title: DNA double-strand break repair in parental chromatin of mouse zygotes, the first cell cycle as an origin of de novo mutation.
abstract: In the human, the contribution of the sexes to the genetic load is dissimilar. Especially for point mutations, expanded simple tandem repeats and structural chromosome mutations, the contribution of the male germline is dominant. Far less is known about the male germ cell stage(s) that are most vulnerable to mutation contraction. For the understanding of de novo mutation induction in the germline, mechanistic insight of DNA repair in the zygote is mandatory. At the onset of embryonic development, the parental chromatin sets occupy one pronucleus (PN) each and DNA repair can be regarded as a maternal trait, depending on proteins and mRNAs provided by the oocyte. Repair of DNA double-strand breaks (DSBs) is executed by non-homologous end joining (NHEJ) and homologous recombination (HR). Differentiated somatic cells often resolve DSBs by NHEJ, whereas embryonic stem cells preferably use HR. We show NHEJ and HR to be both functional during the zygotic cell cycle. NHEJ is already active during replacement of sperm protamines by nucleosomes. The kinetics of G1 repair is influenced by DNA-PK(cs) hypomorphic activity. Both HR and NHEJ are operative in S-phase, HR being more active in the male PN. DNA-PK(cs) deficiency upregulates the HR activity. Both after sperm remodeling and at first mitosis, spontaneous levels of gammaH2AX foci (marker for DSBs) are high. All immunoflurescent indices of DNA damage and DNA repair point at greater spontaneous damage and induced repair activity in paternal chromatin in the zygote.
authors: Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
authors: Alwin
authors: A
authors: Derijck
authors: Godfried
authors: G
authors: van der Heijden
authors: Maud
authors: M
authors: Giele
authors: Marielle
authors: M
authors: Philippens
authors: Peter
authors: P
authors: de Boer
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000528:radiation effects; D042002:Chromatin Assembly and Disassembly; D003497:Cyclic N-Oxides / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair; D005260:Female; D006657:Histones / Q000378:metabolism; D008297:Male; D051379:Mice; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051135:Rad51 Recombinase / Q000032:analysis / Q000378:metabolism; D011839:Radiation, Ionizing; D011995:Recombination, Genetic; D012727:Sex Characteristics; D013094:Spermatozoa / Q000378:metabolism; D015053:Zygote / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D003497:Cyclic N-Oxides; D006657:Histones; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; C013620:4-nitropyridine 1-oxide