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PubMed2005

[A clinical, neurophysiological and molecular study of 12 patients from 4 families with spinal and bulbar muscular atrophy].

INTRODUCTION: Spinal and bulbar muscular atrophy (SBMA) is an X-linked, late-onset neuro-endocrine disorder resulting from an expansion of a CAG repeat in the androgen receptor gene. Material and method. We report the detailed phenotypic study in a series of 12 SBMA patients evaluated in four kindreds. RESULTS: Clinical phenotypic spectrum varied considerably, ranging from childhood-onset weakness and atrophy mimicking limb-girdle myopathy in patients with 53 CAG repeats to isolated hyperCKemia in an adult with 42 CAG repeats. All male patients had gynecomastia. Two female carriers presented with paresthesias and hand action tremor. Homozygous deletions of SMN1 and SMN2 genes were not found in any patients. CONCLUSION: This report demonstrates that SBMA may present with a wider clinical spectrum than previously described and suggests that clinical phenotype severity in SBMA is partially linked to the number of CAG repeats. It also suggests that SMN1 and SMN2 genes do not act as modifying genes in SBMA.

Adolescent↗
PubMed2001

[Echocardiography in storage and neuromuscular disorders].

Storage disorders and neuromuscular disorders may lead to cardiac involvement which can be visualized by echocardiography. In storage disorders like hypothyroidism, haemochromatosis, amyloidosis, mucopolysaccharidosis and Fabry's disease, myocardial thickening and systolic dysfunction can be found. In amyloidosis, atrial enlargement and abnormal texture of the myocardium are additional findings. In advanced haemochromatosis all cardiac chambers may be dilated. In hypothyroidism and amyloidosis, a pericardial effusion can be present. In haemochromatosis and amyloidosis, a restrictive filling pattern may be detected using Doppler-sonography. Mucopolysaccharidosis and Gaucher's disease may lead to aortic and mitral stenosis. In neuromuscular disorders like glycogenosis, mitochondriopathy and myotonic dystrophy, myocardial thickening and systolic dysfunction are found, in spinal muscular atrophy myocardial thickening and in muscular dystrophy Becker/Duchenne systolic dysfunction. An abnormal myocardial texture may be present in glycogenosis, isolated left ventricular abnormal trabeculation (ILVAT) in mitochondriopathy, myotonic dystrophy and muscular dystrophy Becker/Duchenne. Using Doppler-sonography an impaired relaxation of the left ventricle may be detected in mitochondriopathy, myotonic dystrophy and spinal muscular atrophy. Most of these echocardiographic findings are unspecific and may be overlooked, especially if the storage or neuromuscular disorder is yet unknown. Establishing a correct diagnosis is important, since healing or functional improvement is possible in many of these disorders.

Amyloidosis↗
PubMed1993

Clinical application of a noninvasive multi-electrode array EMG for the recording of single motor unit activity.

Using a recently developed noninvasive EMG recording technique with multi-electrode arrays we investigated the pattern and distribution of motor unit action potentials (MUAP) following maximal voluntary contraction of the musculus abductor pollicis brevis. An additional parameter, i.e. muscular conduction velocity (CV) in single motor units, was calculated from the multi-electrode array EMG recordings. From 63 healthy children of various age the normal EMG pattern and CV were derived and compared to the EMG of diagnosed patients known to suffer from Duchenne muscular dystrophy and from spinal muscular atrophy. In normal individuals the muscular CV in neonates was lowest at 1-2 m/s and gradually reached a plateau of 2.9-4 m/s from the age of 4 years onwards. The EMG in 31 children with Duchenne muscular dystrophy showed an abnormal pattern with low amplitude action potentials. In 30 out of 31 patients a significantly lower muscular CV was found. In 10 children with spinal muscular atrophy the EMG showed action potentials of abnormally large amplitude and a reduced recruitment of firing motor units. The muscular CV remained within the normal range. Compared to classical needle EMG the application of this new noninvasive EMG technique in children is painless and offers an easy-to-handle diagnostic tool to differentiate between neuromuscular diseases of denervating or of myopathic origin.

Adolescent↗
PubMed2003

Transgenic mouse models of spinal and bulbar muscular atrophy (SBMA).

Spinal and bulbar muscular atrophy (SBMA) is a late-onset motor neuron disease characterized by proximal muscle atrophy, weakness, contraction fasciculations, and bulbar involvement. Only males develop symptoms, while female carriers usually are asymptomatic. A specific treatment for SBMA has not been established. The molecular basis of SBMA is the expansion of a trinucleotide CAG repeat, which encodes the polyglutamine (polyQ) tract, in the first exon of the androgen receptor (AR) gene. The pathologic hallmark is nuclear inclusions (NIs) containing the mutant and truncated AR with expanded polyQ in the residual motor neurons in the brainstem and spinal cord as well as in some other visceral organs. Several transgenic (Tg) mouse models have been created for studying the pathogenesis of SBMA. The Tg mouse model carrying pure 239 CAGs under human AR promoter and another model carrying truncated AR with expanded CAGs show motor impairment and nuclear NIs in spinal motor neurons. Interestingly, Tg mice carrying full-length human AR with expanded polyQ demonstrate progressive motor impairment and neurogenic pathology as well as sexual difference of phenotypes. These models recapitulate the phenotypic expression observed in SBMA. The ligand-dependent nuclear localization of the mutant AR is found to be involved in the disease mechanism, and hormonal therapy is suggested to be a therapeutic approach applicable to SBMA.

Animals↗
PubMed2006

Pathogenesis, animal models and therapeutics in spinal and bulbar muscular atrophy (SBMA).

Spinal and bulbar muscular atrophy (SBMA) is a hereditary neurodegenerative disease characterized by slowly progressive muscle weakness and atrophy of bulbar, facial, and limb muscles. The cause of SBMA is expansion of a trinucleotide CAG repeat, which encodes the polyglutamine tract, in the first exon of the androgen receptor (AR) gene. SBMA chiefly occurs in adult males, whereas neurological symptoms are rarely detected in females having mutant AR gene. The cardinal histopathological finding of SBMA is loss of lower motor neurons in the anterior horn of spinal cord as well as in brainstem motor nuclei. Animal models carrying human mutant AR gene recapitulate polyglutamine-mediated motor neuron degeneration, providing clues to the pathogenesis of SBMA. There is increasing evidence that testosterone, the ligand of AR, plays a pivotal role in the pathogenesis of neurodegeneration in SBMA. The striking success of androgen deprivation therapy in SBMA mouse models has been translated into clinical trials. In addition, elucidation of pathophysiology using animal models leads to emergence of candidate drugs to treat this devastating disease: HSP inducer, Hsp90 inhibitor, and histone deacetylase inhibitor. Utilizing biomarkers such as scrotal skin biopsy would improve efficacy of clinical trials to verify the results from animal studies. Advances in basic and clinical researches on SBMA are now paving the way for clinical application of potential therapeutics.

Animals↗
PubMed1975

Single fibre electromyography in various processes affecting the anterior horn cell.

SFEMG recordings were carried out in patients with amyotrophic lateral sclerosis, progressive muscular atrophy, familial spinal muscular atrophy and syringomyelia. The fibre density was increased in all conditions, especially in progressive muscular atrophy indicating marked collateral sprouting. The duration of the action potential was increased indicating a mixture of hypertrophic and atrophic fibres and slowly conducting newly formed nerve sprouts. The action potentials were unstable with varying degree of impulse blocking especially in the more progressive cases (ALS), representing recent re-innervation. The SFEMG method is used to characterize the functional status of the motor unit and helps in diagnosis and in predicting prognosis. In addition, SFEMG recordings reveal abnormalities in clinically and electromyographically normal muscles.

Action Potentials↗
PubMedDate not supplied

[Neurological phenocopying].

AIMS: To expand the -supposedly- narrow relationships that exist between genes and clinical syndromes by reflecting on several illustrative examples that disturb current simplistic genotype: phenotype correlations, and to explore a variety of biological mechanisms that account for this emerging phenomenon. DEVELOPMENT: Because it is well known that mutations in a single gene can give rise to numerous phenotypes, it would appear, at least intuitively, that the converse relationship might also hold true: that different genotypes may converge on just one single phenotype. Several examples taken from the study of selected neurological diseases illustrate that the latter principle indeed occurs in nature because disparate human genetic anomalies manifest similarly by exhibiting only a relatively limited phenotypic repertoire. This interesting biological phenomenon and vexing clinical problem is best described as phenocopying. Conditions such as spinal muscular atrophy, congenital glycosylation disorders, and mitochondrial diseases are but a few notorious examples of phenocopying. CONCLUSION: The nervous system is endowed with a limited number of genes and of types of molecules and, especially during development, its functional repertoire, at least from an observable point of view, is also limited. Therefore, ample genotyping capabilities are necessary to avoid erring in the process of diagnostic attribution because of phenocopying.

Calcium Channels↗
PubMed2000

[Triplet repeat disease, with particular emphasis of spinal and bulbar muscular atrophy (SBMA)].

Spinal and bulbar muscular atrophy (SBMA) is an X-linked neurodegenerative disease caused by the expansion of a CAG repeat in the first exon of the androgen receptor (AR) gene. To date, eight CAG-repeat diseases have been identified, including spinal and bulbar muscular atrophy (SBMA). Huntington's disease (HD), dentatorubralpallidoluysian atrophy (DRPLA) and five spinocerebellar ataxias (SCAs 1, 2, 3, 6, 7). These disorders likely share a common pathogenesis caused by the gain of a toxic function associated with the expanded polyglutamine tract. Several mechanisms have been postulated as a pathogenic process for neurodegeneration caused by the expanded polyglutamine tract. Processing of the polyglutamine containing proteins by proteases liberate truncated polyglutamine tract, which may cause neurodegeneration as demonstrated in transgenic mice and transfected cells. In addition to cellular toxicity, truncated and expanded polyglutamine tracts have been shown to form intranuclear inclusions (NI). The NIs formed by the disease protein are a common pathological feature of these diseases. In SBMA, NIs containing AR protein have been observed in regions of SBMA central nervous system susceptible to degenerations. Transcriptional factors or their cofactors, such as cerb or creb-binding protein (CBP) sequestrated in the NI may alter the major intracellular transcriptional signal transduction, and ultimately may result in neuronal degeneration. The ubiquitin-proteasome pathway may also contribute to the pathogenesis of CAG-repeat diseases. As for the therapeutic strategies, many possibilities have been demonstrated. Overexpression of Hsp70 and Hsp40 chaperones act together to protect a cultured neuronal cell model of SBMA from a cellular toxicity of expanded polyglutamine tract.

Animals↗
PubMed2003

[Development of therapeutics for spinal and bulbar muscular atrophy (SBMA)].

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy's disease, is a hereditary motor neuron disease that affects males, caused by the expansion of a polyglutamine (polyQ) tract in androgen receptor (AR). Female carriers are usually asymptomatic. The transgenic mouse (Tg) model carrying a full-length human AR with expanded polyQ has significant gender-related motor impairment. This phenotype is inhibited by castration, which prevents nuclear translocation of mutant AR. Leuprorelin, an LHRH agonist that reduces testosterone release from the testis, also rescues motor dysfunction and nuclear accumulation of mutant AR in the male Tg. Over-expression of a molecular chaperone HSP70, which renatures misfolded mutant AR, ameliorates neuromuscular phenotypes of the Tg by reducing nuclear-localized mutant AR. HSP70 appears to enhance the degradation of mutant AR via ubiquitin-proteasome pathway. These experimental approaches indicate the possibility of clinical application of drugs, such as leuprorelin, for SBMA patients.

Animals↗
PubMed2001

Androgen induced cell death in SHSY5Y neuroblastoma cells expressing wild-type and spinal bulbar muscular atrophy mutant androgen receptors.

Spinal bulbar muscular atrophy (SBMA) is one of a family of inherited neurodegenerative diseases caused by expansion of CAG encoding polyglutamine repeats; in SBMA the affected gene is the androgen receptor. To understand further the mechanisms that lead to neuronal cell death in SBMA, we generated SHSY5Y neuroblastoma cell lines that stably express identical levels of wild-type (19 polyglutamine repeat) or SBMA (52 polyglutamine repeat) androgen receptor. Parental SHSY5Y cells do not express detectable levels of the androgen receptor. In the absence of androgen, the transfected cell lines have similar phenotypes and growth characteristics to parental SHSY5Y cells. However, upon treatment with androgen, both cell lines undergo a marked dose-dependent loss of viability; this loss was significantly greater in cells expressing the SBMA receptor. Morphological analyses of the androgen treated cells revealed that cell death bore hallmarks of apoptosis involving altered nuclear morphology and cleavage of poly(ADP-ribose) polymerase and of caspase 3 in both wild-type and SBMA cell lines. The caspase inhibitor VAD-fmk was able to decrease loss of viability of both cell lines on exposure to androgen.

Apoptosis↗
PubMed2004

Axonal defects in mouse models of motoneuron disease.

Human motoneuron disease is characterized by loss of motor endplates, axonal degeneration, and cell death of motoneurons. The identification of the underlying gene defects for familial ALS, spinal muscular atrophy (SMA), and spinal muscular atrophy with respiratory distress (SMARD) has pointed to distinct pathophysiological mechanisms that are responsible for the various forms of the disease. Accumulating evidence from mouse models suggests that enhanced vulnerability and sensitivity to proapoptotic stimuli is only responsible for some but not all forms of motoneuron disease. Mechanisms that modulate microtubule assembly and the axonal transport machinery are defective in several spontaneous and ENU (ethylnitrososurea) mutagenized mouse models but also in patients with mutations in the p150 subunit of dynactin. Recent evidence suggests that axonal growth defects contribute significantly to the pathophysiology of spinal muscular atrophy. Reduced levels of the survival motoneuron protein that are responsible for SMA lead to disturbed RNA processing in motoneurons. This could also affect axonal transport of mRNAs for beta-actin and other proteins that play an essential role in axon growth and synaptic function. The local translation of specific proteins might be affected, because developing motoneurons contain ribosome-like structures in distal axons and growth cones. Altogether, the evidence from these mouse models and the new genetic data from patients suggest that axon growth and maintenance involves a variety of mechanisms, including microtubule assembly and axonal transport of proteins and ribonucleoproteins (RNPs). Thus, defects in axon maintenance could play a leading role in the development of several forms of human motoneuron disease.

Aged↗
PubMed1997

Identification and characterization of a mouse homologue of the spinal muscular atrophy-determining gene, survival motor neuron.

Spinal muscular atrophy (SMA), the second most common fatal, autosomal recessive disease of infants, manifests as generalized muscle weakness. The most severe form (Type I, Werdnig-Hoffmann disease) is associated with quadriplegia, respiratory muscle paralysis and death in infancy. Less severe forms are classified as Type II and Type III, based on age of onset and ultimate motor disability. Some spinal motor neurons show chromatolysis and the number of these cells is decreased. Recently, SMA has been mapped to chromosome 5q11.2-13.3 (Gilliam et al., 1990), a region that contains three candidate genes: Survival Motor Neuron (SMN) (Lefebvre et al., 1995); Neuronal Apoptosis Inhibitory Protein (NAIP) (Roy et al., 1995); and p44, a subunit of transcription factor II H (TFIIH) (Carter et al., 1995; Bürglen et al., 1997). Homozygous deletions or deleterious mutations in SMN are present in all SMA patients, and in some affected individuals, deletions have been identified in one or both of the other genes. These extensive deletions may be associated with a more severe phenotype. We have identified and characterized the mouse homologue of SMN, MoSMN, which is 82% identical to SMN at the amino-acid level. Unlike the duplicated human SMN, MoSMN is present in single copy. Like its human counterpart, MoSMN is ubiquitously expressed, but unlike SMN, MoSMN does not appear to be alternatively spliced. In-situ hybridization analysis of the mouse nervous system revealed that MoSMN mRNA is expressed in spinal cord and throughout the brain, with relatively higher levels of expression in the hippocampus and cerebellum.

Alternative Splicing↗
PubMed1990

Selective calf weakness suggests intraspinal pathology, not peripheral neuropathy.

Four patients, referred as having peripheral neuropathy, were noted to be able to walk on their heels but not on their toes. In each, intraspinal disease was found: ependymoma of the filum terminale, spinal muscular atrophy, spinal stenosis, and meningeal carcinomatosis. By comparison, in 86 cases of hereditary motor and sensory neuropathy type 1, ankle plantar flexors were never weaker than ankle dorsiflexors. Patients with greater weakness in plantar flexors than in dorsiflexors should be suspected of having intraspinal disease rather than peripheral neuropathy. Physiologic and biomechanical factors may explain why muscles innervated by the peroneal nerve are weaker, or graded weaker, in peripheral neuropathy.

Adult↗