Loss of genomic methylation causes p53-dependent apoptosis and epigenetic deregulation


Cytosine methylation of mammalian DNA is essential for the proper epigenetic regulation of gene expression and maintenance of genomic integrity. To define the mechanism through which demethylated cells die, and to establish a paradigm for identifying genes regulated by DNA methylation, we have generated mice with a conditional allele for the maintenance DNA methyltransferase gene Dnmt1. Cre-mediated deletion of Dnmt1 causes demethylation of cultured fibroblasts and a uniform p53-dependent cell death. Mutational inactivation of Trp53 partially rescues the demethylated fibroblasts for up to five population doublings in culture. Oligonucleotide microarray analysis showed that up to 10% of genes are aberrantly expressed in demethylated fibroblasts. Our results demonstrate that loss of Dnmt1 causes cell-type–specific changes in gene expression that impinge on several pathways, including expression of imprinted genes, cell-cycle control, growth factor/receptor signal transduction and mobilization of retroelements.

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Figure 1: Conditional inactivation of mouse Dnmt1 in ES cells.
Figure 2: Conditional inactivation of mouse Dnmt1 in embryonic fibroblasts.
Figure 3: p53-dependent apoptosis and growth arrest of Dnmt1-deficient fibroblasts.
Figure 4: Recombination and DNA methylation status of Dnmt1, Trp53 double-mutant cultures.
Figure 5: Transcriptional profiling of gene expression changes in Dnmt1-mutant fibroblasts.
Figure 6: Gene induction in Dnmt1-mutant fibroblasts.
Figure 7: Cytoplasmic localization of IAP transcripts by RNA–FISH.


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We thank T. Golub for discussion regarding the Affymetrix GeneCHIP array experiments; M. Gaasenbeek, C. Heard, K. McClure and J. Park for training and technical assistance with GeneCHIP scanning; U. Petersson for help with pilot experiments using adenovirus to transduce Cre into the Dnmt12lox cultures; E. Koh and S. Cherry for advice on retroviral infections; B. Sauer for the loxP cassette pBS246; S. O'Gorman for the cre vector pOG231; J. Bogan for pMXpuro and pMXgfp; E. Koh for Phoenix cells; A. Fazeli and R. Weinberg for the p53 mutant mice; and T. Bestor for the IAP probe. L.J.G. was supported by the NIH and Pfizer. Funding for this work was through NIH grants R-35-CA44339 (R.J.) and HD18184 (C.W.), the March of Dimes (C.W.), and grants from Affymetrix Inc., Millenium Pharmaceuticals Inc., and Bristol-Meyers Squibb Company.

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Correspondence to Rudolf Jaenisch.

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Jackson-Grusby, L., Beard, C., Possemato, R. et al. Loss of genomic methylation causes p53-dependent apoptosis and epigenetic deregulation. Nat Genet 27, 31–39 (2001) doi:10.1038/83730

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