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PubMed1997

Cramps and minimal EMG abnormalities as preclinical manifestations of spinal muscular atrophy patients with homozygous deletions of the SMN gene.

The characterization of deletions in the SMN gene provides a helpful tool to confirm the diagnosis of spinal muscular atrophy (SMA). However, there may be homozygous deletions of the SMN gene in some unaffected siblings of SMA type II and III patients. We present two SMA families with affected siblings demonstrating a homozygous deletion of the SMN gene with extremely different phenotypes. We propose a preclinical category of an SMA patient with homozygous deletion of the SMN gene: those with minimal expression of the disease including cramps and EMG abnormalities that may develop the complete SMA phenotype in the future.

Adolescent↗
PubMed1983

Adult-onset rapidly progressive spinal muscular atrophy of shoulder girdle with gammopathy.

The paper reports on clinical and pathologic findings in a 51-year-old man who presented with rapidly progressive spinal muscular atrophy associated with relatively early respiratory paralysis. Clinical diagnosis was based on typical EMG, and bioptic and enzyme findings. In the CSF protein and cell content were normal, the IgG concentration was high, the IgG/Alb quotient increased, intrathecal synthesis of IgG was evident, and oligoclonal gammopathy was found. All of these findings generally appear in neuroallergic diseases. Total loss of anterior-horn cells, demyelination of fasciculus cuneatus and spinothalamic pathways, as well as round Lafora-body like inclusions, preponderantly in the white matter, were observed with light microscopy. Electron microscopic examination revealed reoviruses in the glia cells of the damaged motor zone.

Anterior Horn Cells↗
PubMed1993

Reduced transcriptional regulatory competence of the androgen receptor in X-linked spinal and bulbar muscular atrophy.

Expansion of the long (CAG; glutamine)n repeat in the first exon of the X-linked human androgen receptor gene (hAR) causes spinal and bulbar muscular atrophy, frequently in association with mild androgen insensitivity. The relevant normal motor neurons are preferentially stimulated by androgen, however no motor neuron disorder occurs with any other known AR mutation, including those that cause complete androgen insensitivity. We have found that a polyglutamine (Gln) expanded AR transactivates an androgen-responsive reporter gene subnormally. Other groups have reported that a poly Gln-deleted AR transactivates normally. A parsimonious interpretation of all these facts is that poly Gln expansion causes the AR to lose a function that is necessary for full androgen sensitivity and to gain a function that is selectively motor neuronotoxic.

Androgens↗
PubMed1991

Mapping of human microtubule-associated protein 1B in proximity to the spinal muscular atrophy locus at 5q13.

A polyclonal antiserum directed against the C-terminal domain of dystrophin was used to isolate a cDNA clone encoding an antigenically cross-reactive protein, microtubule-associated protein 1B (MAP-1B). Physical mapping of the human MAP-1B locus places its chromosomal location at 5q13, in proximity to the spinal muscular atrophy (SMA) locus. SMA is a degenerative disorder primarily affecting motor neurons. Genetic linkage analysis of SMA families using a human dinucleotide repeat polymorphism just 3' of the MAP-1B gene has shown tight linkage to SMA mutations. These mapping data together with the postulated role of MAP-1B in neuronal morphogenesis and its localization in anterior horn motor neurons suggest a possible association with SMA.

Animals↗
PubMed2000

Cervical dural sac and spinal cord in juvenile muscular atrophy of distal upper extremity.

OBJECTIVE: To investigate specificity and significance of dynamic changes of the cervical dural sac and spinal cord during neck flexion in juvenile muscular atrophy of the distal upper extremity. BACKGROUND: The disorder affects young people-predominantly men-and is progressive for several years. One autopsy case showed ischemic necrosis of the cervical anterior horn, suggesting that the disorder is a type of cervical myelopathy. Some authors classify it as monomelic amyotrophy, implying that it is a focal motor neuron disease. METHODS: Neuroradiologic examinations including myelography, CT myelography, and MRI in a fully flexed neck position were performed on 73 patients with this disorder and on 20 disease control subjects. RESULTS: A distinctive finding in the disorder was forward displacement of the cervical dural sac and compressive flattening of the lower cervical cord during neck flexion. The forward displacement was significantly greater in patients with disease duration less than 10 years than in age-matched control subjects and patients in a late, nonprogressive stage. CONCLUSIONS: Radiologic abnormalities of the lower cervical dural sac and spinal cord support the hypothesis that this disorder is a type of cervical myelopathy.

Adolescent↗
PubMed2003

Comparison of PCR-RFLP with allele-specific PCR in genetic testing for spinal muscular atrophy.

PCR-based methods for the detection of homozygous deletion of exon 7 of the SMN1 gene have been widely used in genetic testing for spinal muscular atrophy (SMA). We compared the most commonly used PCRrestriction fragment length polymorphism (PCR-RFLP) assay with an allele-specific PCR method, evaluating their potential application in direct testing, prenatal prediction, and preimplantation diagnosis, in terms of a range of DNA amounts used in such testing. We showed that PCR-RFLP could identify the SMN1 exon 7 by amplifying 10 pg of genomic DNA, and could differentiate SMN1 from SMN2 at the 100-pg DNA level (DraIdigested SMN2 fragments served as an internal control for PCR efficiency). In contrast, allele-specific PCR for SMN1, despite some advantages in a rapid preimplantation diagnosis, quickly lost its specificity when 100 pg of genomic DNA was used. In addition, the absence of a SMN1 fragment at the 10-pg DNA level may be due to a PCR amplification failure, and, thus, it is difficult to interpret without a proper internal control. Our data indicate that PCR-RFLP can be used for most diagnostic purposes, whereas the use of allelespecific PCR may be considered with caution under certain circumstances.

Alleles↗
PubMed1999

A single nucleotide in the SMN gene regulates splicing and is responsible for spinal muscular atrophy.

SMN1 and SMN2 (survival motor neuron) encode identical proteins. A critical question is why only the homozygous loss of SMN1, and not SMN2, results in spinal muscular atrophy (SMA). Analysis of transcripts from SMN1/SMN2 hybrid genes and a new SMN1 mutation showed a direct relationship between presence of disease and exon 7 skipping. We have reported previously that the exon-skipped product SMNDelta7 is partially defective for self-association and SMN self-oligomerization correlated with clinical severity. To evaluate systematically which of the five nucleotides that differ between SMN1 and SMN2 effect alternative splicing of exon 7, a series of SMN minigenes was engineered and transfected into cultured cells, and their transcripts were characterized. Of these nucleotide differences, the exon 7 C-to-T transition at codon 280, a translationally silent variance, was necessary and sufficient to dictate exon 7 alternative splicing. Thus, the failure of SMN2 to fully compensate for SMN1 and protect from SMA is due to a nucleotide exchange (C/T) that attenuates activity of an exonic enhancer. These findings demonstrate the molecular genetic basis for the nature and pathogenesis of SMA and illustrate a novel disease mechanism. Because individuals with SMA retain the SMN2 allele, therapy targeted at preventing exon 7 skipping could modify clinical outcome.

Alleles↗
PubMed1996

Spinal muscular atrophy type II (intermediary) and III (Kugelberg-Welander). Evolution of 50 patients with physiotherapy and hydrotherapy in a swimming pool.

We added hydrotherapy to 50 patients with spinal muscular atrophy (SMA) who were being treated with individual conventional physiotherapy. Hydrotherapy performed at an approximate temperature of 30 degrees Celsius, twice a week, for thirty minutes in children and forty-five minutes in adults during a 2-year period. The outcome derived from this combined modality of treatment was rated according to physiotherapeutic evaluations, the MMT (Manual Muscular Test), and the Barthel Ladder. Patients were reevaluated at 2-month intervals. After two years of ongoing treatment, we were able to observe that the deformities in hip, knee and foot were progressive in all SMA Type II patients, and in some Type III. Muscle strength stabilized in most SMA Type III patients, and improved in some. MMT was not done in SMA Type II. In all patients we were able to detect an improvement in the Barthel Ladder scale. This study suggests that a measurable improvement in the quality of daily living may be obtained in patients with SMA Types II and III subjected to conventional physiotherapy when associated with hydrotherapy.

Adolescent↗
PubMed1995

Abnormal androgen receptor binding affinity in subjects with Kennedy's disease (spinal and bulbar muscular atrophy).

We have investigated androgen-binding properties of the androgen receptor (AR) in cultured suprapubic skin fibroblasts from six subjects with Kennedy's disease (X-linked spinal and bulbar muscular atrophy). Binding of the synthetic androgen methyltrienolone (R1881) was measured in a monolayer assay, and Scatchard analysis was performed to determine the total number of binding sites and the apparent binding affinity (Kd) of the AR for androgen. Five of the six subjects investigated had an abnormal apparent binding affinity, with Kd values ranging from 0.34-11.7 nmol/L, more than 2 SD from the mean of the normal range (0.19 +/- 0.06 nmol/L). In this group of six patients, there was a significant correlation between the AR Kd and the severity of testicular atrophy and gynecomastia. The number of CAG repeats in the expanded region of exon A of the AR gene was determined in all subjects from whom suprapubic skin fibroblasts were cultured and an additional 12 subjects with Kennedy's disease. In the total group of 18 subjects investigated, there was a trend for an increasing number of CAG repeats associated with decreasing age at onset of different symptoms; however, this correlation was not statistically significant. Thus, we report for the first time a quantitative abnormality of the AR apparent binding affinity in subjects with Kennedy's disease, which appears to be related to the severity of the symptoms of androgen insensitivity.

Aged↗
PubMed1987

[Electrophysiologic studies of patients with neural muscular atrophy].

Various nerve conduction velocities, the terminal latency (TL) of facial nerve, the trigeminofacial reflex and fast auditory evoked potentials (FAEP) were investigated in 26 patients with peroneal muscular atrophy (22 with HMSN I and 4 with HMSN II). With the brain nerve status revealing no clinical abnormalities, 85.7% of HMSN I patients showed a longer-than-normal TL of the facial nerve, 66.6% had a prolonged early reflex component of trigeminofacial reflex and 22.7% pathological FAEPs. Normal neurophysiologic findings were obtained for brain nerves of HMSN II subjects. Subclinical involvement of the mid-group of brain nerves did not at all correlate with the impairment of extremity nerves and the duration of the disease. The present results reflect the heterogeneity of HMSN.

Adolescent↗
PubMed1999

Allele-specific amplification for the diagnosis of autosomal recessive spinal muscular atrophy.

The SMN1 gene is homozygously deleted for at least exon 7, interrupted or converted to a non-functional telomeric copy in most cases of proximal spinal muscular atrophies. The presence of a pseudogene hampers direct detection of the exon 7 deletion. We describe a method for the detection of the of exon 7 deletion, based on the amplification refractory mutation system (ARMS), in a multiplex PCR with fluorescent-labelled primers. The gene and pseudogene amplification products differ in the dye bound and in their size, which allows distinction of both products on electrophoresis. The pseudogene is used as an internal control, and this method gives a clear and specific pattern for the patients. Amplification is achieved with 30 cycles, and specificity is retained up to 40 cycles.

Alleles↗
PubMed1992

Moderate instability of the trinucleotide repeat in spino bulbar muscular atrophy.

Increased length of a protein-coding CAG repeat within the androgen receptor gene appears to be the only type of mutation responsible for spino-bulbal muscular atrophy (SBMA or Kennedy disease). We have analysed a large 4-generation SBMA family and found that the mutant allele was unstable upon transmission from parent to child, with a documented variation from 46 to 53 repeats and a tendency to increase in size (7 increases and a single decrease in 17 events), which appeared stronger upon transmission from a male than from a female. Our results suggest also limited somatic instability of the abnormal allele, with observable variation of up to 2-3 repeats. This indicates that the behavior of the CAG repeat is similar to that observed for small premutations in the fragile X syndrome, or small abnormal alleles in myotonic dystrophy, two diseases which are caused by expansion of an unstable trinucleotide repeat.

Alleles↗
PubMed1997

Disturbances of neuromuscular interaction may contribute to muscle weakness in spinal muscular atrophy.

During a critical period of development, motoneurones and muscles are dependent on functional interaction with each other for their survival. In certain neuromuscular disorders such as spinal muscular atrophy (SMA), motoneurones die and muscle development is seriously affected. Recently advances have been made towards understanding the genetic basis of this disease, and a particular gene, i.e. the survival motoneurone gene (SMN), has been identified and found missing in SMA patients. Nevertheless the function of this gene is not clear, it may be involved in the control of the development of either the motoneurone or the muscle. Here we report that disrupting neuromuscular interaction during the early postnatal period has similar consequences on the development of muscles and motoneurones to those seen in patients with SMA, in that there is a loss of motoneurones and muscle function is severely impaired. In view of this, we discuss the possibility that these symptoms in SMA patients may be due to a disturbance of neuromuscular interaction during a critical stage of development.

Animals↗
PubMed2005

Rapid diagnosis of spinal muscular atrophy using denaturing high-performance liquid chromatography.

OBJECTIVE: To introduce the application of denaturing high-performance liquid chromatography (DHPLC) in the diagnosis of childhood type spinal muscular atrophy (SMA). METHODS: Exon 7 and flanking area of survival motor neuron (SMN) gene were amplified by PCR in 1 standard sample, 25 normal individuals and 25 patients with SMA. The PCR products were then directly loaded onto the DHPLC system after denaturing and annealing. Different DNA segments were separated by changing the concentration of buffer A relative to that of buffer B. RESULTS: Different DNA segments were separable on the DHPLC chromatogram. Three peaks including SMN1/SMN2 heteroduplex peak, SMN2 homoduplex peak and SMN1 homoduplex peak were detected in 23 out of 25 normal individuals. Only SMN1 homoduplex peak was detected in 2 normal individuals and the standard sample, indicating the deletion of SMN2 On the contrary, only the SMN2 homoduplex peak was detected in 22 out of 25 patients with SMA, indicating deletion of SMN1. The three peaks as those of normal individuals were detected in the other 3 patients, indicating no SMN1 or SMN2 deletion. CONCLUSION: As a new technology for diagnosing SMA, DHPLC is sensitive, accurate, rapid and convenient.

Chromatography, High Pressure Liquid↗
PubMed1994

Exonic trinucleotide repeats and expression of androgen receptor gene in spinal cord from X-linked spinal and bulbar muscular atrophy.

We studied exonic trinucleotide repeats and expression of androgen receptor (AR) gene in the spinal cord from an autopsied patient with X-linked spinal and bulbar muscular atrophy (SBMA). Forty-nine CAG triplet repeats were found in tissues from the spinal cord, cerebrum, cerebellum, cardiac muscle and bladder, while there were 20-24 CAG repeats in these tissues from control subjects, consisting of three patients with amyotrophic lateral sclerosis (ALS) and three patients with lung cancer. Thus, mitotic instability of the AR gene in SBMA may not occur at the level of somatic cells. To determine whether expression of the AR gene in the spinal cord of SBMA differs from that in control subjects, we used quantitative reverse transcriptase (RT)-PCR and Western blot. AR mRNA and protein were detected in the spinal cord from the patient with SBMA, but the levels of both AR mRNA and protein were less than those from the patients with ALS in whom the loss of motor neurons was similar to findings in the patient with SBMA. These findings suggest that structural alteration plus a reduced level of AR in the spinal cord are involved in the pathogenesis of SBMA, resulting in degeneration of motor neurons.

Adult↗
PubMedDate not supplied

Molecular analysis of spinal muscular atrophy and modification of the phenotype by SMN2.

PURPOSE: This study describes SMN1 deletion frequency, carrier studies, and the effect of the modifying SMN2 gene on the spinal muscular atrophy (SMA) phenotype. A novel allele-specific intragenic mutation panel increases the sensitivity of SMN1 testing. METHODS: From 1995 to 2001, 610 patients were tested for SMN1 deletions and 399 relatives of probands have been tested for carrier status. SMN2 copy number was compared between 52 type I and 90 type III patients, and between type I and type III patients with chimeric SMN genes. A fluorescent allele-specific polymerase chain reaction (PCR) -based strategy detected intragenic mutations in potential compound heterozygotes and was used on 366 patients. RESULTS: Less than half of the patients tested were homozygously deleted for SMN1. A PCR-based panel detected the seven most common intragenic mutations. SMN2 copy number was significantly different between mild and severely affected patients. CONCLUSIONS: SMN1 molecular testing is essential for the diagnosis of SMA and allows for accurate carrier testing. Screening for intragenic mutations in SMN1 increases the sensitivity of diagnostic testing. Finally, SMN2 copy number is conclusively shown to ameliorate the phenotype and provide valuable prognostic information.

Alleles↗
PubMed2005

Moving ahead in language: observations on a report of precocious language development in 3-4 year old children with spinal muscular atrophy type II.

Benony and Benony in a recent issue of this Journal have presented new data on the precocity of language acquisition in children with type II spinal muscular atrophy (SMA), at age 36-47 months. They refer to our interim report of advanced early language development in these motor-impaired children, which covers the age period 18-35 months. Here, we provide more details of our findings and discuss them in relation to their report and our theory of the role of the procedural system in language learning.

Child, Preschool↗