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MIT researchers silence genes with new approach

CAMBRIDGE, Mass.--MIT researchers have developed a way to exploit RNA interference for the first time to silence genes in a wide variety of mammalian cells, including embryonic cells. The study will appear in the Feb. 17 edition of Nature Genetics.

This new approach allows genes to be switched off by inserting short pieces of ribonucleic acid (RNA) into developing cells. It is currently being used to help researchers uncover the function of the more than 30,000 genes found in humans, as well as in animal models of important diseases.

This technology may be used to shut down disease-causing genes such as those involved in cancer, high cholesterol or autoimmune disease; to create easily transplantable organs and tissues; or to convey immunity to viruses such as HIV.

"Imagine finding a gene that is used by a bioterrorism agent," said Luk Van Parijs, assistant professor of biology at MIT's Center for Cancer Research (CCR) and senior author of the study, "and then modifying the cells of the body to no longer express that gene. It's like being vaccinated: the agent can no longer harm the body."

RNA interference is a potentially powerful tool, but important cell types have been resistant to the introduction of short interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs) required to trigger this process.

Van Parijs and colleagues created a system based on a disarmed lentivirus--a retrovirus that can introduce genetic material into almost every cell or tissue, including stem cells and neurons--and have used this virus to successfully deliver shRNAs into mammalian cells and even induce RNA interference (RNAi) in transgenic animals.

Advances in technologies to identify and sequence genes have pointed scientists to sections of the genome that look like they are critical for mammalian tissue function and the development of disease. But current approaches to pinpoint the function of these genes, such as creating knockout mice, are time-consuming and expensive and can't be performed in human tissues and cells.

Using lentiviruses to silence genes will allow researchers to systematically test how they function in virtually all cells of the body and create animal models that will allow them to quickly and efficiently determine which genes are important to the function of different tissues and organs and which might be effective therapeutic targets in diseases.

Using this new technology, the MIT researchers have created transgenic mice in which important immune genes or cancer genes, such as p53, have been silenced. These mice are now being studied to understand more about how these genes contribute to autoimmune disease and cancer.

"We show that lentivirus-delivered shRNAs are capable of specific, highly stable and functional silencing of gene expression in a variety of cell types and also in transgenic mice," said MIT biology graduate student Douglas A. Rubinson, lead author of the study. "This method "should permit rapid and efficient analysis of gene function in primary human and animal cells and tissues and generation of animals that show reduced expression of specific genes. They may also provide new approaches for gene therapy."

In addition to Van Parijs and Rubinson, authors include MIT biology graduate students Christopher P. Dillon and Adam V. Kwiatkowski; Michael McManus, CCR postdoctoral fellow; Frank Gertler, associate professor of biology; visiting researcher Claudia Sievers; Lili Yang of the California Institute of Technology; and Johnny Kopinja and Martin L. Scott of Biogen Inc.

This work is funded by the David Koch Cancer Research Fund, the Arthritis Foundation, the Juvenile Diabetes Foundation and the National Institutes of Health.

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