BRCA2∆105 (deletion of exons 4-7) splice variant of the Fanconi Anemia (FA) related BRCA2 IVS7+2T>G mutation – effect on bone marrow compartment of BRCA2∆105 knock-in mouse, and cell cycle response to IR induced DNA damage in vitro.

Wednesday, September 24, 2014 — Poster Session IV
10:00 a.m. –12:00 p.m.	FAES Academic Center	NCI	CANCER-22

* FARE Award Winner

Authors

• E. Thirthagiri
• K.D. Klarmann
• J.R. Keller
• S.K. Sharan

Abstract

The BRCA2 IVS7+2T>G mutation exist in homozygous state in FA patients; causes protein truncation, but generates a transcript variant lacking exons 4–7, which encodes an in-frame protein with deletion of 105 amino acids (Δ105). The BRCA2∆105 protein is DNA repair proficient in vitro, but confers reduced viability in mES cells, and downregulated transcript associates with disease progression. We generated Brca2∆105/∆105 and Brca2∆105/null knock-in mice and used humanized BRCA2∆105 mES cells to assess effect of ∆105 on BRCA2 function and FA development. Both Brca2∆105/∆105 and Brca2∆105/null mice are viable, fertile and exhibit no developmental defects. Wt, Δ105/Δ105 and Δ105/null bone marrow mononuclear cells showed no difference in viability, with or without irradiation induced stress. BRCA2∆105 mES clones, however, exhibited abrogation of G2/M arrest in response to irradiation compared to wt, which was partially suppressed by inhibition of PLK1. An increase in fragments, gaps, breaks and dicentric chromosomes was seen in irradiated BRCA2∆105 compared to wt mES cells. We hypothesize that exons 4-7 of the BRCA2 gene is dispensable for viability. However, loss of these exons may lead to abrogated G2/M arrest, possibly through early activation of PLK1, leading to production of genomically unstable clones that may contribute to disease progression.

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