H3K9me2/me3去甲基化酶JMJD1A调控肝星状细胞活化的分子机制初探

Hepatic Stellate Cell (HSC) activation is a process in which cells change in morphology from quiescent vitamin A and lipid storing cells to activated myofibroblast-like cells which are pivotal to fibrogenesis.We previous study have found that H3K9 demethylases, jumonji-domain containing protein (Jmjd) Jmjd1a could modulate HSC activation and liver fibrosis, and further investigation showed that PPARγ, a key suppressor of HSC activaiton, was regualted by JMJD1A during HSC activaiton， and the marker by H3K9me2 in its promoter was controled by JMJD1A.It was well known that a certain life process regualted by JMJD1A usually through transcriptional regualtion on hundreds of target genes. so for further investigating the epigenetic mechanism of HSC activaiton modulated by JMJD1A.We will excavate the differential target genes of JMJD1a between quietcent and activated HSC by ChIP-Sequencing and Affymetrix microarray technology, screen the candidate target genes relative to HSC activation, and carry out the functional assay to verify that JMJD1a would regulate target genes expression by controling its marks of methyl-H3K9. Deciphering the epigenetic mechanism of HSC activation will provide a new insight into etiollogy of liver fibrosis and have implication for drug target discovery for this disease.

肝星状细胞（HSC）活化是肝纤维化发生的中心环节，是HSC由具脂肪细胞特性的静息状态转分化为肌成纤维细胞的过程。我们前期实验发现脂肪代谢调控相关H3K9me2/me3去甲基化酶JMJD1A可以调控HSC的活化进程并影响肝纤维化发生，并证明了HSC活化的关键负调控因子PPARG是其靶基因。为进一步深入探索JMJD1A调控HSC活化的表观遗传学机制，本项目将采用ChIP-Seq并结合表达谱芯片技术挖掘HSC活化前后JMJD1A差异结合调控的的候选靶基因，并通过ChIP-qPCR验证JMJD1A与靶基因区的结合及其对靶基因区核小体H3K9的去甲基化作用。同时通过RT-qPCR和Western等验证JMJD1A对靶基因的表达调控作用。以期进一步揭示JMJD1A通过调节靶基因区核小体H3K9甲基化修饰及靶基因的表达进而调控HSC活化的分子机制，丰富对HSC活化和肝纤维化表观遗传学调控规律的认识。

肝星状细胞（HSC）活化是肝纤维化发生的中心环节，是HSC 由具脂肪细胞特性的静息状态转分化为肌成纤维细胞的过程。我们前期的工作发现H3K9 组蛋白去甲基化酶JMJD1A在肝星状细胞活化与肝纤维化发生中具有调控作用，已有研究表明JMJD1A通过调控Pparα表达而参与脂肪代谢。HSC活化与脂肪细胞的转分化过程极为相似，均表现为细胞中的脂滴滴代谢为细胞转分化提供能量。PPARɣ在HSC中是调控脂肪代谢相关的分子，在静止细胞中高表达，而在HSC活化后，表达量明显降低，是维持HSC处于静止状态的一个关键的因子，也是星状细胞活化的负调控因子。因此我们提出，JMDJ1A可能通过调控Pparɣ通路实现对HSC活化的调控，基于这样的认识，在这个项目里深入研究了JMJD1A通过Pparɣ调控HSC活化的表观遗传分子机制。首先在CCl4诱导的肝纤维化小鼠模型中，通过尾静脉注射JMJD1A的干扰载体，检测肝组织的纤维化程度，发现JMJD1A干扰组的纤维化程度明显增强。其次在大鼠HSC活化过程中以及人的HSC细胞系LX-2中，通过外源高表达或干扰JMJD1A后，检测到Pparɣ的表达变化与JMJD1A表达变化相一致；另外，敲低JMJD1A表达后，JMJD1A 启动子区的H3K9me2甲基化水平增高，说明JMJD1A通过调控Pparɣ基因区H3K9甲基化水平，调控基因的表达，进而调控HSC活化及纤维化进程。此项研究丰富了HSC 活化和肝纤维化表观遗传学调控规律的认识。