eLife Assessment
This study offers important insight into the pathogenic basis of intragenic frameshift deletions in the carboxy-terminal domain of MECP2, which account for some Rett syndrome cases, yet similar variants also appear in unaffected individuals. Using base editing and mouse models, the authors present convincing evidence supporting the pathogenicity of select deletion variants, with potential implications for therapeutic development. However, comments regarding the analysis of publicly available genetic databases should be addressed to strengthen the conclusions and provide greater clarity to the field.