title: Essential roles of BCCIP in mouse embryonic development and structural stability of chromosomes.
abstract: BCCIP is a BRCA2- and CDKN1A(p21)-interacting protein that has been implicated in the maintenance of genomic integrity. To understand the in vivo functions of BCCIP, we generated a conditional BCCIP knockdown transgenic mouse model using Cre-LoxP mediated RNA interference. The BCCIP knockdown embryos displayed impaired cellular proliferation and apoptosis at day E7.5. Consistent with these results, the in vitro proliferation of blastocysts and mouse embryonic fibroblasts (MEFs) of BCCIP knockdown mice were impaired considerably. The BCCIP deficient mouse embryos die before E11.5 day. Deletion of the p53 gene could not rescue the embryonic lethality due to BCCIP deficiency, but partially rescues the growth delay of mouse embryonic fibroblasts in vitro. To further understand the cause of development and proliferation defects in BCCIP-deficient mice, MEFs were subjected to chromosome stability analysis. The BCCIP-deficient MEFs displayed significant spontaneous chromosome structural alterations associated with replication stress, including a 3.5-fold induction of chromatid breaks. Remarkably, the BCCIP-deficient MEFs had a ∼20-fold increase in sister chromatid union (SCU), yet the induction of sister chromatid exchanges (SCE) was modestly at 1.5 fold. SCU is a unique type of chromatid aberration that may give rise to chromatin bridges between daughter nuclei in anaphase. In addition, the BCCIP-deficient MEFs have reduced repair of irradiation-induced DNA damage and reductions of Rad51 protein and nuclear foci. Our data suggest a unique function of BCCIP, not only in repair of DNA damage, but also in resolving stalled replication forks and prevention of replication stress. In addition, BCCIP deficiency causes excessive spontaneous chromatin bridges via the formation of SCU, which can subsequently impair chromosome segregations in mitosis and cell division.
authors.affiliation: The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, New Jersey, USA.
authors.forename: Huimei
authors.initials: H
authors.lastname: Lu
authors.forename: Yi-Yuan
authors.initials: YY
authors.lastname: Huang
authors.forename: Sonam
authors.initials: S
authors.lastname: Mehrotra
authors.forename: Roberto
authors.initials: R
authors.lastname: Droz-Rosario
authors.forename: Jingmei
authors.initials: J
authors.lastname: Liu
authors.forename: Mantu
authors.initials: M
authors.lastname: Bhaumik
authors.forename: Eileen
authors.initials: E
authors.lastname: White
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Shen
mesh_terms: D000818:Animals; D024682:BRCA2 Protein / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D043171:Chromosomal Instability / Q000235:genetics*; D020090:Chromosome Segregation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D047108:Embryonic Development / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D012854:Sister Chromatid Exchange
chemical_list: C569563:BCCIP protein, mouse; D024682:BRCA2 Protein; C106711:BRCA2 protein, mouse; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D051135:Rad51 Recombinase