|
|
|
|
|
|
|
||
Department of Ophthalmology and Visual Sciences, Washington University Medical School, St. Louis, Missouri 63110-1093
During development, the lens of the eye becomes transparent, in part because of the elimination of
nuclei and other organelles from the central lens fiber
cells by an apoptotic-like mechanism. Using confocal
microscopy we showed that, at the border of the organelle-free zone (OFZ), fiber cell nuclei became suddenly irregular in shape, with marginalized chromatin.
Subsequently, holes appeared in the nuclear envelope
and underlying laminae, and the nuclei collapsed into
condensed, spherical structures. Nuclear remnants, containing DNA, histones, lamin B2, and fragments of
nuclear membrane, were detected deep in the OFZ.
We used in situ electrophoresis to demonstrate that
fragmented DNA was present only in cells bordering the OFZ. Confocal microscopy of terminal deoxynucleotidyl transferase (TdT)-labeled lens slices confirmed
that DNA fragmentation was a relatively late event in
fiber differentiation, occurring after the loss of the nuclear membrane. DNA fragments with 3
-OH or 3-PO4
ends were not observed elsewhere in the lens under
normal conditions, although they could be produced by
pretreatment with DNase I or micrococcal nuclease, respectively. Dual labeling with TdT and an antibody
against protein disulfide isomerase, an ER-resident protein, revealed a distinct spatial and temporal gap between the disappearance of ER and nuclear membranes and the onset of DNA degradation. Thus, fiber
cell chromatin disassembly differs significantly from
classical apoptosis, in both the sequence of events and
the time course of the process. The fact that DNA degradation occurs only after the disappearance of mitochondrial, ER, and nuclear membranes suggests that
damage to intracellular membranes may be an initiating event in nuclear breakdown.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
