Biruta Kierdaszuk

A novel mutation in the DNM2 gene impairs dynamin 2 localization in skeletal muscle of a patient with late onset centronuclear myopathy

Centronuclear myopathies constitute a group of heterogeneous congenital myopathies characterized by the presence of abnormal, centrally located nuclei within muscle fibers. Centronuclear myopathies can be caused by mutations of several different genes, including DNM2, encoding dynamin 2 (DNM2) a large GTPase involved in membrane trafficking and endocytosis. We report a 52-year-old female with slowly progressive muscle weakness, and a family history of the disease. Clinical, morphological, biochemical and genetic analyses of the proband and her family members were performed, including analyses of the probands muscle biopsy. A novel D614N mutation, located in the C-terminal region pleckstrin-homology (PH) domain of DNM2 was identified in the proband and four family members, who exhibited similar symptoms. The mutation was associated with profound changes in the localization of DNM2 in muscle fibers without significant changes in protein expression. Mutated DNM2 and proteins involved in the membrane trafficking or membrane compartments maintenance were dislocalized within the myofiber, and concentrated at centrally located nuclei. This novel causative mutation (D614N) within the DNM2 gene in a large Polish centronuclear myopathy family with a late age of overt clinical manifestation caused profound changes in DNM2 localization and impaired proper organization of myofibers, and skeletal muscle functioning.

Myosin VI localization and expression in striated muscle pathology.

Myosin VI (MVI) is a unique unconventional myosin translocating, unlike other myosins, towards the minus end of actin filaments. It is involved in numerous cellular processes such as endocytosis, intracellular trafficking, cell migration, and transcription. In mammalian skeletal muscles it localizes mainly to sarcoplasmic reticulum and is also present within the muscle nuclei and at the neuromuscular junction (Karolczak et al. Histochem Cell Biol 2013; 23:219‐228). We have also shown that in denervated rat hindlimb muscle the MVI expression level is significantly increased and its localization is changed, indicating an important role of MVI in striated muscle pathology. Here, we addressed this problem by examining the distribution and expression levels of myosin VI in biopsies of skeletal muscles from patients with different myopathies. We found that, particularly in myopathies associated with fiber atrophy, the amount of MVI was enhanced and its localization in affected fibers was changed. Also, since a mutation within the human MVI gene was shown to be associated with cardiomyopathy, we assessed MVI localization and expression level in cardiac muscle using wild type and MLP(−/−) mice, a dilated cardiomyopathy model. No significant difference in MVI expression level was observed for both types of animals. MVI was found at intercalated discs and also at the sarcoplasmic reticulum. In the knockout mice, it was also present in ring‐like structures surrounding the nuclei. The data indicate that in striated muscle MVI could be engaged in sarcoplasmic reticulum maintenance and/or functioning, vesicular transport, signal transmission and possibly in gene transcription. Anat Rec, 297:1706–1713, 2014.

Inclusion body myositis: therapeutic approaches. A case report

Inclusion body myositis (IBM) seems to be the most common acquired myopathy among patients of age 50 or over. The characteristic clinical features of IBM include involvement of the quadriceps as well as distal muscles, mainly foot extensors and deep finger flexors. The course of the disease is slow but steadily progressive and most patients after 5 to 10 years require the aid of an assistive device. What distinguishes IBM from other inflammatory myopathies is its resistance to corticosteroids and other immunotherapies. We present a case report, the first in the Polish population, of a male patient with a 10-year history of inclusion body myositis responding well to intravenous immunoglobulin (IVIG) therapy. Despite the almost 10 years duration of the disease, its course was slowly progressive and rather stable. Essential aspects of diagnosis and pathogenesis as well as the therapeutic approach adopted are also discussed.

Changing phenotypic expression in a patient with a mitochondrial encephalopathy due to 13042G>A de novo mutation—a 5 year follow up

Mutations in NADH dehydrogenase (ND) subunits of complex I lead to mitochondrial encephalomyopathies associated with various phenotypes. This report aims to present the patient’s clinical symptomatology in the context of a very rare 13042G>A de novo mutation and with an emphasis on changing phenotypic expression and pronounced, long-standing response to levetiracetam.

Yeast model analysis of novel polymerase gamma variants found in patients with autosomal recessive mitochondrial disease

Replication of the mitochondrial genome depends on the single DNA polymerase (pol gamma). Mutations in the POLG gene, encoding the catalytic subunit of the human polymerase gamma, have been linked to a wide variety of mitochondrial disorders that show remarkable heterogeneity, with more than 200 sequence variants, often very rare, found in patients. The pathogenicity and dominance status of many such mutations remain, however, unclear. Remarkable structural and functional conservation of human POLG and its S. cerevisiae ortholog (Mip1p) led to the development of many successful yeast models, enabling to study the phenotype of putative pathogenic mutations. In a group of patients with suspicion of mitochondrial pathology, we identified five novel POLG sequence variants, four of which (p.Arg869Ter, p.Gln968Glu, p.Thr1053Argfs*6, and p.Val1106Ala), together with one previously known but uncharacterised variant (p.Arg309Cys), were amenable to modelling in yeast. Familial analysis indicated causal relationship of these variants with disease, consistent with autosomal recessive inheritance. To investigate the effect of these sequence changes on mtDNA replication, we obtained the corresponding yeast mip1 alleles (Arg265Cys, Arg672Ter, Arg770Glu, Thr809Ter, and Val863Ala, respectively) and tested their effect on mitochondrial genome stability and replication fidelity. For three of them (Arg265Cys, Arg672Ter, and Thr809Ter), we observed a strong, partially dominant phenotype of a complete loss of functional mtDNA, whereas the remaining two led to partial mtDNA depletion and significant increase in point mutation frequencies. These results show good correlation with the severity of symptoms observed in patients and allow to establish these variants as pathogenic mutations.

Intraosseous Lipoma of the Sphenoid: A Case Study

Intraosseous lipoma is very rare, usually benign tumor of flat bones. However, the localization in skull bones is described in sporadic cases. The differential diagnosis includes end stage of infection, infarct lesions, intraosseous meningioma, angiolipoma, or myxofibrous tumors. We report a patient with intraosseous lipoma located in the sphenoid bone. The diagnosis was established due to the characteristic radiological features. According to the history of seizures, the lesion was removed via endoscopic endonasal approach. Histopathological examination showed adipocytes. The patient underwent control neuroimaging studies.

Mitochondrial encephalopathy in a patient with a 13042G>A de novo mutation.

Mitochondrial DNA point mutations are associated with various syndromes, among which mitochondrial myopathy, encephalopathy, lactic acidosis and stroke (MELAS) and myoclonic epilepsy with ragged red fibres (MERRF) are the most common.1 Here we present a case report of a young man with a mitochondrial encephalomyopathy caused by a mutation in the ND5 gene (13042A>G), which has been described previously.1 A 21-year-old man presented with a 2-year history of recurrent generalised epileptic seizures and myoclonus with no family history. Neurological examination revealed discrete nystagmus and multifocal myoclonus in the upper limbs, ataxia and focal dystonia presenting as writers cramp. Neuropsychological examination showed slight working memory impairment and slowed learning of both verbal and visual material. Follow-up examinations conducted 18 and 33 months later did not show evidence of progression of the deficits. The patient exhibited anosodiaphoria throughout the observation period. Laboratory studies showed a normal serum lactic acid level of 9.45 mg% with an abnormal lactic acid curve during ischaemic muscle exercise. Creatine kinase activity was within the normal range. A 50 min video EEG disclosed a pattern characteristic of myoclonic epilepsy. Visual evoked potentials showed delayed P100 responses. Electromyography and nerve conduction studies were within normal ranges. MRI showed hyperintensive lesions on T2 and FLAIR images in the right cerebral peduncle, close to the occipital horns of the lateral ventricles, in the left temporal lobe as well as …

Rola biopsji mięśnia szkieletowego w diagnostyce chorób nerwowo-mięśniowych

Streszczenie Biopsja mieśnia szkieletowego wykonywana w celach diagnostycznych w chorobach nerwowo-mieśniowych umozliwia ocene rodzaju procesu chorobowego (pierwotnie mieśniowy czy neurogenny), dostarcza informacji o przebiegu (ostry czy przewlekly) oraz stopniu zaawansowania choroby. W wielu przypadkach zastosowanie dodatkowych technik histochemicznych i immunohistochemicznych pozwala na jednoznaczne rozpoznanie takich schorzen, jak niektore dystrofie mieśniowe, glikogenozy, miopatie zapalne oraz miopatie wrodzone. Ocena wycinka mieśniowego w mikroskopie elektronowym umozliwia pewne rozpoznanie dystrofii oczno-gardlowej, miopatii mitochondrialnej i wtretowego zapalenia mieśni. W niniejszym artykule omowiono objawy kliniczne sugerujące koniecznośc pobrania wycinka, technike wykonywania biopsji, zasady wyboru mieśnia do badania, a takze praktyczne wskazowki dotyczące przesylania pobranego wycinka i przygotowania preparatow do oceny w mikroskopie. Przedstawiono ponadto podstawowe zasady dotyczące interpretacji wyniku biopsji mieśnia oraz przydatnośc kliniczną biopsji mieśnia w dobie zaawansowanej diagnostyki molekularnej.Muscle biopsy is required to provide a definitive diagnosis in many neuromuscular disorders. Biopsy findings may indicate whether the pathological process is of neurogenic or myopathic origin. The muscle biopsy may give important information on the course of the disease (acute or chronic) and on the disease stage and progression. The interpretation of muscle biopsy, including histochemical and ultrastructural analysis, is a key factor in the diagnosis of muscular dystrophies, glycogenoses, inflammatory myopathies and congenital myopathies. An assessment of muscle biopsy on electron microscopy enables a definite diagnosis of oculopharyngeal muscular dystrophy, mitochondrial myopathy or inclusion body myositis. This paper presents an overview of general indications for muscle biopsy, biopsy procedures, as well as transportation and preparation of muscle tissue for final microscopic analysis. The interpretation of specific microscopic findings and a brief discussion on the clinical usefulness of muscle biopsy in the era of molecular diagnosis are also presented.

Identification of the first in Poland CACNA1A gene mutation in familial hemiplegic migraine. Case report

INTRODUCTION Migraine is a common neurological disorder characterized by a particular phenotype, complex pathophysiology and a heterogeneous genetic background. Among several heritable forms, familial hemiplegic migraine is the best described one. In the majority of cases it is caused by mutations in one of three different genes. CASE REPORT Clinical symptoms of a 47 year old proband (and independently described in his 20 year old son) as well as differential diagnosis are discussed in the presented report. The most characteristic were recurrent attacks of blurred vision, paresthesias and hemiparesis often accompanied by speech disturbances and followed by severe headache with vomiting. Advanced morphological and genetic procedures were required to exclude MELAS, CADASIL and Call-Fleming syndrome. Finally, the definite diagnosis was possible after the application of the whole exome sequencing technique. It confirmed, for the first time in the Polish population, a heterozygous T666M mutation (c.1997C>T; p.Thr666Met) in the CACNA1A gene in the proband, the probands son and in several other family members. CONCLUSION The presented report provides clinical and genetic insight into familial hemiplegic migraine 1 resulting from a mutation in the CACNA1A gene.

Abnormal spontaneous activity in primary myopathic disorders

Reproducible non‐insertional spontaneous activity (SA), with the exception of endplate activity, is an unequivocal sign of abnormality and is one of the most useful findings obtained on electromyography.