Distinct muscle imaging patterns in myofibrillar myopathies

OBJECTIVE

To compare muscle imaging findings in different subtypes of myofibrillar myopathies (MFM) in order to identify characteristic patterns of muscle alterations that may be helpful to separate these genetic heterogeneous muscular disorders.

METHODS

Muscle imaging and clinical findings of 46 patients with MFM were evaluated (19 desminopathy, 12 myotilinopathy, 11 filaminopathy, 1 alphaB-crystallinopathy, and 3 ZASPopathy). The data were collected retrospectively in 43 patients and prospectively in 3 patients.

RESULTS

In patients with desminopathy, the semitendinosus was at least equally affected as the biceps femoris, and the peroneal muscles were never less involved than the tibialis anterior (sensitivity of these imaging criteria to detect desminopathy in our cohort 100%, specificity 95%). In most of the patients with myotilinopathy, the adductor magnus showed more alterations than the gracilis muscle, and the sartorius was at least equally affected as the semitendinosus (sensitivity 90%, specificity 93%). In filaminopathy, the biceps femoris and semitendinosus were at least equally affected as the sartorius muscle, and the medial gastrocnemius was more affected than the lateral gastrocnemius. The semimembranosus mostly showed more alterations than the adductor magnus (sensitivity 88%, specificity 96%). Early adult onset and cardiac involvement was most often associated with desminopathy. In patients with filaminopathy, muscle weakness typically beginning in the 5th decade of life was mostly pronounced proximally, while late adult onset (>50 years) with distal weakness was more often present in myotilinopathy.

CONCLUSIONS

Muscle imaging in combination with clinical data may be helpful for separation of distinct myofibrillar myopathy subtypes and in scheduling of genetic analysis.

Clinical, genetic, and cardiac magnetic resonance imaging findings in primary desminopathies

We report the clinical, genetic and cardiac magnetic resonance imaging (MRI) findings in 11 German patients with heterozygous E245D, D339Y, R350P and L377P desmin mutations and without cardiac symptoms. Clinical evaluation revealed a marked variability of skeletal muscle, respiratory and cardiac involvement even between patients with identical mutations, ranging from asymptomatic to severely affected. While echocardiography did not show any pathological findings in all 11 patients, cine MRI revealed focal left ventricular hypertrophy in 2 patients and MR delayed enhancement imaging displayed intramyocardial fibrosis in the left ventricle in 4 patients indicating early myocardial involvement. Our data argue against distinct genotype-phenotype correlations and suggest that comprehensive cardiac MRI is superior to conventional echocardiography for the detection of early and clinically asymptomatic stages of cardiomyopathy in desminopathy patients. Therefore, cardiac MRI may serve as a screening tool to identify patients at risk, which might benefit from early pharmacological and/or interventional (e.g. implantable cardioverter-defibrillator devices) therapy.

Novel COLQ mutation 950delC in synaptic congenital myasthenic syndrome and symptomatic heterozygous relatives

The synaptic form of congenital myasthenic syndrome (CMS) is a rare autosomal recessive disease affecting neuromuscular transmission. Mutations in the COLQ gene that encodes the collagenic tail subunit (ColQ) of asymmetric acetylcholinesterase lead to endplate acetylcholinesterase deficiency. We report two children suffering from synaptic CMS due to two compound heterozygous COLQ mutations, IVS1-1G>A and a novel mutation, 950delC. Furthermore, we found familial occurrence of congenital ptosis in heterozygous carriers of 950delC, mimicking a dominant negative effect. Considering the lack of a clear genotype-phenotype-relation in synaptic CMS, several authors speculated on the influence of additional modifying factors. Consequently, involvement of such factors in this report of familial congenital ptosis cannot be excluded.

Pathological consequences of VCP mutations on human striated muscle

Mutations in the valosin-containing protein (VCP, p97) gene on chromosome 9p13-p12 cause a late-onset form of autosomal dominant inclusion body myopathy associated with Paget disease of the bone and frontotemporal dementia (IBMPFD). We report on the pathological consequences of three heterozygous VCP (R93C, R155H, R155C) mutations on human striated muscle. IBMPFD skeletal muscle pathology is characterized by degenerative changes and filamentous VCP- and ubiquitin-positive cytoplasmic and nuclear protein aggregates. Furthermore, this is the first report demonstrating that mutant VCP leads to a novel form of dilatative cardiomyopathy with inclusion bodies. In contrast to post-mitotic striated muscle cells and neurons of IBMPFD patients, evidence of protein aggregate pathology was not detected in primary IBMPFD myoblasts or in transient and stable transfected cells using wild-type-VCP and R93C-, R155H-, R155C-VCP mutants. Glutathione S-transferase pull-down experiments showed that all three VCP mutations do not affect the binding to Ufd1, Npl4 and ataxin-3. Structural analysis demonstrated that R93 and R155 are both surface-accessible residues located in the centre of cavities that may enable ligand-binding. Mutations at R93 and R155 are predicted to induce changes in the tertiary structure of the VCP protein. The search for putative ligands to the R93 and R155 cavities resulted in the identification of cyclic sugar compounds with high binding scores. The latter findings provide a novel link to VCP carbohydrate interactions in the complex pathology of IBMPFD.

The oral antidiabetic pioglitazone protects from neurodegeneration and amyotrophic lateral sclerosis-like symptoms in superoxide dismutase-G93A transgenic mice

Amyotrophic lateral sclerosis (ALS) represents a fatal neurodegenerative disorder characterized by progressive death of the upper and lower motor neurons. Because accompanying inflammation may interact with and promote neurodegeneration, anti-inflammatory treatment strategies are being evaluated. Because peroxisome proliferator-activated receptor gamma (PPARgamma) agonists act as potent anti-inflammatory drugs, we tested whether superoxide dismutase (SOD1)-G93A transgenic mice, a mouse model of ALS, benefit from oral treatment with the PPARgamma agonist pioglitazone (Pio). Pio-treated transgenic mice revealed improved muscle strength and body weight, exhibited a delayed disease onset, and survived significantly longer than nontreated SOD1-G93A mice. Quantification of motor neurons of the spinal cord at day 90 revealed complete neuroprotection by Pio, whereas nontreated SOD1-G93A mice had lost 30% of motor neurons. This was paralleled by preservation of the median fiber diameter of the quadriceps muscle, indicating not only morphological but also functional protection of motor neurons by Pio. Activated microglia were significantly reduced at sites of neurodegeneration in Pio-treated SOD1-G93A mice, as were the protein levels of cyclooxygenase 2 and inducible nitric oxide synthase. Interestingly, mRNA levels of the suppressor of cytokine signaling 1 and 3 genes were increased by Pio, whereas both the mRNA and protein levels of endogenous mouse SOD1 and of transgenic human SOD1 remained unaffected.

Proton transfer in bacterial nitric oxide reductase

The NOR (nitric oxide reductase) from Paracoccus denitrificans catalyses the two-electron reduction of NO to N2O (2NO+2H++2e−→N2O+H2O). The NOR is a divergent member of the superfamily of haem-copper oxidases, oxygen-reducing enzymes which couple the reduction of oxygen with translocation of protons across the membrane. In contrast, reduction of NO catalysed by NOR is non-electrogenic which, since electrons are supplied from the periplasmic side of the membrane, implies that the protons needed for NO reduction are also taken from the periplasm. Thus NOR must contain a proton-transfer pathway leading from the periplasmic side of the membrane into the catalytic site. The proton pathway has not been identified, and the mechanism and timing of proton transfer during NO reduction is unknown. To address these questions, we have studied the reaction between NOR and the chemically less reactive oxidant O2 [Flock, Watmough and Ädelroth (2005) Biochemistry 44, 10711–10719]. When fully reduced NOR reacts with O2, proton-coupled electron transfer occurs in a reaction that is rate-limited by internal proton transfer from a group with a pKa of 6.6. This group is presumably an amino acid residue close to the active site that acts as a proton donor also during NO reduction. The results are discussed in the framework of a structural model that identifies possible candidates for the proton donor as well as for the proton-transfer pathway.

Natural occurrence of Fusarium toxins in barley harvested during five years in an area of southwest Germany

A total of 44, 40, 47, 51, and 58 barley samples for feed use were collected randomly after the 1987, 1989, 1990, 1991, and 1992 crops, respectively, from farms located in an area of southwest Germany. The sum of precipitation from May to September was high in 1987 and markedly lower in 1989-1992. Deoxynivalenol, 3-. and 15-acetyldeoxynivalenol, nivalenol, fusarenon-X, T-2 toxin, HT-2 toxin and diacetxyscirpenol were determined by gas chromatography with mass selective detection (GC-MS), zearalenone,alpha- and beta-zearalenol by GC-MS or by HPLC. Deoxynivalenol was the major toxin with incidences at 71-98% and mean contents at 42-400 microg/kg. In contrast, incidences of zearalenone, 3-acetyldeoxynivalenol, nivalenol, HT-2 toxin, and T-2 toxin were at 7-68, 7-48, 11-41, 0-9, and 2-29%, respectively; with mean contents at 3-146 microg/kg. alpha- and beta-zearalenol and diacetoxyscirpenol were not detected in any sample. 15-acetyldeoxynivalenol and fusarenon-X were assayed in samples from 1987, 1991 and 1992. 15-acetyldeoxynivalenol was detected in 30, 0 and 2% of samples, respectively, with an average content of positive samples at 8 and 4 microg/kg, fusarenon-X was not detected. Over the years, incidences and levels of toxins remained constant, decreased or increased. The correlation between the occurrence of toxins and level of precipitation is discussed.

Klinische und molekulargenetische Befunde bei einer Patientin mit Fundus albipunctatus

METHODS

The 38-year-old index patient was examined by visual acuity testing, perimetry, dark adaptometry, funduscopy, electroretinogram (ERG), and multifocal ERG. She was screened for mutations in exons 2-5 and exon/intron boundaries of the 11- cis retinol dehydrogenase gene by direct sequencing.

RESULTS

Visual acuity was 1.0, but perimetry revealed paracentral scotomas associated with reading problems. The optic discs were normal. After 45 min of darkness there was nearly no increase of light sensitivity. After 30 min of dark adaptation, the scotopic ERG showed reduced amplitudes, but after 60 min a nearly normal level was reached. The 30-Hz flicker response of the cone ERG showed borderline implicit times, but no reduction of amplitudes. However, multifocal ERG clearly disclosed a paracentral amplitude reduction as the reason for the visual field defects. The fundus was typical for fundus albipunctatus. The patient is a compound heterozygote carrying a Ile33Asn and a Arg157Trp mutation.

CONCLUSIONS

The paracentral visual field defects were due to cone dysfunction. So far the patient exhibits no cone dystrophy.

Oxidative and premature skin ageing

To elucidate the scientific state of the art with respect to the role of nutrition in skin ageing, nine experts from different disciplines discussed the role of micronutrients on 'oxidative and premature skin ageing'. In this 25th Hohenheim Consensus Meeting, 13 questions were discussed and, based on published valid data, answered by mutual agreement. The consensus answers achieved during the meeting are justified by a scientific background text. The importance of in vitro and in vivo models regarding oxidative and premature skin ageing was critically evaluated. There was a special focus on prevention and intervention of skin ageing with nutrition. Finally, the paper summarizes the scientific background from different areas related to oxidative and premature skin ageing.

Pax7 distribution in human skeletal muscle biopsies and myogenic tissue cultures

Demonstration of the importance of the paired box transcription factor Pax7 for the murine myosatellite cell population, with persistent expression in mature skeletal muscle, prompted us to investigate the distribution of Pax7 protein in biopsy samples of normal and pathological human skeletal limb muscle. Immunostaining for M-cadherin, an adhesion molecule present at the interface between myofibre and satellite cell, and the characteristic position adjacent to the muscle fibre and beneath the fibre's basement membrane were used to identify satellite cells. Anti-Pax7 reactivity was found in the majority of satellite cells but a small population was Pax7 negative. Neither could we identify Pax7-positive nuclei in freshly regenerating myotubes or in presumed myoblasts in these biopsies. Similarly, in myogenic cell cultures derived from the explantation of human foetal muscle Pax7 expression was low or undetectable at the proliferative myoblast stage but it became prominent in an increasing proportion of mononucleate cells after the induction of differentiation. This expression was, however, restricted to mononucleate cells; it did not persist into the differentiation stage of newly formed multinucleate myotubes. Despite this, in the biopsy samples, we occasionally found Pax7-positive nuclei in muscle fibres that seemed to be undergoing degenerative changes. Most of these were found to be the nuclei of cells engaged in focal regenerative processes, but Pax7 re-expression by myonuclei "in distress" cannot be ruled out entirely.

Makrophagische Myofasziitis

HISTORY AND ADMISSION FINDINGS

A 67-year-old man presented with a 6-week history of slowly progressive muscle pain and generalized muscular weakness. Neurological examination showed symmetrical proximal weakness (MRC grade 4/5).

INVESTIGATIONS

Laboratory tests revealed an elevated CK level of 124 U/l (normal < 80). Needle EMG showed pathological spontaneous activity in proximal muscle groups. A diagnostic muscle biopsy taken from the left deltoid muscle revealed a characteristic infiltrate of PAS-positive and acid phosphatase-positive macrophages. Electron microscopic analysis of muscle tissue failed to demonstrate aluminium hydroxide inclusion. Serological analysis excluded antibodies against HAV and HBV but was compatible with a previous tetanus vaccination (antibody titre of 2.3 IE/ml).

TREATMENT

A 2-year treatment with steroids and azathioprine led to complete recovery of muscle strength without relapse after discontinuing the immunosuppression.

CONCLUSION

Macrophagic myofasciitis (MMF) is a rare inflammatory muscle disorder characterized by a characteristic infiltration of muscle tissue by PAS-positive macrophages, which is caused by pathological persistence of vaccine-derived aluminium hydroxide. The diagnosis can only be established by an open muscle biopsy from the muscle that was used for intramuscular vaccination.