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MYO9A deficiency in motor neurons is associated with reduced neuromuscular agrin secretion

Lookup NU author(s): Emily O'Connor, Dr Isabell Cordts, George Cairns, Daniel Cox, Professor Hanns Lochmuller, Dr Andreas Roos

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Congenital myasthenic syndromes (CMS) are a group of rare, inherited disorders characterized by compromised function of the neuromuscular junction, manifesting with fatigable muscle weakness. Mutations in MYO9A were previously identified as causative for CMS but the precise pathomechanism remained to be characterized. On the basis of the role of MYO9A as an actin-based molecular motor and as a negative regulator of RhoA, we hypothesized that loss of MYO9A may affect the neuronal cytoskeleton, leading to impaired intracellular transport. To investigate this, we used MYO9A-depleted NSC-34 cells (mouse motor neuron-derived cells), revealing altered expression of a number of cytoskeletal proteins important for neuron structure and intracellular transport. On the basis of these findings, the effect on protein transport was determined using a vesicular recycling assay which revealed impaired recycling of a neuronal growth factor receptor. In addition, an unbiased approach utilizing proteomic profiling of the secretome revealed a key role for defective intracellular transport affecting proper protein secretion in the pathophysiology of MYO9A-related CMS. This also led to the identification of agrin as being affected by the defective transport. Zebrafish with reduced MYO9A orthologue expression were treated with an artificial agrin compound, ameliorating defects in neurite extension and improving motility. In summary, loss of MYO9A affects the neuronal cytoskeleton and leads to impaired transport of proteins, including agrin, which may provide a new and unexpected treatment option.


Publication metadata

Author(s): O'Connor E, Phan V, Cordts I, Cairns G, Hettwer S, Cox D, Lochm├╝ller H, Roos A

Publication type: Article

Publication status: Published

Journal: Human Molecular Genetics

Year: 2018

Volume: 27

Issue: 8

Pages: 1434-1446

Print publication date: 15/04/2018

Online publication date: 16/02/2018

Acceptance date: 08/02/2018

Date deposited: 08/03/2018

ISSN (print): 0964-6906

ISSN (electronic): 1460-2083

Publisher: Oxford University Press

URL: https://doi.org/10.1093/hmg/ddy054

DOI: 10.1093/hmg/ddy054

PubMed id: 29462312


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