1
|
Brenner D, Sieverding K, Srinidhi J, Zellner S, Secker C, Yilmaz R, Dyckow J, Amr S, Ponomarenko A, Tunaboylu E, Douahem Y, Schlag JS, Rodríguez Martínez L, Kislinger G, Niemann C, Nalbach K, Ruf WP, Uhl J, Hollenbeck J, Schirmer L, Catanese A, Lobsiger CS, Danzer KM, Yilmazer-Hanke D, Münch C, Koch P, Freischmidt A, Fetting M, Behrends C, Parlato R, Weishaupt JH. A TBK1 variant causes autophagolysosomal and motoneuron pathology without neuroinflammation in mice. J Exp Med 2024; 221:e20221190. [PMID: 38517332 PMCID: PMC10959724 DOI: 10.1084/jem.20221190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 05/05/2023] [Accepted: 02/16/2024] [Indexed: 03/23/2024] Open
Abstract
Heterozygous mutations in the TBK1 gene can cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The majority of TBK1-ALS/FTD patients carry deleterious loss-of-expression mutations, and it is still unclear which TBK1 function leads to neurodegeneration. We investigated the impact of the pathogenic TBK1 missense variant p.E696K, which does not abolish protein expression, but leads to a selective loss of TBK1 binding to the autophagy adaptor protein and TBK1 substrate optineurin. Using organelle-specific proteomics, we found that in a knock-in mouse model and human iPSC-derived motor neurons, the p.E696K mutation causes presymptomatic onset of autophagolysosomal dysfunction in neurons precipitating the accumulation of damaged lysosomes. This is followed by a progressive, age-dependent motor neuron disease. Contrary to the phenotype of mice with full Tbk1 knock-out, RIPK/TNF-α-dependent hepatic, neuronal necroptosis, and overt autoinflammation were not detected. Our in vivo results indicate autophagolysosomal dysfunction as a trigger for neurodegeneration and a promising therapeutic target in TBK1-ALS/FTD.
Collapse
Affiliation(s)
- David Brenner
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
- Department of Neurology, University of Ulm, Ulm, Germany
| | | | - Jahnavi Srinidhi
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Susanne Zellner
- Medical Faculty, Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University München, Munich, Germany
| | - Christopher Secker
- Neuroproteomics, Max Delbrück Center for Molecular Medicine, Berlin, Germany
- Department of Neurology and Experimental Neurology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Rüstem Yilmaz
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Julia Dyckow
- Division of Neuroimmunology, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Shady Amr
- Faculty of Medicine, Institute of Biochemistry II, Goethe University Frankfurt, Frankfurt, Germany
| | - Anna Ponomarenko
- Department of Neurology, University of Ulm, Ulm, Germany
- Institute of Anatomy and Cell Biology, Ulm University School of Medicine, Ulm, Germany
| | - Esra Tunaboylu
- Department of Neurology, University of Ulm, Ulm, Germany
| | - Yasmin Douahem
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Joana S. Schlag
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Lucía Rodríguez Martínez
- Institute of Neuronal Cell Biology, Technical University Munich, Munich, Germany
- German Center for Neurodegenerative Diseases, Munich, Germany
| | - Georg Kislinger
- Electron Microscopy Hub, German Center for Neurodegenerative Diseases, Munich, Germany
| | - Cornelia Niemann
- Electron Microscopy Hub, German Center for Neurodegenerative Diseases, Munich, Germany
| | - Karsten Nalbach
- Medical Faculty, Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University München, Munich, Germany
| | | | - Jonathan Uhl
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Johanna Hollenbeck
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Lucas Schirmer
- Division of Neuroimmunology, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Alberto Catanese
- Institute of Anatomy and Cell Biology, Ulm University School of Medicine, Ulm, Germany
| | - Christian S. Lobsiger
- Institut du Cerveau—Paris Brain Institute—Institut du Cerveau et de la Moelle épinière, Inserm, Centre National de la Recherche Scientifique, Assistance Publique–Hôpitaux de Paris, Hôpital de la Pitié-Salpêtrière, Sorbonne Université, Paris, France
| | - Karin M. Danzer
- Department of Neurology, University of Ulm, Ulm, Germany
- German Center for Neurodegenerative Diseases, Ulm, Germany
| | - Deniz Yilmazer-Hanke
- Department of Neurology, Clinical Neuroanatomy Unit, University of Ulm, Ulm, Germany
| | - Christian Münch
- Institute of Anatomy and Cell Biology, Ulm University School of Medicine, Ulm, Germany
| | - Philipp Koch
- University of Heidelberg/Medical Faculty Mannheim, Central Institute of Mental Health, Mannheim, Germany
- Hector Institute for Translational Brain Research, Mannheim, Germany
- German Cancer Research Center, Heidelberg, Germany
| | | | - Martina Fetting
- Medical Faculty, Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University München, Munich, Germany
- Electron Microscopy Hub, German Center for Neurodegenerative Diseases, Munich, Germany
| | - Christian Behrends
- Medical Faculty, Munich Cluster for Systems Neurology (SyNergy), Ludwig-Maximilians-University München, Munich, Germany
| | - Rosanna Parlato
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| | - Jochen H. Weishaupt
- Division of Neurodegeneration, Department of Neurology, Medical Faculty Mannheim, Mannheim Center for Translational Neurosciences, Heidelberg University, Mannheim, Germany
| |
Collapse
|
2
|
Gómez-Tortosa E, MacDonald ME, Friend JC, Taylor SA, Weiler LJ, Cupples LA, Srinidhi J, Gusella JF, Bird ED, Vonsattel JP, Myers RH. Quantitative neuropathological changes in presymptomatic Huntington's disease. Ann Neurol 2001; 49:29-34. [PMID: 11198293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
Morphometric studies of the tail of the caudate nucleus, the site where the pathology is first seen, were performed on 16 brain specimens collected from individuals at risk for inheriting Huntington's disease (HD). Medical records and information obtained from immediate family members indicated that all had died without symptoms of HD. Six individuals had 37 or more CAG repeats and were designated HD gene carriers, whereas 10 were determined to be non-carriers. Cell counts of the tail of the caudate nucleus revealed an increased density of oligodendrocytes among the presymptomatic HD gene carriers (mean cells/field: carriers = 40.0, noncarrier = 21.3; age, sex, repeated measure adjusted F[126] = 11.7, p = 0.0008). No statistically significant differences were found between HD carriers and noncarriers in the density of neurons (carriers = 16.9, noncarriers = 15.5), astrocytes (carriers = 27.8, noncarriers = 21.3) or microglial cells (carriers = 7.9, noncarriers = 5.6). Ubiquitin immunostaining performed in 3 gene carriers revealed intranuclear inclusions in all 3 cases, including 1, with 37 repeats, who died 3 decades before the expected age for onset of the clinical syndrome. Normal densities of other cell types and careful macroscopic examination suggest that the increase in oligodendroglial density is not a consequence of atrophy and may instead reflect a developmental effect of the HD gene.
Collapse
Affiliation(s)
- E Gómez-Tortosa
- Department of Neurology, Massachusetts General Hospital, Boston, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Leeflang EP, Tavaré S, Marjoram P, Neal CO, Srinidhi J, MacFarlane H, MacDonald ME, Gusella JF, de Young M, Wexler NS, Arnheim N. Analysis of germline mutation spectra at the Huntington's disease locus supports a mitotic mutation mechanism. Hum Mol Genet 1999; 8:173-83. [PMID: 9931325 DOI: 10.1093/hmg/8.2.173] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Trinucleotide repeat disease alleles can undergo 'dynamic' mutations in which repeat number may change when a gene is transmitted from parent to offspring. By typing >3500 sperm, we determined the size distribution of Huntington's disease (HD) germline mutations produced by 26 individuals from the Venezuelan cohort with CAG/CTG repeat numbers ranging from 37 to 62. Both the mutation frequency and mean change in allele size increased with increasing somatic repeat number. The mutation frequencies averaged 82% and, for individuals with at least 50 repeats, 98%. The extraordinarily high mutation frequency levels are most consistent with a mutation process that occurs throughout germline mitotic divisions, rather than resulting from a single meiotic event. In several cases, the mean change in repeat number differed significantly among individuals with similar somatic allele sizes. This individual variation could not be attributed to age in a simple way or to ' cis ' sequences, suggesting the influence of genetic background or other factors. A familial effect is suggested in one family where both the father and son gave highly unusual spectra compared with other individuals matched for age and repeat number. A statistical model based on incomplete processing of Okazaki fragments during DNA replication was found to provide an excellent fit to the data but variation in parameter values among individuals suggests that the molecular mechanism might be more complex.
Collapse
Affiliation(s)
- E P Leeflang
- Molecular Biology Program and Department of Mathematics, University of Southern California, Los Angeles, CA 90089-1340, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Wheeler VC, Auerbach W, White JK, Srinidhi J, Auerbach A, Ryan A, Duyao MP, Vrbanac V, Weaver M, Gusella JF, Joyner AL, MacDonald ME. Length-dependent gametic CAG repeat instability in the Huntington's disease knock-in mouse. Hum Mol Genet 1999; 8:115-22. [PMID: 9887339 DOI: 10.1093/hmg/8.1.115] [Citation(s) in RCA: 265] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The CAG repeats in the human Huntington's disease (HD) gene exhibit striking length-dependent intergenerational instability, typically small size increases or decreases of one to a few CAGs, but little variation in somatic tissues. In a subset of male transmissions, larger size increases occur to produce extreme HD alleles that display somatic instability and cause juvenile onset of the disorder. Initial efforts to reproduce these features in a mouse model transgenic for HD exon 1 with 48 CAG repeats revealed only mild intergenerational instability ( approximately 2% of meioses). A similar pattern was obtained when this repeat was inserted into exon 1 of the mouse Hdh gene. However, lengthening the repeats in Hdh to 90 and 109 units produced a graded increase in the mutation frequency to >70%, with instability being more evident in female transmissions. No large jumps in CAG length were detected in either male or female transmissions. Instead, size changes were modest increases and decreases, with expansions typically emanating from males and contractions from females. Limited CAG variation in the somatic tissues gave way to marked mosaicism in liver and striatum for the longest repeats in older mice. These results indicate that gametogenesis is the primary source of inherited instability in the Hdh knock-in mouse, as it is in man, but that the underlying repeat length-dependent mechanism, which may or may not be related in the two species, operates at higher CAG numbers. Moreover, the large CAG repeat increases seen in a subset of male HD transmissions are not reproduced in the mouse, suggesting that these arise by a different fundamental mechanism than the small size fluctuations that are frequent during gametogenesis in both species.
Collapse
Affiliation(s)
- V C Wheeler
- Molecular Neurogenetics Unit, Massachusetts General Hospital East, Building 149, 13th Street, Charlestown, MA 02129, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Abstract
The hallmark neuropathology of Huntington's disease (HD) is due to elongation of a polyglutamine segment in huntingtin, a novel approximately 350 kDa protein of unknown function. We used a yeast two-hybrid interactor screen to identify proteins whose association with huntingtin might be altered in the pathogenic process. Surprisingly, no interactors were found with internal and C-terminal segments of huntingtin. In contrast, huntingtin's N-terminus detected 13 distinct proteins, seven novel and six reported previously. Among these, we identified a major interactor class, comprising three distinct WW domain proteins, HYPA, HYPB and HYPC, that bind normal and mutant huntingtin in extracts of HD lymphoblastoid cells. This interaction is mediated by huntingtin's proline-rich region and is enhanced by lengthening the adjacent glutamine tract. Although HYPB and HYPC are novel, HYPA is human FBP-11, a protein implicated in spliceosome function. The emergence of this class of proteins as huntingtin partners argues that a WW domain-mediated process, such as non-receptor signaling, protein degradation or pre-mRNA splicing, may participate in HD pathogenesis.
Collapse
Affiliation(s)
- P W Faber
- Molecular Neurogenetics Unit, Massachusetts General Hospital East, Building 149, 13th Street, Charlestown, MA 02129, USA
| | | | | | | | | | | |
Collapse
|
6
|
McNeil SM, Novelletto A, Srinidhi J, Barnes G, Kornbluth I, Altherr MR, Wasmuth JJ, Gusella JF, MacDonald ME, Myers RH. Reduced penetrance of the Huntington's disease mutation. Hum Mol Genet 1997; 6:775-9. [PMID: 9158152 DOI: 10.1093/hmg/6.5.775] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Controversy persists concerning the significance of Huntington disease (HD) alleles in the 36-39 repeat range. Although some clinically affected persons have been documented with repeats in this range, elderly unaffected individuals have also been reported. We examined 10 paternal transmissions of HD alleles of 37-39 repeats in collateral branches of families with de novo HD. All 10 descendants, including many who are elderly, are without symptoms of HD. Forty percent of the transmissions were unstable, although none varied by more than one repeat. The observation that individuals with alleles of 37-39 repeats may survive unaffected beyond common life expectancy supports the presence of reduced penetrance for HD among some persons with repeat sizes which overlap the clinical range. Non-penetrance may be increased in the collateral branches of de novo mutation families when compared to penetrance estimates from patient series. There was no CAA-->CAG mutation for the penultimate glutamine in either a de novo expanded 42 repeat allele or the corresponding non-penetrant 38 repeat allele in a family with fresh mutation to HD.
Collapse
Affiliation(s)
- S M McNeil
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Persichetti F, Carlee L, Faber PW, McNeil SM, Ambrose CM, Srinidhi J, Anderson M, Barnes GT, Gusella JF, MacDonald ME. Differential expression of normal and mutant Huntington's disease gene alleles. Neurobiol Dis 1996; 3:183-90. [PMID: 8980018 DOI: 10.1006/nbdi.1996.0018] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Huntingtin expression was examined by Western blot and immunoprecipitation studies of lymphoblastoid cell lines from Huntington's disease (HD) homozygotes, heterozygotes, and a phenotypically normal individual with a t(4p16.3;12p13.3) breakpoint in the HD gene. The latter produced a reduced level of normal huntingtin without evidence of an altered protein, indicating that simple loss of huntingtin activity does not cause HD. In juvenile onset HD heterozygotes, NH2- and COOH-terminal antisera revealed reduced relative expression from the mutant allele. Pulse-chase studies indicated that huntingtin is a stable protein whose differential allelic expression is not due to destabilization of the mutant isoform. No stable breakdown products specific to mutant huntingtin were detected in either HD homozygotes or heterozygotes. These data are consistent with HD involving either a gain of function or a dominant negative loss of function that operates within severe constraints and suggest that in either case the pathogenic process is usually saturated by the amount of abnormal huntingtin produced from a single mutant allele.
Collapse
Affiliation(s)
- F Persichetti
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown 02129, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Gusella JF, McNeil S, Persichetti F, Srinidhi J, Novelletto A, Bird E, Faber P, Vonsattel JP, Myers RH, MacDonald ME. Huntington's disease. Cold Spring Harb Symp Quant Biol 1996; 61:615-26. [PMID: 9246488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- J F Gusella
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown 02129, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Leeflang EP, Zhang L, Tavaré S, Hubert R, Srinidhi J, MacDonald ME, Myers RH, de Young M, Wexler NS, Gusella JF. Single sperm analysis of the trinucleotide repeats in the Huntington's disease gene: quantification of the mutation frequency spectrum. Hum Mol Genet 1995; 4:1519-26. [PMID: 8541834 DOI: 10.1093/hmg/4.9.1519] [Citation(s) in RCA: 113] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The CAG triplet repeat region of the Huntington's disease gene was amplified in 923 single sperm from three affected and two normal individuals. Average-size alleles (15-18 repeats) showed only three contraction mutations among 475 sperm (0.6%). A 30 repeat normal allele showed an 11% mutation frequency. The mutation frequency of a 36 repeat intermediate allele was 53% with 8% of all gametes having expansions which brought the allele size into the HD disease range (> or = 38 repeats). Disease alleles (38-51 repeats) showed a very high mutation frequency (92-99%). As repeat number increased there was a marked elevation in the frequency of expansions, in the mean number of repeats added per expansion and the size of the largest observed expansion. Contraction frequencies also appeared to increase with allele size but decreased as repeat number exceeded 36. Our sperm typing data are of a discrete nature rather than consisting of smears of PCR product from pooled sperm. This allowed the observed mutation frequency spectra to be compared to the distribution calculated using discrete stochastic models based on current molecular ideas of the expansion process. An excellent fit was found when the model specified that a random number of repeats are added during the progression of the polymerase through the repeated region.
Collapse
Affiliation(s)
- E P Leeflang
- Molecular Biology Program, University of Southern California, Los Angeles 90089, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Persichetti F, Ambrose CM, Ge P, McNeil SM, Srinidhi J, Anderson MA, Jenkins B, Barnes GT, Duyao MP, Kanaley L. Normal and expanded Huntington's disease gene alleles produce distinguishable proteins due to translation across the CAG repeat. Mol Med 1995; 1:374-83. [PMID: 8521295 PMCID: PMC2230005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND An expanded CAG trinucleotide repeat is the genetic trigger of neuronal degeneration in Huntington's disease (HD), but its mode of action has yet to be discovered. The sequence of the HD gene places the CAG repeat near the 5' end in a region where it may be translated as a variable polyglutamine segment in the protein product, huntingtin. MATERIALS AND METHODS Antisera directed at amino acid stretches predicted by the DNA sequence upstream and downstream of the CAG repeat were used in Western blot and immunohistochemical analyses to examine huntingtin expression from the normal and the HD allele in lymphoblastoid cells and postmortem brain tissue. RESULTS CAG repeat segments of both normal and expanded HD alleles are indeed translated, as part of a discrete approximately 350-kD protein that is found primarily in the cytosol. The difference in the length of the N-terminal polyglutamine segment is sufficient to distinguish normal and HD huntingtin in a Western blot assay. CONCLUSIONS The HD mutation does not eliminate expression of the HD gene but instead produces an altered protein with an expanded polyglutamine stretch near the N terminus. Thus, HD pathogenesis is probably triggered by an effect at the level of huntingtin protein.
Collapse
Affiliation(s)
- F Persichetti
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown 02129-2060, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Persichetti F, Srinidhi J, Kanaley L, Ge P, Myers RH, D'Arrigo K, Barnes GT, MacDonald ME, Vonsattel JP, Gusella JF. Huntington's disease CAG trinucleotide repeats in pathologically confirmed post-mortem brains. Neurobiol Dis 1994; 1:159-66. [PMID: 9173995 DOI: 10.1006/nbdi.1994.0019] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
CAG repeat expansion in the Huntington's disease gene (HD) was examined in postmortem brains from 310 clinically diagnosed and 15 'at risk' individuals. Presence of an expanded CAG allele (>37 units) was the cause of the disorder in almost all cases (307 of 310). Despite a diversity of reporting clinicians, neurological and psychiatric onset and age at death all displayed significant inverse correlations with CAG number indicating that diagnosis of onset is reasonably accurate, and that most patients die from the disease and its complications. Neuronal changes before clinical onset are not detected by conventional microscopic examination as three out of 15 'at risk' brains had an expanded CAG allele but no neuropathology. The cause of HD-like neuropathology in three exceptional brains from clinically diagnosed individuals is unclear. The disorder in these cases could be an HD phenocopy or result from alternative mutational mechanisms at the HD locus.
Collapse
Affiliation(s)
- F Persichetti
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown, MA, 02129, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Kieburtz K, MacDonald M, Shih C, Feigin A, Steinberg K, Bordwell K, Zimmerman C, Srinidhi J, Sotack J, Gusella J. Trinucleotide repeat length and progression of illness in Huntington's disease. J Med Genet 1994; 31:872-4. [PMID: 7853373 PMCID: PMC1016662 DOI: 10.1136/jmg.31.11.872] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The genetic defect causing Huntington's disease (HD) has been identified as an unstable expansion of a trinucleotide (CAG) repeat sequence within the coding region of the IT15 gene on chromosome 4. In 50 patients with manifest HD who were evaluated prospectively and uniformly, we examined the relationship between the extent of the DNA expansion and the rate of illness progression. Although the length of CAG repeats showed a strong inverse correlation with the age at onset of HD, there was no such relationship between the number of CAG repeats and the rate of clinical decline. These findings suggest that the CAG repeat length may influence or trigger the onset of HD, but other genetic, neurobiological, or environmental factors contribute to the progression of illness and the underlying pace of neuronal degeneration.
Collapse
Affiliation(s)
- K Kieburtz
- Department of Neurology, University of Rochester Medical Center, New York 14642
| | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Barnes GT, Duyao MP, Ambrose CM, McNeil S, Persichetti F, Srinidhi J, Gusella JF, MacDonald ME. Mouse Huntington's disease gene homolog (Hdh). Somat Cell Mol Genet 1994; 20:87-97. [PMID: 8009370 DOI: 10.1007/bf02290678] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The incurable neurodegenerative disorder, Huntington's disease (HD), is caused by an expanded, unstable CAG repeat encoding a stretch of polyglutamine in a 4p16.3 gene (HD) of unknown function. Near the CAG repeat is a polyproline-encoding CCG repeat that shows more limited allelic variation. The mouse homologue, Hdh, has been mapped to chromosome 5, in a region devoid of mutations causing any comparable phenotype. We have isolated overlapping cDNAs from the Hdh gene and compared their sequences with the human transcript. The consensus mouse coding sequence is 86% identical to the human at the DNA level and 91% identical at the protein level. Despite the overall high level of conservation, Hdh possesses an imperfect CAG repeat encoding only seven consecutive glutamines, compared to the 13-36 residues that are normal in man. Although no evidence for polymorphic variation of the CAG repeat was seen, a nearby CCG repeat differed in length by one unit between several strains of laboratory mouse and Mus spretus. The absence of a long CAG repeat in the mouse is consistent with the lack of a spontaneous mouse model of HD. The information presented concerning the sequence of the mouse gene should facilitate attempts to create such a model.
Collapse
Affiliation(s)
- G T Barnes
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown 02129
| | | | | | | | | | | | | | | |
Collapse
|
14
|
MacDonald ME, Barnes G, Srinidhi J, Duyao MP, Ambrose CM, Myers RH, Gray J, Conneally PM, Young A, Penney J. Gametic but not somatic instability of CAG repeat length in Huntington's disease. J Med Genet 1993; 30:982-6. [PMID: 8133508 PMCID: PMC1016628 DOI: 10.1136/jmg.30.12.982] [Citation(s) in RCA: 145] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Instability of a CAG repeat in 4p16.3 has been found in Huntington's disease (HD) chromosomes. Unlike a similar repeat in the fragile X syndrome, the expanded HD repeat showed no evidence of somatic instability in a comparison of blood, lymphoblast, and brain DNA from the same persons. Four pairs of monozygotic HD twins displayed identical CAG repeat lengths suggesting that repeat size is determined in gametogenesis. In contrast with the fragile X syndrome and with HD somatic tissue, mosaicism was readily detected as a diffuse spread of repeat lengths in DNA from HD sperm samples. Typically, the modal repeat size was larger in the sperm DNA than in corresponding lymphoblast DNA, with the greatest degree of gametic mosaicism coinciding with the longest somatic CAG repeats. These data indicate that the developmental timing of repeat instability appears to differ between HD and fragile X syndrome, and that the fundamental mechanisms leading to repeat expansion may therefore be distinct.
Collapse
Affiliation(s)
- M E MacDonald
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown 02129
| | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Myers RH, MacDonald ME, Koroshetz WJ, Duyao MP, Ambrose CM, Taylor SA, Barnes G, Srinidhi J, Lin CS, Whaley WL. De novo expansion of a (CAG)n repeat in sporadic Huntington's disease. Nat Genet 1993; 5:168-73. [PMID: 8252042 DOI: 10.1038/ng1093-168] [Citation(s) in RCA: 187] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Huntington's disease (HD) chromosomes contain an expanded unstable (CAG)n repeat in chromosome 4p16.3. We have examined nine families with potential de novo expression of the disease. With one exception, all of the affected individuals had 42 or more repeat units, well above the normal range. In four families, elderly unaffected relatives inherited the same chromosome as that containing the expanded repeat in the proband, but had repeat lengths of 34-38 units, spanning the gap between the normal and HD distributions. Thus, mutation to HD is usually associated with an expansion from an already large repeat.
Collapse
Affiliation(s)
- R H Myers
- Department of Neurology, Boston University School of Medicine, Massachusetts 02118
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Locke PA, MacDonald ME, Srinidhi J, Gilliam TC, Tanzi RE, Conneally PM, Wexler NS, Haines JL, Gusella JF. A genetic linkage map of the chromosome 4 short arm. Somat Cell Mol Genet 1993; 19:95-101. [PMID: 8096345 DOI: 10.1007/bf01233958] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have generated an 18-interval contiguous genetic linkage map of human chromosome 4 spanning the entire short arm and proximal long arm. Fifty-seven polymorphisms, representing 42 loci, were analyzed in the Venezuelan reference pedigree. The markers included seven genes (ADRA2C, ALB, GABRB1, GC, HOX7, IDUA, QDPR), one pseudogene (RAF1P1), and 34 anonymous DNA loci. Four loci were represented by microsatellite polymorphisms and one (GC) was expressed as a protein polymorphism. The remainder were genotyped based on restriction fragment length polymorphism. The sex-averaged map covered 123 cM. Significant differences in sex-specific rates of recombination were observed only in the pericentromeric and proximal long arm regions, but these contributed to different overall map lengths of 115 cM in males and 138 cM in females. This map provides 19 reference points along chromosome 4 that will be particularly useful in anchoring and seeding physical mapping studies and in aiding in disease studies.
Collapse
Affiliation(s)
- P A Locke
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Boston 02114
| | | | | | | | | | | | | | | | | |
Collapse
|