Combining dynamin 2 myopathy and neuropathy mutations rescues both phenotypes

Area of Science:

• Genetics
• Molecular Biology
• Neurology

Background:

• Dominant mutations in the dynamin 2 (DNM2) gene cause distinct neuromuscular disorders: centronuclear myopathy (CNM) and Charcot-Marie-Tooth neuropathy (CMT).
• CNM involves myofiber structural anomalies, while CMT affects peripheral nerves, both leading to muscle weakness and atrophy.
• The underlying mechanisms and therapeutic strategies for these DNM2-related diseases remain largely unknown.

Purpose of the Study:

• To investigate the opposing in vitro effects of DNM2 mutations associated with CNM (gain-of-function) and CMT (loss-of-function).
• To explore the in vivo compensatory effects of combining CNM and CMT mutations in a Dnm2 mouse model.
• To assess the potential of inverse modulation of DNM2 activity as a therapeutic strategy for CNM and CMT.

Main Methods:

• In vitro assays to characterize the functional impact of specific DNM2 mutations.
• Generation of a compound heterozygous Dnm2 mouse model (Dnm2^S619L/K562E) by intercrossing CNM (Dnm2^S619L/+) and CMT (Dnm2^K562E/+) mouse lines.
• Phenotypic analysis of Dnm2^S619L/K562E mice, including motor coordination, muscle strength, muscle structure, and nerve fiber organization.

Main Results:

• In vitro assays confirmed opposing functional effects of CNM and CMT DNM2 mutations.
• Dnm2^S619L/K562E mice exhibited significantly improved motor coordination, muscle strength, and mass compared to single-mutant littermates.
• Histological analysis revealed normalized muscle structure and nerve fiber organization in compound heterozygous mice.

Conclusions:

• Two distinct disease-causing DNM2 mutations can compensate for each other in vivo, correcting major disease phenotypes.
• The inverse modulation of DNM2 activity presents a promising therapeutic avenue for both centronuclear myopathy and Charcot-Marie-Tooth neuropathy.
• This study highlights the potential for cross-disease therapeutic strategies targeting shared genetic pathways.