Abstract
It is controversial whether the mode of cell death induced by CAG repeat diseases
is apoptotic. One technical problem that affects this issue is that the very methods
used for DNA injection may induce artificial apoptosis. A recent study demonstrated
that the functions of RNA polymerase II are disrupted in spinocerebellar ataxia type
1 (SCA 1) pathology, one of the CAG repeat diseases, and that α-amanitin can inhibit
the activity of RNA polymerase. To examine the cell death mechanisms involved in CAG
repeat diseases, we treated cultured rat neurons with α-amanitin to avoid the artifacts
caused by DNA transfection. Mature and immature rat neurons were treated with α-amanitin
for 4–6 days and the effects of the treatment on the elongation of neurites, the distribution
or morphology of organelles, and the nature of cell death were assessed by immunocytochemistry
and quantitative analysis. Neurons exhibited a disruption of neurite elongation and
eventually died by day 15 of the treatment. However, apoptosis was not detected. When
the neurons survived well, but showed altered neurites, Golgi complexes and lysosomes
exhibited changes in their normal intracellular distribution or morphology, but the
endoplasmic reticulum and mitochondria did not. The distribution of phosphorylated
Trk receptors was also disrupted in the neurites of treated neurons. The signal intensity
of the dynein intermediate chain was markedly decreased in the treated neurons. Thus,
organelle transport systems, particularly a minus-end-directed microtubule-dependent
pathway, would be disrupted by the inhibition of RNA polymerase, and this change is
likely to be an early event involved in SCA 1 pathology.
Keywords
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Article info
Publication history
Accepted:
January 23,
2007
Received in revised form:
January 18,
2007
Received:
May 26,
2006
Identification
Copyright
© 2007 Elsevier B.V. Published by Elsevier Inc. All rights reserved.
