Meiotic stability and genotype-phenotype correlation of the trinucleotide repeat in X-linked spinal and bulbar muscular atrophy.

Expansion of the trinucleotide repeat (CAG)n in the first exon of the androgen receptor gene is associated with a rare motor neuron disorder, X-linked spinal and bulbar muscular atrophy. We have found that expanded (CAG)n alleles undergo alteration in length when transmitted from parent to offspring. Of 45 meioses examined, 12 (27%) demonstrated a change in CAG repeat number. Both expansions and contractions were observed, although their magnitude was small. There was a greater rate of instability in male meiosis than in female meiosis. We also found evidence for a correlation between disease severity and CAG repeat length, but other factors seem to contribute to the phenotypic variability in this disorder.

Charcot-Marie-Tooth type 4B is caused by mutations in the gene encoding myotubularin-related protein-2.

A gene mutated in Charcot-Marie-Tooth disease type 4B (CMT4B), an autosomal recessive demyelinating neuropathy with myelin outfoldings, has been mapped on chromosome 11q22. Using a positional-cloning strategy, we identified in unrelated CMT4B patients mutations occurring in the gene MTMR2, encoding myotubularin-related protein-2, a dual specificity phosphatase (DSP).

Charcot-Marie-Tooth type 1A disease caused by a novel Ser112Arg mutation in the PMP22 gene, coexisting with a slowly progressive hearing impairment.

Among 57 mutations in the peripheral myelin protein 22 gene (PMP22) identified so far in patients affected by Charcot-Marie-Tooth disease (CMT), only 8 have been shown to segregate with a mixed phenotype of CMT and hearing impairment. In this study, we report a new Ser112Arg mutation in the PMP22 gene, identified in a patient with early-onset CMT and slowly progressive hearing impairment beginning in the second decade of life. We suggest that the Ser112Arg mutation in the PMP22 gene might have a causative role in the early-onset CMT with hearing impairment. Thus, our study extends the spectrum of CMT phenotypes putatively associated with PMP22 gene mutations.

Circulating autoantibodies to troponin I in Emery-Dreifuss muscular dystrophy.

The pathogenesis of dilated cardiomyopathy in Emery- Dreifuss muscular dystrophy (EDMD) is still unknown. Autoimmune mechanisms have recently been taken into account. The aim of this investigation was to determine whether the level of circulating antibodies to heart proteins which were previously detected, correlates with disease progression. Troponin I was chosen as the target. Ten patients with EDMD and 10 age-matched normal controls were tested. An enzyme linked immunoassay (ELISA) technique was used to determine the possible relation between the level of anti-troponin I antibodies at diagnosis and at followup. Autoantibodies against troponin I were detected in all EDMD patients. At diagnosis the level was higher in the X-linked EDMD form (X-EDMD), as compared to the autosomal dominant form (AD-EDMD). At follow-up the elevated level of the autoantibodies persisted in all the EDMD cases. However, in the AD-EDMD form, the level was found to be significantly rising with disease progression, in the X-EDMD form, on the other hand, it was declining. No clear-cut relationship between the level of the circulating antibodies and cardiac symptomatology was present. Detection of anti-troponin I antibodies may provide a non-invasive marker of early stages of dilated cardiomyopathy in EDMD.

Charcot-Marie-Tooth disorders with an autosomal recessive mode of inheritance.

In recent years, 13 loci and 10 genes have been identified in Charcot-Marie-Tooth disorders with a recessive mode of inheritance (AR-CMT). Accordingly, the entity of AR-CMT has been divided into subgroups on the basis of genetic linkage. Mutations in the MTMR2, MTMR13, GDAP1, PRX, CTDPI, KIAA1985 and NDRG1 genes have been shown to be associated with specific CMT phenotypes. In AR-CMT disorders associated with mutations in the LMNA and MED25 genes the number of patients is still too low to achieve reliable phenotype-genotype correlations. In the present review, we summarize molecular, electrophysiological, neuropathological and clinical aspects of AR-CMT disorders.

Looking for disease being a model of human aging.

This paper is a part of an introduction to authors' study on systemic laminopathies and their role in human aging. Of special interest is progeria--a type of systemic laminopathy associated usually with mutation 1824 C > T and presenting phenotype of preliminary aging. The authors analyse the differences between the progeria and other syndrome of preliminary aging--Werner's syndrome.

Charcot-Marie-Tooth disease type 4C4 caused by a novel Pro153Leu substitution in the GDAP1 gene.

Charcot-Marie-Tooth type 4C4 disease (CMT4C4) is an early onset, autosomal recessive neuropathy with hoarseness caused by mutations in the GDAP1 gene which maps to the 8q13 region. To date, only 24 mutations in the GDAP1 gene have been reported. Neuropathological findings of sural nerve biopsies have been published for a limited number of CMT4C4 patients. Herein, a novel Pro153Leu mutation in the GDAP1 gene identified in a consanguineous Polish family is described and longitudinal clinical and electrophysiological studies as well as morphological findings are presented.

Evidence for autoimmunity to heart-specific antigens in patients with Emery-Dreifuss muscular dystrophy.

Dilated cardiomyopathy is one of the leading abnormalities in Emery-Dreifuss Muscular Dystrophy (EDMD). The pathogenesis of heart involvement in EDMD is, however, unknown. Autoimmune mechanisms have also to be taken into account. The aim of this study was to search for the presence of anti-heart antibodies in EDMD patients. The anti-heart auto-antibodies were detected in serum of 14 EDMD patients (the X-linked and the AD-Autosomal Dominant form). The control groups comprised 10 patients with Dilated Cardiomyopathy (DCM) and 10 healthy subjects. To screen serum for anti-heart antibodies against ventricular muscle proteins, they were separated by polyacrylamide gel electrophoresis, followed by Western blotting. In EDMD and DCM, IgG anti-heart antibodies against heart ventricular proteins were detected. In both diseases, 85 kD protein appeared to be the most immunogenic. Anti-troponin I (24 kD), anti-tropomyosin (35 kD) and anti-actin (43 kD) reactivity was less intense. There were significant differences in the reactivity of auto-antibodies between both EDMD forms, and also between EDMD and the DCM patients. No clear-cut correlation between the reactivity and frequency of the antibodies and clinical parameters of the EDMD patients was detected. The anti-heart proteins are reliable markers of immune involvement in dilated cardiomyopathy in the course of EDMD. Short- and long-term follow-up may define the role of anti-heart antibodies in predicting the susceptibility at risk of dilated cardiomyopathy in EDMD patients.

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.

Echocardiographic assessment of left ventricular morphology and function in patients with Emery-Dreifuss muscular dystrophy.

BACKGROUND: Emery-Dreifuss muscular dystrophy (EDMD) characterized by musculoskeletal abnormalities is often associated with atrioventricular conduction disturbances. Although some EDMD patients were reported to develop dilated cardiomyopathy, there are limited data on their left ventricular (LV) performance. METHODS: Therefore, we echocardiographically assessed 27 men (23 cases aged 26.4+/-6.8 years with X-linked, and four cases aged 22.2+/-8.6 years with autosomal dominant (AD)) EDMD. Control group included 16 male healthy controls aged 24.8+/-6.0 (18-37) years. RESULTS: Although LV end diastolic dimension was similar in EDMD and controls (4.9+/-0.6 and 4.99+/-1.1 cm, ns), dilated left ventricle was found in three X-linked EDMD subjects. LV ejection fraction was significantly reduced in EDMD (62.3+/-1% vs. 71.2+/-2%, p=0.01) and was below 50% in six (22.2%) X-linked EDMD patients. Doppler analysis disclosed prolonged isovolumetric relaxation time of the left ventricle in the studied group. This finding may indicate impaired LV relaxation. CONCLUSION: A significant subgroup of X-linked EDMD patients shows pronounced abnormalities of left ventricular function. This warrants cardiologic follow up of EDMD patients.

Localization of the gene for X-linked spinal muscular atrophy.

We used probes for DNA polymorphisms on the X chromosome to study genetic linkage in seven families with X-linked adult-onset spinal muscular atrophy. We found significant linkage to the marker DXYS1 on the proximal X chromosome long arm and loose linkage or nonlinkage to markers elsewhere. Our analysis localizes the gene defect for this form of anterior horn cell disease.

Hyperkalemic periodic paralysis: rapid molecular diagnosis and relationship of genotype to phenotype in 12 families.

We studied mutations of the adult voltage-gated skeletal muscle sodium channel gene in 12 families, from diverse ethnic backgrounds, with hyperkalemic periodic paralysis (HyperPP). We describe a novel procedure, using ligase chain reaction (LCR), to simultaneously identify two different point mutations (previously described) and one rare, apparently benign polymorphism that results in a nonconservative amino acid substitution. Three of 12 families showed the Met1592Val mutation, and six of 12 had the Thr704Met mutation. The mutation in three of the 12 families was not identified. In one of these three families, the disease was not linked to the adult voltage-gated sodium channel gene, suggesting the existence of a clinically similar but genetically distinct form of HyperPP. Genotype/phenotype correlations based on patient records and interviews in these families showed the variable and subjective nature of the illness, although the clinical distinctions between hyperkalemic periodic paralysis and paramyotonia congenita were reinforced by the molecular data.

Kearns-Sayre syndrome in twins: lethal dominant mutation or acquired disease?

We studied twin brothers who met all diagnostic criteria for the Kearns-Sayre syndrome (KSS). The twins reinforce the view that KSS is a specific syndrome. They raise the possibility that the condition is inherited as a lethal dominant trait, a mode of inheritance that explains the observed paucity of familial cases. However, these cases do not exclude the possibility of an acquired cause, such as persistent viral infection of the brain.

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.

Coexistence of scleromyositis associated with PM-Scl antibody and myasthenia.

Myasthenia gravis coexists in about 15% of the cases with other autoimmune diseases. Association with polymyositis or dermatomyositis is very rare, although myasthenic reaction is not infrequent in typical polymyositis and myopathic changes may occur in cases of myasthenia. This is the first case of coexistence of myasthenia and scleromyositis, associated with PM-Scl antibody as an immune marker. The patient was found to have persistent thymus. Myasthenia preceded scleromyositis for 9 yr, was at periods asymptomatic, and recurred simultaneously with development of scleromyositis. Scleromyositis should be added to the list of autoimmune disorders coexistent with myasthenia.

Unusual course of nemaline myopathy.

A boy with onset features common for a moderate form of congenital nemaline myopathy, after some years developed scapulo-humeral syndrome. Extra- and intrafusal muscle fibers overloaded with rods and indicating focal degenerative changes were seen in the first biopsy. The biopsy was later repeated and revealed an improvement in muscle architecture with a dramatically decreased number of rods. This transformation suggests that rods, as well as Z-line streaming, might be a reversible anomaly of Z-discs.

A novel mutation, Thr65Ala, in the MPZ gene in a patient with Charcot-Marie-Tooth type 1B disease with focally folded myelin.

Charcot-Marie-Tooth type 1B disease is a demyelinating neuropathy caused by mutations in the Myelin Protein Zero gene. It is inherited in an autosomal dominant fashion. So far only a few patients with a focally folded myelin phenotype on nerve biopsy have been shown to have mutations in the Myelin Protein Zero gene. In this report we describe a Polish patient with Charcot-Marie-Tooth type 1B disease. Sural nerve biopsy demonstrated focally folded myelin. Molecular genetic analysis of the coding region of the Myelin Protein Zero gene revealed a novel mutation, Thr65Ala, in exon 2 of the Myelin Protein Zero gene.

Muscle stiffness and continuous electromyographic activity in old rats; an animal model for spasticity?

A mechanomyographic response of the hind foot to passive straightening and bending, as well as an electromyographic activity of the gastrocnemius and tibialis anterior muscles were recorded in old (35-44-month-old) and young female rats. In old rats, spontaneous, tonic electromyographic activity patterns were concurrently observed in both antagonistic muscles; they were low-amplitude, dense tonic activity and continuous, high-amplitude, sparse electromyographic activity. The tonic electromyographic activity was correlated with a decline in the strength and mass of muscles, as well as with motor disturbances, including paresis of the rigidly straightened backward hind legs, dragged behind by an animal. In muscles of old rats, morphological features of a chronic denervation atrophy were found. Baclofen (10 and 15 mg/kg, i.p.) diminished the spontaneous tonic electromyographic activity and potently decreased the whole body muscle tone, whereas Madopar (50 mg/kg of L-DOPA+12.5 mg/kg of benerazide) was ineffective. It is suggested that old rats in which the above-described pathologic alterations are observed might be a useful animal model in the search for basic etiopathological mechanisms of spasticity and similar disturbances found in humans.

Motoneurons are altered in muscular dystrophy.

The activity of motoneurons supplying the brachial biceps muscle was examined in eight control subjects and 26 patients affected by Duchenne muscular dystrophy. The patients were subdivided into two groups: one whose motor units (MU) fired with normal rates (N group) and the other whose MU firing rates were higher as compared to controls (I group). Firing rates of motoneurons of patients from group I increased more rapidly with increasing force level. The relationship between the standard deviation of interspike intervals and their mean value, sigma(Tm), was shifted towards the shorter intervals and lower standard deviations in both groups of patients. The numerical values describing these changes correlated with the severity of disease. The MU recruitment was comparable for control subjects and for patients. Experimental results as well as computer simulations indicate that the break-point of the function sigma(Tm) is correlated with motoneuronal properties, and in particular with the afterhyperpolarization (AHP) duration. In muscular dystrophy this break-point corresponds to the shorter interspike intervals. Therefore, we propose that the motoneurons in muscular dystrophy are altered either in response to the muscle degeneration or as a result of the disease itself.