A role for the GDAP1 gene in the molecular pathogenesis of Charcot-Marie-Tooth disease

In 2002 a series of mutations in the GDAP1 gene were reported in patients suffering from Charcot-Marie-Tooth disease manifesting as early-onset, progressive distal-muscle wasting and weakness. The molecular etiology of Charcot-Marie-Tooth-GDAP1 disease has been elucidated but its pathogenesis remains unclear, especially given the seemingly contradictory function of the GDAP1 protein. Expression of GDAP1 is observed almost exclusively in neuronal cells, however, the GDAP1 protein is present in mitochondria, where it plays a role in fission, a ubiquitous process occurring in all cells. While GDAP1 contains two glutathione S-transferase (GST) domains, its GST activity is in fact very limited. Additionally, despite GDAP1 affecting mitochondria! functionality, and hence being of great importance to cellular function, the GDAPI-associated Charcot-Marie-Tooth disease is mainly characterized by axonal degeneration. Finally, mutations in the GDAP1 gene may be inherited in a recessive or dominant manner. Given the way such varied observations are hard to reconcile with one another, the investigation of GDAP1 is at one and the same time a difficult but also challenging endeavour. The purpose of this review is to summarize the current knowledge on the GDAP1 protein and its function in the cell. A further part is the characterization of GDAP1-associated Charcot-Marie-Tooth disease, its symptoms and course, as well as an outlining of the possible mechanisms underpinning the disorder.