In the United States, researchers have combined the CRISPR/Cas9 gene-editing scissors with a natural mechanism in order to neutralize the genetic cause of Down syndrome. Within affected cells, scientists have succeeded in deactivating the extra chromosome responsible for the syndrome.
Putting the Extra Chromosome 21 to Sleep
As a reminder, Down syndrome (trisomy 21) is a genetic abnormality characterized by the presence of an extra chromosome 21 (three copies instead of two) in the cells. The condition involves varying intellectual disability from person to person, as well as distinctive facial features and a higher risk of congenital malformations. In the absence of treatment, only regular medical follow-up and early intervention are possible.
As highlighted by a publication in the Proceedings of the National Academy of Sciences (PNAS) on April 13, 2026, the Beth Israel Deaconess Medical Center in Boston (United States) may have uncovered a credible solution to overcome the syndrome. Neurologists demonstrated that it is possible to neutralize the genetic error at the root of the disease.
The study’s authors successfully attempted to tackle the well-known extra chromosome 21 by drawing inspiration from a natural process: in women, the XIST gene naturally silences one of the two X chromosomes. The researchers then conceived using the CRISPR/Cas9 gene-editing scissors to insert the XIST gene onto the third chromosome 21 of the cells affected by the syndrome. According to the results, the chromosome goes to sleep and stops sending disruptive signals to the body.
Chromosome Therapy Becomes a Reality
For the investigators behind these works, the discovery marks a genuine leap forward. Indeed, where previous methods could not achieve a sufficient number of cells, the approach involving the XIST gene and CRISPR/Cas9 offers the possibility of targeting between 20% and 40% of the cells in question. Moreover, the procedure has been calibrated to avoid affecting the other two copies of chromosome 21 and thus to prevent doing more harm than good.
These highly promising results show that chromosome therapy is indeed a reality, which now needs to move beyond the lab. Given that the protocol can be scaled up, neurologists are optimistic. However, the path still seems long before the treatment appears in pharmacies. Nevertheless, researchers do not rule out that, in the long term, it may be possible to conquer other chromosomal diseases—the aneuploidies.
« Our results demonstrate partial transcriptional correction of the dosage of trisomic genes and offer an evolutive and targeted platform for chromosomal therapy in Down syndrome and other aneuploïdies. », the study states.
Ongoing Research Continues
The next step for the scientists involves tests in rodents, with the aim of identifying the optimal moment to intervene and determining whether it might be possible to act during pregnancy (in utero). The challenge will also be to understand whether complete or partial silencing of the extra chromosome could lead to improvements in patients’ cognitive abilities, as well as their overall health. It is worth noting that some parallel studies suggest that a small portion of the XIST gene could suffice, implying easier transport to brain cells.
Meanwhile, parent associations and families are finding renewed hope and are glad to see that the disease is not forgotten by science. As a reminder, globally, about eight million people carry the syndrome, and their typical life expectancy in developed countries generally falls between 50 and 60 years.
