the appropriate scaffold to support the final resealing steps of the process. We hypothesize that the DNA strand breakage and ligation may represent sensitive steps with the potential to alter fertility if the sequence of event is altered. The mutagenic potential of these events may also result in fertility and/or developmental problems.