SOD1 p.D12Y variant is associated with amyotrophic lateral sclerosis/distal myopathy spectrum.

BACKGROUND AND PURPOSE: The aim of our study was to describe patients with the p.D12Y variant (previously reported as D11Y) in SOD1 showing heterogeneous clinicopathological features. METHODS: We performed clinical, electrophysiological, magnetic resonance imaging (MRI) and muscle pathology studies in four SOD1 p.D12Y variant-positive patients. RESULTS: The SOD1 p.D12Y clinical manifestations ranged from a benign phenotype characterized by distal distribution of muscular weakness and long survival to classic forms of amyotrophic lateral sclerosis with poor prognosis. Two patients with the distal clinical phenotype showed MRI and muscle pathology alterations indicating a concurrent muscle involvement. In one of these patients significant myopathic changes were associated with rimmed vacuolar pathology. CONCLUSIONS: We expand the clinical spectrum of SOD1 p.D12Y variant, including predominant lower motor neuron forms with long survival and classic forms with aggressive course. Some patients may have concomitant distal myopathy without other explanations. Given clinical, MRI and muscle pathology alterations, SOD1 should be considered in the differential diagnosis of molecularly undefined distal myopathies with rimmed vacuoles.

Novel mutations in DNAJB6 cause LGMD1D and distal myopathy in French families.

BACKGROUND AND PURPOSE: The aim was to determine the genetic background of unknown muscular dystrophy in five French families. METHODS: Twelve patients with limb girdle muscular dystrophy or distal myopathy were clinically evaluated. Gene mutations were identified using targeted exon sequencing and mutated DNAJB6 was tested in vitro. RESULTS: Five patients presented with distal lower limb weakness whilst others had proximal presentation with a variable rate of progression starting at the mean age of 38.5 years. Two novel mutations (c.284A>T, p.Asn95Ile, two families; and c.293_295delATG, p.Asp98del, one family) as well as the previously reported c.279C>G (p.Phe93Leu, two families) mutation in DNAJB6 were identified. All showed a reduced capacity to prevent protein aggregation. CONCLUSIONS: The mutational and phenotypical spectrum of DNAJB6-caused muscle disease is larger than previously reported, including also dysphagia. The originally reported c.279C>G (p.Phe93Leu) mutation is now identified in four different populations and appears to be a mutational hotspot. Our report confirms that some DNAJB6 mutations cause distal-onset myopathy and hence DNAJB6 defects should be considered broadly in dominant muscular dystrophy families.

Diagnostic anoctamin-5 protein defect in patients with ANO5-mutated muscular dystrophy.

AIMS: Previously, detection of ANO5 protein has been complicated by unspecific antibodies, most of which have not identified the correct protein. The aims of the study were to specify ANO5 protein expression in human skeletal muscle, and to investigate if the ANO5 protein levels are affected by different ANO5 mutations in anoctaminopathy patients. METHODS: Four different antibodies were tested for ANO5 specificity. A sample preparation method compatible with membrane proteins, combined with tissue fractionation was used to determine ANO5 expression in cell cultures expressing ANO5, in normal muscles and eight patient biopsies with six different ANO5 mutations in homozygous or compound heterozygous states, and in other dystrophies. RESULTS: Only one specific monoclonal N-terminal ANO5 antibody was efficient in detecting the protein, showing that ANO5 is expressed as a single 107 kD polypeptide in human skeletal muscle. The truncating mutations c.191dupA and c.1261C>T were found to abolish ANO5 expression, whereas the studied point mutations had variable effects; however, all the ANO5 mutations resulted in clearly reduced ANO5 expression in the patient muscle membrane fraction. Attempts to detect ANO5 using immunohistochemistry were not yet successful. CONCLUSIONS: The data presented here indicate that the ANO5 protein expression is decreased in ANO5-mutated muscular dystrophy and that most of the non-truncating pathogenic ANO5 mutations likely destabilize the protein and cause its degradation. The method described here allows direct analysis of human ANO5 protein, which can be used in diagnostics, for evaluating the pathogenicity of the potentially harmful ANO5 variants of uncertain significance.

Association study reveals novel risk loci for sporadic inclusion body myositis.

BACKGROUND AND PURPOSE: The aim was to identify potential genetic risk factors associated with sporadic inclusion body myositis (sIBM). METHODS: An association based case-control approach was utilized on whole exome sequencing data of 30 Finnish sIBM patients and a control cohort (n = 193). A separate Italian cohort of sIBM patients (n = 12) was used for evaluation of the results. RESULTS: Seven single nucleotide polymorphisms were identified in five genes that have a considerably higher observed frequency in Finnish sIBM patients compared to the control population, and the previous association of the genetic human leukocyte antigen region was confirmed. CONCLUSIONS: All seven identified variants could individually or in combination increase the susceptibility for sIBM.

GNE-Myopathy in a Greek Romani Family with Unusual Calf Phenotype and Protein Aggregation Pathology.

BACKGROUND: GNE-myopathy is increasingly diagnosed in different ethnicities worldwide. No clear genotype-phenotype correlation has been established to date. CASE REPORTS: We describe two affected members of the same family from Balkan population carrying an already known homozygous pathogenic mutation in the kinase domain of the UDP-N-acetylglucosamine 2 epimerase/N-acetylmannosamime kinase (GNE) gene. The patients presented with severe distal weakness of lower legs combined with rimmed vacuoles in muscle biopsy. However, in contrast to the typical pattern of muscle involvement, one of them showed severe involvement of posterior calf muscles with spared anterior compartment of the lower leg muscles. CONCLUSIONS: These patients provide evidence for a larger variability and further extend the phenotypic spectrum of GNE-myopathy to include preferential calf involvement.

Myofibrillar and distal myopathies.

Distal myopathies and myofibrillar myopathies are both rare subcategories of muscle diseases. Myofibrillar myopathies are genetically heterogeneous group of diseases characterized by distinctive histopathology of abnormal protein aggregations and myofibrillar disintegration. All genes causing myofibrillar myopathy encode proteins that either reside in or associate with the Z-disc. Distal myopathies are also genetically heterogeneous muscular dystrophies in which muscle weakness presents distally in the feet and/or hands. A subgroup of distal myopathies, desminopathy, distal myotilinopathy, ZASPopathy and alpha-B crystallin-mutated distal myopathy, belong to myofibrillar myopathies and show similar pathological changes in muscle biopsies. Common features of these diseases are dominant inheritance and adult-onset of symptoms starting in the feet and slowly progressing to encompass other muscle groups. Cardiomyopathy is not a common feature in distal MFM myopathies.

Myofibrillar myopathies: State of the art, present and future challenges.

Myofibrillar myopathies (MFM) have been described in the mid-1990s as a group of diseases sharing common histological features, including an abnormal accumulation of intrasarcoplasmic proteins, the presence of vacuoles and a disorganization of the intermyofibrillar network beginning at the Z-disk. The boundaries of this concept are still uncertain, and whereas six genes (DES, CRYAB, LDB3/ZASP, MYOT, FLNC and BAG3) are now classically considered as responsible for MFM, other entities such as FHL1 myopathy or Hereditary Myopathy with Early Respiratory Failure linked to mutations of titin can now as well be included in this group. The diagnosis of MFM is not always easy; as histological lesions can be focal, and muscle biopsy may be disappointing; this has led to a growing importance of muscle imaging, and the selectivity of muscle involvement has now been described in several disorders. Due to the rarity of these myopathies, if some clinical patterns (such as distal myopathy associated with cardiomyopathy due to desmin mutations) are now well known, surprises remain possible and should lead to systematic testing of the known genes in case of a typical histological presentation. In this paper, we aim at reviewing the data acquired on the six main genes listed above as well as presenting the experience from two French reference centres, Paris and Marseilles.

Laing early-onset distal myopathy in a Belgian family.

We report the first Belgian family with Laing early-onset distal myopathy (MPD1). The proposita started limping at age 7. Later, there was severe weakness of proximal and distal muscles, including neck flexors. Her daughter developed foot drop at age 4. Progressive weakness of distal limb extensor muscles and mild weakness of the neck flexor and proximal muscles were noted. In both patients, CK and nerve conductions were normal, but EMG showed a brief, small amplitude, abundant, polyphasic potential pattern. Heart and respiration were normal. Several muscle biopsies have been performed in each with various diagnoses, including aspecific myopathic changes, congenital fibre type disproportion, and denervation-reinnervation. Analysis of MYH7 revealed a c.4522_4524del mutation (p.Glu1508del). This appears to be a de novo mutation, which has been reported in French, Norwegian, and Finnish patients.

'Pathognomonic' muscle imaging findings in DNAJB6 mutated LGMD1D.

BACKGROUND AND PURPOSE: We have previously reported clinical, genetic and molecular pathomechanistic findings in DNAJB6 mutated LGMD1D. After publishing clinical findings of the original Finnish family we identified more Finnish, Italian and US families with the same disease, ultimately confirmed by mutations in the same gene. METHODS: Of the total number of 28 examined Finnish and Italian patients 23 underwent lower limb muscle imaging. RESULTS: At the early stages of the disease fatty degeneration in T1-weighed MRI sequences were observed in the soleus, adductor magnus, semimembranosus and biceps femoris muscles followed by medial gastrocnemius, adductor longus and later by vasti muscles of the quadriceps. Rectus femoris, lateral gastrocnemius, sartorius, gracilis and the anterolateral group of the lower leg muscles were spared until late senecence. The pattern of differential involvement could be identified at different stages of the disease process. CONCLUSIONS: Since the general clinical findings do not provide clues for diagnosis this distinct pattern of muscle involvement and pathognomonic imaging findings are highly relevant in the clinical setting. The pattern of muscle involvement is so typical that it can be used as a differential diagnostic tool for LGMD1D. The final diagnosis however requires molecular genetic confirmation.

Altered expression and splicing of Ca(2+) metabolism genes in myotonic dystrophies DM1 and DM2.

AIMS: Myotonic dystrophy types 1 and 2 (DM1 and DM2) are multisystem disorders caused by similar repeat expansion mutations, with similar yet distinct clinical features. Aberrant splicing of multiple effector genes, as well as dysregulation of transcription and translation, has been suggested to underlie different aspects of the complex phenotypes in DM1 and DM2. Ca(2+) plays a central role in both muscle contraction and control of gene expression, and recent expression profiling studies have indicated major perturbations of the Ca(2+) signalling pathways in DM. Here we have further investigated the expression of genes and proteins involved in Ca(2+) metabolism in DM patients, including Ca(2+) channels and Ca(2+) binding proteins. METHODS: We used patient muscle biopsies to analyse mRNA expression and splicing of genes by microarray expression profiling and RT-PCR. We studied protein expression by immunohistochemistry and immunoblotting. RESULTS: Most of the genes studied showed mRNA up-regulation in expression profiling. When analysed by immunohistochemistry the Ca(2+) release channel ryanodine receptor was reduced in DM1 and DM2, as was calsequestrin 2, a sarcoplasmic reticulum lumen Ca(2+) storage protein. Abnormal splicing of ATP2A1 was more pronounced in DM2 than DM1. CONCLUSIONS: We observed abnormal mRNA and protein expression in DM affecting several proteins involved in Ca(2+) metabolism, with some differences between DM1 and DM2. Our protein expression studies are suggestive of a post-transcriptional defect(s) in the myotonic dystrophies.

Eight new mutations and the expanding phenotype variability in muscular dystrophy caused by ANO5.

OBJECTIVE: Description of 8 new ANO5 mutations and significant expansion of the clinical phenotype spectrum associated with previously known and unknown mutations to improve diagnostic accuracy. METHODS: DNA samples of 101 patients in 95 kindreds at our quaternary referral center in Finland, who had undetermined limb-girdle muscular dystrophy (LGMD), calf distal myopathy, or creatine kinase (CK) elevations of more than 2,000 IU/L, were selected for ANO5 genetic evaluation, and the clinical findings of patients with mutations were retrospectively analyzed. RESULTS: A total of 25 patients with muscular dystrophy caused by 11 different recessive mutations in the ANO5 gene were identified. The vast majority of mutations, 8 of 11, proved to be previously unknown new mutations. The most frequent mutation, c.2272C>T (p.R758C), was present in 20 patients. The phenotypes associated with this and the common European mutation, c.191dupA, varied from nearly asymptomatic high hyperCKemia to severe LGMD with consistently milder phenotypes in female patients. CONCLUSIONS: Mutations in ANO5 are a frequent cause of undetermined muscular dystrophy, with both distal and proximal presentation. Other types include high hyperCKemia, myalgia, or calf hypertrophy over decades without significant weakness, especially in female patients. Mutations are distributed all over the gene, indicating that muscular dystrophy caused by ANO5 can be expected to occur in all populations.

Spanish MYH7 founder mutation of Italian ancestry causing a large cluster of Laing myopathy patients.

Laing myopathy is a distal myopathy caused by mutations in the tail of the slow beta-myosin heavy chain gene MYH7. A large cluster of patients belonging to different families, with Laing myopathy due to p.K1729del mutation, was found in the Safor region, Spain. The same mutation was previously reported in an American family with Italian ancestry. The possibility that p.K1729del in MYH7 might be a founder mutation in the Safor patients and the chance of a common origin with the Italian-American family mutation was investigated by haplotype analyses, mutation data origin estimation and historical inquiry. Our results show that the p.K1729del in MYH7 harboured by patients from the Safor indeed is a founder mutation. A common ancestral origin of this mutation in the Spanish and Italian families is also suggested because they all share a core SNP haplotype at locus MYH7. Data estimation yields the origin of the mutation in the Safor at the beginning of the XVII century, when the Moorish were spelt and the region was resettled with Italian families.

Late-onset lower motor neuronopathy: a new autosomal dominant disorder.

OBJECTIVE: Characterization of a new type of late-onset autosomal dominant lower motor neuron disease. METHODS: Patients from 2 families underwent detailed neurologic, electrophysiologic, muscle biopsy, and laboratory investigations. MRI of lower limbs was performed in selected patients. DNA samples from leukocytes were used for molecular genetic linkage studies. RESULTS: First symptoms were muscle cramps and fasciculations after age 25-30, followed by a slowly progressive proximal and distal weakness without overt atrophy during the first decades of symptoms. Nerve conduction velocities were within normal range and EMG showed widespread neurogenic alterations. Muscle biopsy revealed characteristic neurogenic findings: fiber type grouping and group atrophy. MRI showed diffuse fatty-degenerative changes, marked in medial gastrocnemius. CONCLUSION: Exactly the same clinical phenotype has not previously been described, and linkage studies showed exclusion of known chromosomal loci for hereditary motor neuropathies, suggesting the disease we report may represent a new disorder.

MYH7 gene tail mutation causing myopathic profiles beyond Laing distal myopathy.

OBJECTIVE: To describe a wide range of clinical and pathologic myopathic profiles associated with the p.K1729del mutation in the MYH7 gene, known to cause Laing distal myopathy. METHODS: A study conducted in the Safor region (Spain), setting of a large cluster of patients. Clinical, neurophysiologic, muscle imaging, and muscle biopsy studies and MYH7 gene sequencing were investigated in 32 patients from 4 kindreds. Data from 36 deceased or nonexamined patients were collected from hospital records or relatives. RESULTS: Onset ranged from congenital to the 6th decade. All patients presented weakness of great toe/ankle dorsiflexors and many had associated neck flexor, finger extensor, and mild facial weakness. In most cases, involvement of proximal and axial muscles was observed either clinically or by muscle imaging, sometimes giving rise to scapuloperoneal and limb-girdle syndromes. Disabling myalgias, skeletal deformities, and dilated cardiomyopathy in one patient were associated features. Life expectancy was not reduced but the spectrum of disability ranged from asymptomatic to wheelchair confined. Electromyographic neurogenic features were frequently recorded. Muscle fiber type disproportion, core/minicore lesions, and mitochondrial abnormalities were the most relevant pathologic alterations. All patients carried the p.K1729del mutation in MYH7. CONCLUSIONS: The p.K1729del mutation in the MYH7 gene expresses notable clinical variability and electromyographic and pathologic features that can lead to the misdiagnosis of neurogenic atrophies, congenital myopathies, or mitochondrial myopathies. Mutations in genes encoding other sarcomeric and reticulo-sarcoplasmic proteins involved in calcium regulation share pathologic characteristics with our patients, suggesting a possible pathogenetic connection.

Myopathies caused by homozygous titin mutations: limb-girdle muscular dystrophy 2J and variations of phenotype.

Limb-girdle muscular dystrophy 2J caused by mutations in C-terminal titin has so far been identified in Finnish patients only. This may in part be due to limited availability of diagnostic tests for titin defects. In this report, a French family with an autosomal-dominant late-onset distal myopathy of the tibial muscular dystrophy phenotype segregating in several members of the family was described. One deceased patient in the family proved to be homozygous for the C-terminal truncating titin mutation because of consanguinity. According to available medical records, the patient had a clearly more severe generalised muscle weakness and atrophy phenotype not recognised as a distal myopathy at the time. Autopsy findings in one of the original Finnish limb-girdle muscular dystrophy 2J patients were reported and the early phenotype in a newly identified young patient with homozygous Finnish C-terminal titin mutation (FINmaj) was detailed.

Mutations in CHMP2B are not a cause of frontotemporal lobar degeneration in Finnish patients.

BACKGROUND: Frontotemporal lobar degeneration (FTLD) is a genetically complex disorder. The majority of mutations linked to FTLD families are found in the microtubule-associated protein tau (MAPT) and progranulin (PGRN) genes. Mutations in the chromatin-modifying protein 2B gene (CHMP2B) have been identified in a few families. However, CHMP2B has been showed to be a rare cause of FTLD. Our aim was to determine the frequency of CHMP2B mutations in a clinical series of patients with FTLD in Northern Finland. PATIENTS AND METHODS: We examined 72 (36 men) Finnish patients with FTLD. The mean age at onset was 58.9 (range 43­80). Symptoms of motor neuron disease (FTLDMND) were present in 12 patients (17%). Positive family history was detected in 28% of the patients. Mutations in MAPT and PGRN were excluded from these patients. All exons and exon­intron boundaries of the CHMP2B gene were sequenced. RESULTS: No pathogenic CHMP2B mutations were found. A rare polymorphism in the non-coding region of exon 1 (rs36098294) and three other previously reported polymorphisms were detected. CONCLUSIONS: Our results confirm that mutations in CHMP2B are not a common cause of FTLD. MAPT and PGRN mutations are also rare in Finnish population, suggesting that other, still unknown genetic factors may play a role in the pathogenesis of FTLD in Finnish population.

Incontinetia pigmenti-related myopathy or unsolved "double trouble"?

Incontinentia pigmenti is an X-linked dominant or sporadic multisystemic disorder with involvement of skin, eyes and central nervous system which results from mutations in the gene for NF-kappaB essential modulator (NEMO). We report on a patient with genetically confirmed Bloch-Sulzberger syndrome, who presented with a progressive myopathy and cardiomyopathy. Genetic analyses revealed an intragenic deletion (Intron3 and Exon10) of the NEMO/IKKgamma/IKKAP/IKBKG gene. Further complete sequencing of genes encoding for desmin, lamin A/C, emerin, and FHL1 showed no evidence of pathogenic mutations. A pathological expansion of CCTG repeats of the ZNF9 gene (PROMM) was ruled out by PCR amplification analysis. MLPA-analysis showed no evidence for duplications or deletions of the dystrophin gene. This report highlights the unusual combination of a genetically confirmed incontinentia pigmenti and a proximal myopathy and dilatative cardiomyopathy of unknown origin. We discuss that the striated muscle involvement (i) might be based on the observed intragenic deletion of the NEMO gene, or (ii) on an additional gene defect leading to an adult onset myopathy. Further studies on neuromuscular involvement in patients with incontinentia pigmenti are needed to clarify this issue.