Sperm-derived histones contribute to zygotic chromatin in humans.
BACKGROUND
about 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.


RESULTS
to 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.


CONCLUSIONS
these 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.
van der Heijden
Godfried W
GW
Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, P,O, Box 9101, 6500 HB Nijmegen, The Netherlands. vanderheijden@ciwemb.edu
Ramos
Liliana
L
Baart
Esther B
EB
van den Berg
Ilse M
IM
Derijck
Alwin A H A
AA
van der Vlag
Johan
J
Martini
Elena
E
de Boer
Peter
P
D000818:Animals; D002843:Chromatin / Q000737:chemistry / Q000235:genetics*; D015925:Cryopreservation; D004261:DNA Replication; D005260:Female; D006657:Histones / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D009707:Nucleosomes / Q000737:chemistry / Q000235:genetics; D009865:Oocytes / Q000737:chemistry; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods*; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000737:chemistry; D015053:Zygote
D002843:Chromatin; D006657:Histones; D009707:Nucleosomes