KIF5A downregulation in spinal muscular atrophy links axonal regeneration defects with ALS
Tetsuya Akiyama, Yi Zeng, Caiwei Guo, Olivia Gautier, Lauren Koepke, Heankel Lyons, Elana Molotsky, Juliane S. Bombosch, Odilia Sianto, Jay P. Ross, Phuong Hoang, Luke Zhao, Cole Spencer, Charlotte J. Sumner, Michelle Monje, John W. Day, Aaron D. Gitler
Tetsuya Akiyama, Yi Zeng, Caiwei Guo, Olivia Gautier, Lauren Koepke, Heankel Lyons, Elana Molotsky, Juliane S. Bombosch, Odilia Sianto, Jay P. Ross, Phuong Hoang, Luke Zhao, Cole Spencer, Charlotte J. Sumner, Michelle Monje, John W. Day, Aaron D. Gitler
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Research Article Genetics Neuroscience

KIF5A downregulation in spinal muscular atrophy links axonal regeneration defects with ALS

Abstract

Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder caused by mutations in the survival motor neuron 1 (SMN1) gene leading to decreased SMN protein levels and motor neuron dysfunction. SMN-restoring therapies offer clinical benefit, but the downstream molecular consequences of SMN reduction remain incompletely understood. SMN deficiency resulted in downregulation of kinesin heavy chain isoform 5A (KIF5A) in human neurons and in a mouse model of SMA. SMN associated with KIF5A mRNA and contributed to its stability. Reduced SMN levels impaired axon regeneration, which was rescued by KIF5A overexpression. Because KIF5A has also been connected to ALS, these findings provide evidence of a molecular link between SMA and ALS pathophysiology, highlighting KIF5A as an SMN-regulated factor. Our findings suggest that SMN-independent interventions targeting KIF5A could represent a complementary therapeutic approach for SMA and other motor neuron diseases.

Authors

Tetsuya Akiyama, Yi Zeng, Caiwei Guo, Olivia Gautier, Lauren Koepke, Heankel Lyons, Elana Molotsky, Juliane S. Bombosch, Odilia Sianto, Jay P. Ross, Phuong Hoang, Luke Zhao, Cole Spencer, Charlotte J. Sumner, Michelle Monje, John W. Day, Aaron D. Gitler

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Figure 3

KIF5A is downregulated in SMA patient–derived iPSC motor neurons.

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KIF5A is downregulated in SMA patient–derived iPSC motor neurons. (A–C) ...
(A–C) Experimental design and characterization of SMA patient–derived motor neurons. (A) Motor neurons were differentiated from 4 healthy donor and 6 SMA patient iPSC lines using small-molecule protocols (cell line information in Supplemental Table 1). (B) Schematic of the differentiation and treatment timeline. SMN overexpression was induced by lentiviral transduction on day 10 after plating, with samples collected on day 20. For nusinersen treatment, administration started on day 10, and samples were collected on day 30. (C) Representative immunocytochemistry images at day 20 showing βIII-tubulin, HB9, and ISL1/2 staining. Additional images and quantifications are shown in Supplemental Figure 3. Scale bar: 20 μm. (D–F) Restoration of KIF5A expression by SMN overexpression in SMA patient–derived motor neurons. (D) qPCR analysis of SMN and KIF5A mRNA levels in WT and SMA motor neurons transduced with empty vector (+ control) or SMN-expressing lentivirus (+ SMN). (E) Representative Western blots of SMN and KIF5A in WT and SMA-iMNs. (F) Quantification of SMN and KIF5A protein levels normalized to ACTB and expressed relative to WT. Individual data points are shown in Supplemental Figure 4D. (G–I) Effects of nusinersen on SMN and KIF5A expression in SMA patient–derived motor neurons. (G) qPCR analysis of SMN and KIF5A mRNA levels following nusinersen or control ASO treatment, with WT samples included for comparison. (H) Representative Western blots of SMN and KIF5A following nusinersen treatment. (I) Quantification of SMN and KIF5A protein levels normalized to ACTB. Individual data points are shown in Supplemental Figure 4H. All experiments were performed in triplicate with 3 biologically independent experiments.