Impaired prenatal motor axon development necessitates early therapeutic intervention in severe SMA.
Sci Transl Med 2021 Jan 27; 13(578):eabb6871
Gene replacement and pre-mRNA splicing modifier therapies represent breakthrough gene targeting treatments for the neuromuscular disease spinal muscular atrophy (SMA), but mechanisms underlying variable efficacy of treatment are incompletely understood. Our examination of severe infantile onset human SMA tissues obtained at expedited autopsy revealed persistence of developmentally immature motor neuron axons, many of which are actively degenerating. We identified similar features in a mouse model of severe SMA, in which impaired radial growth and Schwann cell ensheathment of motor axons began during embryogenesis and resulted in reduced acquisition of myelinated axons that impeded motor axon function neonatally. Axons that failed to ensheath degenerated rapidly postnatally, specifically releasing neurofilament light chain protein into the blood. Genetic restoration of survival motor neuron protein (SMN) expression in mouse motor neurons, but not in Schwann cells or muscle, improved SMA motor axon development and maintenance. Treatment with small-molecule
Kong, Lingling; Valdivia, David O; Simon, Christian M; Hassinan, Cera W; Delestrée, Nicolas; Ramos, Daniel M; Park, Jae Hong; Pilato, Celeste M; Xu, Xixi; Crowder, Melissa; Grzyb, Chloe C; King, Zachary A; Petrillo, Marco; Swoboda, Kathryn J; Davis, Crystal; Lutz, Cathleen; Stephan, Alexander H; Zhao, Xin; Weetall, Marla; Naryshkin, Nikolai A; Crawford, Thomas O; Mentis, George Z; and Sumner, Charlotte J, "Impaired prenatal motor axon development necessitates early therapeutic intervention in severe SMA." (2021). Faculty Research 2021. 35.