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Human Molecular Genetics Dec 2023
PubMed: 37788121
DOI: 10.1093/hmg/ddad168 -
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 -
PLoS Genetics Nov 2020Mutations in the molecular co-chaperone Bcl2-associated athanogene 3 (BAG3) are found to cause dilated cardiomyopathy (DCM), resulting in systolic dysfunction and heart...
Mutations in the molecular co-chaperone Bcl2-associated athanogene 3 (BAG3) are found to cause dilated cardiomyopathy (DCM), resulting in systolic dysfunction and heart failure, as well as myofibrillar myopathy (MFM), which is characterized by protein aggregation and myofibrillar disintegration in skeletal muscle cells. Here, we generated a CRISPR/Cas9-induced Bag3 knockout zebrafish line and found the complete preservation of heart and skeletal muscle structure and function during embryonic development, in contrast to morpholino-mediated knockdown of Bag3. Intriguingly, genetic compensation, a process of transcriptional adaptation which acts independent of protein feedback loops, was found to prevent heart and skeletal muscle damage in our Bag3 knockout model. Proteomic profiling and quantitative real-time PCR analyses identified Bag2, another member of the Bag protein family, significantly upregulated on a transcript and protein level in bag3-/- mutants. This implied that the decay of bag3 mutant mRNA in homozygous bag3-/- embryos caused the transcriptional upregulation of bag2 expression. We further demonstrated that morpholino-mediated knockdown of Bag2 in bag3-/- embryos evoked severe functional and structural heart and skeletal muscle defects, which are similar to Bag3 morphants. However, Bag2 knockdown in bag3+/+ or bag3+/- embryos did not result in (cardio-)myopathy. Finally, we found that inhibition of the nonsense-mediated mRNA decay (NMD) machinery by knockdown of upf1, an essential NMD factor, caused severe heart and skeletal muscle defects in bag3-/- mutants due to the blockade of transcriptional adaptation of bag2 expression. Our findings provide evidence that genetic compensation might vitally influence the penetrance of disease-causing bag3 mutations in vivo.
Topics: Adaptor Proteins, Signal Transducing; Animals; Apoptosis; Apoptosis Regulatory Proteins; Cardiomyopathies; Cardiomyopathy, Dilated; Disease Models, Animal; Heart Failure; Molecular Chaperones; Muscle Fibers, Skeletal; Muscular Diseases; Mutation; Myocardium; Myopathies, Structural, Congenital; Phenotype; Proteomics; Zebrafish; Zebrafish Proteins
PubMed: 33137814
DOI: 10.1371/journal.pgen.1009088 -
European Journal of Human Genetics :... Jan 2023Autosomal dominant variants in LDB3 (also known as ZASP), encoding the PDZ-LIM domain-binding factor, have been linked to a late onset phenotype of cardiomyopathy and...
Autosomal dominant variants in LDB3 (also known as ZASP), encoding the PDZ-LIM domain-binding factor, have been linked to a late onset phenotype of cardiomyopathy and myofibrillar myopathy in humans. However, despite knockout mice displaying a much more severe phenotype with premature death, bi-allelic variants in LDB3 have not yet been reported. Here we identify biallelic loss-of-function variants in five unrelated cardiomyopathy families by next-generation sequencing. In the first family, we identified compound heterozygous LOF variants in LDB3 in a fetus with bilateral talipes and mild left cardiac ventricular enlargement. Ultra-structural examination revealed highly irregular Z-disc formation, and RNA analysis demonstrated little/no expression of LDB3 protein with a functional C-terminal LIM domain in muscle tissue from the affected fetus. In a second family, a homozygous LDB3 nonsense variant was identified in a young girl with severe early-onset dilated cardiomyopathy with left ventricular non-compaction; the same homozygous nonsense variant was identified in a third unrelated female infant with dilated cardiomyopathy. We further identified homozygous LDB3 frameshift variants in two unrelated probands diagnosed with cardiomegaly and severely reduced left ventricular ejection fraction. Our findings demonstrate that recessive LDB3 variants can lead to an early-onset severe human phenotype of cardiomyopathy and myopathy, reminiscent of the knockout mouse phenotype, and supporting a loss of function mechanism.
Topics: Infant; Mice; Animals; Humans; Child; Female; Cardiomyopathy, Dilated; Stroke Volume; Adaptor Proteins, Signal Transducing; LIM Domain Proteins; Ventricular Function, Left; Cardiomyopathies
PubMed: 36253531
DOI: 10.1038/s41431-022-01204-9 -
Neurological Research and Practice Jun 2023Here we report on a patient with Parkinson's Disease and camptocormia due to Myofibrillar Myopathy Type 3. By leading the reader through the clinical reasoning process...
Here we report on a patient with Parkinson's Disease and camptocormia due to Myofibrillar Myopathy Type 3. By leading the reader through the clinical reasoning process and highlighting the respective red flags we aim to increase the readers' awareness for the differential diagnosis of camptocormia.
PubMed: 37287054
DOI: 10.1186/s42466-023-00250-y -
Frontiers in Pediatrics 2022Fatal infantile hypertonic myofibrillar myopathy (FIHMM) is an autosomal recessive hereditary disease characterized by amyotrophy, progressive flexion contracture and...
BACKGROUND
Fatal infantile hypertonic myofibrillar myopathy (FIHMM) is an autosomal recessive hereditary disease characterized by amyotrophy, progressive flexion contracture and ankylosis of the trunk and limb muscles, apnea and respiratory failure, and increased creatine phosphate levels. It is caused by mutations in the gene, and only around 18 cases including genetic mutations have been reported worldwide. All patients with FIHMM develop respiratory distress, progressive stiffness of the limbs, and have a poor prognosis. However, no effective treatment for -associated respiratory failure has been reported. Here, we report a case of FIHMM with a novel heterozygous missense mutation.
CASE PRESENTATION
A 2-year-old female developed scoliosis of the lumbar spine and restrictive ventilatory dysfunction in infancy. She was admitted to the hospital with labored breathing on the third day after the second injection of inactivated poliomyelitis vaccine. Acute respiratory failure, pneumothorax, and cardiac arrest arose in the patient during hospitalization, and progressive stiffness of the trunk and limb muscles appeared, accompanied by obvious abdominal distension and an increase in phosphocreatine kinase levels. Screenings for genetic metabolic diseases in the blood and urine were normal. Electromyography revealed mild myogenic damage. A muscle biopsy indicated the accumulation of desmin, -crystallin, and myotilin in the musculus biceps brachii, and dense granules were observed in muscle fibers using electron microscopy. Mutation analysis of revealed a novel heterozygous missense mutation in the proband, () and (), which inherited from her asymptomatic, heterozygous carrier parents, respectively. The proband was finally diagnosed as FIHMM. One month after the FIHMM diagnosis, the child died of respiratory failure.
CONCLUSION
We report a case of FIHMM with a novel heterozygous missense mutation of . This finding might improve our understanding of FIHMM and highlight a novel mutation in the Chinese population.
PubMed: 36727013
DOI: 10.3389/fped.2022.993165 -
Acta Neuropathologica Communications Feb 2021Mutations in the DNAJB6 gene have been identified as rare causes of myofibrillar myopathies. However, the underlying pathophysiologica mechanisms remain elusive. DNAJB6...
Mutations in the DNAJB6 gene have been identified as rare causes of myofibrillar myopathies. However, the underlying pathophysiologica mechanisms remain elusive. DNAJB6 has two known isoforms, including the nuclear isoform DNAJB6a and the cytoplasmic isoform DNAJB6b, which was thought to be the pathogenic isoform. Here, we report a novel recessive mutation c.695_699del (p. Val 232 Gly fs*7) in the DNAJB6 gene, associated with an apparently recessively inherited late onset distal myofibrillar myopathy in a Chinese family. Notably, the novel mutation localizes to exon 9 and uniquely encodes DNAJB6a. We further identified that this mutation decreases the mRNA and protein levels of DNAJB6a and results in an age-dependent recessive toxic effect on skeletal muscle in knock-in mice. Moreover, the mutant DNAJB6a showed a dose-dependent anti-aggregation effect on polyglutamine-containing proteins in vitro. Taking together, these findings reveal the pathogenic role of DNAJB6a insufficiency in myofibrillar myopathies and expand upon the molecular spectrum of DNAJB6 mutations.
Topics: Aged; Animals; Asian People; Distal Myopathies; Gene Knock-In Techniques; HEK293 Cells; HSP40 Heat-Shock Proteins; Humans; Male; Mice; Mice, Transgenic; Molecular Chaperones; Muscle, Skeletal; Mutation; Myopathies, Structural, Congenital; Nerve Tissue Proteins; Phenotype
PubMed: 33557929
DOI: 10.1186/s40478-020-01046-w -
The American Journal of Pathology Mar 2020BCL-2-associated athanogene 3 (BAG3) is a co-chaperone to heat shock proteins important in degrading misfolded proteins through chaperone-assisted selective autophagy....
BCL-2-associated athanogene 3 (BAG3) is a co-chaperone to heat shock proteins important in degrading misfolded proteins through chaperone-assisted selective autophagy. The recurrent dominant BAG3-P209L mutation results in a severe childhood-onset myofibrillar myopathy (MFM) associated with progressive muscle weakness, cardiomyopathy, and respiratory failure. Because a homozygous knock-in (KI) strain for the mP215L mutation homologous to the human P209L mutation did not have a gross phenotype, compound heterozygote knockout (KO) and KI mP215L mice were generated to establish whether further reduction in BAG3 expression would lead to a phenotype. The KI/KO mice have a significant decrease in voluntary movement compared with wild-type and KI/KI mice in the open field starting at 7 months. The KI/KI and KI/KO mice both have significantly smaller muscle fiber cross-sectional area. However, only the KI/KO mice have clear skeletal muscle histologic changes in MFM. As in patient muscle, there are increased levels of BAG3-interacting proteins, such as p62, heat shock protein B8, and αB-crystallin. The KI/KO mP215L strain is the first murine model of BAG3 myopathy that resembles the human skeletal muscle pathologic features. The results support the hypothesis that the pathologic development of MFM requires a significant decrease in BAG3 protein level and not only a gain of function caused by the dominant missense mutation.
Topics: Adaptor Proteins, Signal Transducing; Animals; Apoptosis Regulatory Proteins; Cardiomyopathies; Disease Models, Animal; Genes, Dominant; Humans; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Electron, Transmission; Muscle Fibers, Skeletal; Muscle, Skeletal; Mutation; Myopathies, Structural, Congenital; Phenotype
PubMed: 31953038
DOI: 10.1016/j.ajpath.2019.11.005 -
Internal Medicine (Tokyo, Japan) May 2022Hereditary myopathy with early respiratory failure (HMERF) is caused by titin A-band mutations in exon 344 and is considered quite rare. Respiratory insufficiency can be...
Hereditary myopathy with early respiratory failure (HMERF) is caused by titin A-band mutations in exon 344 and is considered quite rare. Respiratory insufficiency can be the sole symptom in the disease course. We herein report the first Japanese HMERF patient with a p.P31732L mutation in titin. The patient manifested respiratory failure and mild weakness of the neck flexor muscle at 69 years old and showed fatty replacement of the bilateral semitendinosus muscles on muscle imaging. Our case indicates that HMERF with a heterozygous p.P31732L mutation should be included in the differential diagnosis of muscular diseases presenting with early respiratory failure.
Topics: Aged; Connectin; Genetic Diseases, Inborn; Humans; Japan; Muscle, Skeletal; Muscular Diseases; Mutation; Respiratory Insufficiency
PubMed: 34670883
DOI: 10.2169/internalmedicine.7733-21 -
PloS One 2021αB-crystallin (heat shock protein β5/HSPB5) is a member of the family of small heat shock proteins that is expressed in various organs of the human body including eye...
αB-crystallin (heat shock protein β5/HSPB5) is a member of the family of small heat shock proteins that is expressed in various organs of the human body including eye lenses and muscles. Therefore, mutations in the gene of this protein (CRYAB) might have many pathological consequences. A new mutation has recently been discovered in the α-crystallin domain of this chaperone protein which replaces aspartate 109 with alanine (D109A). This mutation can cause myofibrillar myopathy (MFM), cataracts, and cardiomyopathy. In the current study, several spectroscopic and microscopic analyses, as well as gel electrophoresis assessment were applied to elucidate the pathogenic contribution of human αB-crystallin bearing D109A mutation in development of eye lens cataract and myopathies. The protein oligomerization, chaperone-like activity and chemical/thermal stabilities of the mutant and wild-type protein were also investigated in the comparative assessments. Our results suggested that the D109A mutation has a significant impact on the important features of human αB-crystallin, including its structure, size of the protein oligomers, tendency to form amyloid fibrils, stability, and chaperone-like activity. Given the importance of aspartate 109 in maintaining the proper structure of the α-crystallin domain, its role in the dimerization and chaperone-like activity, as well as preserving protein stability through the formation of salt bridges; mutation at this important site might have critical consequences and can explain the genesis of myopathy and cataract disorders. Also, the formation of large light-scattering aggregates and disruption of the chaperone-like activity by D109A mutation might be considered as important contributing factors in development of the eye lens opacity.
Topics: Cardiomyopathies; Cataract; Humans; Models, Molecular; Point Mutation; Protein Conformation; Protein Folding; Protein Multimerization; Protein Stability; alpha-Crystallin B Chain
PubMed: 34843556
DOI: 10.1371/journal.pone.0260306