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Gogia N, Ni L, Olmos V, Haidery F, Luttik K, Lim J. Exploring the Role of Posttranslational Modifications in Spinal and Bulbar Muscular Atrophy. Front Mol Neurosci 2022; 15:931301. [PMID: 35726299 PMCID: PMC9206542 DOI: 10.3389/fnmol.2022.931301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 05/19/2022] [Indexed: 11/13/2022] Open
Abstract
Spinal and Bulbar Muscular Atrophy (SBMA) is an X-linked adult-onset progressive neuromuscular disease that affects the spinal and bulbar motor neurons and skeletal muscles. SBMA is caused by expansion of polymorphic CAG trinucleotide repeats in the Androgen Receptor (AR) gene, resulting in expanded glutamine tract in the AR protein. Polyglutamine (polyQ) expansion renders the mutant AR protein toxic, resulting in the formation of mutant protein aggregates and cell death. This classifies SBMA as one of the nine known polyQ diseases. Like other polyQ disorders, the expansion of the polyQ tract in the AR protein is the main genetic cause of the disease; however, multiple other mechanisms besides the polyQ tract expansion also contribute to the SBMA disease pathophysiology. Posttranslational modifications (PTMs), including phosphorylation, acetylation, methylation, ubiquitination, and SUMOylation are a category of mechanisms by which the functionality of AR has been found to be significantly modulated and can alter the neurotoxicity of SBMA. This review summarizes the different PTMs and their effects in regulating the AR function and discusses their pathogenic or protective roles in context of SBMA. This review also includes the therapeutic approaches that target the PTMs of AR in an effort to reduce the mutant AR-mediated toxicity in SBMA.
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Affiliation(s)
- Neha Gogia
- Department of Genetics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Luhan Ni
- Department of Genetics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Victor Olmos
- Department of Genetics, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Fatema Haidery
- Yale College, Yale University, New Haven, CT, United States
| | - Kimberly Luttik
- Department of Neuroscience, Yale School of Medicine, Yale University, New Haven, CT, United States,Interdepartmental Neuroscience Program, Yale University, New Haven, CT, United States
| | - Janghoo Lim
- Department of Genetics, Yale School of Medicine, Yale University, New Haven, CT, United States,Department of Neuroscience, Yale School of Medicine, Yale University, New Haven, CT, United States,Interdepartmental Neuroscience Program, Yale University, New Haven, CT, United States,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale School of Medicine, Yale University, New Haven, CT, United States
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Donaldson J, Powell S, Rickards N, Holmans P, Jones L. What is the Pathogenic CAG Expansion Length in Huntington's Disease? J Huntingtons Dis 2021; 10:175-202. [PMID: 33579866 PMCID: PMC7990448 DOI: 10.3233/jhd-200445] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Huntington's disease (HD) (OMIM 143100) is caused by an expanded CAG repeat tract in the HTT gene. The inherited CAG length is known to expand further in somatic and germline cells in HD subjects. Age at onset of the disease is inversely correlated with the inherited CAG length, but is further modulated by a series of genetic modifiers which are most likely to act on the CAG repeat in HTT that permit it to further expand. Longer repeats are more prone to expansions, and this expansion is age dependent and tissue-specific. Given that the inherited tract expands through life and most subjects develop disease in mid-life, this implies that in cells that degenerate, the CAG length is likely to be longer than the inherited length. These findings suggest two thresholds- the inherited CAG length which permits further expansion, and the intracellular pathogenic threshold, above which cells become dysfunctional and die. This two-step mechanism has been previously proposed and modelled mathematically to give an intracellular pathogenic threshold at a tract length of 115 CAG (95% confidence intervals 70- 165 CAG). Empirically, the intracellular pathogenic threshold is difficult to determine. Clues from studies of people and models of HD, and from other diseases caused by expanded repeat tracts, place this threshold between 60- 100 CAG, most likely towards the upper part of that range. We assess this evidence and discuss how the intracellular pathogenic threshold in manifest disease might be better determined. Knowing the cellular pathogenic threshold would be informative for both understanding the mechanism in HD and deploying treatments.
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Affiliation(s)
- Jasmine Donaldson
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Sophie Powell
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Nadia Rickards
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Peter Holmans
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
| | - Lesley Jones
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cardiff, UK
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Monckton DG. The Contribution of Somatic Expansion of the CAG Repeat to Symptomatic Development in Huntington's Disease: A Historical Perspective. J Huntingtons Dis 2021; 10:7-33. [PMID: 33579863 PMCID: PMC7990401 DOI: 10.3233/jhd-200429] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The discovery in the early 1990s of the expansion of unstable simple sequence repeats as the causative mutation for a number of inherited human disorders, including Huntington's disease (HD), opened up a new era of human genetics and provided explanations for some old problems. In particular, an inverse association between the number of repeats inherited and age at onset, and unprecedented levels of germline instability, biased toward further expansion, provided an explanation for the wide symptomatic variability and anticipation observed in HD and many of these disorders. The repeats were also revealed to be somatically unstable in a process that is expansion-biased, age-dependent and tissue-specific, features that are now increasingly recognised as contributory to the age-dependence, progressive nature and tissue specificity of the symptoms of HD, and at least some related disorders. With much of the data deriving from affected individuals, and model systems, somatic expansions have been revealed to arise in a cell division-independent manner in critical target tissues via a mechanism involving key components of the DNA mismatch repair pathway. These insights have opened new approaches to thinking about how the disease could be treated by suppressing somatic expansion and revealed novel protein targets for intervention. Exciting times lie ahead in turning these insights into novel therapies for HD and related disorders.
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Affiliation(s)
- Darren G. Monckton
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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Bertolin C, Querin G, Martinelli I, Pennuto M, Pegoraro E, Sorarù G. Insights into the genetic epidemiology of spinal and bulbar muscular atrophy: prevalence estimation and multiple founder haplotypes in the Veneto Italian region. Eur J Neurol 2018; 26:519-524. [PMID: 30351503 DOI: 10.1111/ene.13850] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 10/18/2018] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE Literature data on spinal and bulbar muscular atrophy (SBMA) epidemiology are limited and restricted to specific populations. The aim of our study was to accurately collect information about SBMA patients living in the Veneto region in Italy to compute reliable epidemiological data. Androgen receptor (AR) lineages were genotyped to evaluate the presence of a founder effect. METHODS A prevalence survey considering all SBMA patients diagnosed in the Italian Veneto region on 31 January 2018 was carried out. The presence of different haplotypes obtained genotyping 15 polymorphic markers (single nucleotide polymorphisms and short tandem repeats) around the AR gene was evaluated. RESULTS Based on 68 patients, the punctual prevalence of the disease on 31 January 2018 was 2.58/100 000 (95% confidence interval 1.65-3.35) in the male population. Five different haplotypes were identified, confirming the existence of multiple founder effects. It was also observed that, within the same haplotype, patients had a similar CAG repeat number (P-value < 0.001). CONCLUSIONS A reliable estimation of SBMA prevalence in the Italian Veneto region was calculated which does not seem to be affected by a strong founder effect. Moreover, our data suggest that the length of the CAG expansion could be preserved in patients harbouring the same haplotype.
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Affiliation(s)
- C Bertolin
- Department of Neurosciences, University of Padova, Padova, Italy
| | - G Querin
- Laboratoire d'Imagerie Biomédicale, Sorbonne University, CNRS, INSERM, Paris, France
| | - I Martinelli
- Department of Neurosciences, University of Padova, Padova, Italy
| | - M Pennuto
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,Venetian Institute of Molecular Medicine, Padova, Italy.,Myology Center, University of Padova, Padova, Italy.,Padova Neuroscience Center, Padova, Italy
| | - E Pegoraro
- Department of Neurosciences, University of Padova, Padova, Italy
| | - G Sorarù
- Department of Neurosciences, University of Padova, Padova, Italy
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Murmann AE, Yu J, Opal P, Peter ME. Trinucleotide Repeat Expansion Diseases, RNAi, and Cancer. Trends Cancer 2018; 4:684-700. [PMID: 30292352 DOI: 10.1016/j.trecan.2018.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/23/2018] [Accepted: 08/24/2018] [Indexed: 01/12/2023]
Abstract
Many neurodegenerative diseases are caused by unstable trinucleotide repeat (TNR) expansions located in disease-associated genes. siRNAs based on CAG repeat expansions effectively kill cancer cell lines in vitro through RNAi. They also cause significant reduction in tumor growth in a human ovarian cancer mouse model with no toxicity to the treated mice. This suggests that cancer cells are particularly sensitive to CAG TNR-derived siRNAs, and explains a reported inverse correlation between the length of CAG TNRs and reduced global cancer incidences in some CAG TNR diseases. This review discusses both mutant proteins and mutant RNAs as a cause of TNR diseases, with a focus on RNAi and its role in contributing to disease pathology and in suppressing cancer.
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Affiliation(s)
- Andrea E Murmann
- Department of Medicine, Division Hematology/Oncology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Jindan Yu
- Department of Medicine, Division Hematology/Oncology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; Department of Biochemistry and Molecular Genetics, Northwestern University, Chicago, IL 60611, USA
| | - Puneet Opal
- Davee Department of Neurology, Northwestern University, Chicago, IL 60611, USA
| | - Marcus E Peter
- Department of Medicine, Division Hematology/Oncology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; Department of Biochemistry and Molecular Genetics, Northwestern University, Chicago, IL 60611, USA.
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Matsumoto T, Sakari M, Okada M, Yokoyama A, Takahashi S, Kouzmenko A, Kato S. The androgen receptor in health and disease. Annu Rev Physiol 2012; 75:201-24. [PMID: 23157556 DOI: 10.1146/annurev-physiol-030212-183656] [Citation(s) in RCA: 166] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Androgens play pivotal roles in the regulation of male development and physiological processes, particularly in the male reproductive system. Most biological effects of androgens are mediated by the action of nuclear androgen receptor (AR). AR acts as a master regulator of downstream androgen-dependent signaling pathway networks. This ligand-dependent transcriptional factor modulates gene expression through the recruitment of various coregulator complexes, the induction of chromatin reorganization, and epigenetic histone modifications at target genomic loci. Dysregulation of androgen/AR signaling perturbs normal reproductive development and accounts for a wide range of pathological conditions such as androgen-insensitive syndrome, prostate cancer, and spinal bulbar muscular atrophy. In this review we summarize recent advances in understanding of the epigenetic mechanisms of AR action as well as newly recognized aspects of AR-mediated androgen signaling in both men and women. In addition, we offer a perspective on the use of animal genetic model systems aimed at eventually developing novel therapeutic AR ligands.
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Affiliation(s)
- Takahiro Matsumoto
- Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima 770-8503, Japan.
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Figiel M, Szlachcic WJ, Switonski PM, Gabka A, Krzyzosiak WJ. Mouse models of polyglutamine diseases: review and data table. Part I. Mol Neurobiol 2012; 46:393-429. [PMID: 22956270 PMCID: PMC3461215 DOI: 10.1007/s12035-012-8315-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Accepted: 07/29/2012] [Indexed: 12/23/2022]
Abstract
Polyglutamine (polyQ) disorders share many similarities, such as a common mutation type in unrelated human causative genes, neurological character, and certain aspects of pathogenesis, including morphological and physiological neuronal alterations. The similarities in pathogenesis have been confirmed by findings that some experimental in vivo therapy approaches are effective in multiple models of polyQ disorders. Additionally, mouse models of polyQ diseases are often highly similar between diseases with respect to behavior and the features of the disease. The common features shared by polyQ mouse models may facilitate the investigation of polyQ disorders and may help researchers explore the mechanisms of these diseases in a broader context. To provide this context and to promote the understanding of polyQ disorders, we have collected and analyzed research data about the characterization and treatment of mouse models of polyQ diseases and organized them into two complementary Excel data tables. The data table that is presented in this review (Part I) covers the behavioral, molecular, cellular, and anatomic characteristics of polyQ mice and contains the most current knowledge about polyQ mouse models. The structure of this data table is designed in such a way that it can be filtered to allow for the immediate retrieval of the data corresponding to a single mouse model or to compare the shared and unique aspects of many polyQ models. The second data table, which is presented in another publication (Part II), covers therapeutic research in mouse models by summarizing all of the therapeutic strategies employed in the treatment of polyQ disorders, phenotypes that are used to examine the effects of the therapy, and therapeutic outcomes.
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Affiliation(s)
- Maciej Figiel
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
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Finsterer J. Perspectives of Kennedy's disease. J Neurol Sci 2010; 298:1-10. [PMID: 20846673 DOI: 10.1016/j.jns.2010.08.025] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2010] [Revised: 08/15/2010] [Accepted: 08/23/2010] [Indexed: 12/17/2022]
Abstract
Kennedy's disease, also known as bulbospinal muscular atrophy (BSMA), is a rare, adult-onset, X-linked, recessive trinucleotide, polyglutamine (poly-G) disorder, caused by expansion of an unstable CAG-tandem-repeat in exon 1 of the androgen-receptor (AR) gene on chromosome Xq11-12. Poly-Q-expanded AR accumulates in nuclei, undergoes fragmentation and initiates degeneration and loss of motor neurons and dorsal root ganglia. Phenotypically, patients present with weakness and wasting of the facial, bulbar and extremity muscles, sensory disturbances, and endocrinological disturbances, such as gynecomastia and reduced fertility. In the limb muscles weakness and wasting may be symmetric or asymmetric, proximal or distal, or may predominate at the lower or upper limb muscles. There may be mild to severe hyper-CK-emia, elevated testosterone or other sexual hormones, abnormal motor and sensory nerve conduction studies, and neuropathic or rarely myopathic alterations on muscle biopsy. BSMA is diagnosed if the number of CAG-repeats exceeds 40. No causal therapy is available but symptomatic therapy may be beneficial for weakness, tremor, endocrinological abnormalities, muscle cramps, respiratory failure, or dysphagia. The course is slowly progressive and the ability to walk lost only late in life. Only few patients require ventilatory support and life expectancy is only slightly compromised.
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Affiliation(s)
- J Finsterer
- Krankenanstalt Rudolfstiftung, Vienna, Austria.
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Johansen JA, Troxell-Smith SM, Yu Z, Mo K, Monks DA, Lieberman AP, Breedlove SM, Jordan CL. Prenatal flutamide enhances survival in a myogenic mouse model of spinal bulbar muscular atrophy. NEURODEGENER DIS 2010; 8:25-34. [PMID: 20689246 DOI: 10.1159/000313682] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 04/14/2010] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Spinal bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion mutation in the androgen receptor (AR) gene, and mutant AR is presumed to act in motoneurons to cause SBMA. However, we found that mice overexpressing wild-type (wt) AR solely in skeletal muscle fibers display the same androgen-dependent disease phenotype as when mutant AR is broadly expressed, challenging the assumptions that only an expanded AR can induce disease and that SBMA is strictly neurogenic. We have previously reported that AR toxicity was ligand dependent in our model, and that very few transgenic (tg) males survived beyond birth. METHODS We tested whether the AR antagonist flutamide could block perinatal toxicity. tg males were treated prenatally with flutamide and assessed for survival and motor behavior in adulthood. RESULTS Prenatal treatment with flutamide rescued tg male pups from perinatal death, and, as adults, such perinatally rescued tg males showed an SBMA phenotype that was comparable to that of previously described untreated tg males. Moreover, tg males carrying a mutant endogenous allele for AR--the testicular feminization mutation (tfm)--and thus having functional AR only in muscle fibers nevertheless displayed the same androgen-dependent disease phenotype as adults. CONCLUSIONS These mice represent an excellent model to study the myogenic contribution to SBMA as they display many of the core features of disease as other mouse models. These data demonstrate that AR acting exclusively in muscle fibers is sufficient to induce SBMA symptoms and that flutamide is protective perinatally.
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Affiliation(s)
- Jamie A Johansen
- Neuroscience Program, Michigan State University, East Lansing, MI 48109, USA.
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Johansen JA, Yu Z, Mo K, Monks DA, Lieberman AP, Breedlove SM, Jordan CL. Recovery of function in a myogenic mouse model of spinal bulbar muscular atrophy. Neurobiol Dis 2008; 34:113-20. [PMID: 19211034 DOI: 10.1016/j.nbd.2008.12.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 12/20/2008] [Indexed: 11/16/2022] Open
Abstract
With this paper, we deliberately challenge the prevailing neurocentric theory of the etiology of spinal bulbar muscular atrophy (SBMA). We offer data supporting an alternative view that androgen receptor (AR) acts in skeletal muscles to cause the symptoms of SBMA. While SBMA has been linked to a CAG repeat expansion in the AR gene and mutant AR is presumed to act in motoneurons to cause SBMA, we find that over-expression of wild type AR solely in skeletal muscle fibers results in the same androgen-dependent disease phenotype as when mutant AR is broadly expressed. Like other recent SBMA mouse models, transgenic (tg) females in our model exhibit a motor phenotype only when exposed to androgens, and this motor dysfunction is independent of motoneuronal or muscle fiber cell death. Muscles from symptomatic females also show denervation-like changes in gene expression comparable to a knock-in model of SBMA. Furthermore, once androgen treatment ends, tg females rapidly recover motor function and muscle gene expression, demonstrating the strict androgen-dependence of the disease phenotype in our model. Our results argue that SBMA may be caused by AR acting in muscle.
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Affiliation(s)
- Jamie A Johansen
- Neuroscience Program, Michigan State University, East Lansing, MI, USA.
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12
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Marsh JL, Lukacsovich T, Thompson LM. Animal models of polyglutamine diseases and therapeutic approaches. J Biol Chem 2008; 284:7431-5. [PMID: 18957429 DOI: 10.1074/jbc.r800065200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The dominant gain-of-function polyglutamine repeat diseases, in which the initiating mutation is known, allow development of models that recapitulate many aspects of human disease. To the extent that pathology is a consequence of disrupted fundamental cellular activities, one can effectively study strategies to ameliorate or protect against these cellular insults. Model organisms allow one to identify pathways that affect disease onset and progression, to test and screen for pharmacological agents that affect pathogenic processes, and to validate potential targets genetically as well as pharmacologically. Here, we describe polyglutamine repeat diseases that have been modeled in a variety of organisms, including worms, flies, mice, and non-human primates, and discuss examples of how they have broadened the therapeutic landscape.
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Affiliation(s)
- J Lawrence Marsh
- Developmental Biology Center and the Department of Developmental and Cell Biology, University of California, Irvine, California 92697, USA.
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Monks DA, Rao P, Mo K, Johansen JA, Lewis G, Kemp MQ. Androgen receptor and Kennedy disease/spinal bulbar muscular atrophy. Horm Behav 2008; 53:729-40. [PMID: 18321505 PMCID: PMC2883265 DOI: 10.1016/j.yhbeh.2007.12.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 12/13/2007] [Accepted: 12/13/2007] [Indexed: 02/06/2023]
Abstract
Kennedy Disease/Spinal Bulbar Muscular Atrophy (KD/SBMA) is a progressive neurodegenerative disease caused by genetic polyglutamine expansion of the androgen receptor. We have recently found that overexpression of wildtype androgen receptor in skeletal muscle of transgenic mice results in a KD/SBMA phenotype. This surprising result challenges the orthodox view that KD/SBMA requires expression of polyglutamine expanded androgen receptor within motoneurons. Theories relating to the etiology of this disease drawn from studies of human patients, cellular and mouse models are considered with a special emphasis on potential myogenic contributions to as well as the molecular etiology of KD/SBMA.
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Affiliation(s)
- Douglas Ashley Monks
- Department of Psychology, University of Toronto at Mississauga, 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.
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Abstract
Unstable repeats are associated with various types of cancer and have been implicated in more than 40 neurodegenerative disorders. Trinucleotide repeats are located in non-coding and coding regions of the genome. Studies of bacteria, yeast, mice and man have helped to unravel some features of the mechanism of trinucleotide expansion. Looped DNA structures comprising trinucleotide repeats are processed during replication and/or repair to generate deletions or expansions. Most in vivo data are consistent with a model in which expansion and deletion occur by different mechanisms. In mammals, microsatellite instability is complex and appears to be influenced by genetic, epigenetic and developmental factors.
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Abstract
Androgen, acting via the androgen receptor (AR), is central to male development, differentiation and hormone-dependent diseases such as prostate cancer. AR is actively involved in the initiation of prostate cancer, the transition to androgen independence, and many mechanisms of resistance to therapy. To examine genetic variation of AR in cancer, we created mice by germ-line gene targeting in which human AR sequence replaces that of the mouse. Since shorter length of a polymorphic N-terminal glutamine (Q) tract has been linked to prostate cancer risk, we introduced alleles with 12, 21 or 48 Qs to test this association. The three "humanized" AR mouse strains (h/mAR) are normal physiologically, as well as by cellular and molecular criteria, although slight differences are detected in AR target gene expression, correlating inversely with Q tract length. However, distinct allele-dependent differences in tumorigenesis are evident when these mice are crossed to a transgenic prostate cancer model. Remarkably, Q tract variation also differentially impacts disease progression following androgen depletion. This finding emphasizes the importance of AR function in androgen-independent as well as androgen-dependent disease. These mice provide a novel genetic paradigm in which to dissect opposing functions of AR in tumor suppression versus oncogenesis.
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Affiliation(s)
- Diane M Robins
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109-0618, USA.
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16
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Abstract
Trinucleotide repeat expansions are an important cause of inherited neurodegenerative disease. The expanded repeats are unstable, changing in size when transmitted from parents to offspring (intergenerational instability, "meiotic instability") and often showing size variation within the tissues of an affected individual (somatic mosaicism, "mitotic instability"). Repeat instability is a clinically important phenomenon, as increasing repeat lengths correlate with an earlier age of onset and a more severe disease phenotype. The tendency of expanded trinucleotide repeats to increase in length during their transmission from parent to offspring in these diseases provides a molecular explanation for anticipation (increasing disease severity in successive affected generations). In this review, I explore the genetic and molecular basis of trinucleotide repeat instability. Studies of patients and families with trinucleotide repeat disorders have revealed a number of factors that determine the rate and magnitude of trinucleotide repeat change. Analysis of trinucleotide repeat instability in bacteria, yeast, and mice has yielded additional insights. Despite these advances, the pathways and mechanisms underlying trinucleotide repeat instability in humans remain largely unknown. There are many reasons to suspect that this uniquely human phenomenon will significantly impact upon our understanding of development, differentiation and neurobiology.
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Affiliation(s)
- A R La Spada
- Department of Laboratory Medicine and Pharmacology, University of Washington Medical Center, Seattle 98195, USA.
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17
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Abstract
Expansions of CAG trinucleotide repeats encoding glutamine have been found to be the causative mutations of seven human neurodegenerative diseases. Similarities in the clinical, genetic, and molecular features of these disorders suggest they share a common mechanism of pathogenesis. Recent progress in the generation and characterization of transgenic mice expressing the genes containing expanded repeats associated with spinal and bulbar muscular atrophy (SBMA), spinocerebellar ataxia type 1 (SCA1), Machado-Joseph disease (MJD/SCA3), and Huntington's disease (HD) is beginning to provide insight into the underlying mechanisms of these neurodegenerative disorders.
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Affiliation(s)
- E N Burright
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis 55455, USA.
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18
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Sutherland GR, Richards RI. Unusual inheritance patterns due to dynamic mutation in fragile X syndrome. CIBA FOUNDATION SYMPOSIUM 2007; 197:119-26; discussion 126-36. [PMID: 8827371 DOI: 10.1002/9780470514887.ch7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Fragile X syndrome is the most common form of familial mental retardation and is one of the world's most common genetic diseases. The inheritance patterns of the disease have many unusual features. It is an X-linked disorder yet there are asymptomatic carrier males. The disease is expressed only when the gene is inherited from the mother. The risk of a carrier woman having a child with the syndrome depends upon her position in the pedigree (the Sherman paradox) and her own intellectual status. The discovery that the disease is due to dynamic mutation (which is a multistage process) that inactivates FMR1 has provided an explanation for the unusual inheritance patterns. The finding of linkage disequilibrium between the fragile X mutations and closely linked DNA markers (haplotype) has required a reinterpretation of this phenomenon for dynamic mutations. Only a small number of normal alleles at the fragile X locus have long stretches of perfect repeat (2% with more than 24 copies) and these form a reservoir of alleles that can increase in length into the premutation range. Dynamic mutation is, so far, an exclusively human phenomenon, but this is probably because it has yet to be discovered in other species. Unusual inheritance patterns are a hallmark of dynamic mutation diseases.
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Affiliation(s)
- G R Sutherland
- Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, North Adelaide, Australia
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Gallo JM, Leigh PN. Chapter 8 Spinobulbar muscular atrophy (Kennedy's disease). HANDBOOK OF CLINICAL NEUROLOGY 2007; 82:155-69. [PMID: 18808893 DOI: 10.1016/s0072-9752(07)80011-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Clark RM, De Biase I, Malykhina AP, Al-Mahdawi S, Pook M, Bidichandani SI. The GAA triplet-repeat is unstable in the context of the human FXN locus and displays age-dependent expansions in cerebellum and DRG in a transgenic mouse model. Hum Genet 2007; 120:633-40. [PMID: 17024371 DOI: 10.1007/s00439-006-0249-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 08/26/2006] [Indexed: 01/28/2023]
Abstract
Friedreich ataxia (FRDA) is caused by homozygosity for FXN alleles containing an expanded GAA triplet-repeat (GAA-TR) sequence. Patients have progressive neurodegeneration of the dorsal root ganglia (DRG) and in later stages the cerebellum may be involved. The expanded GAA-TR sequence is unstable in somatic cells in vivo, and although the mechanism of instability remains unknown, we hypothesized that age-dependent and tissue-specific somatic instability may be a determinant of the progressive pathology involving DRG and cerebellum. We show that transgenic mice containing the expanded GAA-TR sequence (190 or 82 triplets) in the context of the human FXN locus show tissue-specific and age-dependent somatic instability that is compatible with this hypothesis. Small pool PCR analysis, which allows quantitative analysis of repeat instability by assaying individual transgenes in vivo, showed age-dependent expansions specifically in the cerebellum and DRG. The (GAA)(190) allele showed some instability by 2 months, progressed at about 0.3-0.4 triplets per week, resulting in a significant number of expansions by 12 months. Repeat length was found to determine the age of onset of somatic instability, and the rate and magnitude of mutation. Given the low level of cerebellar instability seen by others in multiple transgenic mice with expanded CAG/CTG repeats, our data indicate that somatic instability of the GAA-TR sequence is likely mediated by unique tissue-specific factors. This mouse model will serve as a useful tool to delineate the mechanism(s) of disease-specific somatic instability in FRDA.
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Affiliation(s)
- Rhonda M Clark
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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21
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Albertelli MA, Scheller A, Brogley M, Robins DM. Replacing the mouse androgen receptor with human alleles demonstrates glutamine tract length-dependent effects on physiology and tumorigenesis in mice. Mol Endocrinol 2006; 20:1248-60. [PMID: 16601069 DOI: 10.1210/me.2006-0021] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Polymorphism in the length of the N-terminal glutamine (Q) tract in the human androgen receptor (AR) has been implicated in affecting aspects of male health ranging from fertility to cancer. Extreme expansion of the tract underlies Kennedy disease, and in vitro the AR Q tract length correlates inversely with transactivation capacity. However, whether normal variation influences physiology or the etiology of disease has been controversial. To assess directly the functional significance of Q tract variation, we converted the mouse AR to the human sequence by germline gene targeting, introducing alleles with 12, 21, or 48 glutamines. These three "humanized" AR (h/mAR) mouse lines were grossly normal in growth, behavior, fertility, and reproductive tract morphology. Phenotypic analysis revealed traits that varied subtly with Q tract length, including body fat amount and, more notably, seminal vesicle weight. Upon molecular analysis, tissue-specific differences in AR levels and target gene expression were detected between mouse lines. In the prostate, probasin, Nkx3.1, and clusterin mRNAs trended in directions predicted for inverse correlation of Q tract length with AR activation. Remarkably, when crossed with transgenic adenocarcinoma of mouse prostate (TRAMP) mice, striking genotype-dependent differences in prostate cancer initiation and progression were revealed. This link between Q tract length and prostate cancer, likely due to differential activation of AR targets, corroborates human epidemiological studies. This h/mAR allelic series in a homogeneous mouse genetic background allows examination of numerous physiological traits for Q tract influences and provides an animal model to test novel drugs targeted specifically to human AR.
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Affiliation(s)
- Megan A Albertelli
- Department of Human Genetics, 4909 Buhl Bldg, University of Michigan Medical School, Ann Arbor, Michigan 48109-0618, USA
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22
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Chatzikyriakidou A, Yapijakis C, Sofikitis N, Vassilopoulos D, Georgiou I. Real-time PCR analysis of trinucleotide repeat allele expansions in the androgen receptor gene. ACTA ACUST UNITED AC 2006; 9:217-9. [PMID: 16392902 DOI: 10.1007/bf03260095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
INTRODUCTION The expansion of specific trinucleotide repeats results in certain genetic disorders. METHOD Real-time PCR analysis was used to rapidly discriminate between normal and expanded (CAG)(n) alleles in the androgen receptor gene. RESULT The difference in melting temperature (T(m)) between the most common normal and expanded alleles was approximately 1 degrees C. CONCLUSION Real-time PCR analysis seems to be a highly reliable and rapid method, which may facilitate the first molecular approach to human trinucleotide repeat disorders.
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Affiliation(s)
- Anthoula Chatzikyriakidou
- Genetics Unit, Department of Obstetrics and Gynaecology, Ioannina University School of Medicine, Ioannina, Greece
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23
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Abstract
Since the identification of the polyglutamine repeat expansion responsible for Kennedy disease (KD) more than a decade ago, several laboratories have created animal models for KD. The slowly progressive nature of KD, its X-linked dominant mode of inheritance, and its recently elucidated hormone dependence have made the modeling of this lower motor neuron disease uniquely challenging. Several models have been generated in which variations in specificity, age of onset, and rate of progression have been achieved. Animal models that precisely reproduce the motor neuron specificity, delayed onset, and slow progression of disease may not support preclinical therapeutics testing, whereas models with rapidly progressing symptoms may preclude the ability to fully elucidate pathogenic pathways. Drosophila models of KD provide unique opportunities to use the power of genetics to identify pathogenic pathways at work in KD. This paper reviews the new wealth of transgenic mouse and Drosophila models for KD. Whereas differences, primarily in neuropathological findings, exist in these models, these differences may be exploited to begin to elucidate the most relevant pathological features of KD.
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Affiliation(s)
- Diane E Merry
- Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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24
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McLeod CJ, O'Keefe LV, Richards RI. The pathogenic agent in Drosophila models of 'polyglutamine' diseases. Hum Mol Genet 2005; 14:1041-8. [PMID: 15757976 DOI: 10.1093/hmg/ddi096] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A substantial body of evidence supports the identity of polyglutamine as the pathogenic agent in a variety of human neurodegenerative disorders where the mutation is an expanded CAG repeat. However, in apparent contradiction to this, there are several human neurodegenerative diseases (some of which are clinically indistinguishable from the 'polyglutamine' diseases) that are due to expanded repeats that cannot encode polyglutamine. As polyglutamine cannot be the pathogenic agent in these diseases, either the different disorders have distinct pathogenic pathways or some other common agent is toxic in all of the expanded repeat diseases. Recently, evidence has been presented in support of RNA as the pathogenic agent in Fragile X-associated tremor/ataxia syndrome (FXTAS), caused by expanded CGG repeats at the FRAXA locus. A Drosophila model of FXTAS, in which 90 copies of the CGG repeat are expressed in an untranslated region of RNA, exhibits both neurodegeneration and similar molecular pathology to the 'polyglutamine' diseases. We have, therefore, explored the identity of the pathogenic agent, and specifically the role of RNA, in a Drosophila model of the polyglutamine diseases by the expression of various repeat constructs. These include expanded CAA and CAG repeats and an untranslated CAG repeat. Our data support the identity of polyglutamine as the pathogenic agent in the Drosophila models of expanded CAG repeat neurodegenerative diseases.
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Affiliation(s)
- Catherine J McLeod
- ARC Special Research Centre for the Molecular Genetics of Development, School of Molecular and Biomedical Sciences, The University of Adelaide, Adelaide 5005, South Australia
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25
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Katsuno M, Adachi H, Inukai A, Sobue G. Transgenic mouse models of spinal and bulbar muscular atrophy (SBMA). Cytogenet Genome Res 2004; 100:243-51. [PMID: 14526186 DOI: 10.1159/000072860] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2002] [Accepted: 01/30/2003] [Indexed: 11/19/2022] Open
Abstract
Spinal and bulbar muscular atrophy (SBMA) is a late-onset motor neuron disease characterized by proximal muscle atrophy, weakness, contraction fasciculations, and bulbar involvement. Only males develop symptoms, while female carriers usually are asymptomatic. A specific treatment for SBMA has not been established. The molecular basis of SBMA is the expansion of a trinucleotide CAG repeat, which encodes the polyglutamine (polyQ) tract, in the first exon of the androgen receptor (AR) gene. The pathologic hallmark is nuclear inclusions (NIs) containing the mutant and truncated AR with expanded polyQ in the residual motor neurons in the brainstem and spinal cord as well as in some other visceral organs. Several transgenic (Tg) mouse models have been created for studying the pathogenesis of SBMA. The Tg mouse model carrying pure 239 CAGs under human AR promoter and another model carrying truncated AR with expanded CAGs show motor impairment and nuclear NIs in spinal motor neurons. Interestingly, Tg mice carrying full-length human AR with expanded polyQ demonstrate progressive motor impairment and neurogenic pathology as well as sexual difference of phenotypes. These models recapitulate the phenotypic expression observed in SBMA. The ligand-dependent nuclear localization of the mutant AR is found to be involved in the disease mechanism, and hormonal therapy is suggested to be a therapeutic approach applicable to SBMA.
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Affiliation(s)
- M Katsuno
- Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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26
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Wansink DG, Wieringa B. Transgenic mouse models for myotonic dystrophy type 1 (DM1). Cytogenet Genome Res 2004; 100:230-42. [PMID: 14526185 DOI: 10.1159/000072859] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2002] [Accepted: 12/18/2002] [Indexed: 11/19/2022] Open
Abstract
The study of animal models for myotonic dystrophy type 1 (DM1) has helped us to 'de- and reconstruct' our ideas on how the highly variable multisystemic constellation of disease features can be caused by only one type of event, i.e., the expansion of a perfect (CTG)(n) repeat in the DM1 locus on 19q. Evidence is now accumulating that cell type, cell state and species dependent activities of the DNA replication/repair/recombination machinery contribute to the intergenerational and somatic behavior of the (CTG)(n) repeat at the DNA level. At the RNA level, a gain-of-function mechanism, with dominant toxic effects of (CUG)(n) repeat containing transcripts, probably has a central role in DM1 pathology. Parallel study of DM2, a closely related form of myotonic dystrophy, has revealed a similar mechanism, but also made clear that part of the attention should remain focused on a possible role for candidate loss-of-function genes from the DM1 locus itself (like DMWD, DMPK and SIX5) or elsewhere in the genome, to find explanations for clinical aspects that are unique to DM1. This review will focus on new insight regarding structure-function features of candidate genes involved in DM1 pathobiology, and on the mechanisms of expansion and disease pathology that have now partly been disclosed with the help of transgenic animal models.
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Affiliation(s)
- D G Wansink
- Department of Cell Biology, NCMLS, University Medical Center, Nijmegen, The Netherlands
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27
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Spinobulbar muscular atrophy (Kennedy's disease). ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s1567-4231(04)04023-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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28
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Abstract
Toxicity associated with abnormal protein folding and protein aggregation are major hypotheses for neurodegeneration. This article comparatively reviews the experimental and human tissue-based evidence for the involvement of such mechanisms in neuronal death associated with the motor system disorders of X-linked spinobulbar muscular atrophy (SBMA; Kennedy's disease) and amyotrophic lateral sclerosis (ALS), especially disease related to mutations in the superoxide dismutase (SOD1) gene. Evidence from transgenic mouse, Drosophila and cell culture models of SBMA, in common with other trinucleotide repeat expansion disorders, show protein aggregation of the mutated androgen receptor, and intraneuronal accumulation of aggregated protein, to be obligate mechanisms. Strong experimental data link these phenomena with downstream biochemical events involving gene transcription pathways (CREB-binding protein) and interactions with protein chaperone systems. Manipulations of these pathways are already established in experimental systems of trinucleotide repeat disorders as potential beneficial targets for therapeutic activity. In contrast, the evidence for the role of protein aggregation in models of SOD1-linked familial ALS is less clear-cut. Several classes of intraneuronal inclusion body have been described, some of which are invariably present. However, the lack of understanding of the biochemical basis of the most frequent inclusion in sporadic ALS, the ubiquitinated inclusion, has hampered research. The toxicity associated with expression of mutant SOD1 has been intensively studied however. Abnormal protein aggregation and folding is the only one of the four major hypotheses for the mechanism of neuronal degeneration in this disorder currently under investigation (the others comprise oxidative stress, axonal transport and cytoskeletal dysfunctions, and glutamatergic excitotoxicity). Whilst hyaline inclusions, which are strongly immunoreactive to SOD1, are linked to degeneration in SOD1 mutant mouse models, the evidence from human tissue is less consistent and convincing. A role for mutant SOD1 aggregation in the mitochondrial dysfunction associated with ALS, and in potentially toxic interactions with heat shock proteins, both leading to apoptosis, are supported by some experimental data. Direct in vitro data on mutant SOD1 show evidence for spontaneous oligomerization, but the role of such oligomers remains to be elucidated, and therapeutic strategies are less well developed for this familial variant of ALS.
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Affiliation(s)
- J D Wood
- Academic Neurology Unit, Division of Genomic Medicine, University of Sheffield Medical School, Sheffield, UK.
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29
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Timchenko LT, Tapscott SJ, Cooper TA, Monckton DG. Myotonic dystrophy: discussion of molecular basis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 516:27-45. [PMID: 12611434 DOI: 10.1007/978-1-4615-0117-6_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Lubov T Timchenko
- Section of Cardiovascular Sciences, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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30
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Watase K, Zoghbi HY. Modelling brain diseases in mice: the challenges of design and analysis. Nat Rev Genet 2003; 4:296-307. [PMID: 12671660 DOI: 10.1038/nrg1045] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genetically engineered mice have been generated to model a variety of neurological disorders. Several of these models have provided valuable insights into the pathogenesis of the relevant diseases; however, they have rarely reproduced all, or even most, of the features observed in the corresponding human conditions. Here, we review the challenges that must be faced when attempting to accurately reproduce human brain disorders in mice, and discuss some of the ways to overcome them. Building on the knowledge gathered from the study of existing mutants, and on recent progress in phenotyping mutant mice, we anticipate better methods for preclinical interventional trials and significant advances in the understanding and treatment of neurological diseases.
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Affiliation(s)
- Kei Watase
- Department of Molecular and Human Genetics and Howard Hughes Medical Institute, Baylor College of Medicine, 1 Baylor Plaza, Houston, Texas 77030, USA
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31
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Walcott JL, Merry DE. Trinucleotide repeat disease. The androgen receptor in spinal and bulbar muscular atrophy. VITAMINS AND HORMONES 2003; 65:127-47. [PMID: 12481545 DOI: 10.1016/s0083-6729(02)65062-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
It has been more than 10 years since the discovery that the expansion of a simple CAG trinucleotide repeat within the coding region of the androgen receptor gene leads to the motor neuronopathy spinal and bulbar muscular atrophy (SBMA). A flurry of investigation into this and the other, more recently discovered, polyglutamine diseases has led to an understanding of many aspects of the molecular pathogenesis of this family of diseases. A characteristics pathological feature of the polyglutamine diseases is the occurrence in affected neurons of ubiquitinated aggregates; such aggregates also contain, among others, proteins involved in the folding and degradation of the mutant proteins. Aggregates themselves are likely not directly cytotoxic, but rather mark the accumulation of all or part of the mutant protein. Furthermore, aggregation occurs because of the inefficient clearance of the mutant protein by the ubiquitin-proteasome pathway for protein degradation. These findings are common to the polyglutamine diseases and reflect the general problem of folding/degrading expanded polyglutamines. In SBMA, the altered metabolism of the androgen receptor is ligand dependent. How the accumulation of the mutant protein causes neuronal dysfunction and disease is not well understood, but several cellular processes have been implicated. Although these findings provide insight into the toxic function of the expanded polyglutamine protein, additional investigations have led to the finding that intrinsic AR transactivational function is somewhat diminished in the presence of the expanded polyglutamine; this likely leads to the partial androgen insensitivity that characterizes patients with SBMA. The recent development of useful animal and cell models of SBMA will lead to increased understanding of disease pathogenesis, as well as to the development of new and better therapeutic strategies.
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Affiliation(s)
- Jessica L Walcott
- Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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32
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Abstract
Fragile X syndrome results from the massive expansion of a CGG repeat in the 5' untranslated region of the gene FMR1. Data suggest that the hyperexpansion properties of FMR1 CGG repeats may depend on flanking cis-acting elements. We have therefore used homologous recombination in yeast to introduce an in situ CGG expansion corresponding to a premutation-sized allele into a human YAC carrying the FMR1 locus. Several transgenic lines were generated that carried repeats of varying lengths and amounts of flanking sequence. Length-dependent instability in the form of small expansions and contractions was observed in both male and female transmissions over five generations. No parent-of-origin effect or somatic instability was observed. Alterations in tract length were found to occur exclusively in the 3' uninterrupted CGG tract. Large expansion events indicative of a transition from a premutation to a full mutation were not observed. Overall, our results indicate both similarities and differences between the behavior of a premutation-sized repeat in mouse and that in human.
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Affiliation(s)
- Andrea M Peier
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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33
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Katsuno M, Adachi H, Kume A, Li M, Nakagomi Y, Niwa H, Sang C, Kobayashi Y, Doyu M, Sobue G. Testosterone reduction prevents phenotypic expression in a transgenic mouse model of spinal and bulbar muscular atrophy. Neuron 2002; 35:843-54. [PMID: 12372280 DOI: 10.1016/s0896-6273(02)00834-6] [Citation(s) in RCA: 338] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Spinal and bulbar muscular atrophy (SBMA) is a polyglutamine disease caused by the expansion of a CAG repeat in the androgen receptor (AR) gene. We generated a transgenic mouse model carrying a full-length AR containing 97 CAGs. Three of the five lines showed progressive muscular atrophy and weakness as well as diffuse nuclear staining and nuclear inclusions consisting of the mutant AR. These phenotypes were markedly pronounced in male transgenic mice, and dramatically rescued by castration. Female transgenic mice showed only a few manifestations that markedly deteriorated with testosterone administration. Nuclear translocation of the mutant AR by testosterone contributed to the phenotypic difference with gender and the effects of hormonal interventions. These results suggest the therapeutic potential of hormonal intervention for SBMA.
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Affiliation(s)
- Masahisa Katsuno
- Department of Neurology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Japan
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34
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Abstract
Studies of the molecular pathogenesis of spinal and bulbar muscular atrophy, as well as of the other polyglutamine repeat diseases, has led to an understanding of the role of protein accumulation in disease pathogenesis. Aggregation of the expanded repeat androgen receptor (AR), rather than playing a pathogenic role, likely reflects the insoluble nature of the misfolded AR. Proteolytic processing of the expanded AR at various stages of its metabolism may contribute to cellular toxicity through the enhancement of AR insolubility, and potentially through the disruption of normal proteolytic degradation processes. The finding that molecular chaperones not only promote solubility, but also enhance the degradation of expanded polyglutamines as well, make them promising targets for therapeutic development. Understanding the role of ligand binding in expanded AR metabolism may provide additional avenues of therapeutic manipulation as well.
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Affiliation(s)
- D E Merry
- Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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35
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Bowater RP, Wells RD. The intrinsically unstable life of DNA triplet repeats associated with human hereditary disorders. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2001; 66:159-202. [PMID: 11051764 DOI: 10.1016/s0079-6603(00)66029-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Expansions of specific DNA triplet repeats are the cause of an increasing number of hereditary neurological disorders in humans. In some diseases, such as Huntington's and several spinocerebellar ataxias, the repetitive DNA sequences are translated into long tracts of the same amino acid (usually glutamine), which alters interactions with cellular constituents and leads to the development of disease. For other disorders, including common genetic disorders such as myotonic dystrophy and fragile X syndrome, the DNA repeat is located in noncoding regions of transcribed sequences and disease is probably caused by altered gene expression. In studies in lower organisms, mammalian cells, and transgenic mice, high frequencies of length changes (increases and decreases) occur in long DNA triplet repeats. These observations are similar to other types of repetitive DNA sequences, which also undergo frequent length changes at genomic loci. A variety of processes acting on DNA influence the genetic stability of DNA triplet repeats, including replication, recombination, repair, and transcription. It is not yet known how these different multienzyme systems interact to produce the genetic mutation of expanded repeats. In vitro studies have identified that DNA triplet repeats can adopt several unusual DNA structures, including hairpins, triplexes, quadruplexes, slipped structures, and highly flexible and writhed helices. The formation of stable unusual structures within the cell is likely to disturb DNA metabolism and be a critical intermediate in the molecular mechanism(s) leading to genetic instabilities of DNA repeats and, hence, to disease pathogenesis.
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Affiliation(s)
- R P Bowater
- Molecular Biology Sector, School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
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36
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Jakupciak JP, Wells RD. Gene conversion (recombination) mediates expansions of CTG[middle dot]CAG repeats. J Biol Chem 2000; 275:40003-13. [PMID: 11005819 DOI: 10.1074/jbc.m007153200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Genetic recombination is a robust mechanism for expanding CTG.CAG triplet repeats involved in the etiology of hereditary neurological diseases (Jakupciak, J. P., and Wells, R. D. (1999) J. Biol. Chem. 274, 23468-23479). This two-plasmid recombination system in Escherichia coli with derivatives of pUC19 and pACYC184 was used to investigate the effect of triplet repeat orientation on recombination and extent of expansions; tracts of 36, 50, 80, and 36, 100, and 175 repeats in length, respectively, in all possible permutations of length and in both orientations (relative to the unidirectional replication origins) revealed little or no effect of orientation of expansions. The extent of expansions was generally severalfold the length of the progenitor tract and frequently exceeded the combined length of the two tracts in the cotransformed plasmids. Expansions were much more frequent than deletions. Repeat tracts bearing two G-to-A interruptions (polymorphisms) within either 171- or 219-base pair tracts substantially reduced the expansions compared with uninterrupted repeat tracts of similar lengths. Gene conversion, rather than crossing over, was the recombination mechanism. Prior studies showed that DNA replication, repair, and tandem duplication also mediated genetic instabilities of the triplet repeat sequence. However, gene conversion (recombinational repair) is by far the most powerful expansion mechanism. Thus, we propose that gene conversion is the likely expansion mechanism for myotonic dystrophy, spinocerebellar ataxia type 8, and fragile X syndrome.
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Affiliation(s)
- J P Jakupciak
- Institute of Biosciences and Technology, Center for Genome Research, Texas A & M University, Texas Medical Center, Houston, Texas 77030, USA
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37
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Gusella JF, MacDonald ME. Molecular genetics: unmasking polyglutamine triggers in neurodegenerative disease. Nat Rev Neurosci 2000; 1:109-15. [PMID: 11252773 DOI: 10.1038/35039051] [Citation(s) in RCA: 275] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Two decades ago, molecular genetic analysis provided a new approach for defining the roots of inherited disorders. This strategy has proved particularly powerful because, with only a description of the inheritance pattern, it can uncover previously unsuspected mechanisms of pathogenesis that are not implicated by known biological pathways or by the disease manifestations. Nowhere has the impact of molecular genetics been more evident than in the dominantly inherited neurodegenerative disorders, where eight unrelated diseases have been revealed to possess the same type of mutation--an expanded polyglutamine encoding sequence--affecting different genes.
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Affiliation(s)
- J F Gusella
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
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38
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Laccone F, Maiwald R, Bingemann S. A fast polymerase chain reaction-mediated strategy for introducing repeat expansions into CAG-repeat containing genes. Hum Mutat 2000; 13:497-502. [PMID: 10408780 DOI: 10.1002/(sici)1098-1004(1999)13:6<497::aid-humu10>3.0.co;2-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We describe a simple method for expanding CAG trinucleotides in CAG-repeat containing genes which, in contrast to other techniques, leaves the original gene sequence intact. Here, we expanded the CAG stretches of a plasmid clone containing the cDNA of the SCA3/MJD gene from 22 CAG up to > 130 CAG repeats using polymerase chain reaction (PCR)-mediated mutagenesis. The method reported in this article requires minimal resources, is very fast, and enables to construct recombinant plasmids carrying large CAG expansions.
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Affiliation(s)
- F Laccone
- Institute of Human Genetics, Faculty of Medicine, University of Göttingen, Germany.
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39
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Becker M, Martin E, Schneikert J, Krug HF, Cato AC. Cytoplasmic localization and the choice of ligand determine aggregate formation by androgen receptor with amplified polyglutamine stretch. J Cell Biol 2000; 149:255-62. [PMID: 10769019 PMCID: PMC2175165 DOI: 10.1083/jcb.149.2.255] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Polyglutamine tract expansion in androgen receptor is a recognized cause of spinal and bulbar muscular atrophy (SBMA), an X-linked motor neuronopathy. Similar mutations have been identified in proteins associated with other neurodegenerative diseases. Recent studies have shown that amplified polyglutamine repeat stretches form cellular aggregates that may be markers for these neurodegenerative diseases. Here we describe conditions that lead to aggregate formation by androgen receptor with polyglutamine stretch amplification. In transfection experiments, the mutant, compared with the wild-type receptor, was delayed in its cytoplasmic-nuclear translocation and formed large cytoplasmic aggregates in the presence of androgen. The cytoplasmic environment appears crucial for this aggregation, since retention of both the wild-type and mutant receptors in this cellular compartment by the deletion of their nuclear localization signals resulted in massive aggregation. Conversely, rapid nuclear transport of both receptors brought about by deletion of their ligand binding domains did not result in aggregate formation. However, androgen antagonists that altered the conformation of the ligand binding domain and promoted varying rates of cytoplasmic-nuclear translocation all inhibited aggregate formation. This demonstrates that in addition to the cytoplasmic localization, a distinct contribution of the ligand binding domain of the receptor is necessary for the aggregation. The finding that antiandrogens inhibit aggregate formation may provide the basis for in vivo determination of the role of these structures in SBMA.
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Affiliation(s)
- Matthias Becker
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, D-76021 Karlsruhe, Germany
| | - Elke Martin
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, D-76021 Karlsruhe, Germany
| | - Jean Schneikert
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, D-76021 Karlsruhe, Germany
| | - Harald F. Krug
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, D-76021 Karlsruhe, Germany
| | - Andrew C.B. Cato
- Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, D-76021 Karlsruhe, Germany
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40
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Abstract
The recent broad advance in our understanding of human neurodegenerative diseases is based on the application of a new molecular approach. Through linkage analysis, the genes responsible for Huntington's disease, the spinocerebellar ataxias, and familial forms of Alzheimer's disease and amyotrophic lateral sclerosis (ALS) have been identified and cloned. The characterization of pathogenic mutations in such genes allows the creation of informative transgenic mouse models as, without exception, the genetic forms of adult neurodegenerative disease are due to toxicity of the mutant protein. Transgenic models provide insight into the oxidative mechanisms in ALS pathogenesis, the pathogenicity of expanded polyglutamine tracts in CAG triplet repeat disorders, and amyloidogenesis in Alzheimer's disease. Although such models have their limitations, they currently provide the best entry point for the study of human neurodegenerative diseases.
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Affiliation(s)
- M E Gurney
- CNS Therapeutic Area, Pharmacia and Upjohn, Inc., 301 Henrietta St., Kalamazoo, MI 49007, USA
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41
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Bidichandani SI, Purandare SM, Taylor EE, Gumin G, Machkhas H, Harati Y, Gibbs RA, Ashizawa T, Patel PI. Somatic sequence variation at the Friedreich ataxia locus includes complete contraction of the expanded GAA triplet repeat, significant length variation in serially passaged lymphoblasts and enhanced mutagenesis in the flanking sequence. Hum Mol Genet 1999; 8:2425-36. [PMID: 10556290 DOI: 10.1093/hmg/8.13.2425] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The vast majority of Friedreich ataxia patients are homozygous for large GAA triplet repeat expansions in intron 1 of the X25 gene. Instability of the expanded GAA repeat was examined in 23 chromosomes bearing 97-1250 triplets in lymphoblastoid cell lines passaged 20-39 times. Southern analyses revealed 18 events of significant changes in length ranging from 69 to 633 triplets, wherein the de novo allele gradually replaced the original over 1-6 passages. Contractions and expansions occurred with equal frequency and magnitude. This behavior is unique in comparison with other large, non-coding triplet repeat expansions [(CGG)(n)and (CTG)(n)] which remain relatively stable under similar conditions. We also report a rare patient who, having inherited two expanded alleles, showed evidence of contracted GAA repeats ranging from nine to 29 triplets in DNA from two independent peripheral blood samples. The GAA triplet repeat is known to adopt a triplex structure, and triplexes in transcribed templates cause enhanced mutagenesis. The poly(A) tract and a 135 bp sequence, both situated immediately upstream of the GAA triplet repeat, were therefore examined for somatic mutations. The poly(A) tract showed enhanced instability when in cis with the GAA expansion. The 135 bp upstream sequence was found to harbor a 3-fold excess of point mutations in DNA derived from individuals homozygous for the GAA triplet repeat expansion compared with normal controls. These data are likely to have important mechanistic and clinical implications.
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Affiliation(s)
- S I Bidichandani
- Department of Neurology, Baylor College of Medicine, TX 77030, USA
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42
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Burman RW, Popovich BW, Jacky PB, Turker MS. Fully expanded FMR1 CGG repeats exhibit a length- and differentiation-dependent instability in cell hybrids that is independent of DNA methylation. Hum Mol Genet 1999; 8:2293-302. [PMID: 10545610 DOI: 10.1093/hmg/8.12.2293] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The fragile X syndrome is characterized at the molecular level by expansion and methylation of a CGG trinucleotide repeat located within the FMR1 locus. The tissues of most full mutation carriers are mosaic for repeat size, but these mutational patterns tend to be well conserved when comparing multiple tissues within an individual. Moreover, full mutation alleles are stable in cultured fibroblasts. These observations have been used to suggest that fragile X CGG repeat instability normally is limited to a period during early embryogenesis. DNA methylation of the repeat region is also believed to occur during early development, and some experimental evidence indicates that this modification may stabilize the repeats. To study the behavior of full mutation alleles in mitotic cells, we generated human-mouse somatic cell hybrids that carry both methylated and unmethylated full mutation FMR1 alleles. We observed considerable repeat instability and analyzed repeat dynamics in the hybrids as a function of DNA methylation, repeat length and cellular differentiation. Our results indicate that although DNA methylation does correlate with stability in primary human fibroblasts, it does not do so in the cell hybrids. Instead, repeat stability in the hybrids is dependent on repeat length, except in an undifferentiated cellular background where large alleles are maintained with a high degree of stability. This stability is lost when the cells undergo differentiation. These results indicate that the determinants of CGG repeat stability are more complex than generally believed, and suggest an unexpected role for cellular differentiation in this process.
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Affiliation(s)
- R W Burman
- Department of Molecular and Medical Genetics,Oregon Health Sciences University, Portland 97201, USA
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43
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Cemal CK, Huxley C, Chamberlain S. Insertion of expanded CAG trinucleotide repeat motifs into a yeast artificial chromosome containing the human Machado-Joseph disease gene. Gene 1999; 236:53-61. [PMID: 10433966 DOI: 10.1016/s0378-1119(99)00273-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Machado-Joseph disease or spinocerebellar ataxia 3 (SCA3) is a progressive neurodegenerative disorder caused by pathological expansion of a trinucleotide repeat motif present within exon 4 of the MJD1 gene. Previous attempts to create a transgenic animal model have failed to produce a neurological deficit truly representative of the disease phenotype. This appears to be the result of inappropriate expression of the mutant protein in neuronal populations generally spared in the disease state. Introduction of a human disease gene in the context of a yeast artificial chromosome clone containing endogenous regulatory elements would enhance the potential for correct tissue/cell-specific expression at physiological levels. We report the introduction of expanded CAG repeat motifs into a 250kb yeast artificial chromosome clone spanning the MJD1 locus using two rounds of homologous recombination. Transformants exhibited both expansions and contractions of the motif with alleles ranging in size from 48 to 84 repeat units. The availability of these clones for modelling of the disease in transgenic animals should allow elucidation of the role of repeat length in the phenotypic spectrum of the disease.
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Affiliation(s)
- C K Cemal
- Hereditary Ataxia Research Group, Molecular Genetics, Division of Biomedical Sciences, Imperial College of Science Technology and Medicine, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK.
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44
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White PJ, Borts RH, Hirst MC. Stability of the human fragile X (CGG)(n) triplet repeat array in Saccharomyces cerevisiae deficient in aspects of DNA metabolism. Mol Cell Biol 1999; 19:5675-84. [PMID: 10409756 PMCID: PMC84419 DOI: 10.1128/mcb.19.8.5675] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expanded trinucleotide repeats underlie a growing number of human diseases. The human FMR1 (CGG)(n) array can exhibit genetic instability characterized by progressive expansion over several generations leading to gene silencing and the development of the fragile X syndrome. While expansion is dependent upon the length of uninterrupted (CGG)(n), instability occurs in a limited germ line and early developmental window, suggesting that lineage-specific expression of other factors determines the cellular environment permissive for expansion. To identify these factors, we have established normal- and premutation-length human FMR1 (CGG)(n) arrays in the yeast Saccharomyces cerevisiae and assessed the frequency of length changes greater than 5 triplets in cells deficient in various DNA repair and replication functions. In contrast to previous studies with Escherichia coli, we observed a low frequency of orientation-dependent large expansions in arrays carrying long uninterrupted (CGG)(n) arrays in a wild-type background. This frequency was unaffected by deletion of several DNA mismatch repair genes or deletion of the EXO1 and DIN7 genes and was not enhanced through meiosis in a wild-type background. Array contraction occurred in an orientation-dependent manner in most mutant backgrounds, but loss of the Sgs1p resulted in a generalized increase in array stability in both orientations. In contrast, FMR1 arrays had a 10-fold-elevated frequency of expansion in a rad27 background, providing evidence for a role in lagging-strand Okazaki fragment processing in (CGG)(n) triplet repeat expansion.
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Affiliation(s)
- P J White
- Fragile X Group, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DS, United Kingdom
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45
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Fischbeck KH, Lieberman A, Bailey CK, Abel A, Merry DE. Androgen receptor mutation in Kennedy's disease. Philos Trans R Soc Lond B Biol Sci 1999; 354:1075-8. [PMID: 10434308 PMCID: PMC1692603 DOI: 10.1098/rstb.1999.0461] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Kennedy's disease is an X-linked form of motor neuron disease caused by an expanded polyglutamine repeat in the androgen receptor. While the expansion mutation causes some loss of transcriptional activity by the androgen receptor, the predominant effect of expansion is probably a toxic gain of function, similar to the mechanism of other polyglutamine expansion diseases. Features of the neurodegenerative phenotype of Kennedy's disease have now been reproduced in transgenic animals and neuronal cell culture. Nuclear inclusions of mutant androgen receptor protein are found in these model systems and in autopsy samples from patients with Kennedy's disease.
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Affiliation(s)
- K H Fischbeck
- Neurogenetics Branch, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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46
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Shelbourne PF, Killeen N, Hevner RF, Johnston HM, Tecott L, Lewandoski M, Ennis M, Ramirez L, Li Z, Iannicola C, Littman DR, Myers RM. A Huntington's disease CAG expansion at the murine Hdh locus is unstable and associated with behavioural abnormalities in mice. Hum Mol Genet 1999; 8:763-74. [PMID: 10196365 DOI: 10.1093/hmg/8.5.763] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Huntington's disease (HD) is a dominant disorder characterized by premature and progressive neurodegeneration. In order to generate an accurate model of the disease, we introduced an HD-like mutation (an extended stretch of 72-80 CAG repeats) into the endogenous mouse Hdh gene. Analysis of the mutation in vivo reveals significant levels of germline instability, with expansions, contractions and sex-of-origin effects in evidence. Mice expressing full-length mutant protein display abnormal social behaviour in the absence of acute neurodegeneration. Given that psychiatric changes, including irritability and aggression, are common findings in HD patients, our data are consistent with the hypothesis that some clinical features of HD may be caused by pathological processes that precede gross neuronal cell death. This implies that effective treatment of HD may require an understanding and amelioration of these dysfunctional processes, rather than simply preventing the premature death of neurons in the brain. These mice should facilitate the investigation of the molecular mechanisms that underpin the pathway from genotype to phenotype in HD.
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Affiliation(s)
- P F Shelbourne
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
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47
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Linhartová I, Repitz M, Dráber P, Nemec M, Wiche G, Propst F. Conserved domains and lack of evidence for polyglutamine length polymorphism in the chicken homolog of the Machado-Joseph disease gene product ataxin-3. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1444:299-305. [PMID: 10023088 DOI: 10.1016/s0167-4781(99)00004-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ataxin-3 is a protein of unknown function which is mutated in Machado-Joseph disease by expansion of a genetically unstable CAG repeat encoding polyglutamine. By analysis of chicken ataxin-3 we were able to identify four conserved domains of the protein and detected widespread expression in chicken tissues. In the first such analysis in a non-primate species we found that in contrast to primates, the chicken CAG repeat is short and genetically stable.
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Affiliation(s)
- I Linhartová
- Institute of Biochemistry and Molecular Cell Biology, Vienna Biocenter, University of Vienna, Dr. Bohr-Gasse 9, A-1030, Vienna, Austria
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48
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Abstract
Review During the past 10 years (the "decade of the brain"), some of the genetic causes of many of the primary neurodegenerative diseases, which include Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, prion disease, and many ataxic syndromes, have been found. These breakthroughs mean that for many of these diseases we now know the initiating trigger as well as the final outcome. These diseases have many pathological mechanisms in common, and there may be relatively few pathways to neuronal death seen in these disorders. Thus, treatment strategies developed for a particular disease may be found to have efficacy in more than one disorder.
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Affiliation(s)
- J Hardy
- Department of Pharmacology, Mayo Clinic Jacksonville, Jacksonville, FL 32224, USA.
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49
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Affiliation(s)
- P Djian
- CNRS (Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement), Meudon-Bellevue, France
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50
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Wells RD, Bacolla A, Bowater RP. Instabilities of triplet repeats: factors and mechanisms. Results Probl Cell Differ 1998; 21:133-65. [PMID: 9670316 DOI: 10.1007/978-3-540-69680-3_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- R D Wells
- Institute of Biosciences and Technology, Texas A&M University, Texas Medical Center, Houston 77030-3303, USA
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