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Spinal and bulbar muscular atrophy: androgen receptor dysfunction caused by a trinucleotide repeat expansion.

Kennedy's disease (spinal and bulbar muscular atrophy) is an X-linked form of motor neuron disease that affects adult men. The syndrome is characterized by progressive atrophy of the limb muscles, pelvic and shoulder girdles and dysphagia and dysarthria, and is caused by the degeneration of spinal and bulbar motor neurons. Kennedy's disease is caused by a trinucleotide repeat expansion of a CAG repeat in exon A of the androgen receptor gene, and is one of a group of neurological diseases caused by trinucleotide repeat expansions in different genes. The mutation in Kennedy's disease involves an increased number of glutamine residues in the amino-terminal domain of the receptor. Point mutations and deletions in the androgen receptor gene cause androgen insensitivity syndrome, however subjects with Kennedy's disease have normal virilization, although progressive gynaecomastia, testicular atrophy and infertility may occur. Androgen receptors are expressed widely in the normal brain, and in the anterior horn cells of the spinal cord; however, their role in neuronal tissue is not known, nor is it known how the androgen receptor gene mutation causes neuronal degeneration. Kennedy's disease is likely to be a 'gain of function' abnormality, so that the presence of the receptor with an increased number of glutamines is toxic to motor neurons. It is possible that the mutation alters interaction of the receptor with other neuronal transcription factors, or neuronotoxicity may occur because of a non-specific effect caused by the presence of a protein with a large homoglutamine domain. Studies of patients with Kennedy's disease have shown that expression of androgen receptor mRNA and protein in spinal cord may be decreased, as can be the affinity of the mutant receptor for androgen. In vitro studies have shown impaired transcription activation ability of the mutant androgen receptor. The age at onset of Kennedy's disease may correlate with the size of the CAG repeat, however there is a large degree of variability of age at onset between subjects with the same number of repeats. Further study of the effect of the Kennedy's disease mutation on androgen receptor function in motor neurons will allow us to increase our understanding of the pathogenesis of this disease.

Animals↗

SMN, the product of the spinal muscular atrophy-determining gene, is expressed widely but selectively in the developing human forebrain.

The expression pattern of the survival motor neuron (SMN) protein has been investigated immunohistochemically in the human fetal forebrain from 14 to 38 weeks of gestation. Mutations in the SMN gene cause spinal muscular atrophy (SMA), an autosomal recessive disease characterized by degeneration of lower motor neurons in the spinal cord leading to progressive muscle wasting. SMN is a multifunctional protein and has been implicated in diverse cytoplasmic and nuclear processes. The monoclonal murine SMN antibody used in this study recognized a major band at approximately 34 kDa. In spinal cord anterior horn motor neurons at 13 weeks of gestation, the soma, proximal neurites, and nucleus were immunostained. In the nucleus, SMN immunolabeling was observed at the nuclear membrane, at the nucleolus, and at dot-like structures in the nucleoplasm likely to be coiled bodies and gems. In the fetal forebrain, SMN was immunodetected as early as 14 weeks of gestation. From 14 to 24 weeks of gestation, intense immunostaining was observed in the basal nucleus of Meynert, a major source of cholinergic afferents to the cortex. Less intensely labeled cells at lower packing density were also observed in the thalamus, reticular and perireticular nucleus, globus pallidus, hippocampus, amygdala, and enthorinal cortex. Immunolabeled cells were still detectable at 38 gestational weeks, the latest time point investigated. These findings provide an anatomical basis for future investigations of SMN functions during brain development and for the neuropathological characterization of severe SMA cases.

Anterior Horn Cells↗

Partial 3-methylcrotonyl-CoA carboxylase deficiency in an infant with fatal outcome due to progressive respiratory failure.

UNLABELLED: Isolated partial 3-methylcrotonyl-CoA carboxylase (MCC) deficiency has been described to be the cause for a distinct relatively mild clinical picture in a single patient. We describe another patient with isolated partial MCC deficiency who suffered from failure to thrive, muscular hypotonia and progressive respiratory insufficiency with fatal outcome at the age of 6.5 months. MCC deficiency was suspected at 3 months of age on the basis of mildly elevated urinary excretion of 3-hydroxyisovaleric acid and 3-methylcrotonylglycine and confirmed by enzyme analysis in lymphocyte and fibroblast homogenates. Residual MCC activity in lymphocytes was 25% of the mean normal value. Residual activity in fibroblasts was lower than in lymphocytes (3.8% of mean normal) and not significantly different from that in patients with complete MCC deficiency. However, the residual incorporation of 14C-isovalerate into macromolecules in intact fibroblasts, was clearly higher (28% of mean normal) than in fibroblasts with complete MCC deficiency (<4%). In both patients with partial deficiency the residual MCC activity was higher in lymphocytes than in fibroblasts. Clinical symptoms and signs in our patient attributable to MCC deficiency include muscular hypotonia, failure to thrive (already present at birth), progressive respiratory failure due to diaphragmatic paresis and a moderate brain atrophy. The clinical presentation was more severe than in many patients with complete MCC deficiency. Dietary therapy was biochemically effective as shown by normalization of organic acid excretion, however, had no effect on the CNS symptoms. CONCLUSION: We speculate that the severity of the disease could be related primarily to deficiency of MCC activity in the brain. Variable MCC activity among various organs may explain the peculiar clinical picture in this patient.

Brain↗

Dissociated motor loss syndrome with cavities in the anterior horns.

A 74-year-old man developed proximal muscular weakness and wasting of the left upper extremity without sensory disturbance or myelopathic symptoms. The muscle atrophy had not progressed for a few years. Radiological examination of the spine showed cervical disc herniation. These findings and electrophysiological studies excluded motor neuron diseases, permitting the diagnosis of dissociated motor loss syndrome. Interestingly, delayed computerized tomographic myelography disclosed cavities in the anterior horns of the spinal cord, which coincided with the clinical symptoms. Previous radiological and pathological examinations showed formation of such cavities within the spinal cord resulting from chronic compression, which was followed by ischemic change. In this context, the present case supports ischemia as a cause of dissociated motor loss syndrome.

Aged↗

Reduction of insulin-like growth factor-I expression in the skeletal muscle of noncachectic patients with chronic heart failure.

OBJECTIVES: We sought to assess the role of insulin-like growth factor-I (IGF-I) in muscle wasting in chronic heart failure (CHF), serum concentrations and local muscular IGF-I expression were determined in patients with severe CHF. BACKGROUND: Chronic heart failure is associated with progressive muscle atrophy, leading to cardiac cachexia. Skeletal muscle disuse and inflammatory activation with elevated cytokine levels have been implicated; however, the pathomechanism involved remains largely unknown. METHODS: Serum levels of IGF-I were measured by competitive solid phase immunoassay in 47 patients with severe CHF (left ventricular ejection fraction < or =30%) and 15 age-matched healthy subjects (HS). Insulin-like growth factor-I and IGF-I receptor expression were assessed in vastus lateralis biopsies by real-time PCR and Western blot analysis. RESULTS: Although serum IGF-I was not significantly different (175 +/- 10 ng/ml in CHF vs. 170 +/- 12 ng/ml in HS, p = NS), local muscle IGF-I mRNA expression was reduced by 52% in CHF (6.7 +/- 0.4 vs. 14.0 +/- 0.9 arbitrary units in HS, p < 0.001). This was accompanied by an increase in IGF-I receptor mRNA expression (86.8 +/- 5.4 in CHF vs. 23.1 +/- 1.8 arbitrary units in HS, p < 0.001). Local IGF-I expression was significantly correlated with muscle cross-sectional area (R = 0.75, p = 0.01). Chronic heart failure patients with a body mass index of < 25 kg/m(2) showed signs of peripheral growth hormone (GH) resistance, as indicated by elevated serum GH, and reduced IGF-I levels. CONCLUSIONS: In CHF patients, muscle IGF-I expression is considerably reduced in the presence of normal serum IGF-I levels, possibly contributing to early loss of muscle mass. These findings are consistent with a potential role of IGF-I for skeletal muscle atrophy in CHF.

Body Mass Index↗

Emery-Dreifuss muscular dystrophy.

Emery-Dreifuss muscular dystrophy (EDMD) is the third most common X-linked muscular dystrophy. This disorder is characterized by childhood onset of early contractures, humeroperoneal muscle atrophy, and cardiac conduction abnormalities. Weakness is slowly progressive, but there is a broad spectrum of clinical severity. Patients and carriers are at risk of sudden death. Regular cardiac evaluation is mandatory to assess the risk of cardiac arrhythmias. Unique atrial pathology is seen at autopsy. The mutated gene in EDMD is localized to the long arm of the X chromosome. Mutations in the gene lead to abolished synthesis of the gene product, emerin. Emerin is localized to the nuclear membrane of skeletal, cardiac, and smooth muscle. The term Emery-Dreifuss syndrome describes patients who have the EDMD phenotype without X-linked inheritance. There is no treatment for the underlying disease, but early placement of pacemakers may be lifesaving.

Atrophy↗

Clinico-electrophysiological correlation of extensor digitorum brevis muscle atrophy in children with charcot-marie-tooth disease 1A duplication.

The purpose of the study is to describe the electrophysiologic abnormalities accounting for the appearance and progression of extensor digitorum brevis (EDB) muscle atrophy in Charcot-Marie-Tooth-disease type 1A (CMT-1A) children. Twelve children with CMT-1A duplication were serially evaluated. Initial ages of clinico-electrophysiological exams ranged from 1 month to 4 years (mean: 2 years) and final ages from 6 to 23 years (mean: 13). All subjects had two or more electrophysiological studies of the peroneal nerve. EDB atrophy was observed in two out of 12 (17%) patients by the age of 5, in eight out of ten (80%) examined between 5 and 9 years, and in all eight (100%) patients who had reached the second decade at the end. Nerve conduction maturation was systematically abnormal, but by age of 5 the mean values of nerve conduction parameters of peroneal nerve did not significantly differ from those in older patients. Compound muscle action potential (CMAP) amplitudes of EDB were reduced in 42% of cases initially and 100% upon last exam. Furthermore, a constant finding throughout the study was progressive attenuation of CMAPs, these becoming unobtainable in four cases. EDB muscle atrophy in CMT-1A children is an age-dependent sign which is accounted for by gradual reduction of the distal peroneal nerve CMAP amplitudes.

Action Potentials↗

[Chronic unilateral distal juvenile muscular atrophy localized to the upper extremity (Hirayama type). A European case].

A 40 year-old Frenchman had had for 12 years, an amyotrophy of one upper limb. Clinical features were similar to those previously reported in Japan and India i.e. atrophy limited to one hand and forearm, with mild functional discomfort, and slow progression for 2 years after which the disorder did not progress. Electromyography showed disturbances of anterior horn cell type. The cause of this syndrome is unknown, no pathological case has yet been reported. The prognosis appears to be good.

Adult↗

The thenar index: an objective assessment and classification of thenar atrophy based on static hand imprints and clinical implications.

BACKGROUND: The aims of this study were to test the effectiveness of the subjective clinical evaluation and to search for any possibility of constituting an objective assessment system for the diagnosis of thenar atrophy based on static hand imprints. METHODS: Static hand imprints were obtained from normal subjects (group A, n = 116) and carpal tunnel syndrome patients with thenar atrophy (group B, n = 26). Thenar index and the bilateral thenar index ratio were defined. Cutoff values were considered by analyses with receiver operating characteristic curves. RESULTS: No statistically significant difference could be demonstrated in thenar index values of dominant and nondominant hands between genders and age groups (p > 0.05). A statistically significant difference was observed between severity groups in group B (p < 0.05). There was a statistically significant difference between thenar index and bilateral thenar index ratio values of groups A and B (p < 0.05). Cutoff values were considered a thenar index of 31 and a bilateral thenar index ratio of 0.8, which revealed acceptable specificity (95.3 percent) and sensitivity (77.4 percent). A new quantitative classification for thenar atrophy severity is proposed. CONCLUSIONS: Understanding the true onset and natural progression of thenar atrophy can only be anticipated with the aid of an objective assessment system. Currently, this method should be regarded as a system for patient records and comparison for presurgical and postsurgical data. The authors believe that the thenar index classification has some merit for future use. It seems that additional objective and scientific evaluation systems and novel approaches are still needed to demystify the true nature of carpal tunnel syndrome.

Adult↗

Alleviating neurodegeneration by an anticancer agent: an Hsp90 inhibitor (17-AAG).

Heat shock proteins (HSPs) that function mainly as molecular chaperones play an important role in the folding and quality control of proteins. Compared with these chaperones, Hsp90 is unique in that it binds to substrate proteins, called Hsp90 client proteins. Hsp90 is involved in the folding, activation, and assembly of its client proteins in association with its co-chaperones. Because numerous oncoproteins belonging to the Hsp90 client protein family are selectively degraded by Hsp90 inhibitors, 17-allylamino-17-demethoxygeldanamycin (17-AAG), a first-in-class Hsp90 inhibitor, is now under clinical trials as a novel molecular-targeted agent for a wide range of malignancies. In spinal and bulbar muscular atrophy (SBMA), the pathogenic gene product is polyglutamine (polyQ)-expanded androgen receptor (AR), which belongs to the Hsp90 client protein family and is known to be degraded by 17-AAG. We have recently demonstrated that administration of an anticancer agent 17-AAG significantly ameliorated polyQ-mediated motor neuron degeneration by reducing the total amount of mutant AR. The ability of 17-AAG to degrade mutant protein would be directly applicable to SBMA and other neurodegenerative diseases in which the disease-causing proteins also belong to the Hsp90 client protein family. Our proposed therapeutic approach using a novel anticancer agent 17-AAG has emerged as a candidate for molecular-targeted therapies for neurodegenerative diseases.

Animals↗

[Autosomal dominant adult-onset spinal muscular atrophy with vocal cord paralysis: a case report].

This report concerns a 41-year-old female case of spinal muscular atrophy (SMA) associated with vocal cord paralysis. Her parents were not consanguineous. Her maternal grandmother and younger brother were suspected of having SMA. At age 37, she first experienced gait disturbance and began to have slowly progressive dysarthria and weakness of the extremities. Neurological examination revealed that she had inspiratory stridor, dysarthria and proximal muscular weakness of the extremities. Achilles tendon reflexes were absent, while there were no pathological reflexes or sensory disturbances. She showed a waddling gait and Gowers' sign. The laboratory data indicated mild elevation of serum CK. The nerve conduction study was normal, while the electromyographic study and muscle biopsy revealed neurogenic changes. We diagnosed the case as adult onset SMA of the autosomal dominant type. Laryngoscopy revealed that the patient had vocal cord paralysis, which was predominant in abductor muscles and of the posterior paralysis type according to the categories established by Isozaki. Genetic analysis showed no mutations in the genes of the neuronal apoptosis inhibitory protein and of the survival motor neuron.

Adult↗

Centronuclear myopathy: clinical aspects of ten Brazilian patients with childhood onset.

We herein present 10 patients with the childhood onset form of centronuclear myopathy. All patients underwent a clinical and neurologic examination, and EMG/NVC. A series of ancillary examinations, consisting of muscle enzymes, EEG, EKG, echocardiogram, pulmonary function tests and head CT scan was done in most. The mean age was 16.3 years (3-25). Seven were female. There was no family history in seven and in two it was suggestive of an autosomal recessive inheritance. One patient was adopted and no history was available. Frequent gestational and neonatal abnormalities were present, namely poor fetal movements, maternal polyhydramnios, perinatal hypoxia, hypotonia at birth, and weak crying and feeding. In seven patients there was delayed motor milestones. In most patients the motor involvement was stable or slowly progressive. Upon examination the facies were myopathic and there was a global skeletal muscle involvement in all patients, with muscular hypotonia, atrophy, and areflexia. Characteristically, patients presented with ophthalmoparesis, and weakness of masticatory and facial muscles. We frequently found osteoskeletal abnormalities, namely kyphoscoliosis, tendon retractions and high-arched palate. A restrictive pulmonary function pattern was found in five patients, but only one had a cor pulmonale. CK was abnormally high in one patient, and normal in all others. EMG/NVC disclosed a myopathic pattern in nine; in three there was a mixed neurogenic picture; and in one we found myotonic discharges. A long follow-up (median 8.1 years) showed that only the patient with cor pulmonale had an unfavorable prognosis.

Adolescent↗

Muscle wasting.

The loss of lean body mass (muscle wasting) is initiated by cascades or events that precipitate increased proteolysis. Muscle wasting is stimulated by internal and external factors. Humorally related feedback loops stimulated by disease states, e.g., cancer, inflammatory myopathies, leukemia, or sepsis, and initiated as a response to systemic inflammatory response syndrome can cause a downward progression of events, resulting in chronic illness or even death. This article discusses the pathogenesis of muscle wasting, which is often referred to as cachexia.

Anorexia↗

Neuropeptides and neural cell adhesion molecule (NCAM) in CSF from patients with ALS.

In 10 patients with amyotrophic lateral sclerosis (ALS), the CSF content of the neuropeptides vasoactive intestinal polypeptide (VIP) and cholecystokinin (CCK) as well as neural cell adhesion molecule (NCAM) was investigated. Compared with normal controls, no deviations were found in CCK or NCAM, while the values of VIP were significantly lower in ALS patients. This finding may reflect a loss of motor neurons.

Adult↗

Mouse models of human CAG repeat disorders.

Expansions of CAG trinucleotide repeats encoding glutamine have been found to be the causative mutations of seven human neurodegenerative diseases. Similarities in the clinical, genetic, and molecular features of these disorders suggest they share a common mechanism of pathogenesis. Recent progress in the generation and characterization of transgenic mice expressing the genes containing expanded repeats associated with spinal and bulbar muscular atrophy (SBMA), spinocerebellar ataxia type 1 (SCA1), Machado-Joseph disease (MJD/SCA3), and Huntington's disease (HD) is beginning to provide insight into the underlying mechanisms of these neurodegenerative disorders.

Animals↗