Molecular genetics: Unmasking polyglutamine triggers in neurodegenerative disease

Two decades ago, molecular genetic analysis provided a new approach for def ining the roots of inherited disorders. This strategy has proved particular ly powerful because, with only a description of the inheritance pattern, it can uncover previously unsuspected mechanisms of pathogenesis that are not implicated by known biological pathways or by the disease manifestations. Nowhere has the impact of molecular genetics been more evident than in the dominantly inherited neurodegenerative disorders, where eight unrelated dis eases have been revealed to possess the same type of mutation - an expanded polyglutamine encoding sequence - affecting different genes.