Novel c.191C>G (p.Pro64Arg) MPV17 mutation identified in two pairs of unrelated Polish siblings with mitochondrial hepatoencephalopathy.

This study reports clinical, biochemical and histopathological findings associated with a novel homozygous MPV17 mutation in four patients with mitochondrial depletion syndrome. The severe course of the disease, which started in the first weeks of life, was dominated by a failure to thrive, hypotonia and liver dysfunction, with relatively mild neurological involvement. All affected infants died by 1 year of age. Laboratory findings included progressive liver failure (hypertransaminasaemia, icterus, and coagulopathy), recurrent hypoglycaemia, lactic acidaemia, hyperferritinaemia, and increased transferrin saturation. Histological and ultrastructural analyses uncovered significant lipid accumulation in hepatocytes and myocytes. A severe decrease in the mitochondrial/nuclear DNA (mtDNA/nDNA) ratio was found post-mortem in the livers (and in one muscle specimen) of both examined patients. Oxidative phosphorylation system (OXPHOS) Western blotting revealed low levels of complexes I, III and IV subunits. The highlights of our findings are as follows: (i) The novel p.Pro64Arg mutation is the second recurrent MPV17 mutation reported. The phenotype associated with the p.Pro64Arg mutation differs from the phenotype of the relatively common p.Arg50Gln mutation, suggesting the existence of a genotype-phenotype correlation. (ii) Tissues collected from patients during autopsy may be useful for both mtDNA/nDNA ratio assessment and OXPHOS Western blotting.

X-linked Emery-Dreifuss muscular dystrophy with lamin A deficiency and IBM inclusions.

The study demonstrates a 12-year-old patient with progressive proximal muscle weakness, joint contractures, rigidity of the neck, and absence of emerin and lamin A in the muscle nuclei, which is caused by intronic mutation IVS3-27del18 (c.266-27del18) in the emerin gene. The most surprising finding was the appearance of IBM-like inclusions in euchromatin, as well as aberrant nuclei. It may be speculated that altered expression of the emerin-lamin complex and modification of the nuclear matrix leads to formation of tubulofilamentous structures in the presented case.

Altered distribution of lamin and emerin in muscle nuclei of sIBM patients.

OBJECTIVE: Sporadic inclusion body myositis (sIBM) is a chronic acquired inflammatory myopathy. The cause of sIBM remains unknown and its pathogenesis is controversial. There is a hypothesis [Karpati and Carpenter 1993] that the rimmed vacuoles result from nuclear breakdown, and IBM filaments are formed from components of the nuclear matrix. MATERIAL AND METHODS: For nuclear membrane protein detection, six IBM patients were studied using immunohistochemical and immunochemical techniques. RESULTS: It was demonstrated that in the interior of 10-15% myonuclei emerin and lamin A/C inclusions appeared constantly. This finding indicated an abberant localization of lamin A/C epitopes, the presence of presumptive lamin A (67 KDu) and emerin as in the affected nuclei. CONCLUSION: We support the suggestion that truncated, changed lamin A protein takes part in nuclear disintegration and rimmed vacuole formation.

Early onset Charcot-Marie-Tooth disease caused by a homozygous Leu239Phe mutation in the GDAP1 gene.

Mutations in the ganglioside -induced differentiation-associated protein 1 (GDAP1) gene are common a cause of the Charcot-Marie-Tooth (CMT4A) disease with autosomal recessive mode of inheritance. To date more than twenty mutations in the GDAP1 gene have been reported in patients suffering from the demyelinating, axonal or mixed form of Charcot-Marie-Tooth disease. Only in a few CMT4A affected patients sural nerve biopsy findings have been provided. We report a homozygous Leu239Phe mutation in the GDAP1 gene in a 39-year-old female with a severe form of mixed axonal and demyelinating Charcot-Marie-Tooth disease.

Atypical motor unit potentials in Emery-Dreifuss muscular dystrophy (EDMD).

OBJECTIVE: The aim of the study was to analyse electromyographic changes in Emery-Dreifuss muscular dystrophy (EDMD) that are atypical for myopathy. Our special interest was focused on high amplitude polyphasic motor unit potentials (MUPs), also termed irregular MUPs. METHODS: We studied 21 EDMD patients with the diagnosis based on clinical data, DNA analysis and immunohistochemical muscle studies. Rectus femoris muscle biopsies were investigated in all affected patients. Electrophysiological investigations involved quantitative concentric needle electromyography (CNEMG) of biceps brachii (BB) and rectus femoris (RF) muscles. Simulation studies were performed to approximate the number, diameter and distribution of muscle fibers, which contribute to irregular MUPs. RESULTS: The EMG data in EDMD were compatible with myopathy. Irregular MUPs showed longer duration, larger area, size index and higher amplitude then simple ones (P < 0.05). The approximation of features of muscle fibers contributing to irregular MUP also indicated smaller (<45 microm) and larger (>55 microm) diameters than normal (50 +/- 5 microm). Muscle biopsy specimens revealed the variable muscle fiber size due to atrophy, hypertrophy, and muscle fiber splitting. CONCLUSIONS: Irregular MUPs recorded in EDMD are due to hypertrophied and atrophied fibers as well as increased fiber density. They reflect reorganization of the motor unit in a slow progression myopathic process (muscle fiber hypertrophy and splitting). SIGNIFICANCE: Irregular MUPs in EDMD most probably reflect increased variability of the muscle fiber size.

In vivo and in vitro examination of the functional significances of novel lamin gene mutations in heart failure patients.

CONTEXT: Lamin A/C (LMNA) gene variations have been reported in more than one third of genotyped families with dilated cardiomyopathy (DCM). However, the relationship between LMNA mutation and the development of DCM is poorly understood. METHODS AND RESULTS: We found that end stage DCM patients carrying LMNA mutations displayed either dramatic ultrastructural changes of the cardiomyocyte nucleus (D192G) or nonspecific changes (R541S). Overexpression of the D192G lamin C dramatically increased the size of intranuclear speckles and reduced their number. This phenotype was only partially reversed by coexpression of the D192G and wild type lamin C. Moreover, the D192G mutation precludes insertion of lamin C into the nuclear envelope when co-transfected with the D192G lamin A. By contrast, the R541S phenotype was entirely reversed by coexpression of the R541S and wild type lamin C. As lamin speckle size is known to be correlated with regulation of transcription, we assessed the SUMO1 distribution pattern in the presence of mutated lamin C and showed that D192G lamin C expression totally disrupts the SUMO1 pattern. CONCLUSION: Our in vivo and in vitro results question the relationship of causality between LMNA mutations and the development of heart failure in some DCM patients and therefore, the reliability of genetic counselling. However, LMNA mutations producing speckles result not only in nuclear envelope structural damage, but may also lead to the dysregulation of cellular functions controlled by sumoylation, such as transcription, chromosome organisation, and nuclear trafficking.

Congenital myopathy with tubular aggregates and tubulofilamentous IBM-type inclusions.

We report on a 16-year-old girl with a unique neuromuscular disorder characterised by progressive proximal muscle weakness and numerous tubular aggregates, intracytoplasmic, as well as intranuclear inclusions of the IBM type in her muscle biopsy. The clinical features of the presented case, as manifested by the early childhood onset of the disease, proximal weakness, lumbar hyperlordosis, and bilateral Achilles tendon contractures, were suggestive of congenital myopathy. To the best of our knowledge, the coexistence of tubular aggregates and tubulofilamentous inclusions of the IBM type in a child has never been described.

CADASIL: new cases and new questions.

We described the first two unrelated Polish families with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). In the morphological examination with light microscopy, two kinds of changes were observed: (1). panarteritis nodosa-like changes with eosinophilic fibrinoid necrosis of the vessel wall and perivascular inflammatory infiltrates and (2). basophilic granular material in the tunica media characteristic of CADASIL. At electron microscopy, we found deposits of granular osmophilic material (GOM) within the wall of arteries, veins and capillary vessels. Our findings imply two questions requiring further investigation: Why in the genetically determined vascular disorder are the features of systemic inflammatory vascular disease present? Why in capillary walls deprived of smooth muscle cells are deposits of GOM present?

Congenital myopathy with abundant ring fibres, rimmed vacuoles and inclusion body myositis-type inclusions.

We report a 17-year-old girl with an unusual neuromuscular disorder characterised by slowly progressive proximal muscle weakness whose muscle biopsy showed multiple ring fibres and numerous rimmed vacuoles as well as intracytoplasmic and intranuclear inclusions of the inclusion body myositis-type. The clinical features of the presented case, manifested by the onset of the disease in early childhood, delayed motor development, short stature, lordosis and joint contractures were suggestive of congenital myopathy. The coexistence of ring fibres, rimmed vacuoles and inclusion-body myositis-type inclusions in a child with congenital myopathy has not been previously reported.

Expression of emerin and lamins in muscle of patients with different forms of Emery-Dreifuss muscular dystrophy.

Emerin and lamins are nuclear proteins, which are missing or defective in Emery-Dreifuss muscular dystrophy (EDMD). The aim of this study was to test the expression of these proteins in skeletal muscles in the X-linked (X-EDMD) and autosomal dominant (AD-EDMD) form. The study group consisted of 11 patients with X-EDMD, 11 patients of the AD-EDMD and 20 age-matched normal subjects. Expression of emerin and lamins in muscles were analyzed by Western blotting and the immunocytochemical technique. Using the Western blotting procedure emerin was detected in traces in the X-linked form. In the majority of these cases (6/11) it was connected with a decreased concentration of lamin A, in four patients a lowered concentration of lamin C was present. Lamin B2 was either normal (8/11), or decreased (3/11). Deficit of lamin A was a characteristic feature for AD-EDMD in the majority of these cases (9/11), while in two of these patients a decrease of lamin C, in four cases a lowered level of emerin was also present. In one AD-EDMD patient of a decrease of lamin C, but normal lamin A was present. Following the immunocytochemical examination the decrease of lamin A/C in X-EDMD and of emerin in AD-EDMD was also observed. The above mentioned data demonstrated that in X-EDMD and AD-EDMD the deficit of the appropriate proteins is not restricted either to emerin or lamins. The defect is more widespread and results in disruption of several nuclear proteins. This study also indicated that for the diagnostic EDMD purposes the immunocytochemical detection of emerin/lamins has to be accomplished by quantitative immunochemical analyses of the above mentioned proteins.

Controversies about the function of dystrophin in muscle.

Dystrophin, a product of a gene located at the chromosome Xp21 locus, is a cytoskeletal protein expressed in skeletal, cardiac and smooth muscles, and in the brain, and is located on the inner site of the plasma membrane. Dystrophin in the skeletal muscles is absent or appears only in traces in Duchenne dystrophy, it is reduced with normal/changed molecular weight in Becker dystrophy and it is absent/reduced in mdx mice. It is supposed that dystrophin acts either as a structural scaffold that supports mechanical stress in sarcolemma, or participates in regulating intracellular Ca2+ level. There are also data indicating that dystrophin takes part in force and signal transduction processes, in the aggregation of neurotransmitter receptors, and prevents an excessive generation of reactive oxygen free radical species. The main hypotheses indicate that lack of structural support, an excessive influx of Ca2+ ions into the muscle cell, or a combination of both these mechanisms in dystrophin-deficient muscle fibres, is responsible for muscle pathology in progressive muscular dystrophy. There are arguments supporting these hypotheses. There are, however, also data indicating that the presented arguments are doubtful. Despite recent advances in the knowledge of the pathogenesis of muscular dystrophies and the advent of modern techniques, we are still very far away from understanding what is the real function of dystrophin in muscle.

Dystrophinopathies in females.

Various laboratory tests were performed to establish carriership in 24 familial and sporadic carriers of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). The activity of creatine kinase was in all females but one, very high and significantly higher in isolated carriers; quantitative EMG indicated myopathic changes, muscle biopsies revealed different degrees of changes--from a variability of muscle fibers size and central nuclei to severe dystrophic features. Immunohistochemical evaluation of dystrophin revealed, in all females but one, mosaic pattern of staining--a mixture of dystrophin-positive and dystrophin-negative fibers, the latter consist 15-30% of all fibers. Quantitative evaluation of dystrophin showed a reduced abundance with normal or abnormal molecular weight. The abnormalities were more expressed in sporadic cases. The detection of sporadic carriers, particularly the non-manifesting clinical, is a very important progress--it permits the correct diagnosis (before, these females were diagnosed as limb girdle muscle dystrophy (LGMD) and supply them with the benefit of genetic counselling, which also requires some modification.

Congenital fascial dystrophy: abnormal composition of the fascia.

BACKGROUND: A scleroderma-like genetic disease, congenital fascial dystrophy, probably a variant of stiff skin syndrome described by Esterly and McKusick, was found to be related to genetically determined fascial abnormalities. Our previous electronmicroscopic study disclosed as a main pathologic finding presence of giant amianthoid-like collagen fibrils in the affected fascia. OBJECTIVE: The aim of the present study was to disclose the collagen abnormalities in the affected and control fascias and in the patient's fibroblast cultures derived from the skin and fascia. METHODS: The study was performed by histologic, immunohistochemical, and electronmicroscopic techniques. Immunohistochemical studies were done with the use of monoclonal antibodies: anti-collagens I, III, IV, and VI, anti-laminin, anti-fibronectin, anti-desmin, anti-spectrin, anti-vimentin, anti-laminin, anti-heparan sulfate, and anti-alpha-actinin. Electronmicroscopic studies were performed on the fascia sections and on cultured fibroblasts. RESULTS: The main abnormality leading to giant collagen fibril formation was presence of myofibroblasts, absence of collagen III, and overproduction of spectrin and collagen type VI, mainly its filamentous form. CONCLUSION: Our findings suggest that the abnormal composition of the fascia could depend on modulation of fibroblasts into myofibroblasts capable of producing spectrin and long-spacing collagen.

Correlative ultrastructural and immunohistochemical study of developing vascular basement membrane in postnatal rat spinal cord.

We investigated the development of vascular basement membrane in immature spinal cord vessels during rat spinal cord myelination. Correlative ultrastructural and immunohistochemical study indicated that fibronectin was the first component of extracellular matrix. Then, on the 9th postnatal day, laminin appeared. At that time, lamina lucida of vascular basement membrane was not detectable. On the 15th day, when collagen IV was visible, lamina densa and lamina lucida were occasionally observed. All components of basement membrane--fibronectin, laminin, collagen IV, alpha-2 laminin (merosin)--and ultrastructural division into two layers were detected on the 25th postnatal day. The results of this study indicates that a gradual development of endothelium in immature rat spinal cord blood vessels leads to a gradual increase of synthesis of extracellular matrix components.

Familial inclusion body myopathy with desmin storage.

We report two adult familial cases of inclusion body myopathy (IBM) with desmin storage in skeletal muscle. Clinically, both patients presented late-onset, progressive, symmetrical, both proximal and distal muscle weakness. Muscle biopsy findings were identical in both cases and consisted of marked variability in fiber size, increased number of central nuclei and vacuolation involving 10% of fibers. Single or multiple vacuoles were located subsarcolemmally or in the center, and were rimmed by basophilic material. At the ultrastructural level, tubulofilamentous nuclear and cytoplasmic inclusions of 16-21 nm in diameter were frequently observed. In addition, large subsarcolemmal and central deposits composed of electron-dense granular material were present in many fibers. Immunocytochemistry revealed staining for desmin, vimentin and ubiquitin within both inclusions and vacuolated fibers. Possible structural and functional associations between these two types of muscle changes remain unclear. They may either represent two coexistent disease processes or merely reflect an abnormal form of muscle fiber degradation, with unidentifiable specificity.

Calpain III mutation analysis of a heterogeneous limb-girdle muscular dystrophy population.

OBJECTIVE: To determine the frequency of calpain III mutations in a heterogeneous limb-girdle muscular dystrophy (LGMD) population. BACKGROUND: Mutations of the calpain III gene have been shown to cause a subset of autosomal recessive LGMDs. Patient populations studied to date have been primarily of French and Spanish origin, in which calpain III may cause 30% of autosomal recessive MDs. The incidence of calpain III mutations in non-French/Spanish MD patients has not been studied thoroughly. No sensitive and specific biopsy screening methods for detecting patients with abnormal calpain III protein are available. Thus, detection of patients relies on direct detection of gene mutations. METHODS: The authors studied the calpain III gene in 107 MD patient muscle biopsies exhibiting normal dystrophin. Muscle biopsy RNA was produced for each patient, and the entire calpain III complementary DNA was screened for mutations by reverse-transcriptase PCR/single-strand conformation polymorphism using three different conditions. RESULTS: The authors identified nine patients (eight unrelated) with causative mutations. Six of the seven distinct mutations identified are novel mutations and have not been described previously. CONCLUSION: The results suggest that approximately 9.2% of patients in the heterogeneous population with an LGMD diagnosis will show mutations of the calpain III gene. Interestingly, two patients were heterozygous for a single mutation at the DNA level, whereas only the mutant allele was observed at the RNA level. This suggests that there are undetectable, nondeletion mutations that ablate expression of the calpain III gene.

Macroemg in manifesting carriers of Duchenne muscular dystrophy.

The aim of present study was to analyse possible myopathic changes in the muscles of manifesting carriers of Duchenne Muscular Dystrophy (DMD) using concentric needle emg and macroemg methods. Our material consisted of 10 manifesting carriers aged 9-52 (mean 30 years) and 20 healthy age-matched females. Concentric needle emg (CNEMG) and macroemg was performed in biceps brachii (BB) muscle in both groups: carriers and controls. Myopathic changes were observed in BB muscle in 5 of 10 manifesting carriers using CNEMG and in all cases (10 carriers) using macroemg method. Macro electrode, which reflects total motor unit activity, i.e., the total number and size of component muscle fibres, supplies information about early myogenic lesion of the muscle. Therefore the macroemg seems to be a sensitive and useful electrophysiological diagnostic method in carriers of DMD.

Uncompacted myelin in hereditary neuropathy with liability to pressure palsies with the 17 p11.2 deletion.

A 16-year-old girl with a typical features of hereditary neuropathy with liability to pressure palsies (HNPP) and deletion on chromosome 17p11.2 was described. In the mother who was asymptomatic the same genetic defect was found. In a sural nerve biopsy obtained from the girl myelin thickenings characteristic for this disease and de- and remyelination in nerve fibers were found. Special attention was paid to the occurrence of uncompacted myelin, which was present in diffuse and focal forms. It is concluded that high amount of uncompacted myelin is characteristic for HNPP and it is probably related to the under-expression of peripheral myelin protein 22.

Ultrastructural features of immaturity in blood vessels of neonatal rat spinal cord.

Ultrastructural study was carried out on the lumbo-sacral segment of the spinal cord in 1, 3, 6, 9, 12, 15, 18, 21 and 25-day-old rats. Unusual features of blood vessels in postnatal life of rats were observed: capillaries with abundant endothelial cells, numerous invaginations and narrow lumen. In addition, microvilli of diverse size and number on the luminal surface of capillaries as well as larger vessels were present. They were more numerous in younger animals. An intriguing finding, not observed in older animals, was the appearance of abluminal protrusions projecting into surrounding tissue. Closed endothelial junctions were noted in all the investigated vessels. The above mentioned ultrastructural features indicate an immature character of blood vessels. The presence of this kind of vessels during the postnatal period may be connected with vascularisation of spinal cord due to the myelination process.

A dystrophin missense mutation showing persistence of dystrophin and dystrophin-associated proteins yet a severe phenotype.

A muscle biopsy from an X-linked muscular dystrophy pedigree showed normal dystrophin and dystrophin-associated proteins. Linkage to multiple markers within the dystrophin gene (LOD=2.7, theta=0) indicated a primary dystrophinopathy. Sequencing of the entire dystrophin RNA revealed a single missense mutation (D3335H) in the unique carboxyl-terminal domain. This is the first report showing that a relatively severe dystrophinopathy can occur despite the correct localization of dystrophin and dystrophin-associated proteins.