What genetic mutation is characteristic of Myotonic Dystrophy Type 2?

Myotonic Dystrophy Type 2 is primarily associated with a specific genetic mutation characterized by the expansion of a CCTG repeat in the ZNF9 gene. This mutation leads to the symptoms associated with this form of muscular dystrophy, which include muscle stiffness (myotonia), weakness, and other systemic manifestations.

The CCTG repeat expansion causes abnormal RNA processing and contributes to the pathophysiology of the disease through a gain-of-function mechanism, where the mutant RNA interferes with normal cellular processes. This understanding of the genetic basis of Myotonic Dystrophy Type 2 is crucial, as it aids in diagnosis and potential therapeutic approaches.

Other choices include mutations linked to different conditions: the CTG repeat is associated with Myotonic Dystrophy Type 1, the GAA repeat pertains to Friedreich's ataxia, and the ATG repeat is not commonly associated with a known muscular dystrophy condition. Therefore, the distinct identification of the CCTG repeat on ZNF9 is what firmly aligns with Myotonic Dystrophy Type 2.