Genetically engineered mice yield clues to 'knocking o...( Deleting two genes in mice responsib...)

Deleting two genes in mice responsible for repairing DNA strands damaged by oxidation leads to several types of tumors, providing additional evidence that such stress contributes to the development of cancer. That's the conclusion of a recent study* in DNA Repair by researchers at the National Institute of Standards and Technology (NIST), Oregon Health and Science University (OHSU) and the New York University School of Medicine (NYUSM).

Although all cells need oxygen to survive, the element also can be stressful to cells and their componentsparticularly DNAas part of "reactive species" in the environment, such as free radicals and peroxides. The damage levied on DNA by these compounds can include lesions, breaks, cross-links and deletionserrors in our normal genetic codes that, if left unchecked, may accelerate the aging process and increase susceptibility to several disease states. In humans, DNA repair genes produce enzymes called DNA glycosylases that excise sections of DNA strands already modified by oxidative stress, and thus protect the genetic material.

One of these repair genes, neil1, was identified and characterized in 2002 by Sankar Mitra and his team at the University of Texas Medical Branch in collaboration with NIST researchers Miral Dizdaroglu and Pawel Jaruga. The gene produces a DNA repair protein, NEIL1 that is nearly identical in humans and mice. Therefore, a mouse serves a perfect model for studying the biological function of the neil1 gene in both species.

To do this, OHSU researchers under R. Stephen Lloyd genetically engineered mice without the neil1 gene (known as neil1 knockout mice). During their first 6-10 months of life, the majority of male mice developed severe obesity, dyslipidemia (abnormal levels of lipids in the blood), fatty liver disease and hyperinsulinemia (excess levels of circulating insulin in the blood). In humans, these disorders are collectively known as metabolic syndrome, a condit
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