Japanese scientists have made a historic breakthrough: successfully removing the extra chromosome that causes Down syndrome using CRISPR gene editing technology, effectively restoring normal cellular function.

For the first time, researchers led by Dr. Ryotaro Hashizume at Mie University have eliminated the underlying cause of Down syndrome at the cellular level. Their method precisely targets and removes only the third copy of chromosome 21, leaving the two normal copies intact.

Down syndrome, which affects approximately 1 in every 700 births worldwide, occurs due to trisomy 21—when cells have an additional copy of chromosome 21. This extra genetic material disrupts development, causing intellectual disabilities, distinctive facial features, and an increased risk of health issues such as heart defects and early-onset Alzheimer’s disease.

The team used a technique called "specific allele editing," which programs CRISPR-Cas9 to recognize and cut only the unique sequences of the extra chromosome. Once cut, the unstable chromosome is naturally discarded as the cells divide.

In their experiments, the method achieved a success rate of 30.6% in removing the extra chromosome. The treated cells showed restoration in gene expression, protein production, and survival rates, matching those of typical cells. Notably, this was achieved not only in stem cells but also in mature skin cells taken from individuals with Down syndrome.