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Science: From Skeeters To Down's Sydrome


Chromosome that causes Down's silenced for first time

In a very clever proof of concept experiment, scientists at the University of Massachusetts Medical School successfully silenced the extra copy of chromosome 21 that causes Down's Sydrome.

Skin cells from male Down's Syndrome patients were isolated and reverse engineered to form inducible human pluripotent stem cells (iPSCs -- artificial stem cells that can form many cell types, tissues and organs). These stem cells had a gene called Xist (X inactive specific transcript) inserted into the extra copy of chromosome 21.

Xist is the gene that is responsible for maintaining accurate gene dossage for genes located on the X chromosome. Recall that females have 2 X chromosomes while males have an X and a Y chromosome. Thus, males have only a single copy of each X-linked gene while females have 2 copies. The Xist gene function is to silence one of the two copies of the X chromosome in females insuring the correct X-linked gene dosage.

The UM scientists inserted the Xist gene into one of the 3 copies of chromosome 21 that cause Down's Syndrome. The Xist gene functioned to silence one of the extra copies of chromosome 21 correcting the genetic defect responsible for Down's Syndrome.

The corrected iPSCs were then instructed by specific growth factors to form neural tissues that were normal in every respect.


Could it be a 'cure'? Breakthrough prompts Down syndrome soul-searching

This is a pretty remarkable development and an example of a very clever research concept that has real world implications for the 7000 Down Syndrome born each year in the US.

The idea is to treat the extra copy of chromosome 21 that is the cause of Down Syndrome as if it were the extra copy of the X chromosome that gets silenced during embryonic development of females.