Limits...
Polyglutamine expansion accelerates the dynamics of ataxin-1 and does not result in aggregate formation.

Krol HA, Krawczyk PM, Bosch KS, Aten JA, Hol EM, Reits EA - PLoS ONE (2008)

Bottom Line: Instead of being static, insoluble aggregates, nuclear accumulations formed by the polyQ-expanded ataxin-1 showed enhanced intracellular kinetics as compared to wild-type ataxin-1.Interestingly, polyQ expansion did not affect the nuclear-cytoplasmic shuttling of ataxin-1 as proposed before.These results indicate that polyQ expansion does not necessarily lead to aggregate formation, and that the enhanced kinetics may affect the nuclear function of ataxin-1.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Histology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.

ABSTRACT

Background: Polyglutamine expansion disorders are caused by an expansion of the polyglutamine (polyQ) tract in the disease related protein, leading to severe neurodegeneration. All polyQ disorders are hallmarked by the presence of intracellular aggregates containing the expanded protein in affected neurons. The polyQ disorder SpinoCerebellar Ataxia 1 (SCA1) is caused by a polyQ-expansion in the ataxin-1 protein, which is thought to lead to nuclear aggregates.

Methodology/principal findings: Using advanced live cell fluorescence microscopy and a filter retardation assay we show that nuclear accumulations formed by polyQ-expanded ataxin-1 do not resemble aggregates of other polyQ-expanded proteins. Instead of being static, insoluble aggregates, nuclear accumulations formed by the polyQ-expanded ataxin-1 showed enhanced intracellular kinetics as compared to wild-type ataxin-1. During mitosis, ataxin-1 accumulations redistributed equally among daughter cells, in contrast to polyQ aggregates. Interestingly, polyQ expansion did not affect the nuclear-cytoplasmic shuttling of ataxin-1 as proposed before.

Conclusions/significance: These results indicate that polyQ expansion does not necessarily lead to aggregate formation, and that the enhanced kinetics may affect the nuclear function of ataxin-1. The unexpected findings for a polyQ-expanded protein and their consequences for ongoing SCA1 research are discussed.

Show MeSH

Related in: MedlinePlus

Nuclear ataxin-1 accumulations distribute symmetrically to daughter cells during cell division.Representative series of images showing cell division of a cell containing fluorescent aggregates or nuclear accumulations. (A). Asymmetric distribution of Q65-GFP aggregates in time. Arrows indicate the two daughter cells. (B). Symmetric distribution of Atx1[Q2]GFP nuclear accumulations during cell division. Nuclear accumulations fuse prior to division. After division both daughter cells contain cytoplasmic accumulations and later nuclear accumulations. (C). Symmetric distribution of Atx1[Q85]GFP nuclear accumulations during cell division. Time is indicated in minutes. Sizebar = 1 µm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2200796&req=5

pone-0001503-g003: Nuclear ataxin-1 accumulations distribute symmetrically to daughter cells during cell division.Representative series of images showing cell division of a cell containing fluorescent aggregates or nuclear accumulations. (A). Asymmetric distribution of Q65-GFP aggregates in time. Arrows indicate the two daughter cells. (B). Symmetric distribution of Atx1[Q2]GFP nuclear accumulations during cell division. Nuclear accumulations fuse prior to division. After division both daughter cells contain cytoplasmic accumulations and later nuclear accumulations. (C). Symmetric distribution of Atx1[Q85]GFP nuclear accumulations during cell division. Time is indicated in minutes. Sizebar = 1 µm.

Mentions: Cells containing polyglutamine aggregates are still able to enter mitosis [23] (and unpublished observation). Interestingly, when cells contained multiple aggregates, these aggregates were always distributed to only one of the daughter cells, whereas the other daughter cell was free of any aggregate. We therefore examined whether polyQ-expanded ataxin-1 accumulations are also asymmetrically divided during mitosis, by following the nuclear accumulations in mitotic cells that expressed either Q65-GFP, Atx1[Q2]GFP or Atx1[Q85]GFP, using automated time-lapse fluorescence imaging. Indeed, mitotic cells containing multiple polyQ nuclear aggregates formed by Q65-GFP showed asymmetrical separation of aggregates to only one daughter cell (Fig 3A). In contrast, cells containing multiple nuclear accumulations formed by either Atx1[Q2]GFP or Atx1[Q85]GFP distributed ataxin-1 to both daughter cells, regardless of polyQ expansion (Fig 3B,C). Note that most nuclear accumulations fuse into large accumulations shortly before entering mitosis, while right after cell division, both daughter cells again contain multiple small nuclear accumulations.


Polyglutamine expansion accelerates the dynamics of ataxin-1 and does not result in aggregate formation.

Krol HA, Krawczyk PM, Bosch KS, Aten JA, Hol EM, Reits EA - PLoS ONE (2008)

Nuclear ataxin-1 accumulations distribute symmetrically to daughter cells during cell division.Representative series of images showing cell division of a cell containing fluorescent aggregates or nuclear accumulations. (A). Asymmetric distribution of Q65-GFP aggregates in time. Arrows indicate the two daughter cells. (B). Symmetric distribution of Atx1[Q2]GFP nuclear accumulations during cell division. Nuclear accumulations fuse prior to division. After division both daughter cells contain cytoplasmic accumulations and later nuclear accumulations. (C). Symmetric distribution of Atx1[Q85]GFP nuclear accumulations during cell division. Time is indicated in minutes. Sizebar = 1 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2200796&req=5

pone-0001503-g003: Nuclear ataxin-1 accumulations distribute symmetrically to daughter cells during cell division.Representative series of images showing cell division of a cell containing fluorescent aggregates or nuclear accumulations. (A). Asymmetric distribution of Q65-GFP aggregates in time. Arrows indicate the two daughter cells. (B). Symmetric distribution of Atx1[Q2]GFP nuclear accumulations during cell division. Nuclear accumulations fuse prior to division. After division both daughter cells contain cytoplasmic accumulations and later nuclear accumulations. (C). Symmetric distribution of Atx1[Q85]GFP nuclear accumulations during cell division. Time is indicated in minutes. Sizebar = 1 µm.
Mentions: Cells containing polyglutamine aggregates are still able to enter mitosis [23] (and unpublished observation). Interestingly, when cells contained multiple aggregates, these aggregates were always distributed to only one of the daughter cells, whereas the other daughter cell was free of any aggregate. We therefore examined whether polyQ-expanded ataxin-1 accumulations are also asymmetrically divided during mitosis, by following the nuclear accumulations in mitotic cells that expressed either Q65-GFP, Atx1[Q2]GFP or Atx1[Q85]GFP, using automated time-lapse fluorescence imaging. Indeed, mitotic cells containing multiple polyQ nuclear aggregates formed by Q65-GFP showed asymmetrical separation of aggregates to only one daughter cell (Fig 3A). In contrast, cells containing multiple nuclear accumulations formed by either Atx1[Q2]GFP or Atx1[Q85]GFP distributed ataxin-1 to both daughter cells, regardless of polyQ expansion (Fig 3B,C). Note that most nuclear accumulations fuse into large accumulations shortly before entering mitosis, while right after cell division, both daughter cells again contain multiple small nuclear accumulations.

Bottom Line: Instead of being static, insoluble aggregates, nuclear accumulations formed by the polyQ-expanded ataxin-1 showed enhanced intracellular kinetics as compared to wild-type ataxin-1.Interestingly, polyQ expansion did not affect the nuclear-cytoplasmic shuttling of ataxin-1 as proposed before.These results indicate that polyQ expansion does not necessarily lead to aggregate formation, and that the enhanced kinetics may affect the nuclear function of ataxin-1.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Histology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.

ABSTRACT

Background: Polyglutamine expansion disorders are caused by an expansion of the polyglutamine (polyQ) tract in the disease related protein, leading to severe neurodegeneration. All polyQ disorders are hallmarked by the presence of intracellular aggregates containing the expanded protein in affected neurons. The polyQ disorder SpinoCerebellar Ataxia 1 (SCA1) is caused by a polyQ-expansion in the ataxin-1 protein, which is thought to lead to nuclear aggregates.

Methodology/principal findings: Using advanced live cell fluorescence microscopy and a filter retardation assay we show that nuclear accumulations formed by polyQ-expanded ataxin-1 do not resemble aggregates of other polyQ-expanded proteins. Instead of being static, insoluble aggregates, nuclear accumulations formed by the polyQ-expanded ataxin-1 showed enhanced intracellular kinetics as compared to wild-type ataxin-1. During mitosis, ataxin-1 accumulations redistributed equally among daughter cells, in contrast to polyQ aggregates. Interestingly, polyQ expansion did not affect the nuclear-cytoplasmic shuttling of ataxin-1 as proposed before.

Conclusions/significance: These results indicate that polyQ expansion does not necessarily lead to aggregate formation, and that the enhanced kinetics may affect the nuclear function of ataxin-1. The unexpected findings for a polyQ-expanded protein and their consequences for ongoing SCA1 research are discussed.

Show MeSH
Related in: MedlinePlus