title: Impaired meiotic DNA-damage repair and lack of crossing-over during spermatogenesis in BRCA1 full-length isoform deficient mice.
abstract: Breast tumor suppressor gene 1 (BRCA1) plays an essential role in maintaining genomic integrity. Here we show that mouse Brca1 is required for DNA-damage repair and crossing-over during spermatogenesis. Male Brca1(Delta11/Delta11)p53(+/-) mice that carried a homozygous deletion of Brca1 exon 11 and a p53 heterozygous mutation had significantly reduced testicular size and no spermatozoa in their seminiferous tubules. During spermatogenesis, homologous chromosomes from the mutant mice synapsed and advanced to the pachytene stage but failed to progress to the diplotene stage. Our analyses revealed that the Brca1 mutation affected cellular localization of several DNA damage-repair proteins. This included prolonged association of gammaH2AX with sites of DNA damage, reduced sex body formation, diminished Rad51 foci and absence of Mlh1 foci in the pachytene stage. Consequently, chromosomes from mutant mice did not form chiasmata, a point that connects exchanging homologous chromosomes. Brca1-mutant spermatocytes also exhibited decreased RNA expression levels of several genes that are involved in DNA-damage repair, including RuvB-like DNA helicase, XPB, p62 and TFIID. Of note, the premature termination of spermatogenesis at the pachytene stage was accompanied by increased apoptosis by both p53-dependent and p53-independent mechanisms. Thus, our study revealed an essential role of Brca1 in DNA-damage repair and crossing-over of homologous chromosomes during spermatogenesis.
authors.affiliation: Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA. xiaolingx@intra.niddk.nih.gov
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Xu
authors.forename: Olga
authors.initials: O
authors.lastname: Aprelikova
authors.forename: Peter
authors.initials: P
authors.lastname: Moens
authors.forename: Chu-Xia
authors.initials: CX
authors.lastname: Deng
authors.forename: Priscilla A
authors.initials: PA
authors.lastname: Furth
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D002875:Chromosomes / Q000378:metabolism; D003434:Crossing Over, Genetic; D004249:DNA Damage / Q000502:physiology; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D008297:Male; D008540:Meiosis / Q000502:physiology*; D051379:Mice; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051135:Rad51 Recombinase; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019313:BRCA1 Protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501485:Mlh1 protein, mouse; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D020033:Protein Isoforms; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; D000070957:MutL Protein Homolog 1