title: DNA Double Strand Break Response and Limited Repair Capacity in Mouse Elongated Spermatids.
abstract: Spermatids are extremely sensitive to genotoxic exposures since during spermiogenesis only error-prone non homologous end joining (NHEJ) repair pathways are available. Hence, genomic damage may accumulate in sperm and be transmitted to the zygote. Indirect, delayed DNA fragmentation and lesions associated with apoptotic-like processes have been observed during spermatid elongation, 27 days after irradiation. The proliferating spermatogonia and early meiotic prophase cells have been suggested to retain a memory of a radiation insult leading later to this delayed fragmentation. Here, we used meiotic spread preparations to localize phosphorylate histone H2 variant (γ-H2AX) foci marking DNA double strand breaks (DSBs) in elongated spermatids. This technique enabled us to determine the background level of DSB foci in elongated spermatids of RAD54/RAD54B double knockout (dko) mice, severe combined immunodeficiency SCID mice, and poly adenosine diphosphate (ADP)-ribose polymerase 1 (PARP1) inhibitor (DPQ)-treated mice to compare them with the appropriate wild type controls. The repair kinetics data and the protein expression patterns observed indicate that the conventional NHEJ repair pathway is not available for elongated spermatids to repair the programmed and the IR-induced DSBs, reflecting the limited repair capacity of these cells. However, although elongated spermatids express the proteins of the alternative NHEJ, PARP1-inhibition had no effect on the repair kinetics after IR, suggesting that DNA damage may be passed onto sperm. Finally, our genetic mutant analysis suggests that an incomplete or defective meiotic recombinational repair of Spo11-induced DSBs may lead to a carry-over of the DSB damage or induce a delayed nuclear fragmentation during the sensitive programmed chromatin remodeling occurring in elongated spermatids.
authors.affiliation: Laboratory of Immunology and Molecular Physiology, Department of Zoology, Faculty of Science, Assiut University, Assiut 71516, Egypt. emad.ahmed@science.au.edu.eg.|Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK. emad.ahmed@science.au.edu.eg.
authors.forename: Emad A
authors.initials: EA
authors.lastname: Ahmed
authors.affiliation: Institute für Radiobiologie der Bundeswehr in Verb. mit der University, Ulm, Neuherbergstr, 11, Munich D-80937, Germany. scherth@web.de.
authors.forename: Harry
authors.initials: H
authors.lastname: Scherthan
authors.affiliation: Reproductive Biology Group, Division of Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584CM, The Netherlands. D.G.deRooij@uu.nl.
authors.forename: Dirk G
authors.initials: DG
authors.lastname: de Rooij
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D007700:Kinetics; D000072200:Ku Autoantigen; D008297:Male; D008540:Meiosis / Q000528:radiation effects; D018345:Mice, Knockout; D016513:Mice, SCID; D010766:Phosphorylation / Q000528:radiation effects; D011839:Radiation, Ionizing; D011995:Recombination, Genetic / Q000528:radiation effects; D013087:Spermatids / Q000378:metabolism* / Q000528:radiation effects; D013090:Spermatocytes / Q000378:metabolism / Q000528:radiation effects; D000071857:Tumor Suppressor p53-Binding Protein 1
chemical_list: D034961:Antigens, Nuclear; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D006657:Histones; C498302:Trp53bp1 protein, mouse; D000071857:Tumor Suppressor p53-Binding Protein 1; C475961:gamma-H2AX protein, mouse; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen
keywords: DNA repair; NHEJ; PARP1-inhibited mice; Rad54/Rad54B deficient mice; SCID mice; elongated spermatids