Modeling sporadic loss of heterozygosity in mice by using mosaic analysis with double markers (MADM)
- †Howard Hughes Medical Institute and Department of Biological Sciences and
- *School of Medicine, Stanford University, Stanford, CA 94305
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Edited by Kathryn V. Anderson, Sloan–Kettering Institute, New York, NY, and approved November 20, 2006 (received for review September 7, 2006)
Abstract
The initiation and progression of many human cancers involve either somatic activation of protooncogenes or inactivation of tumor-suppressor genes (TSGs) in sporadic cells. Although sporadic gain-of-function of protooncogenes has been successfully modeled in mice [e.g., Johnson L, Mercer K, Greenbaum D, Bronson RT, Crowley D, Tuveson DA, Jacks T (2001) Nature 410:1111–1116], generating a similar degree of sparseness of TSG loss-of-function remains a challenge. Here, we use mosaic analysis with double markers (MADM) to achieve TSG inactivation and concurrent labeling in sporadic somatic cells of mice, closely mimicking loss of heterozygosity as occurs in human cancers. As proof of principle, we studied the consequence of sporadic loss of p27kip1, a cyclin-dependent kinase inhibitor. MADM-mediated loss of p27kip1 results in mutant cell expansion markedly greater than that observed in conventional p27kip1 knockouts. Moreover, the direct comparison of WT and mutant cells at single-cell resolution afforded by MADM reveals that p27kip1 regulates organ size in vivo by cell-autonomous control of cell cycle exit timing. These studies establish MADM as a high-resolution method for modeling sporadic loss of heterozygosity in mice, providing insights into TSG function.
Footnotes
- ‡To whom correspondence should be addressed. E-mail: lluo{at}stanford.edu
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Author contributions: M.D.M. and H.Z. contributed equally to this work; M.D.M., L.L., and H.Z. designed research; M.D.M. and H.Z. performed research; M.D.M., L.L., and H.Z. analyzed data; and M.D.M. and H.Z. wrote the paper.
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↵ §Present address: Department of Biology, 1210 University of Oregon, Eugene, OR 97403-1210.
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The authors declare no conflict of interest.
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This article is a PNAS direct submission.
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See Commentary on page 4245.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0606491104/DC1.
- Abbreviations:
- EGL,
- external granular layer;
- IGL,
- internal granular layer;
- LOH,
- loss of heterozygosity;
- MADM,
- mosaic analysis with double markers;
- Pn,
- postnatal day n;
- TSG,
- tumor-suppressor gene.
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Freely available online through the PNAS open access option.
- © 2007 by The National Academy of Sciences of the USA
