Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026827 (hypotonia)
 5,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The congenital muscular dystrophies (CMD) constitute a clinically and genetically heterogeneous group of autosomal recessive myopathies. Patients show congenital hypotonia, muscle weakness, and dystrophic changes on muscle biopsy. Mutations in four genes (FKT1, POMGnT1, POMT1, FKRP) encoding putative glycosyltransferases have been identified in a subset of patients characterized by a deficient glycosylation of alpha-dystroglycan on muscle biopsy. FKRP mutations account for a broad spectrum of patients with muscular dystrophy, from a severe congenital form with or without mental retardation (MDC1C) to a much milder limb-girdle muscular dystrophy (LGMD2I). We identified two novel homozygous missense FKRP mutations, one, A455D, in six unrelated Tunisian patients and the other, V405L, in an Algerian boy. The patients, between the ages of 3 and 12 years, presented with a severe form of MDC1C with calf hypertrophy and high serum creatine kinase levels. None had ever walked. Two had cardiac dysfunction and one strabismus. They all had mental retardation, microcephaly, cerebellar cysts, and hypoplasia of the vermis. White matter abnormalities were found in five, mostly when cranial magnetic resonance imaging was performed at a young age. These abnormalities were shown to regress in one patient, as has been observed in patients with Fukuyama CMD. Identification of a new microsatellite close to the FKRP gene allowed us to confirm the founder origin of the Tunisian mutation. These results strongly suggest that particular FKRP mutations in the homozygous state induce structural and clinical neurological lesions in addition to muscular dystrophy. They also relate MDC1C to other CMD with abnormal protein glycosylation and disordered brain function.
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PMID:New FKRP mutations causing congenital muscular dystrophy associated with mental retardation and central nervous system abnormalities. Identification of a founder mutation in Tunisian families. 1465 96

Muscle-eye-brain disease (MEB), is caused by mutations in the POMGnT1 gene. We describe a white family with two siblings affected with congenital hypotonia early-onset glaucoma, and psychomotor delays. Brain magnetic resonance images (MRIs) showed hydrocephalus, bilateral frontal polymicrogyria, abnormal cerebellum, and characteristic flattened dystrophic pons. We identified novel POMGnT1 gene alterations in this family. Both affected siblings were found to be compound hetrozygotes and carried two missense changes inherited from their mother and one missense change (p.R442C) inherited from their father. Our findings further define the phenotypic spectrum of MEB and its occurrence in the US population.
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PMID:POMGnT1 gene alterations in a family with neurological abnormalities. 1523 14

Muscle-eye-brain disease (MEB, OMIM 253280) is an autosomal recessive disorder characterized by a distinct triad of congenital muscular dystrophy, structural eye abnormalities, and cobblestone lissencephaly. Clinically, MEB patients present with early onset muscular hypotonia, severely compromised motor development, and mental retardation. Magnetic resonance imaging reveals a lissencephaly type II with hypoplasia of the brainstem and cerebellum. MEB is associated with mutations in the gene for protein O-mannose beta-1,2-N-acetylglucosaminyltransferase (POMGnT1, OMIM 606822). In this paper, we report the clinical findings of nine MEB patients from eight families. Eight of the nine patients presented typical features of MEB. However, a broad phenotypic variability was observed, ranging from two patients with severe autistic features to another patient with an unusually mild phenotype, initially diagnosed as congenital muscular dystrophy. Furthermore, severe hydrocephalus was reported in two families during a previous pregnancy, emphasizing the phenotypic overlap with Walker-Warburg syndrome. In addition to three previously reported mutations, we identified six novel POMGnT1 mutations (one missense, five truncating) in the present patient cohort. Our data suggest mutational hotspots within the minimal catalytic domain at arginine residue 442 (exon 16) and in intron 17. It is interesting to note that all mutations analyzed so far result in a complete loss of enzyme activity. Therefore, we conclude that the type and position of the POMGnT1 mutations are not of predictive value for the clinical severity. This supports the notion that additional environmental and/or genetic factors may contribute to the observed broad spectrum of POMGnT1-associated phenotypes.
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PMID:Novel POMGnT1 mutations define broader phenotypic spectrum of muscle-eye-brain disease. 1790 81

Muscle-eye-brain disease (MEB) is characterised by congenital muscular dystrophy, structural brain malformations and eye abnormalities. We report a MEB case whose presenting sign was congenital blindness. She was investigated primarily for eye abnormalities at onset. She had bilateral retinal detachment and microphthalmia. Mild axial hypotonia and motor retardation were attributed to cerebral disorder in another center. Muscle biopsy showed mild myopathic changes and significant alpha-dystroglycan deficiency. Analysis of the POMGnT1 showed a novel homozygous mutation 1814G>C, causing p.Arg605Pro change. This case expands the clinical spectrum of MEB with unusually severe eye abnormalities compared to mild skeletal muscle and brain involvement.
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PMID:An unusual presentation of muscle-eye-brain disease: severe eye abnormalities with mild muscle and brain involvement. 1967 78

A term female infant was evaluated for global developmental delay, hypotonia, hyporeflexia, diffuse weakness including facial muscles, and visual impairment with optic nerve hypoplasia. In the absence of family history or perinatal concerns, an extensive investigation was performed, including lab studies, muscle biopsy, brain MRI and focused genetic testing. This revealed elevated serum CK, a structurally abnormal brain, and a dystrophic-appearing muscle biopsy with evidence of a glycosylation defect in the alpha-dystroglycan complex. Of the 6 known related genes, testing of the POMGnT1 gene showed three heterozygous missense mutations. Thus her history, examination, biopsy specimen, imaging, laboratory, and genetic studies are all consistent with the diagnosis of Muscle-Eye-Brain (MEB) disease. MEB is one of an emerging spectrum of congenital disorders that involve both central and peripheral nervous systems, described further in this case report.
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PMID:Muscle-Eye-Brain disease. 2021 85

Dystroglycan is a protein which binds directly to two proteins defective in muscular dystrophies (dystrophin and laminin alpha2) and whose own aberrant post-translational modification is the common aetiological route of neuromuscular diseases associated with mutations in genes encoding at least six other proteins (POMT1, POMT2, POMGnT1, LARGE, FKTN and FKRP). It is surprising, therefore, that to our knowledge no mutations of the human dystroglycan gene itself have yet been reported. In this study, we describe a patient with a heterozygous de novo deletion of a approximately 2-Mb region of chromosome 3, which includes the dystroglycan gene (DAG1). The patient is a 16-year-old female with learning difficulties, white matter abnormalities, elevated serum creatine kinase, oral-motor dyspraxia and facial hypotonia but minimal clinically significant involvement of other muscles. As these symptoms are a subset of those observed in disorders of dystroglycan glycosylation (muscle-eye-brain disease and Warker-Warburg syndrome), we assess the likely contribution to her phenotype of her heterogosity for a null mutation of DAG1. We also show that the transcriptional compensation observed in the Dag1(+/-) mouse is not observed in the patient. Although we cannot show that haploinsufficiency of DAG1 is the sole cause of this patient's myopathy and white matter changes, this case serves to constrain our ideas of the severity of the phenotypic consequences of heterozygosity for null DAG1 mutations.
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PMID:Heterozygous deletion of a 2-Mb region including the dystroglycan gene in a patient with mild myopathy, facial hypotonia, oral-motor dyspraxia and white matter abnormalities. 2023 91

Muscle-eye-brain (MEB) disease is a congenital muscular dystrophy (CMD) phenotype characterized by hypotonia at birth, brain structural abnormalities and ocular malformations. To date, few MEB cases have been reported in China where clinical recognition and genetic confirmatory testing on a research basis are recent developments. Here, we report the clinical and molecular genetics of three MEB disease patients. The patients had different degrees of muscle, eye and brain symptoms, ranging from congenital hypotonia, early-onset severe myopia and mental retardation to mild weakness, independent walking and language problems. This confirmed the expanding phenotypic spectrum of MEB disease with varying degrees of hypotonia, myopia and cognitive impairment. Brain magnetic resonance imaging showed cerebellar cysts, hypoplasia and characteristic brainstem flattening and kinking. Four candidate genes (POMGnT1, FKRP, FKTN and POMT2) were screened, and six POMGnT1 mutations (four novel) were identified, including five missense and one splice site mutation. Pathogenicity of the two novel variants in one patient was confirmed by POMGnT1 enzyme activity assay, protein expression and subcellular localization of mutant POMGnT1 in HeLa cells. Transfected cells harboring this patient's L440R mutant POMGnT1 showed POMGnT1 mislocalization to both the Golgi apparatus and endoplasmic reticulum. We have provided clinical, histological, enzymatic and genetic evidence of POMGnT1 involvement in three unrelated MEB disease patients in China. The identification of novel POMGnT1 mutations and an expanded phenotypic spectrum contributes to an improved understanding of POMGnT1 structure-function relationships, CMD pathophysiology and genotype-phenotype correlations, while underscoring the need to consider POMGnT1 in Chinese MEB disease patients.
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PMID:Novel POMGnT1 mutations cause muscle-eye-brain disease in Chinese patients. 2368 41