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Long-term survival in a child with arthrogryposis multiplex congenita and spinal muscular atrophy.

Spinal muscular atrophy type 0 is a severe form of spinal muscular atrophy that is usually fatal in the first months of life. These children present with arthrogryposis multiplex congenita and respiratory compromise. We describe a child with spinal muscular atrophy and arthrogryposis multiplex congenita who has had a much better course and is alive without ventilator support at age 6 years. This case illustrates that the prognosis for spinal muscular atrophy and arthrogryposis multiplex congenita cannot always be predicted with certainty.

Arthrogryposis↗

Therapeutics development for spinal muscular atrophy.

Spinal muscular atrophy is an autosomal recessive motor neuron disease that is the leading inherited cause of infant and early childhood mortality. Spinal muscular atrophy is caused by mutation of the telomeric copy of the survival motor neuron gene (SMN1), but all patients retain a centromeric copy of the gene, SMN2. SMN2 produces reduced amounts of full-length SMN mRNA, and spinal muscular atrophy likely results from insufficient levels of SMN protein in motor neurons. The SMN protein plays a well-established role in assembly of the spliceosome and may also mediate mRNA trafficking in the axon and nerve terminus of neurons. In patients, spinal muscular atrophy disease severity correlates inversely with increased SMN2 gene copy number and, in transgenic mice lacking endogenous SMN, increasing SMN2 gene copy number from two to eight prevents the SMA disease phenotype. These observations suggest that increasing SMN expression levels may be beneficial to SMA patients. Currently pursued therapeutic strategies for SMA include induction of SMN2 gene expression, modulation of splicing of SMN2-derived transcripts, stabilization of SMN protein, neuroprotection of SMN deficit neurons, and SMN1 gene replacement. Early clinical trials of candidate therapeutics are now ongoing in SMA patients. Clinical trials in this disease present a unique set of challenges, including the development of meaningful outcome measures and disease biomarkers.

Animals↗

High incidence of a survival motor neuron gene/cBCD541 gene ratio of 2 in Japanese parents of spinal muscular atrophy patients: a characteristic background of spinal muscular atrophy in Japan?

Most spinal muscular atrophy (SMA) patients lack the survival motor neuron gene (SMN). However, the patients retain at least one copy of the cBCD541 gene (BCD), which is highly homologous with SMN. Here, we determined the SMN/BCD copy number ratios (the S/B ratios) of 12 parents of Japanese SMA patients with a homozygous SMN deletion, using competitive oligonucleotide priming polymerase chain reaction. We identified an S/B ratio of 2 in 25% of the parents examined, whereas less than 2% of parents of SMA patients in Western populations have an S/B ratio of 2. The high incidence of an S/B ratio of 2 in Japanese parents of SMA patients may reflect the characteristic genetic background of SMA in Japan.

Female↗

De novo and inherited deletions of the 5q13 region in spinal muscular atrophies.

Spinal muscular atrophies (SMAs) represent the second most common fatal autosomal recessive disorder after cystic fibrosis. Childhood spinal muscular atrophies are divided into severe (type I) and mild forms (types II and III). By a combination of genetic and physical mapping, a yeast artificial chromosome contig of the 5q13 region spanning the disease locus was constructed that showed the presence of low copy repeats in this region. Allele segregation was analyzed at the closest genetic loci detected by markers C212 and C272 in 201 SMA families. Inherited and de novo deletions were observed in nine unrelated SMA patients. Moreover, deletions were strongly suggested in at least 18 percent of SMA type I patients by the observation of marked heterozygosity deficiency for the loci studied. These results indicate that deletion events are statistically associated with the severe form of spinal muscular atrophy.

Alleles↗

Cell-specific survival motor neuron gene expression during human development of the central nervous system: implications for the pathogenesis of spinal muscular atrophy.

Spinal muscular atrophy is an autosomal recessive disorder characterized by the progressive loss or degeneration of the motor neurons. To investigate the expression of survival motor neuron (SMN), the spinal muscular atrophy-determining gene, and its relationship with the pathogenesis of the disease, we analyzed by means of in situ hybridization the location of SMN mRNA in fetal, newborn, infant, and adult human central nervous system tissues. The large motor neurons of the spinal cord are the main cells that express SMN together with the neurons of the medulla oblongata, the pyramidal cells of the cortex, and the Purkinje cells of the cerebellum. Some sensory neurons from the posterior horn and dorsal root ganglia express SMN to a lesser degree. Furthermore, strong SMN expression is detected in the ependymal cells of the central canal. The expression is present in the spinal cord at 8 weeks of fetal life throughout postnatal and adult life. The sharp expression of SMN in the motor neurons of the human spinal cord, the target cells in spinal muscular atrophy, suggests that this gene is implicated in neuronal development and in the pathogenesis of the disease. The location of the SMN gene expression in other neuronal structures not clearly or directly associated with clinical manifestations or pathological findings of spinal muscular atrophy may indicate a varying sensitivity to the absence or dysfunction of the SMN gene in motor neurons.

Adult↗

[X-linked recessive bulbospinal muscular atrophy (Kennedy's disease). A family study].

Kennedy's disease is a rare type of motor neuron disease with a sex-linked recessive trait. DNA studies show a mutation at the androgen receptor gene on the long arm of X chromosome (Xq 11-12) with expanded CAG triplets (more than 347 repeats). We present three patients and one carrier among ten patients of a four generation family with clinical phenotype of the disease. The patients' ages ranged from 50 to 60 years with symptomatology usually beginning around 30 years of age. Patients had gynecomastia, testicular atrophy, muscular weakness, fasciculation, amyotrophy, absent deep tendon reflexes and postural tremor. PCR techniques of DNA analysis showed expanded size of CAG repeats on Xq 11-12 in all the three patients and in the carrier asymptomatic woman. This is the first Brazilian family with genetic molecular diagnosis of Kennedy's disease. This disease must be included in the differential diagnosis of motor neuron disease since it has a distinct prognosis and genetic counseling is mandatory to the carriers.

Diagnosis, Differential↗

On the possible role of muscle in the pathogenesis of spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a common human inherited disease characterized by degeneration of motoneurons and muscular atrophy. SMA results from deletions or mutations of the SMN (survival motor neuron) gene. A nerve-muscle coculture model, consisting of human muscle cells innervated by rat embryonic spinal cord explants, was used to study the pathogenesis of SMA. Previous studies have shown that myotubes formed by fusion of satellite muscle cells from patients with SMA I or SMA II (but not SMA III) underwent a characteristic degeneration 1-3 weeks after innervation. To correlate this cellular study with a molecular approach, we used reverse transcriptase-polymerase chain reaction (RT-PCR), and showed that SMN mRNAs were expressed throughout the fusion of normal satellite muscle cells with two peaks, the first appearing prior to the onset of fusion and the second one or two days before innervation. When satellite muscle cells from patients with SMA I or II were used, only the first peak was observed. Because in these cases the SMN telomeric gene (SMNtel) is deleted, it was concluded that the contribution of SMNtel-dependent mRNAs to the second peak is predominant in normal myogenesis and involved in maturation of myotubes. In addition, diseased satellite muscle cells did not fuse at the same rate as normal satellite muscle cells. Studies on myf-5, a muscle specific transcription factor family, showed that its expression was impaired during the fusion of satellite muscle cells from patients with SMA I or II compared with normal satellite muscle cells. Taken together, these observations suggest that (a) there is a muscle specific expression pattern of SMN, and (b) SMN probably plays a crucial role in maintenance of a functional motor unit, by allowing muscle cells to correctly differentiate and to allow motoneuron survival.

Animals↗

The distribution of SMN protein complex in human fetal tissues and its alteration in spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration of motor neurons of the spinal cord and muscular atrophy. SMA is caused by alterations to the survival of motor neuron (SMN) gene, the function of which has hitherto been unclear. Here, we present immunoblot analyses showing that normal SMN protein expression undergoes a marked decay in the postnatal period compared with fetal development. Morphological and immunohistochemical analyses of the SMN protein in human fetal tissues showed a general distribution in the cytoplasm, except in muscle cells, where SMN protein was immunolocalized to large cytoplasmic dot-like structures and was tightly associated with membrane-free heavy sedimenting complexes. These cytoplasmic structures were similar in size to gem. The SMN protein was markedly deficient in tissues derived from type I SMA fetuses, including skeletal muscles and, as previously shown, spinal cord. While our data do not help decide whether SMA results from impaired SMN expression in spinal cord, skeletal muscle or both, they suggest a requirement for SMN protein during embryo-fetal development.

Animals↗

Hybrid survival motor neuron genes in Japanese patients with spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a frequently occurring autosomal recessive disease, characterized by the degeneration of spinal cord anterior horn cells, leading to muscular atrophy. Most SMA patients carry homozygous deletions of the telomeric survival motor neuron gene (SMN) exons 7 and 8. In the study presented here, we examined 20 Japanese SMA patients and found that 4 of these patients were lacking in telomeric SMN exon 7, but retained exon 8. In these 4 patients, who exhibited all grades of disease severity, direct sequencing analysis demonstrated the presence of a hybrid SMN gene in which centromeric SMN exon 7 was adjacent to telomeric SMN exon 8. In an SMA family, a combination of polymerase chain reaction and enzyme-digestion analysis and haplotype analysis with the polymorphic multicopy marker Agl-CA indicated that the patient inherited the hybrid gene from her father. In conclusion, hybrid SMN genes can be present in all grades of disease severity and inherited from generation to generation in an SMA family.

Adult↗

Distal spinal muscular atrophy.

Spinal muscular atrophies (SMA) are clinically heterogenous group of motor system disorders characterised by progressive pure lower motor neuron involvement. The distal form of SMA is an extremely rare disorder, which presents in the adults and has a relatively slow progression with almost no effect on the patients' life-span. Differential diagnosis of this syndrome include other forms of neuromuscular disorders with peroneal muscular atrophy like hereditary motor sensory neuropathy (HMSN) and distal myopathies, which need exclusion before confirming this rare entity. We present a young male with this disorder and briefly discuss the theoretical aspects.

Adult↗

Spinal muscular atrophy.

Spinal muscular atrophy is a common genetic disease of the motor neuron (frequency of eight cases per 100,000 live births) with a high mortality during infancy and no known treatment. Death is caused by severe and progressive restrictive lung disease. New information regarding the nature and function of the SMN protein and the availability of new pharmacologic agents now make it possible to consider clinical trials in this disease. Rehabilitation and proper management of medical complications have improved both the quality and duration of life for children with spinal muscular atrophy.

Animals↗

[A case of post-poliomyelitis muscular atrophy with cranial nerve signs and widespread muscular atrophy of the extremities].

Here we report a case of a 56-year-old male with post-poliomyelitis muscular atrophy (PPMA), who presented with cranial nerve signs and widespread atrophy of the extremities. He had suffered from poliomyelitis at the age of 2 years. After recovery from the acute stage, the paralysis remained in his left arm. He noticed muscle weakness of the right upper and lower extremities at the age of 45 years and the muscle atrophy progressed to his arms, hip and thigh at the age of 55 years. Neurological examination revealed muscle atrophy of the neck and disturbance of left V, VIII, IX, X and bilateral XI cranial nerves. We diagnosed this case as PPMA from his history and electromyographic and muscle biopsy findings which suggested chronic denervation. Among the 21 PPMA cases in the past in which the acute poliomyelitis had resulted in paralysis of the only one limb, ours was the only case that had muscle atrophy of all the limbs. Cranial nerve involvement is known to occur in acute poliomyelitis; therefore, there is a possibility that the involvement of the cranial nerves in our case might be a delayed progressive symptoms.

Cranial Nerves↗

Hereditary canine spinal muscular atrophy is phenotypically similar but molecularly distinct from human spinal muscular atrophy.

Hereditary canine spinal muscular atrophy (HCSMA) is an autosomal dominant motor neuron disease that is similar in pathology and clinical presentation to various forms of human motor neuron disease. We have tested the hypothesis that the canine survival motor neuron (SMN) gene is responsible for HCSMA by genetic and molecular analysis of a colony of mixed breed dogs, all descended from a single affected individual. We cloned the canine SMN gene and determined the DNA sequence in an affected and an unaffected dog. We found no germline mutations in the SMN gene of the affected individual. Using conventional linkage analysis with canine-specific microsatellite repeat markers we screened the canine genome and identified a single linkage group likely to contain the HCSMA gene. Analysis with a panel of canine/rodent hybrid cell lines revealed that the SMN gene did not map to the same chromosome as the HCSMA linkage group. Collectively these results suggest that the molecular basis for HCSMA is distinct from that of phenotypically similar human disorders caused by inherited mutations in the SMN gene. This further suggests that additional studies on the molecular nature of HCSMA may reveal an unknown element of the molecular pathway leading to motor neuron disease.

Amino Acid Sequence↗

Mapping of acute (type I) spinal muscular atrophy to chromosome 5q12-q14. The French Spinal Muscular Atrophy Investigators.

Linkage analysis in twenty-five families with acute (type I) spinal muscular atrophy (SMA) showed that the mutant gene responsible for the disorder is tightly linked to the D5S39 locus. The mutation(s) causing the intermediate (type II) and juvenile chronic (type III) forms of SMA were also mapped to DNA marker D5S39 on chromosome 5 (5q12-q14). Thus, the three forms, which have been differentiated clinically on the basis of age of onset and clinical course, are most probably due to different mutations at a single locus on chromosome 5. Prenatal diagnosis of SMA type I will now be possible.

Acute Disease↗

Molecular analysis of the spinal muscular atrophy and neuronal apoptosis inhibitory protein genes in Saudi patients with spinal muscular atrophy.

OBJECTIVE: Spinal muscular atrophy (SMA) is a common, often fatal, autosomal recessive disease leading to progressive muscle wasting and paralysis as a result of degeneration of anterior horn cells of the spinal cord. The prevalence of SMA cases in the Kingdom of Saudi Arabia (KSA) is much higher than the European and North American population. Deletions or mutations in 2 genes, telomeric form of the survival motor neuron (SMN1) and the neuronal apoptosis inhibitory protein (NAIP), are known to be associated with SMA. The aim of this study is to examine the deletions or interruptions of the SMN1 and NAIP genes in Saudi patients. METHODS: The study included 121 Saudi SMA patients [type I (60 patients); type II (26 patients); and type III (35 patients)]. The deletions or interruptions of the SMN1 and NAIP genes were detected by using polymerase chain reaction. The study was carried out at the King Fahad National Guard Hospital, Riyadh, KSA between 2000 and 2002. RESULTS: The homozygous deletions of exons 7 and 8 of the SMN1 gene were found in 94% and 87% of the patients. Exon 5 of the NAIP gene was deleted in 70%, but its deletion was more frequent in SMA type I (93%) as compared to type II (54%) and type III (43%). Seven patients with SMA diagnosis did not show any of the above homozygous deletions. All 230 control subjects had at least one copy of both SMN1 and NAIP genes, as expected. CONCLUSION: Our results demonstrate that the deletion rate (94%) of the SMN1 gene in Saudi SMA patients is similar, irrespective of types, compared with patients of other ethnic groups. We also show that the incidence of NAIP deletion is higher in the more severe SMA cases and the dual deletion of the SMN1 and NAIP genes are more common in Saudi SMA type I patients compared with patients of other ethnic groups.

Cyclic AMP Response Element-Binding Protein↗

[Incidence of spinal muscular atrophy and Duchenne's muscular dystrophy in the juvenile population of central Slovakia].

Spinal muscular atrophy, type I-III and Duchenne muscular dystrophy belong to the most frequent neuromuscular diseases in children. The purpose of this work was to determine the incidence of these two diseases in liveborn children in the years 1975 to 1989 in the south part of middle Slovakia. The common incidence of all three types of spinal muscular atrophy was 1 in 5631 liveborn children (most frequent was the Werdnig-Hoffmann disease, type I--1 in 12,286). This fact confirms, that this disease belongs to the most frequent autosomal recessive diseases in children of our region too. The incidence of Duchenne muscular dystrophy was 1 in 4827 liveborn boys. The figure is in the range of the published data of the incidence of this disease. The deletion in the dystrofin gene was proved in 70% of affected boys. (Tab. 3, Fig. 1, Ref. 24).

Child↗