Down+Syndrome+Primary+Research

=Primary Research =

====Primary research has been published in the American Journal of Human Genetics to identify what causes certain phenotypes of Down Syndrome. Yahya-Graison predicted that these phenotypes are due to gene-dosage imbalances. When there is overexpression of genes located on the 21st human chromosome, this results in the different phenotypes present when an individual has Down Syndrome. However, when other trisomies occur on other chromosomes, the same health problems or mental disabilities occur which lead to the conclusion that trisomy 21 is the only trisomy to cause these problems. Through microarray data and PCR confirmation, they determined that 29% of genes on the 21st chromosome are found to be over-expressed in Down Syndrome individuals. A high number of these genes were due to gene-dosage effects as well as individual variable genes. From this information, they could also determine that some of the range of phenotypes is most likely caused by the high number of variable genes that are unique to every individual (Yahya-Graison et. al., 2007). ====

====H. E. Lockstone and his colleagues published an article based on their study of gene expression in the brain of an adult with Down Syndrome in the journal titled //Genomics//. Lockstone investigated what type of gene profile is caused by the trisomy of chromosome 21. He discovered that trisomies most commonly occur on chromosome 21, 13 and 18 that still results in postnatal development. However, trisomy 21 is the only one that allows the individual to live past the first few years of life. The relationship between Down Syndrome and Alzheimer's Disease was also extensively explored through gene profiling. The amyloid precursor protein (APP) is closely linked to the development of Alzheimer's and is also found on chromosome 21. This relationship was suspected to be a main cause of the inevitable development of Alzheimer's in Down Syndrome patients around the age of 40. Amyloid-beta plaques are also a main contributing factor to the advancement of Down Syndrome. Considering that Down Syndrome is caused by the triplication of chromosome 21, one would expect that the genes on chromosome 21 would then be overexpressed due to the increase of that chromosome, thus causing overexpression of the APP protein. This was not found to be the case. They suspected that the problems in lipid transfer, also caused by Down Syndrome, causes a build up in the amyloid-beta plaques which has been deemed a major cause of Alzheimer's. It was also a notable finding that over regulation was found mostly in developmental proteins and genes which is consistent with many of the mental and physical problems that individuals with Down Syndrome face. There were several other genes that were studied in both the adult and fetal brain that explained the Down Syndrome phenotypes, such as the APOE gene, BACE2, and Dlx. Overall, they found that gene overexpression is a main cause for the developmental issues found in individuals with Down Syndrome. The only question left fairly uncertain is what causes the triplication of chromosome 21 in the first place, which may be a topic of further research (Lockstone et. al., 2007). ====



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