| 1. |
- de Winter, J M, et al.
(författare)
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KBTBD13 is an actin-binding protein that modulates muscle kinetics
- 2020
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Ingår i: Journal of Clinical Investigation. - : Stanford University Press. - 0021-9738 .- 1558-8238. ; 130:2, s. 754-767
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms that modulate the kinetics of muscle relaxation are critically important for muscle function. A prime example of the impact of impaired relaxation kinetics is nemaline myopathy caused by mutations in KBTBD13 (NEM6). In addition to weakness, NEM6 patients have slow muscle relaxation, compromising contractility and daily life activities. The role of KBTBD13 in muscle is unknown, and the pathomechanism underlying NEM6 is undetermined. A combination of transcranial magnetic stimulation-induced muscle relaxation, muscle fiber- and sarcomere-contractility assays, low-angle x-ray diffraction, and superresolution microscopy revealed that the impaired muscle-relaxation kinetics in NEM6 patients are caused by structural changes in the thin filament, a sarcomeric microstructure. Using homology modeling and binding and contractility assays with recombinant KBTBD13, Kbtbd13-knockout and Kbtbd13(R408c)-knockin mouse models, and a GFP-labeled Kbtbd13-transgenic zebrafish model, we discovered that KBTBD13 binds to actin - a major constituent of the thin filament - and that mutations in KBTBD13 cause structural changes impairing muscle-relaxation kinetics. We propose that this actin-based impaired relaxation is central to NEM6 pathology.
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| 2. |
- Schiava, M., et al.
(författare)
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Genotype-phenotype correlations in valosin-containing protein disease: a retrospective muticentre study
- 2022
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Ingår i: Journal of Neurology Neurosurgery and Psychiatry. - : BMJ. - 0022-3050 .- 1468-330X. ; 93:10, s. 1099-1111
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Tidskriftsartikel (refereegranskat)abstract
- Background Valosin-containing protein (VCP) disease, caused by mutations in the VCP gene, results in myopathy, Paget's disease of bone (PBD) and frontotemporal dementia (FTD). Natural history and genotype-phenotype correlation data are limited. This study characterises patients with mutations in VCP gene and investigates genotype-phenotype correlations. Methods Descriptive retrospective international study collecting clinical and genetic data of patients with mutations in the VCP gene. Results Two hundred and fifty-five patients (70.0% males) were included in the study. Mean age was 56.8 +/- 9.6 years and mean age of onset 45.6 +/- 9.3 years. Mean diagnostic delay was 7.7 +/- 6 years. Symmetric lower limb weakness was reported in 50% at onset progressing to generalised muscle weakness. Other common symptoms were ventilatory insufficiency 40.3%, PDB 28.2%, dysautonomia 21.4% and FTD 14.3%. Fifty-seven genetic variants were identified, 18 of these no previously reported. c.464G>A (p.Arg155His) was the most frequent variant, identified in the 28%. Full time wheelchair users accounted for 19.1% with a median time from disease onset to been wheelchair user of 8.5 years. Variant c.463C>T (p.Arg155Cys) showed an earlier onset (37.8 +/- 7.6 year) and a higher frequency of axial and upper limb weakness, scapular winging and cognitive impairment. Forced vital capacity (FVC) below 50% was as risk factor for being full-time wheelchair user, while FVC Conclusion This study expands the knowledge on the phenotypic presentation, natural history, genotype-phenotype correlations and risk factors for disease progression of VCP disease and is useful to improve the care provided to patient with this complex disease.
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| 3. |
- Ávila-Polo, R., et al.
(författare)
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Loss of Sarcomeric Scaffolding as a Common Baseline Histopathologic Lesion in Titin-Related Myopathies
- 2018
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Ingår i: Journal of Neuropathology and Experimental Neurology. - : Oxford University Press (OUP). - 1554-6578 .- 0022-3069. ; 77:12, s. 1101-1114
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Tidskriftsartikel (refereegranskat)abstract
- Titin-related myopathies are heterogeneous clinical conditions associated with mutations in TTN. To define their histopathologic boundaries and try to overcome the difficulty in assessing the pathogenic role of TTN variants, we performed a thorough morphological skeletal muscle analysis including light and electron microscopy in 23 patients with different clinical phenotypes presenting pathogenic autosomal dominant or autosomal recessive (AR) mutations located in different TTN domains. We identified a consistent pattern characterized by diverse defects in oxidative staining with prominent nuclear internalization in congenital phenotypes (AR-CM) (n = 10), ± necrotic/regenerative fibers, associated with endomysial fibrosis and rimmed vacuoles (RVs) in AR early-onset Emery-Dreifuss-like (AR-ED) (n = 4) and AR adult-onset distal myopathies (n = 4), and cytoplasmic bodies (CBs) as predominant finding in hereditary myopathy with early respiratory failure (HMERF) patients (n = 5). Ultrastructurally, the most significant abnormalities, particularly in AR-CM, were multiple narrow core lesions and/or clear small areas of disorganizations affecting one or a few sarcomeres with M-band and sometimes A-band disruption and loss of thick filaments. CBs were noted in some AR-CM and associated with RVs in HMERF and some AR-ED cases. As a whole, we described recognizable histopathological patterns and structural alterations that could point toward considering the pathogenicity of TTN mutations.
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| 4. |
- Carrington, G., et al.
(författare)
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Human skeletal myopathy myosin mutations disrupt myosin head sequestration
- 2023
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Ingår i: JCI Insight. - 2379-3708. ; 8:21
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Tidskriftsartikel (refereegranskat)abstract
- Myosin heavy chains encoded by MYH7 and MYH2 are abundant in human skeletal muscle and important for muscle contraction. However, it is unclear how mutations in these genes disrupt myosin structure and function leading to skeletal muscle myopathies termed myosinopathies. Here, we used multiple approaches to analyze the effects of common MYH7 and MYH2 mutations in the light meromyosin (LMM) region of myosin. Analyses of expressed and purified MYH7 and MYH2 LMM mutant proteins combined with in silico modeling showed that myosin coiled coil structure and packing of filaments in vitro are commonly disrupted. Using muscle biopsies from patients and fluorescent ATP analog chase protocols to estimate the proportion of myosin heads that were super-relaxed, together with x-ray diffraction measurements to estimate myosin head order, we found that basal myosin ATP consumption was increased and the myosin super-relaxed state was decreased in vivo. In addition, myofiber mechanics experiments to investigate contractile function showed that myofiber contractility was not affected. These findings indicate that the structural remodeling associated with LMM mutations induces a pathogenic state in which formation of shutdown heads is impaired, thus increasing myosin head ATP demand in the filaments, rather than affecting contractility. These key findings will help design future therapies for myosinopathies.
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| 5. |
- Donkervoort, S., et al.
(författare)
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Pathogenic Variants in the Myosin Chaperone UNC-45B Cause Progressive Myopathy with Eccentric Cores
- 2020
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297. ; 107:6, s. 1078-1095
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Tidskriftsartikel (refereegranskat)abstract
- The myosin-directed chaperone UNC-45B is essential for sarcomeric organization and muscle function from Caenorhabditis elegans to humans. The pathological impact of UNC-45B in muscle disease remained elusive. We report ten individuals with bi-allelic variants in UNC45B who exhibit childhood-onset progressive muscle weakness. We identified a common UNC45B variant that acts as a complex hypomorph splice variant. Purified UNC-45B mutants showed changes in folding and solubility. In situ localization studies further demonstrated reduced expression of mutant UNC-45B in muscle combined with abnormal localization away from the A-band towards the Z-disk of the sarcomere. The physiological relevance of these observations was investigated in C. elegans by transgenic expression of conserved UNC-45 missense variants, which showed impaired myosin binding for one and defective muscle function for three. Together, our results demonstrate that UNC-45B impairment manifests as a chaperonopathy with progressive muscle pathology, which discovers the previously unknown conserved role of UNC-45B in myofibrillar organization.
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| 6. |
- Laforet, P., et al.
(författare)
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Deep morphological analysis of muscle biopsies from type III glycogenesis (GSDIII), debranching enzyme deficiency, revealed stereotyped vacuolar myopathy and autophagy impairment
- 2019
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Ingår i: Acta Neuropathologica Communications. - : Springer Science and Business Media LLC. - 2051-5960. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Glycogen storage disorder type III (GSDIII), or debranching enzyme (GDE) deficiency, is a rare metabolic disorder characterized by variable liver, cardiac, and skeletal muscle involvement. GSDIII manifests with liver symptoms in infancy and muscle involvement during early adulthood. Muscle biopsy is mainly performed in patients diagnosed in adulthood, as routine diagnosis relies on blood or liver GDE analysis, followed by AGL gene sequencing. The GSDIII mouse model recapitulate the clinical phenotype in humans, and a nearly full rescue of muscle function was observed in mice treated with the dual AAV vector expressing the GDE transgene. In order to characterize GSDIII muscle morphological spectrum and identify novel disease markers and pathways, we performed a large international multicentric morphological study on 30 muscle biopsies from GSDIII patients. Autophagy flux studies were performed in human muscle biopsies and muscles from GSDIII mice. The human muscle biopsies revealed a typical and constant vacuolar myopathy, characterized by multiple and variably sized vacuoles filled with PAS-positive material. Using electron microscopy, we confirmed the presence of large nonmembrane bound sarcoplasmic deposits of normally structured glycogen as well as smaller rounded sac structures lined by a continuous double membrane containing only glycogen, corresponding to autophagosomes. A consistent SQSTM1/p62 decrease and beclin-1 increase in human muscle biopsies suggested an enhanced autophagy. Consistent with this, an increase in the lipidated form of LC3, LC3II was found in patients compared to controls. A decrease in SQSTM1/p62 was also found in the GSDIII mouse model. In conclusion, we characterized the morphological phenotype in GSDIII muscle and demonstrated dysfunctional autophagy in GSDIII human samples. These findings suggest that autophagic modulation combined with gene therapy might be considered as a novel treatment for GSDIII.
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| 7. |
- Casar-Borota, Olivera, et al.
(författare)
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A novel dynamin-2 gene mutation associated with a late-onset centronuclear myopathy with necklace fibres
- 2015
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Ingår i: Neuromuscular Disorders. - : Elsevier BV. - 0960-8966 .- 1873-2364. ; 25:4, s. 345-348
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear centralisation and internalisation, sarcoplasmic radiating strands and type 1 muscle fibre predominance and hypotrophy characterise dynamin-2 (DNM2) associated centronuclear myopathy, whereas necklace fibres are typically seen in late onset myotubularin-1 (MTM1)-related myopathy. We report a woman with unilateral symptoms probably related to brachial plexus neuritis. Electromyography revealed localised neuropathic and generalised myopathic abnormalities. The typical features of DNM2 centronuclear myopathy with additional necklace fibres were found in the muscle biopsy. Sequencing of the DNM2 and MTM1 genes revealed a novel heterozygous missense mutation in exon 18 of the DNM2, leading to replacement of highly conserved proline at position 647 by arginine. The muscle symptoms have not progressed during the 3-year follow-up. However, the patient has developed bilateral subtle lens opacities. Our findings support the concept that necklace fibres may occasionally be found in DNM2-related myopathy, possibly indicating a common pathogenic mechanism in DNM2 and MTM1 associated centronuclear myopathy. (C) 2015 Elsevier B.V. All rights reserved.
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| 8. |
- Ciralli, Barbara, et al.
(författare)
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Unraveling the role of Slc10a4 in auditory processing and sensory motor gating : Implications for neuropsychiatric disorders?
- 2024
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Ingår i: Progress in Neuro-psychopharmacology and Biological Psychiatry. - : Elsevier. - 0278-5846 .- 1878-4216. ; 131
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPsychiatric disorders, such as schizophrenia, are complex and challenging to study, partly due to the lack of suitable animal models. However, the absence of the Slc10a4 gene, which codes for a monoaminergic and cholinergic associated vesicular transporter protein, in knockout mice (Slc10a4−/−), leads to the accumulation of extracellular dopamine. A major challenge for studying schizophrenia is the lack of suitable animal models that accurately represent the disorder. We sought to overcome this challenge by using Slc10a4−/− mice as a potential model, considering their altered dopamine levels. This makes them a potential animal model for schizophrenia, a disorder known to be associated with altered dopamine signaling in the brain.MethodsThe locomotion, auditory sensory filtering and prepulse inhibition (PPI) of Slc10a4−/− mice were quantified and compared to wildtype (WT) littermates. Intrahippocampal electrodes were used to record auditory event-related potentials (aERPs) for quantifying sensory filtering in response to paired-clicks. The channel above aERPs phase reversal was chosen for reliably comparing results between animals, and aERPs amplitude and latency of click responses were quantified. WT and Slc10a4−/− mice were also administered subanesthetic doses of ketamine to provoke psychomimetic behavior.ResultsBaseline locomotion during auditory stimulation was similar between Slc10a4−/− mice and WT littermates. In WT animals, normal auditory processing was observed after i.p saline injections, and it was maintained under the influence of 5 mg/kg ketamine, but disrupted by 20 mg/kg ketamine. On the other hand, Slc10a4−/− mice did not show significant differences between N40 S1 and S2 amplitude responses in saline or low dose ketamine treatment. Auditory gating was considered preserved since the second N40 peak was consistently suppressed, but with increased latency. The P80 component showed higher amplitude, with shorter S2 latency under saline and 5 mg/kg ketamine treatment in Slc10a4−/− mice, which was not observed in WT littermates. Prepulse inhibition was also decreased in Slc10a4−/− mice when the longer interstimulus interval of 100 ms was applied, compared to WT littermates.ConclusionThe Slc10a4−/− mice responses indicate that cholinergic and monoaminergic systems participate in the PPI magnitude, in the temporal coding (response latency) of the auditory sensory gating component N40, and in the amplitude of aERPs P80 component. These results suggest that Slc10a4−/− mice can be considered as potential models for neuropsychiatric conditions.
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| 9. |
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| 10. |
- Malfatti, E., et al.
(författare)
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A novel neuromuscular form of glycogen storage disease type IV with arthrogryposis, spinal stiffness and rare polyglucosan bodies in muscle
- 2016
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Ingår i: Neuromuscular Disorders. - : Elsevier BV. - 0960-8966. ; 26:10, s. 681-687
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Tidskriftsartikel (refereegranskat)abstract
- Glycogen storage disease type IV (GSD IV) is an autosomal recessive disorder causing polyglucosan storage in various tissues. Neuromuscular forms present with fetal akinesia deformation sequence, lethal myopathy, or mild hypotonia and weakness. A 3-year-old boy presented with arthrogryposis, motor developmental delay, weakness, and rigid spine. Whole body MRI revealed fibroadipose muscle replacement but sparing of the sartorius, gracilis, adductor longus and vastus intermedialis muscles. Polyglucosan bodies were identified in muscle, and GBE1 gene analysis revealed two pathogenic variants. We describe a novel neuromuscular GSD IV phenotype and confirm the importance of muscle morphological studies in early onset neuromuscular disorders. © 2016
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