Evidence for complete epistasis of null mutations in murine Fanconi anemia genes Fanca and Fancg

• Published in: DNA repair 2011-12, Vol.10 (12), p.1252-1261
• Main Authors: van de Vrugt, Henri J., Koomen, Mireille, Bakker, Sietske, Berns, Mariska A.D., Cheng, Ngan Ching, van der Valk, Martin A., de Vries, Yne, Rooimans, Martin A., Oostra, Anneke B., Hoatlin, Maureen E., te Riele, Hein, Joenje, Hans, Arwert, Fré
• Format: Article
• Language: English
• Subjects: Active Transport, Cell Nucleus - drug effects; Anemias. Hemoglobinopathies; Animals; Bacteriology; Biological and medical sciences; Bone Marrow Cells - cytology; Cell Line; Cell Nucleus - drug effects; Cell Nucleus - metabolism; Chromosome Breakage - drug effects; Crosslink repair; Diseases of red blood cells; Embryo, Mammalian; Epistasis, Genetic - genetics; Fanca; Fancg; Fanconi anemia; Fanconi Anemia - genetics; Fanconi Anemia Complementation Group A Protein - genetics; Fanconi Anemia Complementation Group G Protein - genetics; Female; Fertility - genetics; Fibroblasts - cytology; Fluorobenzenes - pharmacology; Fundamental and applied biological sciences. Psychology; Growth, nutrition, cell differenciation; Hematologic and hematopoietic diseases; Hematologic Tests; Humans; Knockout mice; Male; Medical sciences; Mice; Microbiology; Molecular and cellular biology; Molecular genetics; Mutagenesis. Repair; Mutation - genetics; Ovary - metabolism; Phthalazines - pharmacology; Poly(ADP-ribose) Polymerase Inhibitors; Stem Cells - drug effects; Stem Cells - metabolism; Testis - metabolism
• ISSN: 1568-7864; 1568-7856
• DOI: 10.1016/j.dnarep.2011.09.015

► The phenotype of double mutant a −/−/ g −/− mice is highly similar to the phenotype of Fanca and Fancg knockout mice. ► Cells with combined Fanca/ Fancg null mutations show a comparable hypersensitivity to mitomycin C as Fanca −/− or Fancg −/− cells. ► Null mutations in Fanca and Fancg are epistatic. Fanconi anemia (FA) is a heritable disease characterized by bone marrow failure, congenital abnormalities, and cancer predisposition. The 15 identified FA genes operate in a molecular pathway to preserve genomic integrity. Within this pathway the FA core complex operates as an ubiquitin ligase that activates the complex of FANCD2 and FANCI to coordinate DNA repair. The FA core complex is formed by at least 12 proteins. However, only the FANCL subunit displays ubiquitin ligase activity. FANCA and FANCG are members of the FA core complex for which no other functions have been described than to participate in protein interactions. In this study we generated mice with combined null alleles for Fanca and Fancg to identify extended functions for these genes by characterizing the double mutant mice and cells. Double mutant a −/−/ g −/− mice were born at near Mendelian frequencies without apparent developmental abnormalities. Histological analysis of a −/−/ g −/− mice revealed a Leydig cell hyperplasia and frequent vacuolization of Sertoli cells in testes, while ovaries were depleted from developing follicles and displayed an interstitial cell hyperplasia. These gonadal aberrations were associated with a compromised fertility of a −/−/ g −/− males and females. During the first year of life a −/−/ g −/− did not develop malignancies or bone marrow failure. At the cellular level a −/−/ g −/−, Fanca −/−, and Fancg −/− cells proved equally compromised in DNA crosslink and homology-directed repair. Overall the phenotype of a −/−/ g −/− double knockout mice and cells appeared highly similar to the phenotype of Fanca or Fancg single knockouts. The lack of an augmented phenotype suggest that null mutations in Fanca or Fancg are fully epistatic, making additional important functions outside of the FA core complex highly unlikely.