Title: Muscle-specific Bet1L knockdown induces neuromuscular denervation, motor neuron degeneration, and motor dysfunction in a rat model of familial ALS
Legend: In vivo Bet1L gene silencing by intramuscular small interfering RNA (siRNA) injection in ALS model rats (left). Bet1L siRNA was injected weekly into the hindlimb muscle of pre-symptomatic ALS rats (SOD1G93A transgenic) starting at 75 days of age. The motor function in the siRNA-injected limb was monitored once per week. After 3 weeks (96 days old), rats were sacrificed and processed for neuromuscular junction (NMJ) innervation (right top) in the siRNA-injected muscle and motor neuron survival in the lumbar spinal cord (right bottom).
Citation: Eckardt, A., Marble, C., Fern, B., Moritz, H., Kotula, C., Ke, J., Rebancos, C., Robertson, S., Nishimune, H., & Suzuki, M. (2025). Muscle-specific Bet1L knockdown induces neuromuscular denervation, motor neuron degeneration, and motor dysfunction in a rat model of familial ALS. Frontiers in neuroscience, 19, 1527181. https://doi.org/10.3389/fnins.2025.1527181
Abstract: Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by specific loss of motor neurons in the spinal cord and brain stem. Although ALS has historically been characterized as a motor neuron disease, there is evidence that motor neurons degenerate in a retrograde manner, beginning in the periphery at the neuromuscular junctions (NMJs) and skeletal muscle. We recently reported a vesicle trafficking protein Bet1L (Bet1 Golgi Vesicular Membrane Trafficking Protein Like) as a new molecule possibly linked to NMJ degeneration in ALS. In this study, we tested the hypothesis that Bet1L gene silencing in skeletal muscle could influence NMJ integrity, motor neuron function, and survival in a rat model of familial ALS (SOD1G93A transgenic). Small interfering RNA (siRNA) targeting the Bet1L gene was injected on a weekly basis into the hindlimb muscle of pre-symptomatic ALS and wild-type (WT) rats. After 3 weeks, intramuscular Bet1L siRNA injection significantly increased the number of denervated NMJs in the injected muscle. Bet1L knockdown decreased motor neuron size in the lumbar spinal cord, which innervated the siRNA-injected hindlimb. Impaired motor function was identified in the hindlimbs of Bet1L siRNA-injected rats. Notably, the effects of Bet1L knockdown on NMJ and motor neuron degeneration were more significant in ALS rats when compared to WT rats. Together, Bet1L knockdown induces denervation of NMJs, but also this knockdown accelerates the disease progression in ALS. Our results provide new evidence to support the potential roles of Bet1L as a key molecule in NMJ maintenance and ALS pathogenesis.
Investigator: Masatoshi Suzuki, DVM, PhD
About the Lab: About the Lab: The Suzuki group has demonstrated the therapeutic benefits of ex vivo gene therapy (stem cell-based growth/trophic factor delivery) targeting the skeletal muscle to prevent degeneration of motor neurons and associated neuromuscular junctions during ALS. Although most ALS research has focused on mechanisms of motor neuron cell death, degeneration is also observed in skeletal muscle, particularly at the neuromuscular connection. Glial cell line-derived neurotrophic factor and vascular endothelial growth factor (VEGF) promote survival of motor neurons and their neuromuscular junctions in neuromuscular disorders, such as ALS. Most recently, the lab delivered a combination of GDNF and/or VEGF to muscles using hMSCs; the hMSCs survive and synthesize and release growth factors, which slow disease progression in familial ALS model rats.