Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1762617 (weakness)
 37,932 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hereditary spastic paraplegias comprise a group of clinically heterogeneous syndromes characterized by lower extremity spasticity and weakness, with distal axonal degeneration in the long ascending and descending tracts of the spinal cord. The early onset hereditary spastic paraplegia SPG3A is caused by mutations in the atlastin/human guanylate-binding protein-3 gene (renamed here atlastin-1), which codes for a 64-kDa member of the dynamin/Mx/guanylate-binding protein superfamily of large GTPases. The atlastin-1 protein is localized predominantly in brain, where it is enriched in pyramidal neurons in the cerebral cortex and hippocampus. In cultured cortical neurons, atlastin-1 co-localized most prominently with markers of the Golgi apparatus, and immunogold electron microscopy revealed a predominant localization of atlastin-1 to the cis-Golgi. Yeast two-hybrid analyses and co-immunoprecipitation studies demonstrated that atlastin-1 can self-associate, and gel-exclusion chromatography and chemical cross-linking studies indicated that atlastin-1 exists as an oligomer in vivo, most likely a tetramer. Membrane fractionation and protease protection assays revealed that atlastin-1 is an integral membrane protein with two predicted transmembrane domains; both the N-terminal GTP-binding and C-terminal domains are exposed to the cytoplasm. Together, these findings indicate that the SPG3A protein atlastin-1 is a multimeric integral membrane GTPase that may be involved in Golgi membrane dynamics or vesicle trafficking.
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PMID:Cellular localization, oligomerization, and membrane association of the hereditary spastic paraplegia 3A (SPG3A) protein atlastin. 1450 57

The hereditary spastic paraplegias (HSPs) (SPG1-29) comprise a group of inherited neurological disorders characterized principally by spastic lower extremity weakness due to a length-dependent, retrograde axonopathy of corticospinal motor neurons. Mutations in the gene encoding the dynamin superfamily member atlastin-1, an oligomeric GTPase highly localized to the Golgi apparatus in the adult brain, are responsible for SPG3A, a common autosomal dominant HSP. A distinguishing feature of SPG3A is its frequent early onset, raising the possibility that developmental abnormalities may be involved in its pathogenesis. Here, we demonstrate that several missense SPG3A mutant atlastin-1 proteins have impaired GTPase activity and thus may act in a dominant-negative, loss-of-function manner by forming mixed oligomers with wild-type atlastin-1. Using confocal and electron microscopies, we have also found that atlastin-1 is highly enriched in vesicular structures within axonal growth cones and varicosities as well as at axonal branch points in cultured cerebral cortical neurons, prefiguring a functional role for atlastin-1 in axonal development. Indeed, knock-down of atlastin-1 expression in these neurons using small hairpin RNAs reduces the number of neuronal processes and impairs axon formation and elongation during development. Thus, the "long axonopathy" in early-onset SPG3A may result from abnormal development of axons because of loss of atlastin-1 function.
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PMID:SPG3A protein atlastin-1 is enriched in growth cones and promotes axon elongation during neuronal development. 1653 71

Hereditary spastic paraplegia (HSP) is an inherited neurological disorder characterized by progressive spasticity and weakness of the lower extremities. The most common early-onset form of HSP is caused by mutations in the human gene that encodes the dynamin-family GTPase Atlastin-1 (Atl-1). Recently, loss of the Drosophila ortholog of Atl-1 (Atl) has been found to induce locomotor impairments from the earliest adult stages, suggesting the developmental role of atlastin-subfamily GTPases. Here, we provide evidence that Atl is required for normal growth of muscles and synapses at the neuromuscular junction (NMJ). Atl protein is highly expressed in larval body-wall muscles. Loss-of-function mutations in the atl gene reduce the size of muscles and increase the number of synaptic boutons. Rescue of these defects is accomplished by muscular, but not neuronal expression of Atl. Loss of Atl also disrupts ER and Golgi morphogenesis in muscles and reduces the synaptic levels of the scaffold proteins Dlg and alpha-spectrin. We also provide evidence that Atl functions with the microtubule-severing protein Spastin to disassemble microtubules in muscles. Finally, we demonstrate that the microtubule-destabilizing drug vinblastine alleviates synapse and muscle defects in atl mutants. Together, our results suggest that Atl controls synapse development and ER and Golgi morphogenesis by regulating microtubule stability.
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PMID:Drosophila Atlastin regulates the stability of muscle microtubules and is required for synapse development. 1934 24

Mutations in dynamin-2 (DNM2) cause autosomal dominant centronuclear myopathy (CNM). We report a series of 12 patients from eight families with CNM in whom we have identified a number of novel features that expand the reported clinicopathological phenotype. We identified two novel and five recurrent missense mutations in DNM2. Early clues to the diagnosis include relative weakness of neck flexors, external ophthalmoplegia and ptosis, although these are not present in all patients. Pes cavus was present in two patients, and in another two members of one family there was mild slowing of nerve conduction velocities. Whole-body MRI examination in two children and one adult revealed a similar pattern of involvement of selective muscles in head (lateral pterygoids), neck (extensors), trunk (paraspinal) and upper limbs (deep muscles of forearm). Findings in lower limbs and pelvic region were similar to that previously reported in adults with DNM2 mutations. Two patients presented with dystrophic changes as the predominant pathological feature on muscle biopsies; one of whom had a moderately raised creatine kinase, and both patients were initially diagnosed as congenital muscular dystrophy. DNM2 mutation analysis should be considered in patients with a suggestive clinical phenotype despite atypical histopathology, and MRI findings can be used to guide genetic testing. Subtle neuropathic features in some patients suggest an overlap with the DNM2 neuropathy phenotype. Missense mutations in the C-terminal region of the PH domain appear to be associated with a more severe clinical phenotype evident from infancy.
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PMID:Expanding the clinical, pathological and MRI phenotype of DNM2-related centronuclear myopathy. 2022 76

Mutations in the dynamin-2 (DNM2) gene can cause autosomal dominant or sporadic centronuclear myopathy (CNM). We aimed to analyze the clinical, pathological and genetic characteristic of patients with DNM2-related CNM in China. We studied seven patients, all of whom underwent clinical examination, muscle biopsy, electromyography, and genetic tests. DNM2 gene analysis revealed two sporadic patients harboring the p.E368K mutation, two patients from one family carrying p.R369Q, one with p.R369W, one with p.R523G and one with compound heterozygous mutations of p.R522H and p.R718Q. In DNM2-related CNM, ptosis, ophthalmoplegia/paresis, and facial weakness are the frequently observed manifestations. However, among these seven patients, only one had bilateral ptosis; one, external ophthalmoplegia and one, facial weakness. Muscle biopsy showed that the percentage of muscle fibers with centrally located nuclei ranged from 67 to 93 %, all with radial sarcoplasmic strands. To date, five different CNM-related DNM2 mutations have been observed in China. Here, a patient with compound heterozygous DNM2 mutations was reported for the first time. Facial weakness, ptosis and ophthalmoplegia did not appear to be common in Chinese patients. This study on Chinese patients broadens the spectrum of DNM2-related CNM.
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PMID:Clinical, pathological, and genetic features of dynamin-2-related centronuclear myopathy in China. 2550 59

Centronuclear myopathies (CNMs) are genetic diseases whose symptoms are muscle weakness and atrophy (wasting) and centralised nuclei. Recent human genetic studies have isolated several groups of mutations. Among them, many are found in two interacting proteins essential to clathrin-mediated endocytosis, dynamin and the BIN-Amphiphysin-Rvs (BAR) protein BIN1/amphiphysin 2. In this review, by using structural and functional data from the study of endocytosis mainly, we discuss how the CNM mutations could affect the structure and the function of these ubiquitous proteins and cause the muscle-specific phenotype. The literature shows that both proteins are involved in the plasma membrane tubulation required for T-tubule biogenesis. However, this system also requires the regulation of the dynamin-mediated membrane fission, and the formation of a stable protein-scaffold to maintain the T-tubule structure. We discuss how the specific functions, isoforms and partners (myotubularin in particular) of these two proteins can lead to the establishment of muscle-specific features.
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PMID:Structural insights into the centronuclear myopathy-associated functions of BIN1 and dynamin 2. 2734 96

Dynamin-2 is a ubiquitously expressed GTP-ase that mediates membrane remodeling. Recent findings indicate that dynamin-2 also regulates actin dynamics. Mutations in dynamin-2 cause dominant centronuclear myopathy (CNM), a congenital myopathy characterized by progressive weakness and atrophy of skeletal muscles. However, the muscle-specific roles of dynamin-2 affected by these mutations remain elusive. Here we show that, in muscle cells, the GTP-ase activity of dynamin-2 is involved in de novo actin polymerization as well as in actin-mediated trafficking of the glucose transporter GLUT4. Expression of dynamin-2 constructs carrying CNM-linked mutations disrupted the formation of new actin filaments as well as the stimulus-induced translocation of GLUT4 to the plasma membrane. Similarly, mature muscle fibers isolated from heterozygous knock-in mice that harbor the dynamin-2 mutation p.R465W, an animal model of CNM, exhibited altered actin organization, reduced actin polymerization and impaired insulin-induced translocation of GLUT4 to the sarcolemma. Moreover, GLUT4 displayed aberrant perinuclear accumulation in biopsies from CNM patients carrying dynamin-2 mutations, further suggesting trafficking defects. These results suggest that dynamin-2 is a key regulator of actin dynamics and GLUT4 trafficking in muscle cells. Our findings also support a model in which impairment of actin-dependent trafficking contributes to the pathological mechanism in dynamin-2-associated CNM.
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PMID:Dynamin-2 mutations linked to Centronuclear Myopathy impair actin-dependent trafficking in muscle cells. 2867 41

Centronuclear myopathy (CNM) is a group of rare genetic muscle disorders characterized by muscle fibers with centrally located nuclei. The most common forms of CNM have been attributed to X-linked recessive mutations in the MTM1 gene; autosomal-dominant mutations in the DNM2 gene-encoding dynamin-2, the BIN1 gene; and autosomal-recessive mutations in BIN1, RYR1, and TTN genes. Dominant CNM due to DNM2 mutations usually follows a mild clinical course with the onset in adolescence. Currently, around 35 mutations of the DNM2 gene have been identified in CNM; however, the underlying molecular mechanism of DNM2 mutation in the pathology of CNM remains elusive, and the standard clinical characteristics have not yet been defined. Here, we describe the case of a 17-year-old female who presented with proximal muscle weakness along with congenital anomalous pulmonary venous connection (which has not been described in previous cases of CNM), scoliosis, and lung disease without a significant family history. Her creatine kinase level was normal. Histology, special stains, and electron microscope findings on her skeletal muscle biopsy showed CNM with the characteristic features of a DNM2 mutation, which was later confirmed by next-generation sequencing. This case expands the known clinical and pathological findings of CNM with DNM2 gene mutation.
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PMID:A rare case of centronuclear myopathy with DNM2 mutation: genotype-phenotype correlation. 2874 Aug 38

Mitochondrial quality control is essential in highly structured cells such as neurons and muscles. In skeletal muscle the mitochondrial fission proteins are reduced in different physiopathological conditions including ageing sarcopenia, cancer cachexia and chemotherapy-induced muscle wasting. However, whether mitochondrial fission is essential for muscle homeostasis is still unclear. Here we show that muscle-specific loss of the pro-fission dynamin related protein (DRP) 1 induces muscle wasting and weakness. Constitutive Drp1 ablation in muscles reduces growth and causes animal death while inducible deletion results in atrophy and degeneration. Drp1 deficient mitochondria are morphologically bigger and functionally abnormal. The dysfunctional mitochondria signals to the nucleus to induce the ubiquitin-proteasome system and an Unfolded Protein Response while the change of mitochondrial volume results in an increase of mitochondrial Ca2+ uptake and myofiber death. Our findings reveal that morphology of mitochondrial network is critical for several biological processes that control nuclear programs and Ca2+ handling.
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PMID:DRP1-mediated mitochondrial shape controls calcium homeostasis and muscle mass. 3118