Sperm Chromatin Dynamics Associated with Male Fertility in Mammals
Animal Models and Human Reproduction
Instead of two protamines (PRM1 and PRM2) as in human and mouse sperms, presence of only PRM1 in bull sperm raises an interesting question about the mechanism(s) regulating sperm chromatin structure. During spermatogenesis, spermatozoa that are present in syncytium share mRNA and proteins through cytoplasmic bridges and are phenotypically diploid. Chromatin remodeling occurs during spermatogenesis where linker histones are gradually replaced by testis-specific variants, followed by the replacement of histones with transition proteins and then with protamines. Increased percentage of histone retention is expected to cause infertility in males. Although protamines are involved in sperm chromatin condensation and function, there is restrictive positive selection on only a few functional sites. Improper packaging of sperm DNA caused partly by reduced protamination predisposes sperm DNA to damage, which then interferes with fertilization and early embryonic development. Abnormal chromatin condensation in sperm during spermatogenesis and abnormal chromatin decondensation during pronucleus formation (postfertilization) can result in reproductive problems.
Kutchy, N., Dogan, S., Kaya, A., Moura, A., & Memili, E. (2017). Sperm Chromatin Dynamics Associated with Male Fertility in Mammals. Animal Models and Human Reproduction, 427-434. https://doi.org/10.1002/9781118881286.ch16