Early experiments conducted by researchers with a modified version of the gene-editing tool known as CRISPR suggest that it may be able to “knock out” the extra chromosome that causes Down syndrome.
People with Down syndrome are born with an extra copy of chromosome 21, making their number of chromosomes 47 instead of the normal number of 46.
According to Reuters, Dr. Volney Shin, who led the study from Beth Israel Deaconess Medical Center in Boston, said, “Because of this additional copy, a number of genes are disrupted, and this contributes to cognitive disability and early Alzheimer’s disease” associated with this condition.
Shen added that since it is not clear which of the hundreds of genes on the extra chromosome are responsible for these effects, inactivating the entire chromosome would be the ideal treatment.
In biologically healthy females, a gene called xist silences or inactivates the extra X chromosome, which is found in all female cells except eggs.
Laboratory test flight
Scientists had previously assumed that inserting EXIST into the extra chromosome 21 would disable it in a similar way, but technical limitations led to their attempts to insert the gene often failing.
Shen pointed out that among the challenges they faced was that “EXIST” must be inserted into only one of the three copies of chromosome 21 in the cell, and that this should happen in the largest possible number of cells.
According to a report published in the journal Proceedings of the National Academy of Sciences, the modified version of CRISPR developed by the team enhanced the integration of the EXIST gene into the extra chromosome by about 30-fold compared to the traditional CRISPR approach.
Although this technology is still in the laboratory testing stage, researchers hope that it will lead to treatments in the future.
Dr. Ryotaro Hashizumi, from Mie University Hospital in Japan, who was not involved in the research, said that although the chromosome inactivation strategy is “very promising” for Down syndrome, and enhancing the efficiency of inserting the Xist gene is “very important in general,” the new results only represent a proof of this concept at the cell level.