Elena Gargaun, MD, PhD in cellular and molecular biology, has been working in the “Gene therapy for DMD & pathophysiology of the skeletal muscle” team at the Institute of Myology for her thesis: “Genotype and phenotype characterisation of Becker muscular dystrophy patients with deletion of exons 45-55”, under the supervision of France Piétri-Rouxel. Her work, conducted in collaboration with other scientific and clinical teams and neuromuscular disease reference centres in France*, has just been published in the journal Biomedicines.
Duchenne muscular dystrophy (DMD) and Becker muscle dystrophy (BMD) are X-linked myopathies characterised by progressive muscular dystrophy with or without dilated cardiomyopathy. DMD patients do not express the dystrophin protein and experience severe disease impairment, whereas BMD patients express a dystrophin protein that is shorter but still functional, leading to a moderate phenotype. As described in the literature, 63% of DMD patients are eligible for multi-exon skipping treatment, thus becoming BMD patients with deletion of exons 45 to 55 (BMDdel45-55). As a result, the characterisation of a population of BMDdel45-55 patients is of major interest for therapeutic approaches.
Our study looked at new myogenesis regulation agents such as long non-coding RNA (lncRNA). Several lncRNA have been described, localised in introns 44 and 56 of the gene coding dystrophin, introns that are modified in BMDdel45-55 patients.
We studied a population of 54 BMDdel45-55 patients. The objective was to evaluate phenotype variability among these patients by: performing a detailed clinical characterisation, evaluating a whole genome sequencing (WGS) analysis, and examining the modified lncRNA sequences in these patients. We have established the profile for the presence of lncRNA in 38/54 patients, genomically, and the profile for the expression of these lncRNA in healthy control subjects and in immortalised myoblasts from DMD patients. We have identified the fact that one of the lncRNAs, lncRNA44s2, acts as a possible differentiation accelerator. And interestingly, we have shown that the expression of another lncRNA, lncRNA44s, was associated with a favourable clinical phenotype.
These results suggest that these two lncRNAs could be involved, respectively, in the muscle differentiation process, and could become a potential biomarker for disease progression.
Finally, based on these results, we are suggesting that new therapeutic approaches for DMD patients, notably deletion of exons 45 to 55 by CRISPR-Cas9 strategy, should take into account lncRNA sequences present in the introns bordering this deletion, in order to optimise therapeutic benefit.
*Centre de Référence des Maladies Neuromusculaires AOC, Service de Neuropédiatrie, CHU Bordeaux, 33000 Bordeaux, France ; Centre de Référence des Maladies Neuromusculaires AOC, CHU Angers, 49933 Angers, France ; Centre de Référence des Maladies Neuromusculaires Nord/Est/Ile de France, Service de Médecine Physique et de Réadaptation, CHRU de Lille, 59000 Lille, France ; CEA, Centre National de Recherche en Génomique Humaine, Université Paris-Saclay, 91057 Evry, France ; INSERM, Marseille Medical Genetics, Aix Marseille University, 13005 Marseille, France ; Département de Génétique Médicale, APHM, Hôpital d’Enfants de la Timone, 13005 Marseille, France ; Laboratoire d’Optiques et Biosciences (LOB), CNRS, INSERM, École polytechnique, Institut Polytechnique de Paris, 91120 Palaiseau, France ; IRIS, Institut de Recherches Internationales Servier, 92150 Suresnes, France ; AP-HP, Laboratoire de génétique et biologie moléculaires, Hôpital Cochin, Université Paris Descartes-Sorbonne Paris Cité, 75014 Paris, France