Biomedical subjects

Jens Reimann

Publications and source records attributed to Jens Reimann.

8 recordsLinked to original sources

PubMed2006

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.

Adenosine Triphosphatases↗

PubMed2005

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.

Administration, Oral↗

PubMed2003

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.

Biopsy↗

PubMed2003

On noxious desmin: functional effects of a novel heterozygous desmin insertion mutation on the extrasarcomeric desmin cytoskeleton and mitochondria.

Recent studies in desmin (-/-) mice have shown that the targeted ablation of desmin leads to pathological changes of the extrasarcomeric intermediate filament cytoskeleton, as well as structural and functional abnormalities of mitochondria in striated muscle. Here, we report on a novel heterozygous single adenine insertion mutation (c.5141_5143insA) in a 40-year-old patient with a distal myopathy. The insertion mutation leads to a frameshift and a truncated desmin (K239fs242). Using transfection studies in SW13 and BHK21 cells, we show that the K239fsX242 desmin mutant is incapable of forming a desmin intermediate filament network. Furthermore, it induces the collapse of a pre-existing desmin cytoskeleton, alters the subcellular distribution of mitochondria and leads to abnormal cytoplasmic protein aggregates reminiscent of desmin-immunoreactive granulofilamentous material seen in the ultrastructural analysis of the patient's muscle. Analysis of mitochondrial function in isolated saponin-permeablized skeletal muscle fibres from our patient showed decreased maximal rates of respiration with the NAD-dependent substrate combination glutamate and malate, as well as a higher amytal sensitivity of respiration, indicating an in vivo inhibition of complex I activity. Our findings suggest that the heterozygous K239fsX242 desmin insertion mutation has a dominant negative effect on the polymerization process of desmin intermediate filaments and affects not only the subcellular distribution, but also biochemical properties of mitochondria in diseased human skeletal muscle. As a consequence, the intermediate filament pathology-induced mitochondrial dysfunction may contribute to the degeneration/regeneration process leading to progressive muscle dysfunction in human desminopathies.

Adenine↗

PubMed2003

Mitochondrial dysfunction in myofibrillar myopathy.

'Myofibrillar myopathy' defines a myopathic condition with focal myofibrillar destruction and accumulation of degraded myofibrillar elements. Despite the fact that a number of mutations in different genes as well as cytotoxic agents lead to the disease, abnormal accumulation of desmin is a typical, common feature. Pathological changes of mitochondrial morphology and function have been observed in animal models with intermediate filament pathology. Therefore, in the present study we tested for mitochondrial pathology in skeletal muscle of five patients with the pathohistological diagnosis of myofibrillar myopathy. Screening for large-scale mtDNA deletions and the frequent MERRF (myoclonic epilepsy; ragged red fibres) and MELAS (mitochondrial encephalomyopathy; lactic acidosis; stroke) point mutations was negative in all patients. Histologically, all muscle biopsies showed nonspecific abnormalities of the oxidative/mitochondrial enzyme stainings (histochemistry for reduced nicotinamide adenine dinucleotide, succinic dehydrogenase, cytochrome c oxidase), only one of them had ragged red fibres and a significant number of cytochrome c oxidase-negative fibres. Upon biochemical investigation, four of our patients showed pathologically low respiratory chain complex I activities. Only one of our patients had a pathologically low complex IV activity, while the measurements of the others were within low normal range. The single patient with pathological values for both complex I and IV was the one with the clear histological hallmarks (ragged red and cytochrome c oxidase-negative fibres) of mitochondrial pathology. She also was the only patient with clinical signs hinting at a mitochondrial disorder. Together with data from observations in desmin- and plectin-deficient mice, our results support the view that desmin intermediate filament pathology in these cases is closely linked to mitochondrial dysfunction in skeletal muscle.

Aged↗

PubMed2002

Primary longitudinal adhesion structures: plectin-containing precursors of costameres in differentiating human skeletal muscle cells.

Plectin is a high molecular mass protein (ca 530 kDa) that binds actin, intermediate filaments, and microtubules. Mutations of the human plectin gene cause epidermolysis bullosa simplex with muscular dystrophy. In mature human skeletal muscle, plectin is localized between neighboring myofibrils and between myofibrils and the sarcolemma, both at the level of Z-discs. In the present study we have analyzed plectin expression patterns with emphasis on its sarcolemmal localization during human skeletal muscle differentiation in vitro. In myoblasts plectin showed a cytoplasmic intermediate filament-like distribution, whereas in myotubes plectin is also found at the level of the sarcolemma. In particular, in early myotubes a specific plectin isoform colocalizes with the costameric proteins vinculin and beta1D integrin in longitudinally orientated structures which increased in number and longitudinal extension upon further maturation. In mature myotubes processes perpendicular to the parallel system of longitudinal structures became apparent. Subsequent to the occurrence of spontaneous myofibrillar contractions, the number of longitudinal streaks decreased, and plectin and other costameric proteins were found in an orderly cross-striated sarcolemmal lattice overlying myofibrillar Z-discs. Our study demonstrates that plectin is preassembled together with vinculin and beta1D integrin into primary longitudinal adhesion structures. After the occurrence of spontaneous contractions, these structures reorient and mature costameres are assembled.

Cell Differentiation↗

PubMed2002

Expression, localization and functional divergence of alphaB-crystallin and heat shock protein 27 in core myopathies and neurogenic atrophy.

AlphaB-crystallin (alphaBC) and heat shock protein 27 (hsp 27) are members of the family of small heat shock proteins (shsps), which exert a role as molecular chaperones by binding unfolded or denatured proteins, thereby suppressing irreversible protein aggregation and consecutive cell damage. The essential role of shsps in human neuromuscular disorders is highlighted by the observation that a mutation of the human alphaBC gene causes an autosomal dominant "myofibrillar myopathy" characterized by alphaBC and desmin accumulation. Furthermore, an aberrant immunostaining of alphaBC was recently reported in sporadic inclusion body myositis. In the present study we analyzed the expression and localization of alphaB-crystallin and hsp 27 in various congenital myopathies by means of indirect immunofluorescence, immunogold electron microscopy and Western blotting. We demonstrate an increased immunoreactivity of alphaBC and hsp 27 in central and minicore lesions as well as in target fibers, which renders both shsps as reliable, but nonspecific, markers for core and target structures. In contrast, Western blotting demonstrated a normal expression level of alphaBC and hsp 27, which indicates that the increased immunostaining is not the result of an enhanced protein expression. Furthermore, thiocyanate-induced degradation of actin filaments led to a dramatic decrease of hsp 27 immunostaining in core and target lesions, whereas the increased alphaBC and desmin immunostaining was found to be even more enhanced. The latter findings imply a functional diversity of both shsps with a preferential association of hsp 27 with the actin microfilament system and alphaBC with the intermyofibrillar desmin cytoskeleton in human skeletal muscle.

Actins↗

PubMed2002

Disorganization of the desmin cytoskeleton and mitochondrial dysfunction in plectin-related epidermolysis bullosa simplex with muscular dystrophy.

Mutations of the human plectin gene (Plec1) cause autosomal recessive epidermolysis bullosa simplex with muscular dystrophy (EBS-MD). Here, we report on molecular mechanisms leading to severe dystrophic muscle alterations in EBS-MD. Analysis of a 25-yr-old EBS-MD patient carrying a novel homozygous 16-bp insertion mutation (13803ins16/13803ins16) close to the intermediate filament (IF) binding site of plectin showed severe disorganization of the myogenic IF cytoskeleton. Intermyofibrillar and subsarcolemmal accumulations of assembled but highly unordered desmin filaments may be attributed to impaired desmin binding capability of the mutant plectin. This IF pathology was also associated with severe mitochondrial dysfunction, suggesting that the muscle pathology of EBS-MD caused by IF disorganization leads not only to defects in mechanical force transduction but also to metabolic dysfunction. Beyond EBS-MD, our data may contribute to the understanding of other myopathies characterized by sarcoplasmic IF accumulations such as desminopathies or alpha-B-crystallinopathies.

Adult↗