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Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches

Huntingtin-lowering approaches that target huntingtin expression are a major focus for therapeutic intervention for Huntington’s disease. When the cytosine, adenine and guanine repeat is expanded, the huntingtin pre-mRNA is alternatively processed to generate the full-length huntingtin and HTT1a tra...

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Autores principales: Smith, Edward J, Sathasivam, Kirupa, Landles, Christian, Osborne, Georgina F, Mason, Michael A, Gomez-Paredes, Casandra, Taxy, Bridget A, Milton, Rebecca E, Ast, Anne, Schindler, Franziska, Zhang, Chuangchuang, Duan, Wenzhen, Wanker, Erich E, Bates, Gillian P
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9901570/
https://www.ncbi.nlm.nih.gov/pubmed/36756307
http://dx.doi.org/10.1093/braincomms/fcad010
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author Smith, Edward J
Sathasivam, Kirupa
Landles, Christian
Osborne, Georgina F
Mason, Michael A
Gomez-Paredes, Casandra
Taxy, Bridget A
Milton, Rebecca E
Ast, Anne
Schindler, Franziska
Zhang, Chuangchuang
Duan, Wenzhen
Wanker, Erich E
Bates, Gillian P
author_facet Smith, Edward J
Sathasivam, Kirupa
Landles, Christian
Osborne, Georgina F
Mason, Michael A
Gomez-Paredes, Casandra
Taxy, Bridget A
Milton, Rebecca E
Ast, Anne
Schindler, Franziska
Zhang, Chuangchuang
Duan, Wenzhen
Wanker, Erich E
Bates, Gillian P
author_sort Smith, Edward J
collection PubMed
description Huntingtin-lowering approaches that target huntingtin expression are a major focus for therapeutic intervention for Huntington’s disease. When the cytosine, adenine and guanine repeat is expanded, the huntingtin pre-mRNA is alternatively processed to generate the full-length huntingtin and HTT1a transcripts. HTT1a encodes the aggregation-prone and highly pathogenic exon 1 huntingtin protein. In evaluating huntingtin-lowering approaches, understanding how the targeting strategy modulates levels of both transcripts and the huntingtin protein isoforms that they encode will be essential. Given the aggregation-propensity of exon 1 huntingtin, the impact of a given strategy on the levels and subcellular location of aggregated huntingtin will need to be determined. We have developed and applied sensitive molecular approaches to monitor the levels of aggregated and soluble huntingtin isoforms in tissue lysates. We have used these, in combination with immunohistochemistry, to map the appearance and accumulation of aggregated huntingtin throughout the CNS of zQ175 mice, a model of Huntington’s disease frequently chosen for preclinical studies. Aggregation analyses were performed on tissues from zQ175 and wild-type mice at monthly intervals from 1 to 6 months of age. We developed three homogeneous time-resolved fluorescence assays to track the accumulation of aggregated huntingtin and showed that two of these were specific for the exon 1 huntingtin protein. Collectively, the homogeneous time-resolved fluorescence assays detected huntingtin aggregation in the 10 zQ175 CNS regions by 1–2 months of age. Immunohistochemistry with the polyclonal S830 anti-huntingtin antibody showed that nuclear huntingtin aggregation, in the form of a diffuse nuclear immunostain, could be visualized in the striatum, hippocampal CA1 region and layer IV of the somatosensory cortex by 2 months. That this diffuse nuclear immunostain represented aggregated huntingtin was confirmed by immunohistochemistry with a polyglutamine-specific antibody, which required formic acid antigen retrieval to expose its epitope. By 6 months of age, nuclear and cytoplasmic inclusions were widely distributed throughout the brain. Homogeneous time-resolved fluorescence analysis showed that the comparative levels of soluble exon 1 huntingtin between CNS regions correlated with those for huntingtin aggregation. We found that soluble exon 1 huntingtin levels decreased over the 6-month period, whilst those of soluble full-length mutant huntingtin remained unchanged, data that were confirmed for the cortex by immunoprecipitation and western blotting. These data support the hypothesis that exon 1 huntingtin initiates the aggregation process in knock-in mouse models and pave the way for a detailed analysis of huntingtin aggregation in response to huntingtin-lowering treatments.
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spelling pubmed-99015702023-02-07 Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches Smith, Edward J Sathasivam, Kirupa Landles, Christian Osborne, Georgina F Mason, Michael A Gomez-Paredes, Casandra Taxy, Bridget A Milton, Rebecca E Ast, Anne Schindler, Franziska Zhang, Chuangchuang Duan, Wenzhen Wanker, Erich E Bates, Gillian P Brain Commun Original Article Huntingtin-lowering approaches that target huntingtin expression are a major focus for therapeutic intervention for Huntington’s disease. When the cytosine, adenine and guanine repeat is expanded, the huntingtin pre-mRNA is alternatively processed to generate the full-length huntingtin and HTT1a transcripts. HTT1a encodes the aggregation-prone and highly pathogenic exon 1 huntingtin protein. In evaluating huntingtin-lowering approaches, understanding how the targeting strategy modulates levels of both transcripts and the huntingtin protein isoforms that they encode will be essential. Given the aggregation-propensity of exon 1 huntingtin, the impact of a given strategy on the levels and subcellular location of aggregated huntingtin will need to be determined. We have developed and applied sensitive molecular approaches to monitor the levels of aggregated and soluble huntingtin isoforms in tissue lysates. We have used these, in combination with immunohistochemistry, to map the appearance and accumulation of aggregated huntingtin throughout the CNS of zQ175 mice, a model of Huntington’s disease frequently chosen for preclinical studies. Aggregation analyses were performed on tissues from zQ175 and wild-type mice at monthly intervals from 1 to 6 months of age. We developed three homogeneous time-resolved fluorescence assays to track the accumulation of aggregated huntingtin and showed that two of these were specific for the exon 1 huntingtin protein. Collectively, the homogeneous time-resolved fluorescence assays detected huntingtin aggregation in the 10 zQ175 CNS regions by 1–2 months of age. Immunohistochemistry with the polyclonal S830 anti-huntingtin antibody showed that nuclear huntingtin aggregation, in the form of a diffuse nuclear immunostain, could be visualized in the striatum, hippocampal CA1 region and layer IV of the somatosensory cortex by 2 months. That this diffuse nuclear immunostain represented aggregated huntingtin was confirmed by immunohistochemistry with a polyglutamine-specific antibody, which required formic acid antigen retrieval to expose its epitope. By 6 months of age, nuclear and cytoplasmic inclusions were widely distributed throughout the brain. Homogeneous time-resolved fluorescence analysis showed that the comparative levels of soluble exon 1 huntingtin between CNS regions correlated with those for huntingtin aggregation. We found that soluble exon 1 huntingtin levels decreased over the 6-month period, whilst those of soluble full-length mutant huntingtin remained unchanged, data that were confirmed for the cortex by immunoprecipitation and western blotting. These data support the hypothesis that exon 1 huntingtin initiates the aggregation process in knock-in mouse models and pave the way for a detailed analysis of huntingtin aggregation in response to huntingtin-lowering treatments. Oxford University Press 2023-01-20 /pmc/articles/PMC9901570/ /pubmed/36756307 http://dx.doi.org/10.1093/braincomms/fcad010 Text en © The Author(s) 2023. Published by Oxford University Press on behalf of the Guarantors of Brain. https://creativecommons.org/licenses/by/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Original Article
Smith, Edward J
Sathasivam, Kirupa
Landles, Christian
Osborne, Georgina F
Mason, Michael A
Gomez-Paredes, Casandra
Taxy, Bridget A
Milton, Rebecca E
Ast, Anne
Schindler, Franziska
Zhang, Chuangchuang
Duan, Wenzhen
Wanker, Erich E
Bates, Gillian P
Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches
title Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches
title_full Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches
title_fullStr Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches
title_full_unstemmed Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches
title_short Early detection of exon 1 huntingtin aggregation in zQ175 brains by molecular and histological approaches
title_sort early detection of exon 1 huntingtin aggregation in zq175 brains by molecular and histological approaches
topic Original Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9901570/
https://www.ncbi.nlm.nih.gov/pubmed/36756307
http://dx.doi.org/10.1093/braincomms/fcad010
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