Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0016719 (Friedreich's ataxia)
 2,098 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several human disorders are now known to be caused by expansion of unstable trinucleotide repeat sequences, including fragile X syndrome (FRAX), myotonic dystrophy (DM), spinal and bulbar muscular atrophy (SBMA, also known as Kennedy disease), Huntington disease (HD), dentatorubral-pallidoluysian atrophy (DRPLA), spinocerebellar ataxia type 1 (SCA1), Machado-Joseph disease (MJD), and Friedreich ataxia. As these diseases are studied in more detail, important differences have emerged in the nature of the unstable repeats and the mechanism by which the repeat expansions cause disease symptoms. There are already animal models of some of these disorders, and these are important resources for studying pathology and therapeutic strategies. Diagnostic procedures for these disorders are only beginning to be standardized, and effective therapy will have to wait for further information on disease mechanisms. Much has been learned since discovery of the fragile X syndrome gene in 1991, but much remains to be done.
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PMID:Trinucleotide repeat disorders in humans: discussions of mechanisms and medical issues. 900 50

Expansion of trinucleotide repeats has been identified as a common mechanism of hereditary neurodegenerative diseases including spinal and bulbar muscular atrophy (SBMA), Huntington's disease, dentatorubral-pallidoluysian atrophy (DRPLA), Machado-Joseph disease (MJD), fragile X syndrome, myotonic dystrophy and Friedreich's ataxia. These diseases share unique features, which are difficult to explain based on Mendelian inheritance. These unique clinical genetic features include genetic anticipation and a broad spectrum of clinical presentations, which have been shown to be associated with the instability of the trinucleotide repeats. Recent studies suggest that gene products with expanded polyglutamine tracts may be toxic to neuronal cells, and the mechanisms of neurotoxicity should be thoroughly investigated. To develop therapeutic measures, creation of animal models or cell culture systems for the investigation of neurotoxicity will be indispensable.
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PMID:Molecular genetics of triplet repeats: unstable expansion of triplet repeats as a new mechanism for neurodegenerative diseases. 905 92

In the past few years, a new type of genetic mutation, expansion of trinucleotide repeats, has been shown to cause neurologic disease. This new class of mutations was first identified in 1991 as the underlying genetic defect in spinal and bulbar muscular atrophy and the fragile X syndrome, and in recent years, trinucleotide repeat expansions have been found to be the causative mechanism in 10 other neurologic diseases. These mutations are produced by heritable unstable DNA and are termed "dynamic mutations" because of changes in the number of repeat units inherited from generation to generation. In the normal population, these repeat units, although polymorphic, are stably inherited. To date four types of trinucleotide repeat expansions have been identified: (1) long cytosine-guanine-guanine (CGG) repeats in the two fragile X syndromes (FRAXA and FRAXE), (2) long cytosine-thymine-guanine (CTG) repeat expansions in myotonic dystrophy, (3) long guanine-adenine-adenine repeat expansions in Friedreich's ataxia and (4) short cytosine-adenine-guanine repeat expansions (CAG) which are implicated in eight neurodegenerative disorders and are the focus of this review. Diseases that are caused by trinucleotide repeat expansions exhibit a phenomenon called anticipation that can not be explained by conventional Mendelian genetics. Anticipation is defined as increase in the severity of disease with an earlier age of onset of symptoms in successive generations. Anticipation is often influenced by the sex of the transmitting parent, and for most CAG repeat disorders, the disease is more severe when paternally transmitted. The severity and the age of onset of the disease have been correlated with the size of the repeats on mutant alleles, with the age of onset being inversely correlated with the size of the expansion. In all eight disorders caused by CAG repeat expansion, the repeat is located within the coding region of the gene involved and in all cases it is translated into a stretch of polyglutamines in the respective proteins. All the proteins are unrelated outside of the polyglutamine stretch and most are novel with exception of the androgen receptor and the voltage gated alpha 1A calcium channel, which are mutated in spinal and bulbar muscular atrophy and spinocerebellar ataxia type 6. It is intriguing that the proteins are ubiquitously expressed in both peripheral and nervous tissue but in each disorder only a select population of nerve cells are targeted for degeneration as a consequence of the expanded CAG repeat. Current thinking among scientists working on the molecular mechanisms of neurodegeneration in these diseases is that the presence of an expanded polyglutamine confers a gain of function onto the involved protein. To understand the mechanisms underlying the pathogenesis of these diseases, investigators have turned to generating transgenic mice which recapitulate some of the features of the human disease and hence are excellent model systems to study the progression of the disease in vivo.
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PMID:The CAG/polyglutamine tract diseases: gene products and molecular pathogenesis. 921 76

The human genome has many nucleotide repeat sequences. These range from a single repeating base to entire duplicated genes. Expansion of repeating triplets of nucleotides in the genome has recently been associated with nine degenerative and developmental neuropsychiatric diseases: fragile X syndrome, fragile X-linked mental retardation, myotonic dystrophy, Friedreich's ataxia, spinal and bulbar muscular atrophy, Huntington's disease, spinocerebellar ataxia type 1, dentatorubral-pallidoluysian atrophy, and Machado-Joseph disease. These diseases are all conditions of the central nervous system; in all of them, the inheritance pattern usually exhibits the phenomenon of anticipation (defined as progressively earlier age of onset or a worsening disease severity over successive generations), and the severity of the phenotypic expression and penetrance appears to be related to the extent of the triplet expansion. Identification of this pathological genetic phenomenon solves several of the mysteries that surrounded these conditions but raises many important questions regarding pathogenic mechanisms that may be shared. There is some indication that triplet expansions may also underlie other neuropsychiatric conditions such as schizophrenia or bipolar disorder.
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PMID:Triplet repeat gene sequences in neuropsychiatric diseases. 938 23

The discovery of unstable DNA sequences as the cause of genetic disease is a fascinating new area in human genetics, raising a number of important questions addressing the understanding of both the mechanisms and the effects of this new type of mutation. Trinucleotide repeat expansion mutations have been identified in a number of neurodegenerative diseases, including spinal and bulbar muscular atrophy (SBMA), fragile X syndrome (FRAXA and FRAXE), myotonic dystrophy (DM), Huntington's disease (HD), spinocerebellar ataxia types 1, 2, 3, 6, 7 (SCA1, SCA2, SCA3, SCA6, SCA7), dentatorubral-pallidoluysian atrophy (DRPLA), Friedreich's ataxia (FRDA) and autosomal dominant pure spastic paraplegia (ADPSP). They have been traced to genetic variation in the length of (CTG)n/(CAG)n, (CGG)n/(CCG)n, or (GAA)n/(TTC)n triplet repeats in DNA. In normal individuals these loci contain a short length of triplet repeats (usually 5-40), which is polymorphic within the population. Increases in the lengths of the translated triplet repeats to 40-100 are associated with disease symptoms, whereas the untranslated triplet repeats to 200-3000 are associated with the disease. We concentrated on repeat expansions in myotonic dystrophy. In this symposium, we outline the molecular aspects of myotonic dystrophy including DNA diagnosis and anticipation, and review the similarities and differences among these triplet repeat diseases.
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PMID:[Genomic instability and neurodegenerative disease]. 1006 64