Homologous recombination conserves DNA sequence integrity throughout the cell cycle in embryonic stem cells.
The maintenance of genomic integrity is crucial to embryonic stem cells (ESC) considering the potential for propagating undesirable mutations to the resulting somatic and germ cell lineages. Indeed, mouse ESC (mESC) exhibit a significantly lower mutation frequency compared to differentiated cells. This could be due to more effective elimination of genetically damaged cells via apoptosis, or especially robust, sequence-conserving DNA damage repair mechanisms such as homologous recombination (HR). We used fluorescence microscopy and 3-dimensional image analysis to compare mESC and differentiated cells, with regard to HR-mediated repair of spontaneous and X-ray-induced double-strand breaks (DSBs). Microscopic analysis of repair foci, flow cytometry, and functional assays of the major DSB repair pathways indicate that HR is greater in mESC compared to fibroblasts. Strikingly, HR appears to be the predominant pathway choice to repair induced or spontaneous DNA damage throughout the ESC cycle in contrast to fibroblasts, where it is restricted to replicated chromatin. This suggests that alternative templates, such as homologous chromosomes, are more frequently used to repair DSB in ESC. Relatively frequent HR utilizing homolog chromosome sequences preserves genome integrity in ESC and has distinctive and important genetic consequences to subsequent somatic and germ cell lineages.
Serrano
Lourdes
L
Department of Genetics, Human Genetics Institute, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8082, USA.
Liang
Li
L
Chang
Yiming
Y
Deng
Li
L
Maulion
Christopher
C
Nguyen
Son
S
Tischfield
Jay A
JA
D000818:Animals; D002453:Cell Cycle / Q000235:genetics*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair; D003857:Deoxyuridine / Q000031:analogs & derivatives / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D051379:Mice; D051135:Rad51 Recombinase / Q000378:metabolism; D011995:Recombination, Genetic
D006657:Histones; C475961:gamma-H2AX protein, mouse; D004247:DNA; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; C031086:5-ethynyl-2'-deoxyuridine; D003857:Deoxyuridine