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Lehtokari VL, Sagath L, Davis M, Ho D, Kiiski K, Kettunen K, Demczko M, Stein R, Vatta M, Winder TL, Shohet A, Orenstein N, Krcho P, Bohuš P, Huovinen S, Udd B, Pelin K, Laing NG, Wallgren-Pettersson C. A recurrent ACTA1 amino acid change in mosaic form causes milder asymmetric myopathy. Neuromuscul Disord 2024; 34:32-40. [PMID: 38142473 DOI: 10.1016/j.nmd.2023.11.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 10/25/2023] [Accepted: 11/26/2023] [Indexed: 12/26/2023]
Abstract
We describe three patients with asymmetric congenital myopathy without definite nemaline bodies and one patient with severe nemaline myopathy. In all four patients, the phenotype had been caused by pathogenic missense variants in ACTA1 leading to the same amino acid change, p.(Gly247Arg). The three patients with milder myopathy were mosaic for their variants. In contrast, in the severely affected patient, the missense variant was present in a de novo, constitutional form. The grade of mosaicism in the three mosaic patients ranged between 20 % and 40 %. We speculate that the milder clinical and histological manifestations of the same ACTA1 variant in the patients with mosaicism reflect the lower abundance of mutant actin in their muscle tissue. Similarly, the asymmetry of body growth and muscle weakness may be a consequence of the affected cells being unevenly distributed. The partial improvement in muscle strength with age in patients with mosaicism might be due to an increased proportion over time of nuclei carrying and expressing two normal alleles.
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Affiliation(s)
- Vilma-Lotta Lehtokari
- Folkhälsan Research Center, 00290 Helsinki, Finland; Department of Medical and Clinical Genetics, Medicum, 00014 University of Helsinki, Finland.
| | - Lydia Sagath
- Folkhälsan Research Center, 00290 Helsinki, Finland; Department of Medical and Clinical Genetics, Medicum, 00014 University of Helsinki, Finland
| | - Mark Davis
- Department of Diagnostic Genomics, PathWest Laboratory Medicine WA, Nedlands WA 6009, SA
| | - Desiree Ho
- Department of Diagnostic Genomics, PathWest Laboratory Medicine WA, Nedlands WA 6009, SA
| | - Kirsi Kiiski
- Folkhälsan Research Center, 00290 Helsinki, Finland; Laboratory of Genetics, Division of Genetics and Clinical Pharmacology, HUS Diagnostic Center, 00029 Helsinki University Hospital and 00014 University of Helsinki, Helsinki, Finland
| | - Kaisa Kettunen
- Laboratory of Genetics, Division of Genetics and Clinical Pharmacology, HUS Diagnostic Center, 00029 Helsinki University Hospital and 00014 University of Helsinki, Helsinki, Finland
| | - Matthew Demczko
- Division of Diagnostic Referral Services, Nemours Children's Hospital, Wilmington, DE 19803, United States
| | - Riki Stein
- Genetics Unit, Schneider Children's Medical Center, Petach Tikva 4920235, Israel
| | - Matteo Vatta
- Invitae Corporation, San Francisco, CA 94103, United States
| | | | - Adi Shohet
- Genetics Unit, Schneider Children's Medical Center, Petach Tikva 4920235, Israel
| | - Naama Orenstein
- Genetics Unit, Schneider Children's Medical Center, Petach Tikva 4920235, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Peter Krcho
- Department of Neonatology, Pavol Jozef Safarik University, 041 80 Košice, Slovakia
| | - Peter Bohuš
- Department of Pathology, L. Pasteur University Hospital, 040 11 Košice, Slovakia
| | - Sanna Huovinen
- Department of Pathology, Fimlab Laboratories, Tampere University Hospital, 33101 Tampere, Finland
| | - Bjarne Udd
- Folkhälsan Research Center, 00290 Helsinki, Finland; Neuromuscular Research Center, Department of Neurology, Tampere University and University Hospital, 33520 Tampere, Finland; Department of Neurology, Vaasa Central Hospital, 65130 Vaasa, Finland
| | - Katarina Pelin
- Folkhälsan Research Center, 00290 Helsinki, Finland; Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, 00014 University of Helsinki, Finland
| | - Nigel G Laing
- Department of Diagnostic Genomics, PathWest Laboratory Medicine WA, Nedlands WA 6009, SA; Harry Perkins Institute of Medical Research, and University of Western Australia Centre for Medical Research, Nedlands Western Australia 6009, Australia
| | - Carina Wallgren-Pettersson
- Folkhälsan Research Center, 00290 Helsinki, Finland; Department of Medical and Clinical Genetics, Medicum, 00014 University of Helsinki, Finland
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