-
International Journal of Molecular... Feb 2024Alpha-B-crystallin, a member of the small heat shock family of proteins, has been implicated in a variety of cardiomyopathies and in normal cardiac homeostasis. It is... (Review)
Review
Alpha-B-crystallin, a member of the small heat shock family of proteins, has been implicated in a variety of cardiomyopathies and in normal cardiac homeostasis. It is known to function as a molecular chaperone, particularly for desmin, but also interacts with a wide variety of additional proteins. The molecular chaperone function is also enhanced by signal-dependent phosphorylation at specific residues under stress conditions. Naturally occurring mutations in , the gene that encodes alpha-B-crystallin, have been suggested to alter ionic intermolecular interactions that affect dimerization and chaperone function. These mutations have been associated with myofibrillar myopathy, restrictive cardiomyopathy, and hypertrophic cardiomyopathy and promote pathological hypertrophy through different mechanisms such as desmin aggregation, increased reductive stress, or activation of calcineurin-NFAT signaling. This review will discuss the known mechanisms by which alpha-B-crystallin functions in cardiac homeostasis and the pathogenesis of cardiomyopathies and provide insight into potential future areas of exploration.
Topics: Humans; Desmin; Cardiomyopathies; Mutation; Cardiomyopathy, Restrictive; Molecular Chaperones
PubMed: 38474073
DOI: 10.3390/ijms25052826 -
Stem Cell Research Apr 2024Myofibrillar myopathy (MFM) is a rare genetic disorder characterized by muscular dystrophy that is often associated with cardiac disease. This disease is caused by...
Myofibrillar myopathy (MFM) is a rare genetic disorder characterized by muscular dystrophy that is often associated with cardiac disease. This disease is caused by mutations in several genes, among them DES (encoding desmin) is the most frequently affected. Peripheral blood mononuclear cells from 5 different MFM patients with different DES mutations were reprogrammed into induced pluripotent stem cells (IPSC) using non-integrative vectors. For each patient, one IPSC clone was selected and demonstrated pluripotency hallmarks without genomic abnormalities. SNP profiles were identical to the cells of origin and all the clones have the capacity to differentiate into all three germ layers.
Topics: Humans; Induced Pluripotent Stem Cells; Leukocytes, Mononuclear; Myopathies, Structural, Congenital; Mutation
PubMed: 38354647
DOI: 10.1016/j.scr.2024.103338 -
MedRxiv : the Preprint Server For... Feb 2024Myofibrillar myopathy 6 (MFM6) is a rare childhood-onset myopathy characterized by myofibrillar disintegration, muscle weakness, and cardiomyopathy. The genetic cause of...
Myofibrillar myopathy 6 (MFM6) is a rare childhood-onset myopathy characterized by myofibrillar disintegration, muscle weakness, and cardiomyopathy. The genetic cause of MFM6 is p.Pro209Leu mutation (rs121918312-T) in the gene, which generates the disease outcomes in a dominant fashion. Since the consequences of the mutation are strong and rapidly progressing, most MFM6 patients are due to mutation. There are no effective treatments for MFM6 despite its well-known genetic cause. Given p.Pro209Leu mutation is dominant, regenerative medicine approaches employing orthologous stem cells in which mutant is inactivated offer a promising avenue. Here, we developed personalized allele-specific CRISPR-Cas9 strategies capitalizing on PAM-altering SNP and PAM-proximal SNP. In order to identify the disease chromosome carrying the mutation in our two affected individuals, haplotype phasing through cloning-sequencing was performed. Based on the sequence differences between mutant and normal , we developed personalized allele-specific CRISPR-Cas9 strategies to selectively inactivate the mutant allele 1) by preventing the transcription of the mutant and 2) by inducing nonsense-mediated decay (NMD) of mutant mRNA. Subsequent experimental validation in patient-derived induced pluripotent stem cell (iPSC) lines showed complete allele specificities of our CRISPR-Cas9 strategies and molecular consequences attributable to inactivated mutant . In addition, mutant allele-specific CRISPR-Cas9 targeting did not alter the characteristics of iPSC or the capacity to differentiate into cardiomyocytes. Together, our data demonstrate the feasibility and potential of personalized allele-specific CRISPR-Cas9 approaches to selectively inactivate the mutant to generate cell resources for regenerative medicine approaches for MFM6.
PubMed: 38352343
DOI: 10.1101/2024.02.03.24302252 -
Heliyon Feb 2024Myofibrillar myopathies (MFM) are a group of sporadic and inherited progressive skeletal muscle disorders that can lead to physical disability and premature death. To...
OBJECTIVE
Myofibrillar myopathies (MFM) are a group of sporadic and inherited progressive skeletal muscle disorders that can lead to physical disability and premature death. To date, pathogenic variants in different genes are associated with MFM. MFM induced by variants in the Desmin () gene is the most common subtype of MFM.
CASE PRESENTATION
A 15-year-old boy with MFM was described, whose symptoms first presented as cardiac symptoms. Enlarged right and left atria, thickened ventricular septal (IVS) and mild mitral (MR) and tricuspid regurgitation (TR) in the echocardiography were found. Atrial fibrillation, intermittent atrioventricular (AV) block, ST-T changes in the dynamic electrocardiogram (ECG) were shown. Mild myopathic changes in the electromyographic exam were detected. Ultrastructural analysis found slight Z-line changes and a few small myolysis lesions, but no abnormal inclusion bodies. Genetic testing detected a heterozygous missense variant (c.1216C > T) of DES, and 2 rare variants: (c.1102C > G) and (c.3074G > A). The patient's parents didn't show skeletal and cardiac muscle disorders. DNA sequencing analysis showed no variant of was carried by them. Thus, we detected a case of MFM caused by de novo variant c.1216C > T/p.Arg406Trp with predominantly myocardial alterations.
PubMed: 38314304
DOI: 10.1016/j.heliyon.2024.e25009 -
International Journal of Molecular... Dec 2023Small heat shock proteins (sHsps) are a family of ATP-independent molecular chaperones that function as "holdases" and prevent protein aggregation due to changes in...
Small heat shock proteins (sHsps) are a family of ATP-independent molecular chaperones that function as "holdases" and prevent protein aggregation due to changes in temperature, pH, or oxidation state. sHsps have a conserved α-crystallin domain (ACD), which forms the dimer building block, flanked by variable N- and C-terminal regions. sHsps populate various oligomeric states as a function of their sequestrase activity, and these dynamic structural features allow the proteins to interact with a plethora of cellular substrates. However, the molecular mechanisms of their dynamic conformational assembly and the interactions with various substrates remains unclear. Therefore, it is important to gain insight into the underlying physicochemical properties that influence sHsp structure in an effort to understand their mechanism(s) of action. We evaluated several disease-relevant mutations, D109A, F113Y, R116C, R120G, and R120C, in the ACD of HspB5 for changes to in vitro chaperone activity relative to that of wildtype. Structural characteristics were also evaluated by ANS fluorescence and CD spectroscopy. Our results indicated that mutation Y113F is an efficient holdase, while D109A and R120G, which are found in patients with myofibrillar myopathy and cataracts, respectively, exhibit a large reduction in holdase activity in a chaperone-like light-scattering assay, which indicated alterations in substrate-sHsp interactions. The extent of the reductions in chaperone activities are different among the mutants and specific to the substrate protein, suggesting that while sHsps are able to interact with many substrates, specific interactions provide selectivity for some substrates compared to others. This work is consistent with a model for chaperone activity where key electrostatic interactions in the sHsp dimer provide structural stability and influence both higher-order sHsp interactions and facilitate interactions with substrate proteins that define chaperone holdase activity.
Topics: Humans; alpha-Crystallins; Biological Assay; Heat-Shock Proteins, Small; Molecular Chaperones; Protein Folding
PubMed: 38203641
DOI: 10.3390/ijms25010471 -
Stem Cell Research & Therapy Jan 2024Beyond the observed alterations in cellular structure and mitochondria, the mechanisms linking rare genetic mutations to the development of heart failure in patients...
BACKGROUND
Beyond the observed alterations in cellular structure and mitochondria, the mechanisms linking rare genetic mutations to the development of heart failure in patients affected by desmin mutations remain unclear due in part, to the lack of relevant human cardiomyocyte models.
METHODS
To shed light on the role of mitochondria in these mechanisms, we investigated cardiomyocytes derived from human induced pluripotent stem cells carrying the heterozygous DES mutation that were either isolated from a patient or generated by gene editing. To increase physiological relevance, cardiomyocytes were either cultured on an anisotropic micropatterned surface to obtain elongated and aligned cardiomyocytes, or as a cardiac spheroid to create a micro-tissue. Moreover, when applicable, results from cardiomyocytes were confirmed with heart biopsies of suddenly died patient of the same family harboring DES mutation, and post-mortem heart samples from five control healthy donors.
RESULTS
The heterozygous DES mutation leads to dramatic changes in the overall cytoarchitecture of cardiomyocytes, including cell size and morphology. Most importantly, mutant cardiomyocytes display altered mitochondrial architecture, mitochondrial respiratory capacity and metabolic activity reminiscent of defects observed in patient's heart tissue. Finally, to challenge the pathological mechanism, we transferred normal mitochondria inside the mutant cardiomyocytes and demonstrated that this treatment was able to restore mitochondrial and contractile functions of cardiomyocytes.
CONCLUSIONS
This work highlights the deleterious effects of DES mutation, demonstrates the crucial role of mitochondrial abnormalities in the pathophysiology of desmin-related cardiomyopathy, and opens up new potential therapeutic perspectives for this disease.
Topics: Humans; Desmin; Induced Pluripotent Stem Cells; Cardiomyopathies; Mutation; Myocytes, Cardiac; Mitochondria
PubMed: 38167524
DOI: 10.1186/s13287-023-03619-7 -
Molecular Genetics and Metabolism... Mar 2024gene encodes for Filamin-C (FLNC) protein, a sacromeric protein with important structural and signaling functions in the myocyte. Pathogenic dominant variants in were...
gene encodes for Filamin-C (FLNC) protein, a sacromeric protein with important structural and signaling functions in the myocyte. Pathogenic dominant variants in were initially linked to myofibrillar myopathy and over time, evidence showed association of this gene with different forms of autosomal dominant cardiomyopathy including hypertrophic, dilated and restrictive forms. Recently, two cases of recessive mutations have been reported by Reinstein et al. and Kölbel et al., one with only cardiomyopathy and other with only myopathy. In this report, we describe a third case, a boy who was diagnosed at 10 years of age with shortness of breath and dilated cardiomyopathy who on sequencing was found to have a novel homozygous splice site variant (NM_001458.4 c.2122-1G>C) in . This case suggests that the phenotype associated with variants in FLNC is very heterogenous and can be inherited in dominant or recessive forms, with later being more severe and of earlier onset.
PubMed: 38077956
DOI: 10.1016/j.ymgmr.2023.101027 -
BMJ Case Reports Dec 2023Myofibrillar myopathies (MFMs) are a group of rare genetic disorders that affect the function of skeletal, cardiac and smooth muscle.MFM exhibits a considerable degree...
Myofibrillar myopathies (MFMs) are a group of rare genetic disorders that affect the function of skeletal, cardiac and smooth muscle.MFM exhibits a considerable degree of clinical heterogeneity. In numerous instances of MFM, muscle weakness is the predominant manifestation. Certain MFM subtypes are distinguished by respiratory and cardiac impairment.There is little information available about anaesthetic management in MFM, and even less is known about obstetric anaesthesia.A successful case of a patient with MFM undergoing a caesarean section under combined neuraxial anaesthesia is reported. The patient experienced no complications, and functional recovery was swift.
Topics: Pregnancy; Humans; Female; Cesarean Section; Myopathies, Structural, Congenital; Muscle Weakness; Anesthetics; Muscle, Skeletal
PubMed: 38050391
DOI: 10.1136/bcr-2023-257198 -
Human Molecular Genetics Dec 2023
PubMed: 37788121
DOI: 10.1093/hmg/ddad168 -
Stem Cell Research Oct 2023Here we introduce the human induced pluripotent stem cell (hiPSC) line HIMRi001-A generated from cultured dermal fibroblasts of a 60-year-old male patient with a...
Here we introduce the human induced pluripotent stem cell (hiPSC) line HIMRi001-A generated from cultured dermal fibroblasts of a 60-year-old male patient with a myofibrillar myopathy, carrying a heterozygous c.4984C > T [p.Q1662X] mutation in the filamin C (FLNC)-gene, via lentiviral expression of OCT4, SOX2, KLF4 and c-MYC. HIMRi001-A displays typical embryonic stem cell-like morphology, carries the c.4984C > T FLNC gene mutation, expressed several pluripotent stem cell makers, retained normal karyotype (46, XY) and holds the potential to differentiate in all three germ layers. We postulate that HIMRi001-A can be used for the elucidation of FLNC-associated pathomechanisms and for developing new therapeutic options.
Topics: Male; Humans; Middle Aged; Induced Pluripotent Stem Cells; Kruppel-Like Factor 4; Pluripotent Stem Cells; Fibroblasts; Mutation; Cell Differentiation
PubMed: 37748332
DOI: 10.1016/j.scr.2023.103210