Severe ACTA1-related nemaline myopathy: intranuclear rods, cytoplasmic bodies, and enlarged perinuclear space as characteristic pathological features on muscle biopsies

Clémence Labasse, Guy Brochier, Ana Lia Taratuto, Bruno Cadot, John Rendu, Soledad Monges, Valérie Biancalana, Susana Quijano-Roy, Mai Thao Bui, Anaïs Chanut, Angéline Madelaine, Emmanuelle Lacène, Maud Beuvin, Helge Amthor, Laurent Servais, Yvan de Feraudy, Marcela Erro, Maria Saccoliti, Osorio Abath Neto, Julien FauréBéatrice Lannes, Vincent Laugel, Sandra Coppens, Fabiana Lubieniecki, Ana Buj Bello, Nigel Laing, Teresinha Evangelista, Jocelyn Laporte, Johann Böhm, Norma B. Romero

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Nemaline myopathy (NM) is a muscle disorder with broad clinical and genetic heterogeneity. The clinical presentation of affected individuals ranges from severe perinatal muscle weakness to milder childhood-onset forms, and the disease course and prognosis depends on the gene and mutation type. To date, 14 causative genes have been identified, and ACTA1 accounts for more than half of the severe NM cases. ACTA1 encodes α-actin, one of the principal components of the contractile units in skeletal muscle. We established a homogenous cohort of ten unreported families with severe NM, and we provide clinical, genetic, histological, and ultrastructural data. The patients manifested antenatal or neonatal muscle weakness requiring permanent respiratory assistance, and most deceased within the first months of life. DNA sequencing identified known or novel ACTA1 mutations in all. Morphological analyses of the muscle biopsy specimens showed characteristic features of NM histopathology including cytoplasmic and intranuclear rods, cytoplasmic bodies, and major myofibrillar disorganization. We also detected structural anomalies of the perinuclear space, emphasizing a physiological contribution of skeletal muscle α-actin to nuclear shape. In-depth investigations of the nuclei confirmed an abnormal localization of lamin A/C, Nesprin-1, and Nesprin-2, forming the main constituents of the nuclear lamina and the LINC complex and ensuring nuclear envelope integrity. To validate the relevance of our findings, we examined muscle samples from three previously reported ACTA1 cases, and we identified the same set of structural aberrations. Moreover, we measured an increased expression of cardiac α-actin in the muscle samples from the patients with longer lifespan, indicating a potential compensatory effect. Overall, this study expands the genetic and morphological spectrum of severe ACTA1-related nemaline myopathy, improves molecular diagnosis, highlights the enlargement of the perinuclear space as an ultrastructural hallmark, and indicates a potential genotype/phenotype correlation.

Original languageEnglish
Article number101
JournalActa Neuropathologica Communications
Volume10
Issue number1
DOIs
Publication statusPublished - Dec 2022

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