Wallace Deborah M, Donovan Maryanne, Cotter Thomas G
Cell Development and Disease Laboratory, Department of Biochemistry, Biosciences Institute, University College Cork, Cork, Ireland.
Invest Ophthalmol Vis Sci. 2006 Jul;47(7):2765-72. doi: 10.1167/iovs.05-1383.
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.
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.
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).
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.
细胞凋亡是一种程序性细胞死亡形式，对组织发育和组织稳态的维持至关重要。凋亡蛋白酶激活因子（Apaf）-1和半胱天冬酶3在出生后视网膜发育过程中表达下调。这些基因表达的降低可能是一种关键的生存策略，用于防止意外的细胞死亡。本研究的目的是探讨参与Apaf-1和半胱天冬酶3下调的转录机制。
采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和半定量聚合酶链反应检测发育过程中Apaf-1和半胱天冬酶3的表达水平。采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL）和DNA梯状条带分析鉴定凋亡细胞。
视网膜发育过程中Apaf-1和半胱天冬酶3的表达降低与对凋亡刺激的敏感性降低相关。此外，用组蛋白去乙酰化酶（HDAC）抑制剂曲古抑菌素A（TSA）处理导致视网膜广泛的高乙酰化，同时伴有Apaf-1和半胱天冬酶3的转录激活以及出生后第5天（P）和第15天视网膜随后的凋亡诱导。然而，抑制HDAC活性不足以在成熟视网膜（P60）中诱导凋亡。
总体而言，这些结果得出结论，发育中的视网膜中Apaf-1和半胱天冬酶3的下调与对凋亡刺激的敏感性降低相关，并确保视网膜的存活。此外，作者提出，在出生后早期视网膜中，HDAC活性控制这些基因的转录调控。Apaf-1和半胱天冬酶3的上调与凋亡诱导同时发生。在成熟视网膜中未观察到这些基因的转录激活或凋亡诱导。
