Every year dozens of children born with Down syndrome. The Briton John Langdon Haydon Down was the first to describe the syndrome in detail in 1866. The typical almond-shaped, slanted eyes, he came up with the term of mongoloid idiocy. We also called the Down syndrome, trisomy-21. The latter term refers to the reason of the syndrome: a third copy of chromosome 21. Down syndrome is caused by a process through which the body creates proteins overdose for that chromosome. Proteins disturb the development of the patient and cause soon mental retardation. Moreover, often deformities for the heart, bones and intestines, and increases the risk of childhood leukemia and, from the age of fifty, Alzheimer.
French pediatrician Jérôme Lejeune discovered the excessive chromosomes in Down patients more than half a century ago. However, to turn that insight into a therapeutic approach i proved extremely difficult. There are at least five hundred genes on the chromosome. Together they account for hundreds of proteins that interact in endless ways to train or compete. Developments recently, don’t provide an option for that extra chromosome fishing one by one among all cells. But what then? Development Biologist Jeanne Lawrence and her colleague Lisa Hall from the University of Massachusetts thought that it had to be short wings activity whenever happens a possible excess chromosome. Our body reveals that fact already at the level of the sex chromosomes. Women have two X chromosome, males have one X and one Y chromosome
When our body feels that it should construct particular protein, the gene responsible for the construction sometimes produces the more of that protein than needed. This would therefore lead to a doubling in women. Fortunately there is a solution: one of the X chromosomes activates its XIST gene (“X-inactive specific transcript) which makes it difficult to overwrite on genes, as it is a RNA molecul. This continues until the whole chromosome painted with RNA . Lawrence Hall wanted to make it the excess chromosome 21 with such XIST gene saddle in a harmless way but that was easier to say than do, because the gene consists of a long chain of DNA . Such a string has been never smuggled earlier in the genetic material of a living cell. The researchers prepared stem cells from connective tissue cells of a man with Down’s syndrome, and then succeeded in those cells with the one of the chromosome 21 XIST.
Mission accomplished but the question still remains whether the gene is working on other chromosomes. That was indeed the case: the genes on the chromosome excess were nipped in the bud. This left the unusual cell division and abnormal development of stem cell to nerve cell, typically in patients down, omitted. The findings of the experiment are described in the journal Nature . What does that mean for people with Down syndrome? A therapeutic application which engages directly on the chromosomes is not for tomorrow. But research into the mechanisms underlying the deviation will be a strong boost. While earlier confusion created by the individual differences between cells from donors with and without Down, scientists can now create the exact same genetic cells and excess chromosome on or off. The consequences provide crucial clues about the control of embryonic development. The team will now advance to the method testing on mice with Down syndrome.