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Time-lapse analysis of aggregate formation in an inducible PC12 cell model of huntington's disease reveals time-dependent aggregate formation that transiently delays cell death

Time-lapse analysis of aggregate formation in an inducible PC12 cell model of huntington's disease reveals time-dependent aggregate formation that transiently delays cell death
Time-lapse analysis of aggregate formation in an inducible PC12 cell model of huntington's disease reveals time-dependent aggregate formation that transiently delays cell death
Huntington's disease (HD) is a progressive neurodegenerative disease caused by a CAG repeat expansion in the coding region of the HD gene. The translated polyglutamine expansion causes the formation of insoluble aggregates in the brains of HD patients and transgenic mouse models. However, the relationship between aggregate formation and neuropathology remains unknown.

We used fluorescent protein tagging and live-cell time-lapse microscopy to study visible aggregate formation and its relationship to cell death in transgenic PC12 cells. We used cell lines expressing a fragment of huntingtin exon 1 with either 23 (wild type) or 74 (mutant) glutamines fused to enhanced green fluorescent protein under the control of an inducible promoter. Live cells were observed in real time after transgene induction for up to 96 h. We found that aggregate formation was time-dependent and predominantly nuclear in these cells. We followed inclusion formation in individual cells, examining the cells every 10 min for up to 48 h. This revealed new details of inclusion formation. Initial aggregate formation was rapid (often <1 h), but many (18–>48) h were needed to establish a final aggregate phenotype. Aggregates formed in a dynamic manner and were in constant motion within cell nuclei throughout their maturation.

The formation of large aggregates occurred more frequently in cells that survived longer. However, aggregate size was not a good predictor of cell death, since cells could die with either large (>2 ?m), small (<0.5 ?m) or no visible aggregates. Cells that formed large aggregates survived longer than cells that formed small aggregates or no aggregates at all. However, the time taken for a cell to die decreased as a function of increasing size of final aggregate formed.

Further, cells that formed aggregates earlier tended to die earlier. Together our data are compatible with a toxic role for aggregates/aggregation and support the ‘toxic precursor’ hypothesis. However, they also suggest that at some stages, the process of aggregate formation is cytoprotective.
inclusions, aggregates, huntingtin, PC12 cell, time-lapse microscopy
0361-9230
146-157
Gong, B.
112d9ffc-1cdc-447b-a665-b8006c520c93
Lim, M. C. Y.
c8a7f9e7-9d97-4cc2-aafd-e700b48d47f3
Wyttenbach, A.
69846a0f-fb60-4a28-84eb-ed865a5e31fa
Morton, A. J.
52cdcfd7-fa26-4a14-96d1-2103839f90db
Gong, B.
112d9ffc-1cdc-447b-a665-b8006c520c93
Lim, M. C. Y.
c8a7f9e7-9d97-4cc2-aafd-e700b48d47f3
Wyttenbach, A.
69846a0f-fb60-4a28-84eb-ed865a5e31fa
Morton, A. J.
52cdcfd7-fa26-4a14-96d1-2103839f90db

Gong, B., Lim, M. C. Y., Wyttenbach, A. and Morton, A. J. (2008) Time-lapse analysis of aggregate formation in an inducible PC12 cell model of huntington's disease reveals time-dependent aggregate formation that transiently delays cell death. Brain Research Bulletin, 75 (1), 146-157. (doi:10.1016/j.brainresbull.2007.08.005).

Record type: Article

Abstract

Huntington's disease (HD) is a progressive neurodegenerative disease caused by a CAG repeat expansion in the coding region of the HD gene. The translated polyglutamine expansion causes the formation of insoluble aggregates in the brains of HD patients and transgenic mouse models. However, the relationship between aggregate formation and neuropathology remains unknown.

We used fluorescent protein tagging and live-cell time-lapse microscopy to study visible aggregate formation and its relationship to cell death in transgenic PC12 cells. We used cell lines expressing a fragment of huntingtin exon 1 with either 23 (wild type) or 74 (mutant) glutamines fused to enhanced green fluorescent protein under the control of an inducible promoter. Live cells were observed in real time after transgene induction for up to 96 h. We found that aggregate formation was time-dependent and predominantly nuclear in these cells. We followed inclusion formation in individual cells, examining the cells every 10 min for up to 48 h. This revealed new details of inclusion formation. Initial aggregate formation was rapid (often <1 h), but many (18–>48) h were needed to establish a final aggregate phenotype. Aggregates formed in a dynamic manner and were in constant motion within cell nuclei throughout their maturation.

The formation of large aggregates occurred more frequently in cells that survived longer. However, aggregate size was not a good predictor of cell death, since cells could die with either large (>2 ?m), small (<0.5 ?m) or no visible aggregates. Cells that formed large aggregates survived longer than cells that formed small aggregates or no aggregates at all. However, the time taken for a cell to die decreased as a function of increasing size of final aggregate formed.

Further, cells that formed aggregates earlier tended to die earlier. Together our data are compatible with a toxic role for aggregates/aggregation and support the ‘toxic precursor’ hypothesis. However, they also suggest that at some stages, the process of aggregate formation is cytoprotective.

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More information

Published date: 31 January 2008
Keywords: inclusions, aggregates, huntingtin, PC12 cell, time-lapse microscopy

Identifiers

Local EPrints ID: 145299
URI: http://eprints.soton.ac.uk/id/eprint/145299
ISSN: 0361-9230
PURE UUID: 95639464-0458-45d8-858c-a2b1a6b08e46

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Date deposited: 19 Apr 2010 10:00
Last modified: 14 Mar 2024 00:50

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Contributors

Author: B. Gong
Author: M. C. Y. Lim
Author: A. Wyttenbach
Author: A. J. Morton

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