Limits...
A polyalanine tract expansion in Arx forms intranuclear inclusions and results in increased cell death.

Nasrallah IM, Minarcik JC, Golden JA - J. Cell Biol. (2004)

Bottom Line: Transfection of these constructs results in nuclear protein aggregation, filamentous nuclear inclusions, and an increase in cell death.Coexpressing Hsp70 decreases the percentage of cells with nuclear inclusions.Finally, we show that expressing mutant Arx in mouse brains results in neuronal nuclear inclusion formation.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Program, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.

ABSTRACT
A growing number of human disorders have been associated with expansions of a tract of a single amino acid. Recently, polyalanine (polyA) tract expansions in the Aristaless-related homeobox (ARX) protein have been identified in a subset of patients with infantile spasms and mental retardation. How alanine expansions in ARX, or any other transcription factor, cause disease have not been determined. We generated a series of polyA expansions in Arx and expressed these in cell culture and brain slices. Transfection of these constructs results in nuclear protein aggregation, filamentous nuclear inclusions, and an increase in cell death. These inclusions are ubiquitinated and recruit Hsp70. Coexpressing Hsp70 decreases the percentage of cells with nuclear inclusions. Finally, we show that expressing mutant Arx in mouse brains results in neuronal nuclear inclusion formation. Our data suggest expansions in one of the ARX polyA tracts results in nuclear protein aggregation and an increase in cell death; likely underlying the pathogenesis of the associated infantile spasms and mental retardation.

Show MeSH

Related in: MedlinePlus

PolyA expansion of Arx increases cell death in vitro. COS cells were transfected with Arx or ArxE and harvested 24 or 48 h later. At 48 h, the amount of cell death in transfected neurons between these two groups was significantly higher. * indicates P < 0.05.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172475&req=5

fig2: PolyA expansion of Arx increases cell death in vitro. COS cells were transfected with Arx or ArxE and harvested 24 or 48 h later. At 48 h, the amount of cell death in transfected neurons between these two groups was significantly higher. * indicates P < 0.05.

Mentions: In diseases caused by polyQ expansions and one other polyA expansion, the formation of nuclear inclusions is accompanied by an increase in cell death (Cummings and Zoghbi, 2000; Fan et al., 2001). To test whether expression of ArxE causes an increase in cell death, we determined the rate of cell death in transfected COS cells (n = 8 transfections for each construct at each time point; n > 70 transfected cells per time point). Although no significant difference in the rate of cell death was observed after 24 h, by 48 h an average of 3.6% of cells transfected with wild-type Arx were TUNEL-positive, whereas 5.2% of cells transfected with ArxE were TUNEL-positive (P = 0.048; Fig. 2).


A polyalanine tract expansion in Arx forms intranuclear inclusions and results in increased cell death.

Nasrallah IM, Minarcik JC, Golden JA - J. Cell Biol. (2004)

PolyA expansion of Arx increases cell death in vitro. COS cells were transfected with Arx or ArxE and harvested 24 or 48 h later. At 48 h, the amount of cell death in transfected neurons between these two groups was significantly higher. * indicates P < 0.05.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172475&req=5

fig2: PolyA expansion of Arx increases cell death in vitro. COS cells were transfected with Arx or ArxE and harvested 24 or 48 h later. At 48 h, the amount of cell death in transfected neurons between these two groups was significantly higher. * indicates P < 0.05.
Mentions: In diseases caused by polyQ expansions and one other polyA expansion, the formation of nuclear inclusions is accompanied by an increase in cell death (Cummings and Zoghbi, 2000; Fan et al., 2001). To test whether expression of ArxE causes an increase in cell death, we determined the rate of cell death in transfected COS cells (n = 8 transfections for each construct at each time point; n > 70 transfected cells per time point). Although no significant difference in the rate of cell death was observed after 24 h, by 48 h an average of 3.6% of cells transfected with wild-type Arx were TUNEL-positive, whereas 5.2% of cells transfected with ArxE were TUNEL-positive (P = 0.048; Fig. 2).

Bottom Line: Transfection of these constructs results in nuclear protein aggregation, filamentous nuclear inclusions, and an increase in cell death.Coexpressing Hsp70 decreases the percentage of cells with nuclear inclusions.Finally, we show that expressing mutant Arx in mouse brains results in neuronal nuclear inclusion formation.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Program, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.

ABSTRACT
A growing number of human disorders have been associated with expansions of a tract of a single amino acid. Recently, polyalanine (polyA) tract expansions in the Aristaless-related homeobox (ARX) protein have been identified in a subset of patients with infantile spasms and mental retardation. How alanine expansions in ARX, or any other transcription factor, cause disease have not been determined. We generated a series of polyA expansions in Arx and expressed these in cell culture and brain slices. Transfection of these constructs results in nuclear protein aggregation, filamentous nuclear inclusions, and an increase in cell death. These inclusions are ubiquitinated and recruit Hsp70. Coexpressing Hsp70 decreases the percentage of cells with nuclear inclusions. Finally, we show that expressing mutant Arx in mouse brains results in neuronal nuclear inclusion formation. Our data suggest expansions in one of the ARX polyA tracts results in nuclear protein aggregation and an increase in cell death; likely underlying the pathogenesis of the associated infantile spasms and mental retardation.

Show MeSH
Related in: MedlinePlus