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Deletions of the survival motor neuron gene in unaffected siblings of patients with spinal muscular atrophy.

DNA studies in 103 spinal muscular atrophy (SMA) patients from The Netherlands revealed homozygosity for a survival motor neuron (SMN) deletion in 96 (93%) of 103. Neuronal apoptosis inhibitory protein deletions were found in 38 (37%) of 103 and occurred most frequently in SMA type I. SMN deletions have not yet been described to occur in healthy subjects. In this study, however, four unaffected sibs from two SMA families showed homozygosity for SMN deletions. Homozygosity for an SMN deletion in unaffected persons seems to be very rare. Therefore, demonstration of a homozygous SMN deletion in a clinically presumed SMA patient should be considered as a confirmation of the diagnosis, whether or not SMN is in fact the causal gene for SMA.

DNA↗

Screening of deletions in SMN, NAIP and BTF2p44 genes in Turkish spinal muscular atrophy patients.

Deletions of the spinal muscular atrophy (SMA)-determining gene, SMN1, NAIP, and a third multicopy gene, BTF2p44tel were investigated in 60 unrelated Turkish SMA patients. SMN1 was deleted for at least exons 7 and 8 in 85% of the Turkish SMA patients. The NAIP gene was deleted in 75 and 33% of type I and type II SMA patients, respectively. Analysis of the 5'end of the BTF2p44tel gene indicated the extension of deletion in 13.3% of the cases, mainly in type I patients. Deletions of the NAIP and BTF2p44tel genes were detected in 1.3 and 3.9% of carrriers, respectively, in Turkish SMA families. Two patients were detected to harbor the hybrid SMN gene, one type II with deletion of the NAIP gene, and one type III without deletion of the NAIP gene.

Chromosomes, Human, Pair 5↗

The role of palliative care in advanced muscular dystrophy and spinal muscular atrophy.

OBJECTIVE: This study examines the potential role for palliative care services in the care of individuals with muscular dystrophy and spinal muscular atrophy, and the support of their families. METHODOLOGY: Semistructured interviews were conducted in South Australia with nine bereaved and four current family members of individuals with muscular dystrophy or spinal muscular atrophy. Issues explored during interview included: (i) the family perceptions of the difficulties in caring; (ii) the psychological and physical resources which were available to assist them; and (iii) family recall of the management of the terminal phase of the illness. RESULTS: Significant issues identified included: (i) a lack of coordination of care and access to skilled, competent carers; (ii) a lack of support for siblings; (iii) inadequate bereavement care; and (iv) limited discussion of options of ventilatory support and advance directives. CONCLUSIONS: The terminal care for individuals with muscular dystrophy and spinal muscular atrophy and their families requires improvement. Although many individuals with these conditions will die following an acute event, palliative care services may be appropriate for those who require a period of terminal care at home.

Adolescent↗

Prenatal onset spinal muscular atrophy.

Five patients with severe spinal muscular atrophy (SMA) type I, all of whom presented with reduced fetal movements in utero, severe weakness at birth, and short survival time were assessed to attempt to determine whether their phenotype could be explained by their genotype. The diagnosis was confirmed by clinical, electrophysiological and histopathological features. Polymerase chain reaction assays were used to define the molecular diagnosis. A gene-dosage assay was used to assess the quantity of centromeric survival motor neuron gene (SMNc) present. In all cases the telomeric survival motor neuron gene (SMNt) was absent. The SMNc gene was present but in reduced copy number compared with a control group of children with less severe type I SMA, so may be important in determining severity. In the differential diagnosis of reduced fetal movements, SMA should be considered. The clinical classification may in future be clarified by molecular genetic findings.

Cell Survival↗

Descriptive epidemiology of spinal muscular atrophy type I in Estonia.

Spinal muscular atrophy is the second most frequent autosomal-recessive disorder in Europeans. There are no published epidemiological data on SMA in Estonia and other Baltic countries. The aim of this study was to estimate the incidence of SMA I in Estonia. All patients with SMA I diagnosed between January 1994 and December 2003 were included in the study. The diagnosis was established on the basis of neurological evaluation, ENMG findings, molecular studies and muscle biopsy. PCR and restriction enzyme analysis was used to detect the homozygous deletion of the SMN1 gene. A total of 9 cases of SMA I were identified during this 10-year period. The incidence of SMA I in Estonia is 1 in 14,400 live births, which is similar to the result from Hungary but lower than average incidence in the world. Only one of the patients was female. Typical SMN1 gene deletion was found in all cases.

Cyclic AMP Response Element-Binding Protein↗

Spinal muscular atrophy.

The history of the spinal muscular atrophies (SMA) began in the 1890s with Guido Werdnig and Johann Hoffmann. Together, their papers present a rather complete picture of the clinical and pathologic aspects of infantile SMA: onset during the first year of life, occurrence in siblings with normal parents, progressive floppiness and weakness, hand tremor, and death from pneumonia in early childhood. Based on the work of an international collaboration, the following is current nomenclature: SMA type 1 (or I) for onset of symptoms before age 6 months, SMA type 2 (II) for onset between 6 and 18 months, and SMA type 3 (III) for onset after age 18 months. Linkage of autosomal recessive SMA to chromosome 5q11.2-13.3 was reported by Gilliam et al in 1990. A novel gene, whose function remains unknown, called the survival motor neuron gene (SMN) at 5q13, contains deletions in more than 98% of SMA patients. Some patients with atypical forms of SMA have been shown to have mutations in SMN. Because there is no effective therapy for SMA, management consists of preventing or treating the complications of severe weakness, such as restrictive lung disease, poor nutrition, orthopedic deformities, immobility, and psychosocial problems.

Child↗

[Role of signs of fetal hypokinesia in the diagnosis of spinal muscular atrophy of neonatal onset].

INTRODUCTION: Spinal muscular atrophy (SMA) is characterized by early degeneration of anterior horn cells. The most frequent and severe type of neonatal onset is Werdnig-Hoffmann disease. The neurologic and genetic characteristics of SMA are well-known. The aim of this study was to analyze the dysmorphologic features of this disease. PATIENTS AND METHODS: We present an analysis of 10 cases of SMA identified among 27,864 infants with congenital defects registered by the Spanish Collaborative Study of Congenital Malformations (ECEMC) between April 1976 and December 1998. We also report a clinical case of neonatal SMA presenting the classical signs of fetal hypokinesia deformation sequence. RESULTS: The minimum estimation of the prevalence of SMA with congenital defects in our population is 0.32 per 100,000 live births. We found a male-to-female ratio of 3.5. The most frequently associated congenital defects in our population of neonatal SMA were located in the extremities (mainly arthrogryposis), face and thorax and could be explained by intrinsic fetal hypomobility secondary to the neuromuscular disorder. The characteristics of fetal hypokinesia deformation sequence are discussed in the case report presented herein: dystocic delivery, short umbilical cord, polyhydramnios, intrauterine growth retardation, craniofacial malformations, skeletal abnormalities with multiple articular contractures, pulmonary hypoplasia, etc. CONCLUSIONS: It is important to recognize the congenital defects associated with neuromuscular disorders, because dysmorphologic features are sometimes more marked than neurologic features in the neonatal period and because of the wide spectrum of congenital defects in neonatal SMA that result in a fetal hypokinesia deformation sequence.

Female↗

Determinants of exon 7 splicing in the spinal muscular atrophy genes, SMN1 and SMN2.

Spinal muscular atrophy is a neurodegenerative disorder caused by the deletion or mutation of the survival-of-motor-neuron gene, SMN1. An SMN1 paralog, SMN2, differs by a C-->T transition in exon 7 that causes substantial skipping of this exon, such that SMN2 expresses only low levels of functional protein. A better understanding of SMN splicing mechanisms should facilitate the development of drugs that increase survival motor neuron (SMN) protein levels by improving SMN2 exon 7 inclusion. In addition, exonic mutations that cause defective splicing give rise to many genetic diseases, and the SMN1/2 system is a useful paradigm for understanding exon-identity determinants and alternative-splicing mechanisms. Skipping of SMN2 exon 7 was previously attributed either to the loss of an SF2/ASF-dependent exonic splicing enhancer or to the creation of an hnRNP A/B-dependent exonic splicing silencer, as a result of the C-->T transition. We report the extensive testing of the enhancer-loss and silencer-gain models by mutagenesis, RNA interference, overexpression, RNA splicing, and RNA-protein interaction experiments. Our results support the enhancer-loss model but also demonstrate that hnRNP A/B proteins antagonize SF2/ASF-dependent ESE activity and promote exon 7 skipping by a mechanism that is independent of the C-->T transition and is, therefore, common to both SMN1 and SMN2. Our findings explain the basis of defective SMN2 splicing, illustrate the fine balance between positive and negative determinants of exon identity and alternative splicing, and underscore the importance of antagonistic splicing factors and exonic elements in a disease context.

Base Sequence↗

[Childhood spinal muscular atrophies].

Current knowledge of infantile spinal muscular atrophies (ISA) is reviewed by analyzing cases seen by the neurology service at Hospital Sant Joan de Déu in Barcelona from 1978 through 1986. The assessment is mainly clinical. The total number of patients is 60, as follows: 24 with severe or type I forms, 24 with intermediate or type II forms and 12 with type III forms. All type I patients presented hypotonia and weakness before age four months and died before the age of two years. DNA genome tests were performed for eight, revealing that four had deletions in the seventh and eighth exons. One patient had a single deletion in exon 7, one had a deletion in the neuronal apoptosis inhibitory protein gene as well as in exon 7. No deletions were detected in two patients. Four type II patients died of respiratory complications. All except one acquired autonomous sedestation. Severe scoliosis presented in 14 patients, with most requiring corsets. Fourteen required arthrodesis of the spinal column by way of Luque's technique. DNA genome studies were performed for 19, revealing that 14 had deletions in both exons 7 and 8. Exon 7 deletion was present in two. Two also had deletions in exon 3, an abnormality known as the "Spanish mutation". Genetic conversion or an equivalent deletion in exon 7 was observed in the remaining patients. Five of the type III patients walked autonomously, although with pelvic balancing and Gower's maneuver upon rising from the floor. Braces were required for walking by four, whereas three walked so precariously that they only achieved partial autonomy inside the home. DNA genome studies were performed in seven, revealing exon 7 and 8 deletions in six patients. Only one presented a partial deletion in exon three.

Adolescent↗

Focal spinal muscular atrophy in two German shepherd pups.

Focal spinal muscular atrophy evolved rapidly in two German Shepherd pups 2 weeks after birth. By 1 month, the male and female littermates had developed a valgus deformity of the right forelimb, a flexed carpus, and arm and forearm muscle weakness and atrophy. In the male, less severe left forelimb weakness and wasting also occurred, and bilateral forelimb denervation potentials were recorded. Postmortem study of the male revealed asymmetric loss and degeneration of motoneurons in the cervical spinal cord intumescence. Degenerating neurons appeared vacuolated or chromatolytic. Chromatolysis was often peripheral and resulted from dispersion and loss of the free and attached ribosomes which normally from Nissl bodies. Although this focal neuronopathy was unlike motoneuron diseases described previously in animals, it resembled the asymmetric and unilateral, benign spinal muscular atrophies found in humans.

Animals↗

[Enzyme-and immuno-histochemistry of muscle biopsies in severe infantile spinal muscular atrophy].

The basic lesions in the muscle biopsies of 11 cases of severe infantile spinal muscular atrophy showed typical neurogenic fascicular muscular atrophy. It was found through histochemistry staining that both types of muscle fibres were involved which were characterised by the presence of type grouping of the damaged fibers, anyhow, the original mosaic pattern of both types were still partially reserved. With anti-laminin immunofluorescence staining, it was demonstrated that the basal membrane of atrophied small muscle fibre was still intact. It is considered that the main manifestation of damage on spinal anterior horn neuron is denervation of the skeletal muscle; meanwhile, the function of the muscle fibre in regulations carbohydrate metabolism is not apparently obstructs. The pathologic process of this disease develops from denervation to renervation and then back to denervation again. Therefore the clinical feature of muscle atrophy in this disease is progressive and developmental.

Anterior Horn Cells↗

The use of chromosome 5q markers for confirming the diagnosis of proximal spinal muscular atrophy.

1. Five Brazilian families referred to us with a probable diagnosis of chronic proximal spinal muscular atrophy (Kugelberg-Welander) were identified, and permanent (Epstein Barr virus transformed) cell lines were established from members of four of the families. 2. A genetic linkage study was carried out on 70 individuals using nine polymorphic DNA markers (eight RFLP and one microsatellite) from chromosome 5q11.2-13.3 which have been shown to flank the spinal muscular atrophy (SMA) gene. 3. The segregation of the markers in two of the five families was compatible with the disease-causing locus being located in this same region. In one family the pattern of segregation clearly excludes the causative gene from this region. In one of the remaining two families the analysis was inconclusive because the markers were not informative. In the fifth family the possibility of two concurrent neuromuscular diseases did not permit a definite conclusion. 4. These results further support the location of the major SMA gene at 5q11.2-13.3. 5. The possibility of non-allelic heterogeneity for the spinal muscular atrophy gene is discussed.

Adolescent↗

[Anatomoclinical correlations of spinal muscular atrophy in infancy].

Forty-three cases of infantile spinal muscular atrophy diagnosed in our department between 1977 to 1991 are presented. Following clinical-pathologic evaluation, 27 cases were included in type I, 7 in type II and 9 cases in type III. The most frequent pathologic finding was the presence of large groups of atrophic fibers and hypertrophy of isolated fibers in muscle biopsy. Enzyme study showed higher mean levels of CPK and aldolase in type I with respect to the other two. Likewise, a significant statistical difference was found in the age of onset of the different groups. Finally, the clinical classification of spinal muscular atrophies in infancy is discussed.

Biopsy↗

Surgical treatment of scoliosis in a spinal muscular atrophy population.

Seventy-eight patients were diagnosed with spinal muscular atrophy between 1969 and 1988. Scoliosis developed in 34 of these patients, an incidence of 60%. Thirty-one patients could be retrospectively reviewed by chart review or interview. The average follow-up was 11.5 years. Onset of scoliosis averaged 8.8 years. Twenty-two patients were treated nonsurgically and nine surgically. Patients had improved sitting balance and endurance after surgery. Complications of surgery included loss of correction in one patient, one pseudarthrosis, and one patient who required prolonged ventilatory support. The prolonged survival of patients with spinal muscular atrophy justifies aggressive orthopaedic management of scoliosis to prevent progression of deformity and improve sitting comfort.

Braces↗

Infantile spinal muscular atrophy with respiratory distress type 1 (SMARD1).

Autosomal recessive spinal muscular atrophy with respiratory distress type 1 (SMARD1) is the second anterior horn cell disease in infants in which the genetic defect has been defined. SMARD1 results from mutations in the gene encoding the immunoglobulin micro-binding protein 2 (IGHMBP2) on chromosome 11q13. Our aim was to review the clinical features of 29 infants affected with SMARD1 and report on 26 novel IGHMBP2 mutations. Intrauterine growth retardation, weak cry, and foot deformities were the earliest symptoms of SMARD1. Most patients presented at the age of 1 to 6 months with respiratory distress due to diaphragmatic paralysis and progressive muscle weakness with predominantly distal lower limb muscle involvement. Sensory and autonomic nerves are also affected. Because of the poor prognosis, there is a demand for prenatal diagnosis, and clear diagnostic criteria for infantile SMARD1 are needed. The diagnosis of SMARD1 should be considered in infants with non-5q spinal muscular atrophy, neuropathy, and muscle weakness and/or respiratory distress of unclear cause. Furthermore, consanguineous parents of a child with sudden infant death syndrome should be examined for IGHMBP2 mutations.

Carrier Proteins↗

[Development of therapeutics for spinal and bulbar muscular atrophy (SBMA)].

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy's disease, is a hereditary motor neuron disease that affects males, caused by the expansion of a polyglutamine (polyQ) tract in androgen receptor (AR). Female carriers are usually asymptomatic. The transgenic mouse (Tg) model carrying a full-length human AR with expanded polyQ has significant gender-related motor impairment. This phenotype is inhibited by castration, which prevents nuclear translocation of mutant AR. Leuprorelin, an LHRH agonist that reduces testosterone release from the testis, also rescues motor dysfunction and nuclear accumulation of mutant AR in the male Tg. Over-expression of a molecular chaperone HSP70, which renatures misfolded mutant AR, ameliorates neuromuscular phenotypes of the Tg by reducing nuclear-localized mutant AR. HSP70 appears to enhance the degradation of mutant AR via ubiquitin-proteasome pathway. These experimental approaches indicate the possibility of clinical application of drugs, such as leuprorelin, for SBMA patients.

Animals↗