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Biotech / Medical : Stem Cell Research -- Ignore unavailable to you. Want to Upgrade?

To: DewDiligence_on_SI who wrote (151)	9/4/2005 4:29:49 PM
From: tuck	Read Replies (1) \| Respond to of 495

Hopkins and NIH look deep into laboratory stem cell line genomes with GeneChips, and find previously undetected mutations in 8 of 22 lines. >>SANTA CLARA, Calif.--(BUSINESS WIRE)--Sept. 4, 2005--Affymetrix Inc. (Nasdaq:AFFX - News) announced today that a research group led by scientists at Johns Hopkins School of Medicine and the NIH used Affymetrix GeneChip® microarrays to discover that eight of the stem cell lines approved for federally-funded research have mutated, raising concern about the use of the remaining 14 approved cell lines in future research or therapeutic applications. The researchers used two GeneChip microarrays -- the Human the Mapping 100K Set and Mitochondrial Resequencing Array 2.0 -- to scan the stem cell genome at a level of detail never before possible. They found previously undetectable mutations in stem cells that had been grown in the laboratory for dozens of generations. The results of their study are published in today's online issue of Nature Genetics. Senior authors include Aravinda Chakravarti, Ph.D., director of the McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins, and Mahendra Rao, Ph.D. head of the Stem Cell Group at the National Institute on Aging, NIH. Mutations occur all the time as cells grow, but inside the body, mutated cells with harmful effects are often cleared out by the immune system, whereas in the laboratory culture dish -- where there is no immune system -- mutated cells can grow uncontrolled like a cancer. Over time, any cell line grown in the laboratory -- including stem cells -- can develop mutations that are compounded over many generations. The danger is that scientists may think they are studying stem cells identical to those present in the human body, but in reality the laboratory-grown cells have mutated, and any discoveries may not accurately reflect what is happening in people. The cell lines discovered as mutant in this study are part of the limited number of existing human embryonic stem cell lines (hESC) approved by President Bush for federally-funded research in August 2001. At the time, scientists estimated that more than 60 genetically distinct stem cell lines existed, but today only 22 are available for purchase in federally-supported research. To find the embryonic stem cell mutations, the group used three different analysis methods -- two of them microarrays -- to compare the genomes of early generation and late generation cells. The researchers looked at human nuclear DNA for mutations using the Mapping 100K Set; they used the Human Mitochondrial Resequencing Array 2.0 to look for mutations in mitochondrial DNA. By combining two different whole-genome microarray experiments with a complementary technology that focused on a handful of individual genes, the stem cell group was able to explore the genome in many different ways that together proved far more effective than any single approach. << snip Cheers, Tuck