The selection of L-CMD iPSCs is expanded, disease-associated readouts are validated using a transgene-free differentiation protocol and gene editing strategies are assessed using 2D and 3D cultures, providing an advanced, humanised platform for translational research and precision medicine in laminopathies.
Abstract
LMNArelated congenital muscular dystrophy (L-CMD) is one of the most severe laminopathies, which are incurable diseases primarily caused by pathogenic LMNA variants. LMNA encodes Lamin A/C: key components of the nuclear lamina, which provides structural stability to the nucleus, whilst regulating chromatin organisation and gene expression. L-CMD research is hindered by lack of humanised, tissue-specific models that accurately recapitulate disease phenotypes. We previously reported nuclear shape abnormalities and Lamin mislocalisation in LMNA-mutant induced pluripotent stem cell (iPSC)-derived skeletal muscle cells. Here, we expand the selection of L-CMD iPSCs, validate disease-associated readouts using a transgene-free differentiation protocol and assess gene editing strategies using 2D and 3D cultures. Results showed no overt defects in developmental myogenesis but recapitulated pathological nuclear shape abnormalities in monolayer cultures and engineered muscles, nuclear envelope protein mislocalisation and transcriptomic alterations across multiple pathogenic LMNA variants. We then used our platform to assess outcomes of LMNA gene editing. CRISPR-based exon-removal generated sRNA and protein Lamin A/C species, without normalisation of nuclear morphology or transcriptomic profile. Conversely, precise editing of the same variant corrected nuclear morphometrics, alongside normalisation of the pro-inflammatory transcriptomic signature, providing an advanced, humanised platform for translational research and precision medicine in laminopathies.
Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common dominant muscular dystrophies and remains without an approved disease modifying therapy. Caused by the aberrant expression of the cytotoxic gene DUX4, FSHD is typically diagnosed in adulthood, however clinical onset in children (<18 years of age) is often associated with a more severe and rapid disease. While clinical trials are underway, a lack of human-specific pre-clinical models limit effective testing of potential therapies, particularly in children. To fill this gap, we describe here the development of induced pluripotent stem cell-derived 2-and 3-dimensional skeletal muscle models of children with clinically defined mild, moderate, and severe FSHD. These iPSC-derived muscle models replicate key features of FSHD, including aberrant DUX4 mRNA expression, muscle atrophy, and weakness, which correlate with the individuals’ specific disease severity. Next, we assessed the efficacy of adenine base editing (ABE) as a potential gene therapy approach to treat FSHD. DUX4-targeted ABE reduced DUX4 mRNA expression, improved muscle area and force generation in the most severe individual. Together this work supports the use of iPSC-derived skeletal muscle models as a less invasive method to study childhood-onset FSHD and establishes targeted DUX4 gene editing therapies as a potential treatment approach.
P. Houweling, Vanessa G. Crossman, L. Kiriaev et al.· bioRxiv· 0 citations
Cortical organoids are established as a robust human model of CDM-associated neurodevelopmental defects, uncover MBNL-dependent mechanisms underlying early corticogenesis impairment and demonstrate the utility of this platform for translational therapeutic discovery in DM1.
Azania Abatan, Jérôme Polentes, M. Bouquier et al.· bioRxiv· 0 citations
Background LMNA codes a widely expressed nuclear cytoskeletal protein (lamin A/C) with multiple important functions. Pathogenic LMNA genetic variation may lead to autosomal dominant cardiomyopathy, though the severity and rate of progression can vary with the specific nucleotide change and location. Prior studies showed that induced pluripotent stem cells (iPSC)-derived cardiomyocytes (iCMs) with LMNA R541C exhibited reduced LMNA protein abundance, increased sarcomere disorganization, and abnormal electrophysiology. Methods We investigated the LMNA-R541C variant that exhibits a highly penetrant and severe clinical cardiomyopathy phenotype using transcriptomic analysis of iCMs. Patient-derived iPSCs with CRISPR-corrected (clustered regularly interspersed short palindromic repeats) isogenic control cells and CRISPR knock-in LMNA-R541C heterozygous iPSCs were generated for isogenic controlled experiments. Results In differential gene expression analyses we observed that LMNAR541C/WT iPSC-derived cardiomyocytes had consistent perturbations in 123 genes across CRISPR-corrected and knock-in experiments compared to controls. Pathway analysis identified that the G2M checkpoint and oxidative phosphorylation processes were consistently dysregulated and confirm these findings in previously published iPSC and murine models. Discussion These results implicate perturbed gene expression and pathways that may contribute to the severe phenotypes in LMNA-R541C. Informatic analysis of pathways suggests several drug classes including multiple cardiac glycosides as potential targeted therapeutic candidates to be explored.
Thomas E. Keller, Ci Koehring, Brett W. Higgins et al.· bioRxiv· 0 citations
DOK7-related Congenital Myasthenic Syndrome (CMS) is a rare genetic neuromuscular junction disorder. This is one of the most common of the recessive forms of CMS, often presenting with more static proximal weakness (hence also referred to as limb girdle CMS). Whole-genome sequencing of affected patients implicates frameshift duplication mutations in DOK7 as drivers of impaired neuromuscular-junction signaling. In this study, we generated a human induced pluripotent stem cell (hiPSC) line TRNDi045-A-38 from the KOLF2.1J reference line, engineered to carry homozygous DOK7 c.1124_1127dupTGCC mutation knock-in using CRISPR/Cas9. This iPSC line could be used for in vitro disease modeling to study disease pathophysiology and for therapeutic development.
B. M. Jones, Miao Xu, J. Zou et al.· Stem Cell Research· 0 citations
These results demonstrate that ABE can effectively target the LMNA c.745C>T mutation but also reveal the significant impact of bystander edits on cellular physiology, underscoring the necessity of precise editing technologies to ensure both efficacy and safety in future clinical translation.
M. Santafé, I. Hernández, D. Mazzeo et al.· bioRxiv· 0 citations
AIMS
Mutations in the LMNA gene, which encodes lamin A/C, cause a variety of diseases known as laminopathies. Some mutations are particularly associated with the occurrence of dilated cardiomyopathy and heart failure, but the genotype-phenotype relationship and underlying mechanisms are unclear.
METHODS AND RESULTS
Induced pluripotent stem cells (hiPSCs) from a patient carrying a LMNA point mutation (c.665A>C, p.His222Pro) and a CRISPR/Cas9 corrected isogenic control hiPSCs clones were differentiated into cardiomyocytes (hiPSC-CMs), with no difference in the differentiation yield and in sarcomere organisation between the two cell lines. However, 3D cardiac organoids generated with LMNA p.H222P hiPSC-CMs showed an impaired contractility compared to control organoids. Calcium transient recordings in LMNA p.H222P mutant cardiomyocytes showed a significantly higher calcium transient amplitude with a significantly slower calcium re-uptake. Transcriptomic analyses suggested a global mitochondrial dysfunction and in particular an impaired mitochondrial calcium uptake with a significantly decreased expression of the mitochondrial calcium uniporter (MCU). This decrease in MCU expression was confirmed by western blot and was accompanied by an increased MICU1:MCU ratio, as well as an increased PDH Ser232 and PDH Ser300 phosphorylation, indicating an altered mitochondrial calcium uptake in the LMNA mutant hiPSC-CMs. Consistently, lower mitochondrial respiration and ATP levels were found in LMNA p.H222P hiPSC-CMs as compared to isogenic controls. Strikingly, treatment with the MCU activator amorolfine restored mitochondrial calcium uptake and improved contractility in LMNA mutant hiPSC-CMs.
CONCLUSIONS
Our results establish a direct mechanistic link between nuclear envelope dysfunction and impaired mitochondrial function, and highlight the MCU complex as a potential therapeutic target in LMNA-related cardiomyopathy. More broadly, this work provides a paradigm for connecting gene-specific nuclear defects to mitochondrial dysfunction in inherited cardiomyopathies.
M. Seguret, C. Jouve, A. Ruiz-Velasco et al.· Cardiovascular Research· 0 citations
