Lamin A/C Assembly Defects in LMNA-Congenital Muscular Dystrophy Is Responsible for the Increased Severity of the Disease Compared with Emery-Dreifuss Muscular Dystrophy

Anne T Bertrand (1) , Astrid Brull (1) , Feriel Azibani (1) , Louise Benarroch (1) , Khadija Chikhaoui (1) , Colin L Stewart (2) , Ohad Medalia (3) , Rabah Ben Yaou (1, 4) , Gisèle Bonne (1)

1 Centre de recherche en Myologie – U974 SU-INSERM
2 Institute of Medical Biology
3 UZH - Universität Zürich [Zürich] = University of Zurich
4 Institut de Myologie

LMNA encodes for Lamin A/C, type V intermediate filaments that polymerize under the inner nuclear membrane to form the nuclear lamina. A small fraction of Lamin A/C, less polymerized, is also found in the nucleoplasm. Lamin A/C functions include roles in nuclear resistance to mechanical stress and gene regulation. LMNA mutations are responsible for a wide variety of pathologies, including Emery-Dreifuss (EDMD) and LMNA-related congenital muscular dystrophies (L-CMD) without clear genotype-phenotype correlations. Both diseases presented with striated muscle disorders although L-CMD symptoms appear much earlier and are more severe. Seeking for pathomechanical differences to explain the severity of L-CMD mutations, we performed an in silico analysis of the UMD-LMNA database and found that L-CMD mutations mainly affect residues involved in Lamin dimer and tetramer stability. In line with this, we found increased nucleoplasmic Lamin A/C in L-CMD patient fibroblasts and mouse myoblasts compared to the control and EDMD. L-CMD myoblasts show differentiation defects linked to their inability to upregulate muscle specific nuclear envelope (NE) proteins expression. NE proteins were mislocalized, leading to misshapen nuclei. We conclude that these defects are due to both the absence of Lamin A/C from the nuclear lamina and its maintenance in the nucleoplasm of myotubes.

Mots clés: Emery-Dreifuss muscular dystrophy; LMNA-related congenital muscular dystrophy; Lamin A/C; LMNA

Domaines: Biologie cellulaire; Génétique; Biologie moléculaire; Biologie animale; Biochimie [q-bio.BM]

Anne T Bertrand, Astrid Brull, Feriel Azibani, Louise Benarroch, Khadija Chikhaoui, et al.. Lamin A/C Assembly Defects in LMNA-Congenital Muscular Dystrophy Is Responsible for the Increased Severity of the Disease Compared with Emery-Dreifuss Muscular Dystrophy. Cells, 2020, ⟨10.3390/cells9040844⟩. ⟨hal-02527633⟩