Scientists in Japan have achieved a remarkable step in chromosome-level gene editing. 🧬 Researchers at Mie University used CRISPR-Cas9 to target the extra copy of chromosome 21 found in cells with Down syndrome, also known as trisomy 21. Normally, human cells have two copies of chromosome 21. In Down syndrome, there are three. The Japanese research team developed a technique designed to distinguish the extra chromosome from the two copies that should remain, then used CRISPR to make multiple targeted cuts so the extra chromosome could be eliminated. In their experiments, the researchers successfully removed the targeted extra chromosome from laboratory-grown human trisomy 21 cells, including induced pluripotent stem cells and fibroblasts. The reported chromosome-loss efficiency reached up to about 37.5% under certain experimental conditions. The edited cells also showed changes in gene expression and cellular characteristics toward those seen after chromosome correction. 🧬🔬 But ...