Alexander Disease
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What is Alexander disease?Alexander disease is a rare disorder of the nervous system. It is considered one of the leukodystrophies, a group of disorders in which the primary abnormality is the inability to maintain myelin. Myelin is a whitish substance that wraps around certain nerve cells and ensures the rapid transmission of nerve impulses. If myelin is not properly maintained, the transmission of nerve impulses is disrupted. As myelin deteriorates in leukodystrophies such as Alexander disease, nervous system functions are impaired. Most cases of Alexander disease begin before age 2 years (the infantile form). Signs and symptoms of the infantile form typically include an enlarged brain and head (megalencephaly), seizures, stiffness in the arms and/or legs (spasticity), mental retardation, and delayed physical development. Less frequently, onset occurs later in childhood (the juvenile form) or adulthood. Common problems in juvenile and adult forms of Alexander disease include speech abnormalities, swallowing difficulties, and poor coordination (ataxia). Alexander disease is also characterized by abnormal protein deposits known as Rosenthal fibers, which are found in specialized brain cells called astroglial cells. Astroglial cells support and nourish nerve cells in the brain and spinal cord. How common is Alexander disease?The prevalence of Alexander disease is unknown. About 500 cases have been reported since the disorder was first described in 1949. What genes are related to Alexander disease?Mutations in the GFAP gene cause Alexander disease. The GFAP gene provides instructions for making a protein called glial fibrillary acidic protein. Several molecules of this protein bind together to form intermediate filaments. Intermediate filaments are important for the normal activities of astroglial cells. Mutations in the GFAP gene alter the structure of glial fibrillary acidic protein. The altered protein probably disturbs the formation of normal intermediate filaments. As a result, glial fibrillary acidic protein may accumulate as a component of Rosenthal fibers and interfere with the normal activities of astroglial cells. It is not well understood how impaired astroglial cells contribute to the abnormal formation or maintenance of myelin. How do people inherit Alexander disease?Alexander disease is considered an autosomal dominant disorder, which means one copy of the altered gene in each cell is sufficient to cause the disease. Almost all cases result from new mutations in the gene and occur in people with no history of the disorder in their family. In some rare adult cases, a GFAP mutation may be passed to children of an affected parent.
Source: National Institutes of Health
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Scientists at University of California, Department of Molecular target cell biology
2007 APR 24 -- Scientists discuss in "Glial cells more than support cells" new findings in cell biology. "Glial cells are the most abundant cells in the human brain and have long been considered as passive supporting cells for neurons. In contrast to the extensive studies on various neuronal functions in the nervous system, we still have limited knowledge about glial cells," scientists in the United States report. "Recently a number of pioneering studies have provided convincing evidence that glia play active roles in development and function of the central nervous system. This review discusses recent advances in our understanding of the molecular mechanisms underlying glial cell differentiation. We then highlight some of the novel findings about glial function, i.e. the role of glia in synaptogenesis and the intricate relationship between astrocytes and adult neural stem cells," wrote F. He and colleagues, University of California, Department of Molecular. The researchers concluded: "Finally, we summarize the emerging studies that implicate abnormalities in the formation or maintenance of glia leading to severe brain diseases, such as Alexander disease, glioblastoma and multiple sclerosis, and potential therapeutic strategies to tackle these diseases." He and colleagues published their study in The International Journal of Biochemistry & Cell Biology (Glial cells more than support cells?. The International Journal of Biochemistry & Cell Biology, 2007;39(4):661-5). For additional information, contact F. He, David Geffen School of Medicine at University of California, Dept. of Molecular & Medical Pharmacology, Los Angeles USA. The publisher's contact information for the The International Journal of Biochemistry & Cell Biology is: Pergamon-Elsevier Science Ltd., the Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, England. Keywords: United States, Biochemistry, Cell Biology. This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2007, Life Science Weekly via NewsRx.com.
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