Faulty stem cell regulation may contribute to cognitive deficits associated with Down syndrome

Sep. 11, 2013 — Michael Clarke and his colleagues were the first to discover that Down syndrome may be linked to faulty stem cell regulation.The learning and physical disabilities that affect people with Down syndrome may be due at least in part to defective stem cell regulation throughout the body, according to researchers at the Stanford University School of Medicine. The defects in stem cell growth and self-renewal observed by the researchers can be alleviated by reducing the expression of just one gene on chromosome 21, they found.The finding marks the first time Down syndrome has been linked to stem cells, and addresses some long-standing mysteries about the disorder. Although the gene, called Usp16, is unlikely to be the only contributor to the disease, the finding raises the possibility of an eventual therapy based on reducing its expression.”There appear to be defects in the stem cells in all the tissues that we tested, including the brain,” said Michael Clarke, MD, Stanford’s Karel H. and Avice N. Beekhuis Professor in Cancer Biology. The researchers conducted their studies in both mouse and human cells. “We believe Usp16 overexpression is a major contributor to the neurological deficits seen in Down syndrome.”Clarke is the senior author of the research, published Sept. 11 in Nature. Postdoctoral scholar Maddalena Adorno, PhD, is the lead author.”Conceptually, this study suggests that drug-based strategies to slow the rate of stem cell use could have profound effects on cognitive function, aging and risk for Alzheimer’s disease in people with Down syndrome,” said co-author Craig Garner, PhD, who is the co-director of Stanford’s Center for Research and Treatment of Down Syndrome and a professor of psychiatry and behavioral sciencesDown syndrome, which is caused by an extra copy of chromosome 21, affects about 400,000 people in the United States and 6 million worldwide. …

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Exercise rescues mutated neural stem cells

July 5, 2013 — CHARGE syndrome* is a severe developmental disorder affecting multiple organs. It affects 1 in 8500 newborns worldwide. The majority of patients carry a mutation in a gene called CHD7. How this single mutation leads to the broad spectrum of characteristic CHARGE symptoms has been a mystery.CHD7 encodes a so-called chromatin remodeler, an important class of epigenetic regulators. DNA is wound around bead-like nucleosomes consisting of histone proteins. The string of beads is then twisted into a structure called chromatin. The more nucleosomes that occupy a gene, the less active it is. Chromatin remodelers like CHD7 are essential for the regulation of gene activity because they create nucleosome-free regions in the regulatory sequences of genes. Thus, a mutation in a gene coding for a chromatin remodeler may lead to a wide pattern of misregulated genes.Dr. Haikun Liu’s lab at the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) is interested in the regulation of adult neural stem cells. …

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Genetics of dyslexia and language impairment unraveled

June 13, 2013 — A new study of the genetic origins of dyslexia and other learning disabilities could allow for earlier diagnoses and more successful interventions, according to researchers at Yale School of Medicine. Many students now are not diagnosed until high school, at which point treatments are less effective.The study is published online and in the July print issue of the American Journal of Human Genetics. Senior author Dr. Jeffrey R. Gruen, professor of pediatrics, genetics, and investigative medicine at Yale, and colleagues analyzed data from more than 10,000 children born in 1991-1992 who were part of the Avon Longitudinal Study of Parents and Children (ALSPAC) conducted by investigators at the University of Bristol in the United Kingdom.Gruen and his team used the ALSPAC data to unravel the genetic components of reading and verbal language. In the process, they identified genetic variants that can predispose children to dyslexia and language impairment, increasing the likelihood of earlier diagnosis and more effective interventions.Dyslexia and language impairment are common learning disabilities that make reading and verbal language skills difficult. Both disorders have a substantial genetic component, but despite years of study, determining the root cause had been difficult.In previous studies, Gruen and his team found that dopamine-related genes ANKK1 and DRD2 are involved in language processing. In further non-genetic studies, they found that prenatal exposure to nicotine has a strong negative affect on both reading and language processing. They had also previously found that a gene called DCDC2 was linked to dyslexia.In this new study, Gruen and colleagues looked deeper within the DCDC2 gene to pinpoint the specific parts of the gene that are responsible for dyslexia and language impairment. They found that some variants of a gene regulator called READ1 (regulatory element associated with dyslexia1) within the DCDC2 gene are associated with problems in reading performance while other variants are strongly associated with problems in verbal language performance.Gruen said these variants interact with a second dyslexia risk gene called KIAA0319. …

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