A protein tied to ALS and dementia may have a much bigger role in disease than scientists realized. Researchers found that TDP43 controls a key DNA repair process, but when the protein becomes imbalanced, the repair system can spiral out of control, harming neurons and destabilizing DNA. The team also discovered that high levels of the protein are linked to increased mutation rates in cancer. The discovery places TDP43 at the center of both neurodegeneration and cancer biology.