1. Protein-extending ACTN2 frameshift variants cause variable myopathy phenotypes by protein aggregation.
- Author
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Ranta-Aho J, Felice KJ, Jonson PH, Sarparanta J, Yvorel C, Harzallah I, Touraine R, Pais L, Austin-Tse CA, Ganesh VS, O'Leary MC, Rehm HL, Hehir MK, Subramony S, Wu Q, Udd B, and Savarese M
- Subjects
- Humans, Male, Distal Myopathies genetics, Distal Myopathies pathology, Female, Protein Aggregation, Pathological genetics, Protein Aggregation, Pathological pathology, Animals, Mice, Genetic Association Studies, Adult, Mutation, Missense, Actinin genetics, Frameshift Mutation, Phenotype
- Abstract
Objective: The objective of the study is to characterize the pathomechanisms underlying actininopathies. Distal myopathies are a group of rare, inherited muscular disorders characterized by progressive loss of muscle fibers that begin in the distal parts of arms and legs. Recently, variants in a new disease gene, ACTN2, have been shown to cause distal myopathy. ACTN2, a gene previously only associated with cardiomyopathies, encodes alpha-actinin-2, a protein expressed in both cardiac and skeletal sarcomeres. The primary function of alpha-actinin-2 is to link actin and titin to the sarcomere Z-disk. New ACTN2 variants are continuously discovered; however, the clinical significance of many variants remains unknown. Thus, lack of clear genotype-phenotype correlations in ACTN2-related diseases, actininopathies, persists., Methods: Functional characterization in C2C12 cell model of several ACTN2 variants is conducted, including frameshift and missense variants associated with dominant and recessive actininopathies. We assess the genotype-phenotype correlations of actininopathies using clinical data from several patients carrying these variants., Results: The results show that the missense variants associated with a recessive form of actininopathy do not cause detectable alpha-actinin-2 aggregates in the cell model. Conversely, dominant frameshift variants causing a protein extension do form alpha-actinin-2 aggregates., Interpretation: The results suggest that alpha-actinin-2 aggregation is the disease mechanism underlying some dominant actininopathies, and thus, we recommend that protein-extending frameshift variants in ACTN2 should be classified as pathogenic. However, this mechanism is likely elicited by only a limited number of variants. Alternative functional characterization methods should be explored to further investigate other molecular mechanisms underlying actininopathies., (© 2024 The Author(s). Annals of Clinical and Translational Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association.)
- Published
- 2024
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