J LI1, E LANCASTER1, A YOUSAF1, T HANANIA2, D CHAN3, J.S. LUNN4, G KIDD4, J SVAREN5, M SCHEIDELER6, S.S SCHERER1.
1Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA; 2PsychoGenics, Tarrytown, NY, USA; 3California Institute of Technology, Pasadena, CA, USA; 4Renovo Neural Inc, Cleveland, OH, USA; 5University of Wisconsin, Madison, WI, USA; 6HumanFirst Therapeutics LLC, Silver Spring, MD, USA
We have generated a rat model of Charcot-Marie-Tooth disease 2A (CMT2A) harboring the p.Arg364Trp Mfn2 mutation, whose human counterpart results in a severe, early-onset axonal neuropathy. The mutation was made using zinc finger nuclease-mediated genome editing in fertilized rat eggs. A large cohort of mutant and WT littermates were characterized behaviorally and found to develop multiple motor deficits that worsened over time. Nerve conductions of the tail (caudal nerve) was performed on a separate cohort of mutant (n=14) and WT littermates (n=13) every 4 weeks from 8 to 48 weeks. Mutant rats showed a progressively decline in the amplitude of the compound action potential after 20 weeks, whereas the amplitude progressively increased in their WT littermates. Separate cohorts of rats were sacrificed at 7, 40, and 48 weeks and analyzed by light microscopy. In mutant rats, there was a reduced density of myelinated axons and active axonal degeneration in distal but not proximal nerves, and in the fasciculus gracilis of the cervical spinal cord at 40 and 48 weeks. These findings were not present in the 7-week-old cohort of mutant rats, or in WT rats at 7 or 40 weeks. A genetically authentic animal model of CMT2A that develops a progressive, length-dependent axonal neuropathy will be a valuable tool for examining the pathogenesis and treatment of CMT2A.