Abstract
Backgroundabout 15% to 30% of the DNA in human sperm is packed in nucleosomes and transmission of this fraction to the embryo potentially serves as a mechanism to facilitate paternal epigenetic programs during embryonic development. However, hitherto it has not been established whether these nucleosomes are removed like the protamines or indeed contribute to paternal zygotic chromatin, thereby potentially contributing to the epigenome of the embryo.Resultsto clarify the fate of sperm-derived nucleosomes we have used the deposition characteristics of histone H3 variants from which follows that H3 replication variants present in zygotic paternal chromatin prior to S-phase originate from sperm. We have performed heterologous ICSI by injecting human sperm into mouse oocytes. Probing these zygotes with an antibody highly specific for the H3.1/H3.2 replication variants showed a clear signal in the decondensed human sperm chromatin prior to S-phase. In addition, staining of human multipronuclear zygotes also showed the H3.1/H3.2 replication variants in paternal chromatin prior to DNA replication.Conclusionthese findings reveal that sperm-derived nucleosomal chromatin contributes to paternal zygotic chromatin, potentially serving as a template for replication, when epigenetic information can be copied. Hence, the execution of epigenetic programs originating from transmitted paternal chromatin during subsequent embryonic development is a logical consequence of this observation.
Highlights
A hallmark of spermiogenesis is the transformation of the chromatin of the germ cell
The replacement of nucleosomes by protamines is frequently observed throughout the animal kingdom [2], though the degree of this chromatin substitution varies among species
Localisation of replication H3 variants in human paternal chromatin after heterologous intracytoplasmic sperm injection (ICSI) To find out whether human sperm derived histones are retained in paternal chromatin after decondensation, we determined the presence of H3 replication variants in paternal chromatin in zygotic G1
Summary
A hallmark of spermiogenesis is the transformation of the chromatin of the germ cell. In elongating spermatids nucleosomes are replaced by transition proteins, which are subsequently replaced by protamines. The protaminebased chromatin allows a dense packing of the DNA, which facilitates its protection and transportation to the oocyte (see for a review [1]). Protamination in mouse and boar is almost complete and only an estimated 1% of the total DNA in mouse sperm cells remains nucleosome bound, whereas in human sperm this is estimated to be about 15% [3,4,5]. Characterisation of the histones in human sperm identified H2A, H2AX, H2AZ, H2B, H3.1, H3.3, CenH3 and H4 [4,6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
