Dataset Information

Identification of an Alu element-mediated deletion in the promoter region of GNE in siblings with GNE myopathy.

ABSTRACT: GNE myopathy is a rare genetic disease characterized by progressive muscle atrophy and weakness. It is caused by biallelic mutations in the GNE gene that encodes for the bifunctional enzyme, uridine diphosphate (UDP)-N-acetylglucosamine (GlcNAc) 2-epimerase/N-acetylmannosamine (ManNAc) kinase. Typical characteristics of GNE myopathy include progressive myopathy, first involving anterior tibialis muscle and sparing the quadriceps, and rimmed vacuoles on muscle biopsy. Identifying biallelic mutations by sequencing of the GNE gene confirms the diagnosis of GNE myopathy. In a subset of patients, diagnostic confirmation is challenged by the identification of mutations in only one allele, suggesting mutations in deep intronic regions or regulatory regions.We performed targeted sequencing and copy number variant (CNV) analysis of GNE in two siblings who clinically presented with GNE myopathy. Further molecular and biochemical studies were done to characterize the effect of a previously uncharacterized GNE mutation.We report two siblings of Indian descent with characteristic features of GNE myopathy, including progressive skeletal muscle weakness initially involving the anterior tibialis, and rimmed vacuoles on muscle biopsy, in which a heterozygous mutation, p.Val727Met, was identified in both affected siblings, but no other deleterious variants in either coding region or exon-intron boundaries of the gene. Subsequent insertion/deletion analysis identified a novel 11.3-kb deletion (Chr9 [GRCh37]: g.36257583_36268910del) encompassing the GNE promoter region, with breakpoints residing in Alu repeats. Gene expression analysis revealed reduced GNE mRNA and protein levels, confirming decreased expression of the deleted allele harboring the deletion.We have identified GNE as one of the genes susceptible to Alu-mediated recombination. Our findings suggest that the deletion may encompass the promoter or another region necessary for GNE expression. In patients with typical manifestations of GNE myopathy and a single GNE variant identified, copy number variant (CNV) analysis may be useful in arriving at the diagnosis.

SUBMITTER: Garland J

PROVIDER: S-EPMC5511805 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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Identification of an <i>Alu</i> element-mediated deletion in the promoter region of <i>GNE</i> in siblings with GNE myopathy.

Garland Jennifer J Stephen Joshi J Class Bradley B Gruber Angela A Ciccone Carla C Poliak Aaron A Hayes Christina P CP Singhal Vandana V Slota Christina C Perreault John J Gavrilova Ralitza R Shrader Joseph A JA Chittiboina Prashant P Joe Galen G Heiss John J Gahl William A WA Huizing Marjan M Carrillo Nuria N Malicdan May Christine V MCV

Molecular genetics & genomic medicine 20170614 4

<h4>Background</h4>GNE myopathy is a rare genetic disease characterized by progressive muscle atrophy and weakness. It is caused by biallelic mutations in the <i>GNE</i> gene that encodes for the bifunctional enzyme, uridine diphosphate (UDP)-N-acetylglucosamine (GlcNAc) 2-epimerase/N-acetylmannosamine (ManNAc) kinase. Typical characteristics of GNE myopathy include progressive myopathy, first involving anterior tibialis muscle and sparing the quadriceps, and rimmed vacuoles on muscle biopsy. Id ...[more]

PMID: 28717665

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Project description:Genetic causes of ocular conditions remain largely unknown. To reveal the molecular basis for a congenital ocular phenotype associated with glaucoma we performed whole-exome sequencing (WES) and whole-genome copy number analyses of patient DNA. WES did not identify a causative variant. Copy number variation analysis identified a deletion of 10p13 in the patient and his unaffected father; the deletion breakpoint contained a single 37-bp sequence that is normally present in two distinct Alu repeats separated by ~181 kb. The deletion removed part of the upstream region of optineurin (OPTN) as well as the upstream sequence and two coding exons of coiled-coil domain containing 3 (CCDC3); analysis of the patient's second allele showed normal OPTN and CCDC3 sequences. Studies of zebrafish orthologs identified expression in the developing eye for both genes. OPTN is a known factor in dominant adult-onset glaucoma and Amyotrophic Lateral Sclerosis (ALS). The deletion eliminates 98 kb of the OPTN upstream sequence leaving only ~1 kb of the proximal promoter region. Comparison of transcriptional activation capability of the 3 kb normal and the rearranged del(10)(p13) OPTN promoter sequences demonstrated a statistically significant decrease for the deleted allele; sequence analysis of the entire deleted region identified multiple conserved elements with possible cis-regulatory activity. Additional screening of CCDC3 indicated that heterozygous loss-of-function alleles are unlikely to cause congenital ocular disease. In summary, we report the first regulatory region deletion involving OPTN, caused by Alu-mediated nonallelic homologous recombination and possibly contributing to the patient's ocular phenotype. In addition, our data indicate that Alu-mediated rearrangements of the OPTN upstream region may represent a new source of affected alleles in human conditions. Evaluation of the upstream OPTN sequences in additional ocular and ALS patients may help to determine the role of this region, if any, in human disease.

Project description:GNE myopathy is a slowly progressive autosomal recessive myopathy caused by mutations in the GNE (glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase) gene. This study aimed to (1) develop a nationwide patient registry for GNE myopathy in order to facilitate the planning of clinical trials and recruitment of candidates, and (2) gain further insight into the disease for the purpose of improving therapy and care.Medical records of genetically-confirmed patients with GNE myopathy at the National Center Hospital of the National Center of Neurology and Psychiatry (NCNP) were retrospectively reviewed in order to obtain data reflecting the severity and progression of the disease. We also referred to items in the datasheet of the nationwide registry of dystrophinopathy patients in the Registry of Muscular Dystrophies (Remudy). Items selected for the registration sheet included age, sex, age at onset, past history and complications, family history, body weight and height, pathological findings of muscle biopsy, grip power, walking ability, respiratory function, cardiac function, willingness to join upcoming clinical trials, and participation in patient associations. A copy of the original genetic analysis report was required of each patient.We successfully established the Remudy-GNE myopathy. Currently, 121 patients are registered nationwide, and 93 physicians from 73 hospitals collaborated to establish the registry. The mean age at onset was 27.7?±?9.6 years, and 19.8% (24/121) of patients could walk without assistance. Mean presumed durations from onset to use of assistive devices (cane and/or braces) and a wheelchair, and loss of ambulation were 12.4, 15.2, and 21.1 years, respectively. Three patients had a past history and/or complication of idiopathic thrombocytopenia. To share the progress of this study with the community, newsletters were published on a regular basis, and included information regarding new phase I clinical trials for GNE myopathy. The newsletters also served as a medium to bring attention to the importance of respiratory evaluation and care for respiratory insufficiency.The Japanese Remudy-GNE myopathy is useful for clarifying the natural history of the disease and recruiting patients with genetically-confirmed GNE myopathy for clinical trials.

Dataset Information

Identification of an Alu element-mediated deletion in the promoter region of GNE in siblings with GNE myopathy.

Publications

Identification of an <i>Alu</i> element-mediated deletion in the promoter region of <i>GNE</i> in siblings with GNE myopathy.

Similar Datasets

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