Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin, USA.
Invest Ophthalmol Vis Sci. 2012 Mar 15;53(3):1428-35. doi: 10.1167/iovs.11-8872. Print 2012 Mar.
Downregulation of normal gene expression in dying retinal ganglion cells has been documented in both acute and chronic models of optic nerve disease. The authors examined the mechanism and timing of this phenomenon in DBA/2J mice, using genetically modified substrains of this inbred line.
DBA/2J mice, doubly congenic for the Bax mutant allele and the ganglion cell reporter gene Fem1c(Rosa3) (R3), were evaluated to elucidate the timing of loss of normal gene expression during the apoptotic process. The localization of histone deacetylase 3 (HDAC3) and nuclear histone H4 acetylation were examined by immunofluorescence in dying cells. The role of HDACs in gene silencing during glaucoma was interrogated using the global HDAC inhibitor trichostatin A (TSA).
Silencing of the R3 allele occurred in Bax(-/-) ganglion cells, indicating that this process preceded the committed step of the intrinsic apoptotic pathway. Weekly TSA treatment, between the ages of 6 and 10 months, was able to attenuate the loss of R3 expression in the retina, but had no effect on optic nerve degeneration. Dying cells in aging DBA/2J mice exhibited nuclear localization of HDAC3 and a decrease in the level of H4 acetylation.
Retinal ganglion cells exhibit a loss of normal gene expression as an early (pre-BAX involvement) part of their apoptotic program during glaucomatous degeneration. This process can be ameliorated, but not completely blocked, using HDAC inhibitors. Epigenetic changes to active chromatin, such as deacetylation, may be mediated by HDAC3 in dying neurons.
在急性和慢性视神经病变模型中，已经记录到濒死的视网膜神经节细胞中正常基因表达的下调。作者使用这种近交系的基因修饰亚系，检查了 DBA/2J 小鼠中这种现象的机制和时间进程。
使用 Bax 突变等位基因和神经节细胞报告基因 Fem1c（Rosa3）（R3）双重纯合的 DBA/2J 小鼠，阐明凋亡过程中正常基因表达丧失的时间进程。通过免疫荧光在濒死细胞中检测组蛋白去乙酰化酶 3（HDAC3）和核组蛋白 H4 乙酰化的定位。使用全局 HDAC 抑制剂曲古抑菌素 A（TSA）研究 HDAC 在青光眼过程中的基因沉默作用。
R3 等位基因的沉默发生在 Bax（-/-）神经节细胞中，表明该过程发生在内在凋亡途径的决定性步骤之前。6 至 10 月龄时每周 TSA 处理能够减轻视网膜中 R3 表达的丧失，但对视神经变性没有影响。衰老 DBA/2J 小鼠中的濒死细胞表现出 HDAC3 的核定位和 H4 乙酰化水平降低。
在青光眼变性过程中，视网膜神经节细胞表现出正常基因表达的丧失，作为其凋亡程序的早期（早于 BAX 参与）部分。使用 HDAC 抑制剂可以改善，但不能完全阻止该过程。活性染色质的表观遗传变化，如去乙酰化，可能由垂死神经元中的 HDAC3 介导。
