Histone deacetylase activity regulates apaf-1 and caspase 3 expression in the developing mouse retina.
OBJECTIVE
Apoptosis is a form of programmed cell death essential for both tissue development and maintenance of tissue homeostasis. Apoptosis protease activating factor (Apaf)-1 and caspase 3 are downregulated in the retina during postnatal development. The decreased expression of these genes is potentially a critical survival strategy adopted to protect against accidental cell death. The purpose of this study was to investigate the transcriptional mechanism involved in the downregulation of Apaf-1 and caspase 3.


METHODS
SDS-polyacrylamide gel electrophoresis and semiquantitative PCR were used to examine Apaf-1 and caspase 3 expression levels during development. TdT-mediated dUTP nick-end labeling (TUNEL) and DNA laddering were used to identify cells undergoing apoptosis.


RESULTS
A decrease in expression of Apaf-1 and caspase 3 during retinal development correlated with a decreased susceptibility to an apoptotic stimulus. Furthermore, treatment with a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), resulted in widespread hyperacetylation in the retina, coinciding with transcriptional activation of Apaf-1 and caspase 3 and subsequent induction of apoptosis in postnatal day (P)5 and P15 retinas. However, inhibition of HDAC activity is not sufficient to induce apoptosis in the mature retina (P60).


CONCLUSIONS
Overall, these results elicit the conclusion that downregulation of Apaf-1 and caspase 3 in the developing retina correlates with a decreased susceptibility to apoptotic stimuli and ensures the survival of the retina. Furthermore, the authors propose that, in the early postnatal retina, HDAC activity governs the transcriptional regulation of these genes. Upregulation of Apaf-1 and caspase 3 coincides with an induction of apoptosis. In the mature retina transcriptional activation of these genes or induction of apoptosis was not observed.
Wallace
Deborah M
DM
Cell Development and Disease Laboratory, Department of Biochemistry, Biosciences Institute, University College Cork, Cork, Ireland.
Donovan
Maryanne
M
Cotter
Thomas G
TG
D000107:Acetylation; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism*; D006877:Hydroxamic Acids / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012160:Retina / Q000254:growth & development* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012333:RNA, Messenger; C012589:trichostatin A; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D006655:Histone Deacetylases