Characterization of Spo11-dependent and independent phospho-H2AX foci during meiotic prophase I in the male mouse.
Meiotic DNA double strand breaks (DSBs) are indicated at leptotene by the phosphorylated form of histone H2AX (gamma-H2AX). In contrast to previous studies, we identified on both zygotene and pachytene chromosomes two distinct types of gamma-H2AX foci: multiple small (S) foci located along autosomal synaptonemal complexes (SCs) and larger signals on chromatin loops (L-foci). The S-foci number gradually declined throughout pachytene, in parallel with the repair of DSBs monitored by repair proteins suggesting that S-foci mark DSB repair events. We validated this interpretation by showing the absence of S-foci in Spo11(-/-) spermatocytes. By contrast, the L-foci number was very low through pachytene. Based on the analysis of gamma-H2AX labeling after irradiation of spermatocytes, the formation of DSBs clearly induced L-foci formation. Upon DSB repair, these foci appear to be processed and lead to the above mentioned S-foci. The presence of L-foci in wild-type pachytene and diplotene could therefore reflect delayed or unregulated DSB repair events. Interestingly, their distribution was different in Spo11(+/-) spermatocytes compared with Spo11(+/+) spermatocytes, where DSB repair might be differently regulated as a response to homeostatic control of crossing-over. The presence of these L-foci in Spo11(-/-) spermatocytes raises the interesting possibility of yet uncharacterized alterations in DNA or chromosome structure in Spo11(-/-) cells.
Chicheportiche
Alexandra
A
Laboratory of Differentiation and Radiobiology of the Gonads, Unit of Gametogenesis and Genotoxicity, Unité Mixte de Recherche-S 566, Commissariat à l'Energie Atomique DSV/IRCM/SEGG/LDRG, F-92265 Fontenay aux Roses, France. alexandra.chicheportiche@cea.fr
Bernardino-Sgherri
Jacqueline
J
de Massy
Bernard
B
Dutrillaux
Bernard
B
D000818:Animals; D002478:Cells, Cultured; D002682:Chinchilla; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004260:DNA Repair / Q000235:genetics / Q000528:radiation effects; D004706:Endodeoxyribonucleases; D004950:Esterases / Q000235:genetics / Q000378:metabolism*; D006168:Guinea Pigs; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008540:Meiosis / Q000502:physiology* / Q000528:radiation effects; D049469:Meiotic Prophase I / Q000235:genetics* / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D049471:Pachytene Stage / Q000235:genetics / Q000528:radiation effects; D013090:Spermatocytes / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects; D013737:Testis / Q000166:cytology / Q000378:metabolism*; D000099257:Meiotic Recombination Protein SPO11
D004706:Endodeoxyribonucleases; D004950:Esterases; D006657:Histones; D000099257:Meiotic Recombination Protein SPO11; C475961:gamma-H2AX protein, mouse