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PubMed1994

Disorders of the motor neurone.

The spinal muscular atrophies (SMAs) are defined as a group of inherited disorders sharing the common pathological feature of degeneration of the anterior horn cells of the spinal cord and, in some cases, additionally of the bulbar motor nuclei. They are classified according to clinical features, including severity and distribution of muscle weakness and on their modes of inheritance. The SMAs are not uncommon: SMA type I (severe, acute infantile SMA) alone has a gene frequency in the UK estimated at 0.006. Together they represent a significant source of morbidity and mortality. Over the past 3 years, two major advances have been made towards understanding the molecular basis of these clinically heterogeneous disorders. First, in 1990, it was reported that all three forms of childhood-onset proximal SMA were linked to probes mapping to the proximal long arm of chromosome 5. Significant progress has been made towards isolating the gene or genes responsible, and a protocol for prenatal disease prediction in families with a previously severely affected child has been established. Second, in 1991, the molecular defect in adult-onset X-linked spinal and bulbar muscular atrophy was defined as an expansion of a (CAG)n trinucleotide repeat which encodes a string of glutamine residues in the first exon of the androgen receptor. Little progress has been made in elucidating the molecular pathology of the other SMAs. None of them has been linked to chromosome 5q markers, or indeed to markers elsewhere; the conditions are rare and pedigrees generally small. When the gene (or genes) on proximal 5q underlying SMA types I, II and III is cloned, mutations in this can then be sought in the other SMAs. The product of the chromosome 5q gene presumably plays a crucial role in maintaining the integrity of motor neurones, so determination of its structure and function may well have consequences far beyond those pertaining to the inherited SMAs. The identification of pathogenic mutations in the SOD-1 gene in familial amyotrophic lateral sclerosis is of great interest, although it is not clear that similar mechanisms contribute to the more common sporadic form of the disease.

Age of Onset↗
PubMed2003

Heat shock protein 70 chaperone overexpression ameliorates phenotypes of the spinal and bulbar muscular atrophy transgenic mouse model by reducing nuclear-localized mutant androgen receptor protein.

Spinal and bulbar muscular atrophy (SBMA) is an inherited motor neuron disease caused by the expansion of the polyglutamine (polyQ) tract within the androgen receptor (AR). The nuclear inclusions consisting of the mutant AR protein are characteristic and combine with many components of ubiquitin-proteasome and molecular chaperone pathways, raising the possibility that misfolding and altered degradation of mutant AR may be involved in the pathogenesis. We have reported that the overexpression of heat shock protein (HSP) chaperones reduces mutant AR aggregation and cell death in a neuronal cell model (Kobayashi et al., 2000). To determine whether increasing the expression level of chaperone improves the phenotype in a mouse model, we cross-bred SBMA transgenic mice with mice overexpressing the inducible form of human HSP70. We demonstrated that high expression of HSP70 markedly ameliorated the motor function of the SBMA model mice. In double-transgenic mice, the nuclear-localized mutant AR protein, particularly that of the large complex form, was significantly reduced. Monomeric mutant AR was also reduced in amount by HSP70 overexpression, suggesting the enhanced degradation of mutant AR. These findings suggest that HSP70 overexpression ameliorates SBMA phenotypes in mice by reducing nuclear-localized mutant AR, probably caused by enhanced mutant AR degradation. Our study may provide the basis for the development of an HSP70-related therapy for SBMA and other polyQ diseases.

Animals↗
PubMed1990

Werdnig-Hoffmann disease: myosin isoform expression not arrested at prenatal stage of development.

It has been suggested, on the basis of mostly morphological and some biochemical evidence, that defective innervation of muscle of patients with Werdnig-Hoffmann (WH) disease results in maturational arrest of the fibers at a stage comparable to 20-week gestational muscle. Therefore, with the use of recently developed and characterized, myosin-isoform-specific monoclonal antibodies (McAbs), an immunocytochemical study of muscle of 6 children with Werdnig-Hoffmann disease was done to determine if the pattern of expression of myosin heavy chain isoforms (MHC) in these fibers was similar to that of 20-week gestation muscle. This work showed that the MHC isoform expression in the muscle of the children with WH did not mimic that seen in 20-week gestation muscle since only a few fibers (less than 1-11%) in each specimen expressed prenatal MHC as detected by reactivity to McAb, ALD 180 (specific for a prenatal MHC) whereas virtually all of the fibers from 20-week gestation muscle were strongly reactive with ALD 180. The majority of the fibers expressed either adult fast MHC or adult slow MHC similar to that seen in normal muscle, although some co-expressed multiple MHC isoforms. Our results indicate that the difference of adult MHC isoforms in the muscle fibers of WH patients either proceeds in the absence of innervation or that denervation of muscle fibers is subsequent to the neural input required to initiate myosin isoform transitions to the adult isoforms.

Antibodies, Monoclonal↗
PubMed1987

Early fatal nemaline myopathy: case report and review.

A newborn girl with atonia and arthrogryposis multiplex required mechanical ventilation; she died on the 14th day. Postmortem muscle histology disclosed nemaline myopathy with a lack of myofibrils. Peripheral nerves appeared to be normal. The parents are first cousins. The findings for 13 other patients who died from nemaline myopathy within the first year of life are reviewed. It is suggested that early fatal cases, in contrast to patients with the 'benign' childhood form, are homozygotic for the disease gene, and that the myopathy results from abnormal myosin synthesis.

Biopsy↗
PubMed2004

Apoptosis: a key in neurodegenerative disorders.

Apoptosis is an important process in the development of the nervous system. Typically, approximately 50% of the neurons apoptose during neurogenesis before the nervous system matures. However, recent paradigms implicate premature apoptosis and/or aberrations in the fine control of neuronal apoptosis in the pathogenesis of a variety of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, spinal muscular atrophy, stroke, brain trauma, spinal cord injury, and diabetic neuropathy. This review will focus on the current concepts salient to understanding the apoptosis death program, the mediators and control of cellular apoptosis, and the relationship between aberrant apoptosis and genesis of neurodegenerative disorders. The discussion will also highlight current advances in methodology, such as utilization of neuronal cell lines and mutant animal models, in investigations of neuronal apoptotic death. The knowledge of apoptosis mechanisms could underpin the basis for development of novel therapeutic strategies and treatment modalities that are directed at control of the neuronal apoptotic death program.

Animals↗
PubMedDate not supplied

A body-powered functional upper limb orthosis.

This paper describes the development and preliminary testing of a functional upper-limb orthosis for people that have limited strength in their arms. This is symptomatic of conditions such as muscular dystrophy (MD), spinal muscular atrophy (SMA), and partial spinal cord injury. The exoskeletal orthosis is wheelchair mounted, has two links and four degrees of freedom. It uses linear elastic elements to balance out the effects of gravity in three dimensions. Preliminary results on testing with ten subjects will be presented.

Adolescent↗
PubMed1989

Werdnig-Hoffmann disease in a Nigerian infant.

A Nigerian infant with the classical features of Werdnig-Hoffmann disease is described. According to the literature the incidence in black Africans is very low. Attention is drawn to the fact that neurological illnesses are often overlooked in negroid races; several reasons are given.

Black People↗
PubMed1994

[Expansion of triplet repeat and neurodegenerative disorders].

Recent studies on human genetic analysis have revealed that there is hitherto unknown category of genomic abnormality in human genetic diseases; an abnormal expansion of trinucleotide repeat. For example, Huntington's disease is caused by the CAG expansion to more than 40 in IT15 gene Up to the present, we have 7 disorders which are revealed to be apparently caused by the triple repeat expansion: fragile X syndrome (two types), myotonic dystrophy, Huntington's disease, spinocerebellar atrophy type 1, dentatorubropallidoluysian atrophy and bulbo-spinal muscular atrophy. In this symposium, I would like to show first a clear inverse relationship between a length of CAG repeat and the age at onset in each Huntington's disease patient in Japan. Next, we would like to review and discuss on 1) the possible role of normal trinucleotide repeat in human gene, 2) the mechanisms for expansion of triplet repeat and for instability of the repeat length, and 3) the actual mechanism for neuronal cell death related to the expansion of triplet repeat.

Cell Death↗
PubMed2003

Cervical spinal cord atrophy in the atraumatically born neonate: one form of prenatal or perinatal ischaemic insult?

After atraumatic birth, three neonates presented with muscle hypotonia and weakness. Flaccid paresis of the upper extremities, spasticity of the lower extremities, dissociate sensory loss and autonomic dysfunction developed later. This ruled out the initial, tentative diagnoses of cerebral palsy, spinal muscular atrophy or hereditary neuropathy. Diagnostic imaging revealed marked thinning of the cervical spinal cord in all patients. The possible aetiology of these lesions is considered. In all cases, an antenatal or perinatal infarction is thought to be the most probable cause. Different clinical pictures following intrauterine spinal cord ischemia are discussed. Spinal cord lesion must be considered even after atraumatic birth.

Birth Injuries↗
PubMed2005

Gemin proteins are required for efficient assembly of Sm-class ribonucleoproteins.

Spinal muscular atrophy (SMA) is a neurodegenerative disease characterized by loss of spinal motor neurons. The gene encoding the survival of motor neurons (SMN) protein is mutated in >95% of SMA cases. SMN is the central component of a large oligomeric complex, including Gemins2-7, that is necessary and sufficient for the in vivo assembly of Sm proteins onto the small nuclear (sn)RNAs that mediate pre-mRNA splicing. After cytoplasmic assembly of the Sm core, both SMN and splicing snRNPs are imported into the nucleus, accumulating in Cajal bodies for additional snRNA maturation steps before targeting to splicing factor compartments known as "speckles." In this study, we analyzed the function of individual SMN complex members by RNA interference (RNAi). RNAi-mediated knockdown of SMN, Gemin2, Gemin3, and Gemin4 each disrupted Sm core assembly, whereas knockdown of Gemin5 and Snurportin1 had no effect. Assembly activity was rescued by expression of a GFP-SMN construct that is refractive to RNAi but not by similar constructs that contain SMA patient-derived mutations. Our results also demonstrate that Cajal body homeostasis requires SMN and ongoing snRNP biogenesis. Perturbation of SMN function results in disassembly of Cajal bodies and relocalization of the marker protein, coilin, to nucleoli. Moreover, in SMN-deficient cells, newly synthesized SmB proteins fail to associate with U2 snRNA or accumulate in Cajal bodies. Collectively, our results identify a previously uncharacterized function for Gemin3 and Gemin4 in Sm core assembly and correlate the activity of this pathway with SMA.

Biological Transport↗
PubMed1999

Autosomal dominant familial spinal and bulbar muscular atrophy with gynecomastia.

The proband, a 53-year-old man, developed progressive spinal and bulbar muscular atrophy and gynecomastia at the age of 50. His father had weakness of lower limbs, and his son had a nasal voice, ocular movement abnormalities, and gynecomastia, whereas two of the proband's brothers showed either gynecomastia or tongue fasciculations. None of the patients showed any expansion of CAG repeat in the androgen receptor gene or any hormonal abnormality. Thus, this family is affected by a form of autosomal dominant spinal and bulbar muscular atrophy with gynecomastia.

Chromosome Aberrations↗