Limb-girdle Muscular Dystrophy Type 2L Research Articles

The Genetic Mutation of ANO5 in Rabbits Recapitulates Human Cardiomyopathy

The limb girdle muscular dystrophy type 2L (LGMD2L) is caused by mutations of the ANO5 gene in humans which encodes a 913 amino-acid integral membrane protein. Although cardiomyopathy has been reported in patients with an ANO5 mutation, the ANO5 mutant mice did not recapitulate this phenotype in previous studies. This study demonstrated that the ANO5−/− rabbits recapitulated the typical signs of cardiomyopathy with decreased ejection fraction (EF) and fraction shortening (FS) with increased interstitial fibrosis. This ANO5−/− rabbit model would promote basic research to comprehend the pathogenesis and mechanism of ANO5-related cardiomyopathy.

P.299Disease progression using quantitative MRI outcome measures in limb girdle muscular dystrophy 2L

Traditionally outcome measures for clinical trials in neuromuscular diseases are based on physical assessments which are dependent on patient effort, and may not be sensitive to progression over short trial periods in slow-progressing diseases. Limb girdle muscular dystrophy type 2L (LGMD2L) is a slowly progressive disease with weakness and atrophy of proximal muscles; elevated creatine kinase levels; and dystrophic findings on muscle biopsy. There is no effective treatment available for LGMD2L, but clinical trials have been conducted over the past years, which call for quantitative and reliable outcome measures to be developed. In this study, we investigated disease progression over 12 months in 16 patients with genetically confirmed LGMD2L, using quantitative outcome measures, including Dixon magnetic resonance imaging (MRI). We used MRI to assess changes in muscle fat content and stationary dynamometry to assess changes in muscle strength. Disease progression was also investigated with handheld dynamometry, handgrip strength and manual muscle testing (MMT). Preliminary results show a tendency of increased muscle fat fraction in the muscles analyzed using the quantitative MRI technique from baseline to 12 months follow up. The muscle fat fraction increased with 2% on average and the intrinsic back muscles showed the largest increase. Stationary dynamometry and handgrip strength decreased slightly, whereas handheld dynamometry and manual muscle testing did not change. The present study demonstrates a slow disease progression in LGMD2L. Dixon MRI detected increases in muscle fat content and is therefore a suitable candidate for an outcome measure in natural history or treatment studies in LGMD2L. The stationary dynamometry also seems to be reliable outcome measures for LMGMD2L.

Deficiency of Anoctamin 5/TMEM16E causes nuclear positioning defect and impairs Ca2+ signaling of differentiated C2C12 myotubes.

Anoctamin 5 (ANO5)/TMEM16E belongs to a member of the ANO/TMEM16 family member of anion channels. However, it is a matter of debate whether ANO5 functions as a genuine plasma membrane chloride channel. It has been recognized that mutations in the ANO5 gene cause many skeletal muscle diseases such as limb girdle muscular dystrophy type 2L (LGMD2L) and Miyoshi muscular dystrophy type 3 (MMD3) in human. However, the molecular mechanisms of the skeletal myopathies caused by ANO5 defects are poorly understood. To understand the role of ANO5 in skeletal muscle development and function, we silenced the ANO5 gene in C2C12 myoblasts and evaluated whether it impairs myogenesis and myotube function. ANO5 knockdown (ANO5-KD) by shRNA resulted in clustered or aggregated nuclei at the body of myotubes without affecting differentiation or myotube formation. Nuclear positioning defect of ANO5-KD myotubes was accompanied with reduced expression of Kif5b protein, a kinesin-related motor protein that controls nuclear transport during myogenesis. ANO5-KD impaired depolarization-induced [Ca2+]i transient and reduced sarcoplasmic reticulum (SR) Ca2+ storage. ANO5-KD resulted in reduced protein expression of the dihydropyridine receptor (DHPR) and SR Ca2+-ATPase subtype 1. In addition, ANO5-KD compromised co-localization between DHPR and ryanodine receptor subtype 1. It is concluded that ANO5-KD causes nuclear positioning defect by reduction of Kif5b expression, and compromises Ca2+ signaling by downregulating the expression of DHPR and SERCA proteins.

Anoctamin 5/TMEM16E facilitates muscle precursor cell fusion.

Limb-girdle muscular dystrophy type 2L (LGMD2L) is a myopathy arising from mutations in ANO5; however, information about the contribution of ANO5 to muscle physiology is lacking. To explain the role of ANO5 in LGMD2L, we previously hypothesized that ANO5-mediated phospholipid scrambling facilitates cell-cell fusion of mononucleated muscle progenitor cells (MPCs), which is required for muscle repair. Here, we show that heterologous overexpression of ANO5 confers Ca2+-dependent phospholipid scrambling to HEK-293 cells and that scrambling is associated with the simultaneous development of a nonselective ionic current. MPCs isolated from adult Ano5 -/- mice exhibit defective cell fusion in culture and produce muscle fibers with significantly fewer nuclei compared with controls. This defective fusion is associated with a decrease of Ca2+-dependent phosphatidylserine exposure on the surface of Ano5 -/- MPCs and a decrease in the amplitude of Ca2+-dependent outwardly rectifying ionic currents. Viral introduction of ANO5 in Ano5 -/- MPCs restores MPC fusion competence, ANO5-dependent phospholipid scrambling, and Ca2+-dependent outwardly rectifying ionic currents. ANO5-rescued MPCs produce myotubes having numbers of nuclei similar to wild-type controls. These data suggest that ANO5-mediated phospholipid scrambling or ionic currents play an important role in muscle repair.

LIMB-GIRDLE MUSCULAR DYSTROPHY I: P.2ANO5 - Three different phenotypes and a new histological pattern

Anoctamin 5 (ANO5) is a putative intracellular calcium- activated chloride channel. Recessive mutations in ANO5 cause primary muscle disease, and the clinical spectrum ranges from asymptomatic hyperCKemia and exercise-induced myalgia to proximal and/or distal muscle weakness. The most typical presentation is limb-girdle muscular dystrophy type 2L (LGMD2L). The objective of this work was to describe the clinical, pathological and molecular findings of three unrelated patients with ANO5 - related muscle dystrophy. To that end, we did a retrospective study, analyzing our database from October 2004 to February 2018 where 1,500 muscle biopsies for diagnostic purposes were performed. Patients were attended by two myology experts, who performed and analyzed muscle biopsies. Muscle biopsies were frozen in cooled isopenthane, cryostat sectioned and stained and reacted routinely (minimum 16 stainings). A custom panel including 115 genes (Nextera Rapid Capture, Illumina) and TruSight One Panel (Clinical Exome, Illumina) was used for NGS sequencing in those cases without a definite pathological diagnosis. All samples were sequenced in a MiSeq (Illumina) platform. As a result, three patients were diagnosed of ANO5 -related muscle dystrophy, all of them presenting the common exon 5 mutation c.191dup plus a missense mutation in the other allele. They showed three different phenotypes (LGMD2L, distal myopathy and asymptomatic hyperCKemia). Curiously, all three muscle biopsies showed different patterns, but in one of them it was seen numerous ragged-red fibers with little endomysial inflammation and partial invasion cell by T lymphocytes. In conclusion, ANO5 - related muscle dystrophy is a heterogeneous disease with different clinical phenotypes as we already knew, but also different histological patterns, even mimicking a mitochondrial myopathy. This work widens clinical, histological and anatomo-pathological features related to ANO5 mutations.

Development of muscular dystrophy in a CRISPR-engineered mutant rabbit model with frame-disrupting ANO5 mutations

Limb girdle muscular dystrophy type 2L (LGMD2L) and Miyoshi myopathy type 3 (MMD3) are autosomal recessive muscular dystrophy caused by mutations in the gene encoding anoctamin-5 (ANO5), which belongs to the anoctamin protein family. Two independent lines of mice with complete disruption of ANO5 transcripts did not exhibit overt muscular dystrophy phenotypes; instead, one of these mice was observed to present with some abnormality in sperm motility. In contrast, a third line of ANO5-knockout (KO) mice with residual expression of truncated ANO5 expression was reported to display defective membrane repair and very mild muscle pathology. Many of the ANO5-related patients carry point mutations or small insertions/deletions (indels) in the ANO5 gene. To more closely mimic the human ANO5 mutations, we engineered mutant ANO5 rabbits via co-injection of Cas9 mRNA and sgRNA into the zygotes. CRISPR-mediated small indels in the exon 12 and/or 13 in the mutant rabbits lead to the development of typical signs of muscular dystrophy with increased serum creatine kinase (CK), muscle necrosis, regeneration, fatty replacement and fibrosis. This novel ANO5 mutant rabbit model would be useful in studying the disease pathogenesis and therapeutic treatments for ANO5-deficient muscular dystrophy.

Limb-girdle muscular dystrophy type 2L - A case series from a tertiary center (P5.449)

Limb-girdle muscular dystrophy type 2L - A case series from a tertiary center (P5.449)

Hyperckemia and myalgia are common presentations of anoctamin-5-related myopathy in French patients.

Patients with anoctamin-5 (ANO5) mutations may present not only with limb-girdle muscular dystrophy type 2L or adult-onset Miyoshi-type myopathy but also with asymptomatic hyperCKemia, exercise intolerance, or rhabdomyolysis. Data from 38 patients in France with ANO5 mutations with and without muscle weakness on first examination were compared. Twenty patients presented without muscle weakness. Median age at symptom onset or discovery of hyperCKemia was 23 years. Creatine kinase levels ranged from 200 to 40,000 U/L. Electromyography showed a myopathic pattern in 5 patients, and muscle imaging showed involvement of posterior calf muscles in 10 patients. Mild cardiac involvement was observed in 2 patients. Sixteen patients remain free of weakness after a median follow-up period of 5 years. Asymptomatic, sometimes mild hyperCKemia or exercise intolerance is a presentation of ANO5-related myopathy and may remain isolated or precede muscle weakness by many years. Muscle Nerve 56: 1096-1100, 2017.

Defective membrane fusion and repair in Anoctamin5-deficient muscular dystrophy.

Limb-girdle muscular dystrophies are a genetically diverse group of diseases characterized by chronic muscle wasting and weakness. Recessive mutations in ANO5 (TMEM16E) have been directly linked to several clinical phenotypes including limb-girdle muscular dystrophy type 2L and Miyoshi myopathy type 3, although the pathogenic mechanism has remained elusive. ANO5 is a member of the Anoctamin/TMEM16 superfamily that encodes both ion channels and regulators of membrane phospholipid scrambling. The phenotypic overlap of ANO5 myopathies with dysferlin-associated muscular dystrophies has inspired the hypothesis that ANO5, like dysferlin, may be involved in the repair of muscle membranes following injury. Here we show that Ano5-deficient mice have reduced capacity to repair the sarcolemma following laser-induced damage, exhibit delayed regeneration after cardiotoxin injury and suffer from defective myoblast fusion necessary for the proper repair and regeneration of multinucleated myotubes. Together, these data suggest that ANO5 plays an important role in sarcolemmal membrane dynamics. Genbank Mouse Genome Informatics accession no. 3576659.

Genetic disruption of Ano5 in mice does not recapitulate human ANO5-deficient muscular dystrophy.

BackgroundAnoctamin 5 (ANO5) is a member of a conserved gene family (TMEM16), which codes for proteins predicted to have eight transmembrane domains and putative Ca2+-activated chloride channel (CaCC) activity. It was recently reported that mutations in this gene result in the development of limb girdle muscular dystrophy type 2L (LGMD2L), Miyoshi myopathy type 3 (MMD3), or gnathodiaphyseal dysplasia 1 (GDD1). Currently, there is a lack of animal models for the study of the physiological function of Ano5 and the disease pathology in its absence.ResultsHere, we report the generation and characterization of the first Ano5-knockout (KO) mice. Our data demonstrate that the KO mice did not present overt skeletal or cardiac muscle pathology at rest conditions from birth up to 18 months of age. There were no significant differences in force production or force deficit following repeated eccentric contractions between wild type (WT) and KO mice. Although cardiac hypertrophy developed similarly in both KO and WT mice after daily isoproterenol (ISO, 100 mg/kg) treatment via intraperitoneal injection for 2 weeks, they were functionally indiscernible. However, microarray analysis identified the genes involved in lipid metabolism, and complement pathways were altered in the KO skeletal muscle.ConclusionsTaken together, these data provide the evidence to show that genetic ablation of Ano5 in C57BL/6J mice does not cause overt pathology in skeletal and cardiac muscles, but Ano5 deficiency may lead to altered lipid metabolism and inflammation signaling.Electronic supplementary materialThe online version of this article (doi:10.1186/s13395-015-0069-z) contains supplementary material, which is available to authorized users.

Clinical and genetic features of anoctaminopathy in Saudi Arabia.

Objectives:Characterization of the phenotypic, pathological, radiological, and genetic findings in 2 Saudi Arabian families with anoctaminopathies, and limb girdle muscular dystrophy type 2L (LGMD2L).Methods:Over a 2-year period from December 2010 to January 2013, the clinical presentations were analyzed and all genes responsible for limb girdle muscular dystrophy (LGMD) were screened in families seen at King Faisal Specialist Hospital and Research Centre, a tertiary care hospital in Riyadh, Saudi Arabia. Out of 66 families with LGMD, we identified 2 families (3.1%) with anoctaminopathy, ANO5 muscular dystrophy.Results:In the first case, a man presented with asymmetrical calves’ muscles weakness and atrophy, which was first noted at age 39. The creatinine kinase (CK) level was >20x normal, muscle biopsy showed necrotizing myopathic changes, and an MRI of the legs showed fatty-tissue replacement to muscle tissue with volume loss involving the gastrocnemius and soleus muscles in an asymmetrical fashion. Minimal disease progression was noted over 18 years of follow up. Exercise induced recurrent rhabdomyolysis was noted over the last 2 years. A novel ANO5 gene mutation (Arg58Trp) was found. In the second family, a male presented at the age of 41 with asymptomatic hyperCkemia and intermittent dyspnea. Over 10 years follow up, he became disabled with muscle cramps, rhabdomyolysis, myoglobinurea, and difficulty ambulating. Muscle biopsy showed necrotizing myopathy and perivascular and interstitial amyloid deposit in skeletal muscle. A homozygous deletion of 11.9 Kb encompassing exon 13 to exon 17 was found in the ANO5 gene. Full cardiac investigations were normal in both patients.Conclusion:The prevalence of LGMD2L is approximately 3.1% in a Saudi Arabian native LGMD cohort. Slowly progressive, late onset, and asymmetrical weakness was the salient features in these 2 families. The genetic findings were novel and will add to the spectrum of ANO5 known mutations.

G.P.289: Novel ANO5 KO mouse provides new insight into LGMD2L pathogenesis

Limb girdle muscular dystrophy type 2L (LGMD2L) is caused by mutations in the anoctamin 5 (ANO5) gene. ANO5 encodes a predicted 107kDa protein containing 8 transmembrane domains and is part of a family that encodes at least 2 calcium-activated chloride channels; however the exact function of ANO5 has yet to be determined. The clinical phenotype overlaps with that of LGMD2B patients having mutations in dysferlin, a gene required for membrane repair. We have developed an ANO5 deficient mouse model (ANO5 KO) for LGMD2L for which no model currently exists. This model is necessary to study disease pathophysiology and test potential therapies. This deficient mouse model has been fundamental to characterize disease pathogenesis, discovering several proteins that may be associated with ANO5, and related functional incapacities. Based on the phenotypic overlap with dysferlin deficiency, we tested whether our ANO5 KO mouse model had a deficit in muscle membrane repair. Following laser induced injury, the flexor digitorum brevis muscles from ANO5 KO mice demonstrated reduced capacity to repair compared to WT strain controls. In addition, we also showed a loss of force compared to wild type mice after mechanical repetitive eccentric contraction in the extensor digitorum longus muscle.. Furthermore, we identified histopathological changes along with mislocalization or reduction in several muscle proteins which are linked and/or secondary to AN05. The ANO5 deficient mouse is novel and represents an important animal model for study of LGMD2L. It is the ideal model to develop proof of principle for gene replacement therapy or pharmacologic approaches and permits studies defining ANO5 function, a critical parameter for therapeutic intervention. The functional deficits we identified provide critical outcome measures to test efficacy of potential therapies and demonstrate feasibility of translation.

Aerobic training in patients with anoctamin 5 myopathy and hyperckemia

Anoctamin 5 deficiency has recently been defined to cause limb-girdle muscular dystrophy type 2L (LGMD2L) with pronounced hyperCKemia. No treatment interventions have been made so far in this condition. In 6 patients with LGMD2L, we studied the effect of home-based, pulse-watch monitored, moderate-intensity exercise on a cycle ergometer for 30 minutes, 3 times weekly, for 10 weeks. Plasma creatine kinase (CK) was assessed before, during, and after the program as a marker of muscle damage. Primary outcome measures were maximum oxygen uptake (VO(2max)) and time in the 5-repetitions-sit-to-stand test (FRSTST). Training resulted in improvements in VO(2max) (27 ± 7%; P = 0.0001) and FRSTST time (35 ± 12%; P = 0.007). Improvements in physiologic and functional muscle testing were accompanied by stable CK levels and no reports of adverse effects. These findings suggest that supervised aerobic exercise training is safe and effective in improving oxidative capacity and muscle function in patients with anoctamin 5 deficiency.

Macular dystrophy presenting in one of two siblings with limb-girdle muscular dystrophy type 2L due to mutation of ANO5

Macular dystrophy presenting in one of two siblings with limb-girdle muscular dystrophy type 2L due to mutation of ANO5

P.5.6 Aerobic training in patients with myopathy and hyperCKemia caused by anoctamin 5 deficiency

Several papers describing the phenotype and prevalence of the recently discovered limb-girdle muscular dystrophy type 2L (LGMD2L) caused by anoctamin 5 deficiency have been published, but no interventional studies have been performed. Aerobic training programs have previously been shown to improve physical conditioning in a range of similar myopathies. Therefore, we sought to investigate whether a supervised aerobic training program could improve endurance and functional outcomes in LGMD2L patients, as well, or whether the pronounced hyperCKemia associated with LGMD2L would escalate as a result of exercise-induced strain on muscles. The study included ten patients, of whom six completed. Patients performed home-based, but pulse-watch monitored, moderate-intensity exercise on a bike ergometer for 30 min, three times per week, for 10 weeks. Plasma CK was assessed before, during and after the program, as a marker of muscle damage. Primary outcomes were maximum oxygen uptake (VO2max) and time in the 5-repetitions-sit-to-stand test (FRSTST). Training resulted in improvements in VO2max (27 ± 7%; p = 0.0001) and FRSTST time (35 ± 12%; p = 0.007). Improvements in physiologic and functional muscle testing were accompanied by stabile levels of CK and no reports of adverse effects. Our findings suggest that supervised aerobic exercise training is both safe and effective in improving oxidative capacity and muscle function in muscular dystrophy patients with anoctamin 5 deficiency. Several papers describing the phenotype and prevalence of the recently discovered limb-girdle muscular dystrophy type 2L (LGMD2L) caused by anoctamin 5 deficiency have been published, but no interventional studies have been performed. Aerobic training programs have previously been shown to improve physical conditioning in a range of similar myopathies. Therefore, we sought to investigate whether a supervised aerobic training program could improve endurance and functional outcomes in LGMD2L patients, as well, or whether the pronounced hyperCKemia associated with LGMD2L would escalate as a result of exercise-induced strain on muscles. The study included ten patients, of whom six completed. Patients performed home-based, but pulse-watch monitored, moderate-intensity exercise on a bike ergometer for 30 min, three times per week, for 10 weeks. Plasma CK was assessed before, during and after the program, as a marker of muscle damage. Primary outcomes were maximum oxygen uptake (VO2max) and time in the 5-repetitions-sit-to-stand test (FRSTST). Training resulted in improvements in VO2max (27 ± 7%; p = 0.0001) and FRSTST time (35 ± 12%; p = 0.007). Improvements in physiologic and functional muscle testing were accompanied by stabile levels of CK and no reports of adverse effects. Our findings suggest that supervised aerobic exercise training is both safe and effective in improving oxidative capacity and muscle function in muscular dystrophy patients with anoctamin 5 deficiency.

Late-onset myopathy of the posterior calf muscles mimicking Miyoshi myopathy unrelated to dysferlin mutation: a case report

IntroductionMiyoshi myopathy, a type of distal myopathy with predominant involvement of the posterior calf muscles, has been assigned to mutations in the dysferlin gene. However, many of the late-onset limb-girdle and distal myopathies that resemble dysferlinopathy or Miyoshi myopathy remain unclassified, even after extensive immunohistological and genetic analysis.Case presentationWe report the case of a 59-year-old Caucasian man with distal myopathy and exercise-induced myalgia, preferentially of the leg muscles, closely resembling the Miyoshi phenotype. Magnetic resonance imaging of his calf muscles showed typical fatty replacement of the medial heads of the gastrocnemius muscles and soleus muscles, with progression to the adductor longus muscles over a time course of two years. However, genetic analysis revealed that the phenotype of our patient was not related to a mutation in the dysferlin gene but to a novel homozygous splice mutation in the anoctamin 5 gene. Mutations in the anoctamin 5 gene have so far been identified only in some cases of limb-girdle and distal myopathy. Mutations in the anoctamin 5 gene have been assigned to limb-girdle muscular dystrophy type 2L, while distal Miyoshi-like phenotypes have been classified as Miyoshi myopathy type 3.ConclusionThe case presented in this report further strengthens the underlying genetic heterogeneity in Miyoshi myopathy-like phenotypes and adds another family to non-dysferlin, Miyoshi myopathy type 3 of late-onset. Furthermore, our case supports the recent observation that anoctamin 5 mutations are a primary cause of distal non-dysferlin myopathies. Therefore, given the increasing number of anoctamin 5 mutations in Miyoshi-like phenotypes, genetic analysis should include an anoctamin 5 screen in late-onset limb-girdle and distal myopathies.

Muscle MRI findings in limb girdle muscular dystrophy type 2L

Limb girdle muscular dystrophy type 2L (LGMD2L) is an adult-onset slowly progressive muscular dystrophy associated with recessive mutations in the ANO5 gene. We analysed the muscle MRI pattern in a cohort of 25 LGMD2L patients in order to understand the extent and progression of muscle pathology in LGM2L and assess if muscle MRI might help in the diagnostic work-up of these patients. Our results showed a homogeneous pattern of muscle pathology on muscle MRI, with a predominant involvement of the posterior compartment muscles in both the thighs and calves. The muscles of the anterior compartments in the leg together with the sartorius and gracilis muscles were best preserved, which partially overlaps with patterns observed for other recessive LGMDs. Muscle MRI therefore does not appear to be as useful in the diagnostic work up of LGMD2L as for other neuromuscular diseases, such as Bethlem myopathy or myofibrillar myopathy.

Limb Girdle Muscular Dystrophy Type 2L (Anoctamin 5 Deficiency): Cardiac Involvement and Characterization of the Skeletal Muscle Phenotype (S15.006)

Objective: To test the prevalence of the newly discovered limb girdle muscular dystrophy type 2L (LGMD2L) in Denmark, and further characterize the phenotype. Background Mutations in the anoctamin 5 gene causes LGMD2L, which was first described in 2010. Two existing reports on small LGMD2L cohorts, suggest that LGMD2L may be a relatively common cause of LGMD2. Less than 30 patients have been reported so far. It appears that the disease, like LGMD2B (dysferlinopathy) may present as either classical LGMD2 or as a distal myopathy (MMD3), primarily involving the posterior calf musculature. In this study, we determined the prevalence of anoctamin 5 deficiency in a cohort of patients with unclassified LGMD2, hyperCKemia or distal myopathy. Design/Methods: All unclassified LGMD2 patients (26 out of 161), unexplained hyperCKemia (15 patients) and distal myopathies (5 patients) were tested for mutations in ANO5. All mutation-positive patients underwent a clinical exam, echocardiography and 48-h Holter monitoring. Results: Ten of 26 unclassified LGMD2 patients, 2 of the 15 hyperCKemia patients and 4 of 5 distal myopathy patients had LGMD2L. All patients carried the common c.191dupA mutation on at least one allele. Echocardiograhies were unremarkable, but Holter monitoring showed a 2.5-fold increase in premature ventricular contractions, which predicts an increased risk of cardiovascular disease. Only 2 of the 16 patients were women. In distal forms, the medial gastrocnemius muscle was the preferentially affected muscle, but the phenotype converges into a LGMD2 phenotype in all patients with time. Calpain 3 expression on Western blots was decreased in about half the patients. Conclusions: This study suggests that LGMD2L (16 patients) is the third commonest LGMD2 type in Denmark, only surpassed by LGMD2I (64 patients) and LGMD2A (22 patients). The study demonstrates for the first time that cardiac involvement may occur in this disease, and suggests a regular electrocardiographic follow-up of these patients. Disclosure: Dr. Vissing has received personal compensation for activities with Genzyme Corporation. Dr. Witting has nothing to disclose. Dr. Lauritsen has nothing to disclose. Dr. Duno has nothing to disclose.

P1.26 Occurrence of ANO5 mutation R758C in patients with a muscular dystrophy of unknown etiology

Recessive ANO5 gene mutations were recently reported to be the cause of limb-girdle muscular dystrophy type 2L (LGMD2L) and distal non-dysferlin Miyoshi-like myopathy. One of these mutations, c.2272C > T that leads to an amino acid substitution R758C, was found in two Finnish brothers with Miyoshi-like myopathy. R758C mutation was detected in two out of 578 Finnish control chromosomes which gives this mutation a frequency of 0.35% in Finnish population. With such frequency there should be some 50 R758C homozygote patients in Finland on a population of 5 million people. We screened 45 patients with a distal calf myopathy of unknown etiology and/or CK level over 3000. Four of these patients had ancestral origins in Germany and the rest were of Finnish origin. We identified three Finnish patients homozygous and two Finnish and three American patients heterozygous for R758C. In addition, one Finnish patient was a compound heterozygote with R758C in one chromosome and a previously unknown mutation c.2311_2312delCA in the other. R758C homozygote patients had both Miyoshi-like phenotypes and limb-girdle phenotypes as with LGMD2L. Our results indicate that R758C is a frequent cause of muscular dystrophy in Finland. Besides R758C there are at least two other ANO5 mutations in Finland, one of which is the new mutation c.2311_2312delCA. Moreover, R758C occurs also in other European populations.

P4.27 Muscle MRI findings in anoctaminopathy

Recessive mutations in the ANO5 gene have recently been identified in patients with either limb girdle muscular dystrophy type 2L (LGMD2L) or Miyoshi-like Myopathy (MMD3), collectively called anoctaminopathies. Our cohort of patients with anoctaminopathy shows a predominantly proximal pattern of weakness affecting the pelvic girdle and the lower limbs. Variable distal involvement is also observed, and sometimes presents as the first or predominant feature, similar to Miyoshi Myopathy. The upper extremities are affected only late in the disease process, usually with selective M.