Base editing is a precise gene-editing technique that changes a single DNA letter (like turning an A into a G) without cutting both strands of the DNA helix (which is how traditional CRISPR works). The December 2023 study used whole-brain in vivo base editing, delivering the base editor throughout the brain of Mef2c-mutant mice, which then corrected the mutation in brain cells and reversed behavioral abnormalities.
Why this is significant: It demonstrates that MCHS-related behavioral symptoms can be reversed even after the brain has already developed abnormally. This suggests there's a therapeutic window — you don't have to catch MCHS at birth to fix it later. Traditional CRISPR "cuts" the DNA (which risks errors), while base editing "rewrites" a single letter (much more precise and safer).