Relevance of sperm chromatin protamination, condensation and DNA integrity for sperm function and fertility: the role of toroid linker regions

Viñolas Vergés, Estel
Male fertilising capacity has traditionally been predicted by the assessment of sperm concentration, motility and morphology. During the last few decades, however, research has been particularly focused on the analysis of sperm chromatin, in terms of protamination, condensation and DNA integrity, as a valuable approach to evaluate male fertility. During spermiogenesis nuclear histones are replaced by protamines, resulting in a tightly condensed structure that is stabilised through intra- and inter-protamine disulphide bonds formed during epididymal maturation. This highly condensed organisation protects the paternal genetic information from damaging agents during the transit of sperm through both male and female genital tracts. Poor protamination after spermiogenesis may result in an elevated number of sperm cells with immature chromatin, which is featured by a higher incidence of histone-packed DNA regions; these regions have been described to be more susceptible to DNA damage than those properly protaminated. Sperm DNA fragmentation is defined by the incidence of single- and double-strand breaks caused by oxidative stress and enzymatic activity, respectively. Sperm DNA fragmentation has been associated to poor sperm quality and impaired fertility outcomes both in vitro and in vivo. Because of the relationship between DNA and chromatin integrity, it is reasonable to hypothesise that abnormal chromatin protamination and condensation can also affect sperm DNA negatively, which could ultimately cause male subfertility or infertility. In the light of the aforementioned, the present Doctoral Thesis aimed to investigate the relationship of sperm chromatin protamination and condensation, and DNA integrity with sperm function and fertilising ability. ​
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