Open AccessAlkylpurine–DNA–N-Glycosylase Knockout Mice Show Increased Susceptibility to Induction of Mutations by Methyl Methanesulfonate
Author(s) -
Rhoderick H. Elder,
Jacob G. Jansen,
Robert J. Weeks,
M. A. Willington,
Bryan Deans,
Amanda J. Watson,
K. J. Mynett,
J. A. Bailey,
Donald P. Cooper,
Joseph A Rafferty,
Mel C. Heeran,
Susan Wijnhoven,
A.A. van Zeeland,
Geoffrey P. Margison
Publication year - 1998
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.18.10.5828
Subject(s) - biology , methyl methanesulfonate , microbiology and biotechnology , null allele , in vivo , ethyl methanesulfonate , mutant , knockout mouse , dna glycosylase , dna repair , dna , genetics , gene
Alkylpurine-DNA-N -glycosylase (APNG) null mice have been generated by homologous recombination in embryonic stem cells. The null status of the animals was confirmed at the mRNA level by reverse transcription-PCR and by the inability of cell extracts of tissues from the knockout (ko) animals to release 3-methyladenine (3-meA) or 7-methylguanine (7-meG) from3 H-methylated calf thymus DNA in vitro. Following treatment with DNA-methylating agents, increased persistence of 7-meG was found in liver sections of APNG ko mice in comparison with wild-type (wt) mice, demonstrating an in vivo phenotype for the APNG null animals. Unlike other null mutants of the base excision repair pathway, the APNG ko mice exhibit a very mild phenotype, show no outward abnormalities, are fertile, and have an apparently normal life span. Neither a difference in the number of leukocytes in peripheral blood nor a difference in the number of bone marrow polychromatic erythrocytes was found when ko and wt mice were exposed to methylating or chloroethylating agents. These agents also showed similar growth-inhibitory effects in primary embryonic fibroblasts isolated from ko and wt mice. However, treatment with methyl methanesulfonate resulted in three- to fourfold morehprt mutations in splenic T lymphocytes from APNG ko mice than in those from wt mice. These mutations were predominantly single-base-pair changes; in the ko mice, they consisted primarily of AT→TA and GC→TA transversions, which most likely are caused by 3-meA and 3- or 7-meG, respectively. These results clearly show an important role for APNG in attenuating the mutagenic effects ofN -alkylpurines in vivo.