Dysferlinopathy in the Jews of the Caucasus: A frequent mutation in the dysferlin gene

doi:10.1016/j.nmd.2007.07.010

Neuromuscular Disorders

Volume 17, Issues 11–12, December 2007, Pages 950-954

https://doi.org/10.1016/j.nmd.2007.07.010 Get rights and content

Abstract

Dysferlin encoding gene (DYS) is mutated in the autosomal recessive disorders Miyoshi myopathy, Limb Girdle Muscular Dystrophy type 2B (LGMD2B) and distal anterior compartment myopathy, causing dysferlin deficiency in muscle biopsy. Three ethnic clusters have previously been described in Dysferlinopathy: the Libyan Jewish population originating in the area of Tripoli, Italian and Spanish populations. We report another cluster of this muscular dystrophy in Israel among Jews of the Caucasus region. A genomic analysis of the dysferlin coding sequence performed in patients from this ethnic group, who demonstrated an absence of dysferlin expression in muscle biopsy, revealed a homozygous frameshift mutation of G deletion at codon 927 (2779delG) predicting a truncated protein and a complete loss of functional protein. The possible existence of a founder effect is strengthened by our finding of a 4% carrier frequency in this community. These findings are important for genetic counseling and also enable a molecular diagnosis of LGMD2B in Jews of the Caucasus region.

Introduction

Limb Girdle Muscular Dystrophy type 2B (LGMD2B), Miyoshi myopathy (MM) and distal anterior compartment myopathy are autosomal recessive muscular disorders caused by mutations in the dysferlin gene (DYSF) [1], [2]. Dysferlin deficiency is demonstrated in muscle biopsy by immunohistochemistry and immunoblotting. The DYSF gene is located on chromosome 2p13, contains 55 coding exons and spans 150 kb of genomic DNA [3], [4]. The transcript is 6.3 kb large and is mainly expressed in skeletal muscle and heart [5]. The protein is involved in calcium dependent membrane fusion step of the muscle fiber repair process [6], [7]. No hot spot has been identified, and missense, nonsense and frameshift mutations have all been reported (Leiden Muscular Dystrophy database http://www.dmd.nl). About 400 allelic variants were described, 70% base substitutions and 20% small deletions consequently mutation analysis of DYSF remains a time-consuming task. Three ethnic clusters have been reported in LGMD2B: Libyan Jews [1], [8], Italian [9] and Spanish [10] populations with a clear founder effect. In the Libyan Jews there is only a single DYSF mutation while in the Italy and Spain other mutations were found.

We have lately noticed another potential ethnic cluster of Dysferlinopathy in the Israel among Jews originating from the Caucasus Mountains region. Jews from the area bordered on the south by Anatolia and Iran in Asia, on the west by the Black Sea, on the east by the Caspian Sea and on the north by Russia belong to a highly inbred community, thus we assumed a founder effect and a common mutation in Dysferlinopathy patients originating from this geographical area.

The aim of this study was to perform a genomic analysis of the dysferlin coding sequence in this community.

Section snippets

Patients

Ten patients from eight families originating from the Caucasus affected by muscular dystrophy were examined by neurologists from four Medical Centers in Israel. An informed consent was obtained from all patients, as well as from the healthy individuals. In three families, various degrees of consanguinity were established. At least one subject in every family had a muscle biopsy that confirmed the diagnosis of Dysferlinopathy. All patients had serum CK measurements and had had an EMG study at

Western blot analysis

Western blot analysis revealed a complete absence of the dysferlin signal while merosin (as a reference protein) was normal. Fig. 1 shows a representing three patients from the Caucasus with LGMD2B.

Genomic sequencing

Genetic analysis was first performed on the entire coding region and intron/exon boundaries of the DYSF gene in one patient. A single G base deletion at codon 927 (c.2779, exon 26) was found in a homozygous status, the parents being carriers (Fig. 2). The mutation was confirmed by a mismatch PCR

Discussion

We describe here a common mutation in Dysferlinopathy Jewish patients originating from Caucasus region. This mutation (2779delG) in exon 26 (codon 927) causes a frameshift in translation resulting in a downstream termination and consequently a truncated protein. The total absence of dysferlin protein analyzed by Western blot in our patients is well understood since antibodies used for dysferlin detection are aimed at amino acids 1999–2016 of the dysferlin, which are predicted to be absent in

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Genetic cause of heterogeneous inherited myopathies in a cohort of Greek patients
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Inherited muscle disorders are caused by pathogenic changes in numerous genes. Herein, we aimed to investigate the etiology of muscle disease in 24 consecutive Greek patients with myopathy suspected to be genetic in origin, based on clinical presentation and laboratory and electrophysiological findings and absence of known acquired causes of myopathy. Of these, 16 patients (8 females, median 24 years-old, range 7 to 67 years-old) were diagnosed by Whole Exome Sequencing as suffering from a specific type of inherited muscle disorder. Specifically, we have identified causative variants in 6 limb-girdle muscular dystrophy genes (6 patients; ANO5, CAPN3, DYSF, ISPD, LAMA2, SGCA), 3 metabolic myopathy genes (4 patients; CPT2, ETFDH, GAA), 1 congenital myotonia gene (1 patient; CLCN1), 1 mitochondrial myopathy gene (1 patient; MT-TE) and 3 other myopathy-associated genes (4 patients; CAV3, LMNA, MYOT). In 6 additional family members affected by myopathy, we reached genetic diagnosis following identification of a causative variant in an index patient. In our patients, genetic diagnosis ended a lengthy diagnostic process and, in the case of Multiple acyl-CoA dehydrogenase deficiency and Pompe’s disease, it enabled specific treatment to be initiated. These results further expand the genotypic and phenotypic spectrum of inherited myopathies.
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Milder forms were also identified within this community making the issue of genotype-phenotype correlation of lesser importance in this group, since they all are homozygous for the same founder mutation. Interestingly, in an even smaller Jewish community which was very isolated through history in the Caucasus mountain area, another founder mutation (2779delG) was found in 2007 with an estimated carrier rate of 4% [4]. The dysferlin story in Libyan Jews is typical for a recessively-inherited myopathy in a closed, well-defined small community.
Where do we stand in trial readiness for autosomal recessive limb girdle muscular dystrophies?
2016, Neuromuscular Disorders
Autosomal recessive limb girdle muscular dystrophies (LGMD2) are a group of genetically heterogeneous diseases that are typically characterised by progressive weakness and wasting of the shoulder and pelvic girdle muscles. Many of the more than 20 different conditions show overlapping clinical features with other forms of muscular dystrophy, congenital, myofibrillar or even distal myopathies and also with acquired muscle diseases. Although individually extremely rare, all types of LGMD2 together form an important differential diagnostic group among neuromuscular diseases. Despite improved diagnostics and pathomechanistic insight, a curative therapy is currently lacking for any of these diseases. Medical care consists of the symptomatic treatment of complications, aiming to improve life expectancy and quality of life. Besides well characterised pre-clinical tools like animal models and cell culture assays, the determinants of successful drug development programmes for rare diseases include a good understanding of the phenotype and natural history of the disease, the existence of clinically relevant outcome measures, guidance on care standards, up to date patient registries, and, ideally, biomarkers that can help assess disease severity or drug response. Strong patient organisations driving research and successful partnerships between academia, advocacy, industry and regulatory authorities can also help accelerate the elaboration of clinical trials. All these determinants constitute aspects of translational research efforts and influence patient access to therapies. Here we review the current status of determinants of successful drug development programmes for LGMD2, and the challenges of translating promising therapeutic strategies into effective and accessible treatments for patients.
Dysferlinopathy in Iran: Clinical and genetic report
2015, Journal of the Neurological Sciences
Citation Excerpt :
In our patients, clinically the weakest proximal muscles were the iliopsoas, quadriceps and hamstrings and at advanced stages, the feet and toes dorsiflexors were usually weaker than the gastrocnemius. Our findings are similar to Leshinsky-Silver et al. study who described 10 patients from 8 families originating from the Caucasus affected by dysferlinopathy [13]. In another report from China, 43 different disease-causing mutations (including 31 novel ones) have been identified in 34 patients [18].
Dysferlinopathy is caused by a very wide range of autosomal recessively inherited mutations of the Dysferlin gene. It causes a spectrum of muscle diseases including limb-girdle muscular dystrophy (LGMD) 2B and Miyoshi myopathy (MM). We describe the clinical course and mutational analyses of 15 Iranian patients with dysferlinopathy from 9 different families.
Genomic DNA was extracted from peripheral blood and 55 exons and flanking intronic boundaries of the dysferlin gene (DYSF; NM_003494.2) were screened for mutations and analyzed.
From 15 studied patients in 9 families, 5 patients were male. Seven families had consanguineous marriage. Median age of onset was 16.8; and the median age of diagnosis was 26.6. The onset was clearly distal in 7 patients, and proximal in 6 patients. Three patients had partial biceps atrophy and 13 showed prominent calf muscle wasting. Foot plantar flexors, deep finger flexors and hip adductors were predominantly involved. Genetic testing showed homozygous mutation of dysferlin gene in 9 probands, 5 of which were not previously reported.
This work, in fact, may help shed some light on the pattern of this morbidity in Iran, an effort that may have not been attempted so far.
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In our patients, there was not a single identical mutation found in DYSF gene. No one had the founder mutations identified in the Western patients [19,20]. The phenotypes of dysferlinopathy patients were diverse.
Muscular dystrophies and congenital myopathies are a large group of heterogeneous inherited muscle disorders. The spectrum of muscular dystrophies and congenital myopathies extends to more than 50 diseases today, even excluding the common forms Duchenne Muscular Dystrophy, Myotonic Dystrophy and Facioscapulohumeral Dystrophy. Unfortunately, even by critical clinical evaluation and muscle pathology, diagnosis is still difficult. To potentially remediate this difficulty, we applied a microarray-based targeted next-generation sequencing (NGS) technology to diagnose these patients. There were 55 consecutive unrelated patients who underwent the test, 36 of which (65%) were found to have a causative mutation. Our result shows the accuracy and efficiency of next-generation sequencing in clinical circumstances and reflects the features and relative distribution of inherited myopathies in the Chinese population.
McArdle disease: A novel mutation in Jewish families from the Caucasus region
2012, Molecular Genetics and Metabolism
Citation Excerpt :
The c.632delG (p.S211T-294X) mutation was initially identified in patient 1 by sequence analysis of all 20 exons of the PYGM gene. Given that Jews of the Caucasus (also called Mountain Jews) are distinct ethnic group that are highly inbreeded [8] and in view of the similar clinical and laboratory findings, when patients 2 and 3 presented later we searched directly for the same mutation. Molecular analysis was preferred for confirmation over the myophosphorylase assay because it does not require an invasive procedure and has advantages in terms of genetic consults.
McArdle disease is caused by a myophosphorylase deficiency consequent to defects in the PYGM gene. A minority of the over-133 known mutations are associated with ethnicity, occurring mainly in patients from western Europe, the United States, and Japan. We identified a novel mutation, c.632delG, in three unrelated families of Jewish descent originating from the Caucasus region. This possibly ethnicity-associated mutation can significantly facilitate the diagnosis in Jews of the Caucasus and contribute to genetic consultations.

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Neuromuscular Disorders

Abstract

Introduction

Section snippets

Patients

Western blot analysis

Genomic sequencing

Discussion

References (15)

Dysferlin interacts with annexins A1 and A2 and mediates sarcolemmal wound-healing

J Biol Chem

A gene related to Caenorhabditis elegans spermatogenesis factor fer-1 is mutated in limb-girdle muscular dystrophy type 2B

Nat Genet

Dysferlin, a novel skeletal muscle gene, is mutated in Miyoshi myopathy and limb girdle muscular dystrophy

Nat Genet

Linkage of Miyoshi myopathy (distal autosomal recessive muscular dystrophy) locus to chromosome 2p12–14

Neurology

Genomic organization of the dysferlin gene and novel mutations in Miyoshi myopathy

Neurology

Dysferlin is a plasma membrane protein and is expressed early in human development

Hum Mol Genet

Defective membrane repair in dysferlin-deficient muscular dystrophy

Nature

Cited by (34)

Genetic cause of heterogeneous inherited myopathies in a cohort of Greek patients

Neuromuscular disorders in Israel: A model country for ethnic clusters

Where do we stand in trial readiness for autosomal recessive limb girdle muscular dystrophies?

Dysferlinopathy in Iran: Clinical and genetic report

A comprehensive genetic diagnosis of Chinese muscular dystrophy and congenital myopathy patients by targeted next-generation sequencing

McArdle disease: A novel mutation in Jewish families from the Caucasus region