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Cell death and decreased synaptic protein expression in the ventral horn of Holstein-Friesian calves with spinal muscular atrophy.

A neuropathological study of Holstein-Friesian calves with spinal muscular atrophy (SMA) demonstrated decreased numbers of motor neurons in the brachial and lumbo-sacral regions of the spinal cord, together with swelling and accumulation of phosphorylated neurofilaments, and neuronophagia in most of the remaining motor neurons. The pyramidal tracts, motor cortex and thalamus were not affected. Synaptophysin immunohistochemistry revealed a marked reduction of punctate terminals but only around swollen neurones, suggesting loss of terminal afferents on motor neurons at advanced stages of the degenerative process. An immunohistochemical study of proteins linked with cell death and cell survival demonstrated reduced expression of Fas, Fas-L, Bcl-2 and Bax in swollen motor neurons. Punctate cytochrome C immunoreactivity, consistent with mitochondrial localization, was detected in the soma of normal motor neurons, but not in swollen motor neurons. Finally, no labelling of motor neurons with antibodies to cleaved (active) caspase-3 (17kD) was detected, suggesting a lack of involvement of the apoptotic pathways in motor neuron death. Taken together, the present findings point to necrosis as a major cause of motor neuron death in the advanced stages of SMA in Holstein-Friesian calves.

Animals↗

SMN(T) and NAIP mutations in Canadian families with spinal muscular atrophy (SMA): genotype/phenotype correlations with disease severity.

Childhood-onset spinal muscular atrophy (SMA) is an autosomal recessive neuropathy characterized by selective degeneration of alpha-motor neuron cells of the spinal cord. Age of onset and motor development varies greatly among patients, but the molecular basis of this variability remains unclear. The SMA locus contains two copies of a 500-kb element and deletions within the telomeric element have been shown to be the most common cause of SMA. To study the relationship between genotype and phenotype, 60 SMA families, all but two of which are of French Canadian origin, were screened for deletions in the telomeric survival motor neuron (SMN(T)) and the intact neuronal apoptosis inhibitory protein (NAIP) genes. Combining these results with those obtained for the multicopy microsatellite marker Ag1-CA (D5S1556) indicated that there are at least two types of SMA alleles. Most type I SMA patients are homozygous for large scale deletions involving the entire SMN(T) gene as well as exons 5 and 6 of the NAIP gene. The strong association between the 100-bp allele of Ag1-CA and large scale deletions in populations of diverse ethnic origin suggests that this allele marks an unstable or founder SMA chromosome. In contrast, most chronic SMA patients have at least one SMA allele with either an intragenic SMN(T) deletion or a SMN(C):SMN(T) chimeric gene which replaces the normal SMN(T) gene. The broad continuum of disease presentation in chronic SMA is most likely a consequence of the interaction between different SMA alleles.

Canada↗

[Proximal spinal muscular atrophy in the adult].

Based on personal experience and recent advances in the molecular genetics of spinal muscular atrophies (SMA), the author reviews the main features of adult SMA predominantly affecting the proximal musculature. Hereditary SMA forms linked to characteristic chromosome abnormalities are distinguished from those that have not been linked to any known gene. Among the first type, recessive autosomal inherited forms linked to chromosome 5 are mentioned and the description is extended to progressive bulbar-spinal amyotrophy and Kennedy syndrome, linked to the X chromosome, whose gene also codifies androgenic receptors, constituting a syndrome with clear neuro-endocrine involvement. In dealing with SMA forms that have not been linked to a gene, the author details, always from personal experience, those with scapuloperoneal involvement, of which Stark-Kaeser syndrome is the prototype. Finally, the author discusses non hereditary types, covering current knowledge of chronic anterior poliomyelitis, the concept of monomelic spinal muscular atrophy and post-poliomyelitis muscle syndrome. The author's extensive personal bibliography completes the chapter.

Adult↗

Infantile spinal muscular atrophy (morbus Werdnig-Hoffmann) causing neonatal asphyxia.

A case of infantile spinal muscular atrophy (Werdnig-Hoffmann's disease) with complete proximal pareses obvious at birth giving rise to neonatal asphyxia is reported. Reduction of fetal movements was noted from the 32nd week of pregnancy. The infant was extremely floppy at birth and spontaneous movements were restricted to hands, feet and face. Fibrillations of the tongue, diaphragmatic hemiparesis and dysphagia were observed. Unassisted ventilation was not compatible with survival and the infant succumbed to the disease in the neonatal period. Muscle biopsy and autopsy confirmed the clinical diagnosis. Infantile spinal muscular atrophy causing neonatal asphyxia seems to be unusual and not earlier described. Constant muscular hypotonus in an asphyctic newborn should raise suspicion of a neuromuscular disorder.

Asphyxia Neonatorum↗

Neonatal adrenoleukodystrophy presenting as infantile progressive spinal muscular atrophy.

Two siblings with neonatal adrenoleukodystrophy are described. The signs and laboratory data documenting infantile progressive spinal muscular atrophy included the initial presentation of 1 sibling with neonatal adrenoleukodystrophy. These patients indicate that neonatal adrenoleukodystrophy should be considered in the differential diagnosis of infantile progressive spinal muscular atrophy.

Adrenoleukodystrophy↗

Spinal muscular atrophy variant with congenital fractures.

A single report of brothers born to first-cousin parents with a form of acute spinal muscular atrophy (SMA) and congenital fractures suggested that this combination represented a distinct form of autosomal recessive SMA. We describe a boy with hypotonia and congenital fractures whose sural nerve and muscle biopsies were consistent with a form of spinal muscular atrophy. Molecular studies identified no abnormality of the SMN(T) gene on chromosome 5. This case serves to validate the suggestion of a distinct and rare form of spinal muscular atrophy while not excluding possible X-linked inheritance.

Adolescent↗

Two independent mutations of the SMN1 gene in the same spinal muscular atrophy family branch: lessons for carrier diagnosis.

PURPOSE: We present the results of carrier studies in 33 relatives of the paternal branch of a spinal muscular atrophy patient with homozygous absence of the SMN1 gene. METHODS AND RESULTS: Once linkage and quantitative analyses were performed, a number of first-, second- and third-degree relatives were identified as carriers given that they shared the at-risk haplotype and showed one SMN1 copy. In the fourth-degree relatives, linkage analysis demonstrated discordance with the quantitative results because the members with one copy were carriers of the mutation, but in a different haplotype background. We concluded that two independent mutations were present in this branch of the family. Furthermore, the combination of both methods of analysis allowed us to identify carriers with two SMN1 genes in one chromosome and none in the remaining chromosome. CONCLUSIONS: Carrier testing in spinal muscular atrophy should be performed by employing both quantitative and linkage analyses in order to guarantee accurate carrier identification.

Cyclic AMP Response Element-Binding Protein↗

Autosomal dominant spinal muscular atrophy: a clinical and genetic study.

A clinical and genetic study of 6 kindreds (13 patients) with autosomal dominant spinal muscular atrophy is presented. Evidence is presented to indicate that two separate autosomal dominant genes are involved. One of these causes clinical disease with onset in early childhood (birth--8 years), which is relatively benign and in which proximal selectively of muscle involvement is not marked. A separate autosomal dominant gene causes a disease with onset in adult life (median age 37 years), showing marked initial proximal selectively; this disease may be more rapid in its clinical progression. Penetrance of both genes approaches 100%. Incidence figures are presented; less than 2% of all cases of childhood onset spinal muscular atrophy, but 30% of adult onset cases, are due to an autosomal dominant gene transmitted from an affected parent. Implications for prognosis, diagnosis and genetic counselling are discussed. A review of 11 kindreds of dominant spinal muscular atrophy in the literature is presented.

Adolescent↗

Distinct and overlapping alterations in motor and sensory neurons in a mouse model of spinal muscular atrophy.

Motor neuron degeneration is the predominant pathological feature of spinal muscular atrophy (SMA). In patients with severe forms of the disease, additional sensory abnormalities have been reported. However, it is not clear whether the loss of sensory neurons is a common feature in severe forms of the disease, how many neurons are lost and how loss of sensory neurons compares with motor neuron degeneration. We have analysed dorsal root ganglionic sensory neurons in Smn-/-;SMN2 mice, a model of type I SMA. In contrast to lumbar motor neurons, no loss of sensory neurons in the L5 dorsal root ganglia is found at post-natal days 3-5 when these mice are severely paralyzed and die from motor defects. Survival of cultured sensory neurons in the presence of NGF and other neurotrophic factors is not reduced in comparison to wild-type controls. However, isolated sensory neurons have shorter neurites and smaller growth cones, and beta-actin protein and beta-actin mRNA are reduced in sensory neurite terminals. In footpads of Smn-deficient mouse embryos, sensory nerve terminals are smaller, suggesting that Smn deficiency reduces neurite outgrowth during embryogenesis. These data indicate that pathological alterations in severe forms of SMA are not restricted to motor neurons, but the defects in the sensory neurons are milder than those in the motor neurons.

Actins↗

Familial progressive bulbar-spinal muscular atrophy: case report with muscle biopsy study.

A case of familial progressive bulbar and spinal muscular atrophy was presented. The patient was a 59-year-old male with chief complaints of gait disturbance and nasal voice. His illness started at the age of 39 and very slowly progressed over 20 years. The clinical symptoms and signs were characterized by muscle weakness and atrophy due to lower motor neuron disease in the brain stem below the lower pons and the spinal cord. The electromyograms and muscle biopsy findings are basically neurogenic. In spite of the bulbar signs, the course of the disease is extremely slow. The diagnostic criteria was proposed after reviewing eight other cases reported in the literature.

Adult↗

Molecular analysis of candidate genes on chromosome 5q13 in autosomal recessive spinal muscular atrophy: evidence of homozygous deletions of the SMN gene in unaffected individuals.

Proximal spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration of anterior horn cells in the spinal cord leading to weakness and wasting of voluntary muscles. Here we present the molecular analysis of both SMA candidate genes, the survival motor neuron gene (SMN; exons 7 and 8) and the neuronal apoptosis inhibitory protein gene (NAIP; exons 5, 6 and 13), in 195 patients and 348 parents of SMA families mainly of German origin. The SMN gene is homozygously deleted for both exons 7 and 8 or exon 7 only in 96% of type I SMA, 94% of type II SMA and 82% of type III SMA as well as in 0.3% of SMA parents. The NAIP gene is homozygously deleted in 46% of type I SMA, 17% of type II SMA, 7% of type III SMA and 2% of SMA parents. The frequencies of deletions in patients for both genes, SMN and NAIP, correspond to those for the NAIP gene only. SMA patients of this series who did not show deletions were clinically indistinguishable from deleted patients. In addition to one unaffected mother of a type II SMA patient, we found homozygous deletions of the SMN gene exons 7 and 8 in six further unaffected individuals, all sibs of type II and III patients. These belonged to four families with affected and unaffected sibs who showed identical haplotypes for all SMA flanking markers; therefore, we had regarded these families as chromosome 5 unlinked. All seven unaffected individuals in whom we detected SMA deletions do not show any signs of muscle weakness and are physically inconspicuous. The largest divergence between age at onset of an affected subject and the present age of unaffected deleted sibs is four decades now. The occurrence of SMN deletions in unaffected individuals suggests that other genes or mechanisms may be necessary to produce the SMA phenotype.

Adolescent↗

Juvenile proximal spinal muscular atrophy with early hypertrophy of calves.

The clinical, electrophysiological, histological and ultrastructural features of a patient with chronic spinal muscular atrophy of adolescent onset associated with hypertrophied calf-muscle are described. This recently recognised entity must be distinguished from other types of spinal muscular atrophy.

Adolescent↗

Abnormal fatty acid metabolism in childhood spinal muscular atrophy.

Our previous experience with abnormal fatty acid metabolism in several children with spinal muscular atrophy (SMA) prompted evaluation of fatty acid metabolism in a larger cohort. Thirty-three infants with severe infantile SMA were shown to have a significantly increased ratio of dodecanoic to tetradecanoic acid in plasma compared with normal infants and 6 infants affected with equally debilitating, non-SMA denervating disorders. Seventeen children with milder forms of SMA had normal fatty acid profiles. In addition, all 5 infants with severe SMA evaluated in a fasting state developed a distinctive and marked dicarboxylic aciduria, including saturated, unsaturated, and 3-hydroxy forms, comparable in severity with the dicarboxylic aciduria of children with primary defects of mitochondrial fatty acid beta-oxidation. Nine children with chronic SMA and 23 control patients did not develop an abnormal dicarboxylic aciduria during fasting. No known disorder of fatty acid metabolism explains all of the abnormalities we find in SMA. Our data suggest, however, that the abnormalities are not a consequence of SMA-related immobility, systemic illness, muscle denervation, or muscle atrophy. These abnormalities in fatty acid metabolism may be caused by changes in cellular physiology related to the molecular defects of the SMA-pathogenic survival motor neuron gene or neighboring genes.

Age Distribution↗

The relationship between SMN, the spinal muscular atrophy protein, and nuclear coiled bodies in differentiated tissues and cultured cells.

The spinal muscular atrophy protein, SMN, is a cytoplasmic protein that is also found in distinct nuclear structures called "gems." Gems are closely associated with nuclear coiled bodies and both may have a direct role in snRNP maturation and pre-RNA splicing. There has been some controversy over whether gems and coiled bodies colocalize or form adjacent/independent structures in HeLa and other cultured cells. Using a new panel of antibodies against SMN and antibodies against coilin-p80, a systematic and quantitative study of adult differentiated tissues has shown that gems always colocalize with coiled bodies. In some tissues, a small proportion of coiled bodies (<10%) had no SMN, but independent or adjacent gems were not found. The most striking observation, however, was that many cell types appear to have neither gems nor coiled bodies (e.g., cardiac and smooth muscle, blood vessels, stomach, and spleen) and this expression pattern is conserved across human, rabbit, and pig species. This shows that assembly of distinct nuclear bodies is not essential for RNA splicing and supports the view that they may be storage sites for reserves of essential proteins and snRNPs. Overexpression of SMN in COS-7 cells produced supernumerary nuclear bodies, most of which also contained coilin-p80, confirming the close relationship between gems and coiled bodies. However, when SMN is reduced to very low levels in type I SMA fibroblasts, coiled bodies are still formed. Overall, the data suggest that gem/coiled body formation is not determined by high cytoplasmic SMN concentrations or high metabolic activity alone and that a differentiation-specific factor may control their formation.

Animals↗

Spinal muscular atrophy: a deficiency in a ubiquitous protein; a motor neuron-specific disease.

Spinal muscular atrophy (SMA) is a neurodegenerative disease in humans and the most common genetic cause of infant mortality. The disease results in motor neuron loss and skeletal muscle atrophy. Despite a range of disease phenotypes, SMA is caused by mutations in a single gene, the Survival of Motor Neuron 1 (SMN1) gene. Recent advances have shed light on functions of the protein product of this gene and the pathophysiology of the disease, yet, fundamental questions remain. This review attempts to highlight some of the recent advances made in the understanding of the disease and how loss of the ubiquitously expressed survival of motor neurons (SMN) protein results in the SMA phenotype. Answers to some of the questions raised may ultimately result in a viable treatment for SMA.

Animals↗

Use of rapacuronium in a child with spinal muscular atrophy.

We report the case of an 18-month-old girl with spinal muscular atrophy (SMA) that received 1 mg x kg(-1) rapacuronium for laryngospasm during induction of anaesthesia. Within 15 min, we observed some diaphragmatic recovery and, after emergence from anaesthesia, the child demonstrated adequate respiratory efforts. However, the child showed diminished strength of the upper extremity muscles. Since the preoperative workup had revealed bulbar symptoms and laryngeal function could not be easily assessed, the patient was kept intubated until upper extremity strength had returned to preoperative levels. Small doses of midazolam had been given to reduce the patient's anxiety but the patient was extubated within 5 h without any complications. Train of four (TOF) monitoring of the right adductor pollicis muscle, performed during anaesthetic recovery, was equivocal. In SMA, muscle groups are differentially affected so that TOF responses may be inconclusive and not reflect the state of the upper airway muscles. To our knowledge, this is the first report of use of a nondepolarizing neuromuscular blocking agent in a child with SMA.

Anesthesia, Inhalation↗

Glycyl tRNA synthetase mutations in Charcot-Marie-Tooth disease type 2D and distal spinal muscular atrophy type V.

Charcot-Marie-Tooth disease type 2D (CMT2D) and distal spinal muscular atrophy type V (dSMA-V) are axonal peripheral neuropathies inherited in an autosomal dominant fashion. Our previous genetic and physical mapping efforts localized the responsible gene(s) to a well-defined region on human chromosome 7p. Here, we report the identification of four disease-associated missense mutations in the glycyl tRNA synthetase gene in families with CMT2D and dSMA-V. This is the first example of an aminoacyl tRNA synthetase being implicated in a human genetic disease, which makes genes that encode these enzymes relevant candidates for other inherited neuropathies and motor neuron diseases.

Amino Acid Sequence↗