DNA Demethylation and Muller Glia Reprogramming During Retina Regeneration

描述（由申请人提供）：与哺乳动物不同，斑马鱼能够再生受损的视网膜并恢复视力。这种再生能力依赖于Muller神经胶质细胞（MG），它对视网膜损伤的反应是在去分化、增殖和最终分化为再生新的神经元和神经胶质的过程中经历多重身份转变。虽然可以诱导MG在受伤的哺乳动物视网膜中增殖，但它们不表现出多能性，并且很少再生受损的神经元。因此，了解驱动斑马鱼MG重编程到多能性的机制可能为从哺乳动物MG中产生多能性祖细胞提供新的策略。最近的研究表明，MG重编程伴随着与胚胎干细胞和视网膜祖细胞相似的基因表达程序的激活。我们假设驱动MG去分化和多能性的遗传程序由DNA甲基化控制。在动物中，DNA甲基化主要发生在CpG二核苷酸上，并控制转录调控过程，如印迹、x染色体失活、转座子沉默和基因活性的稳定沉默。基因编码区近端的DNA甲基化与基因沉默相关。重要的是，DNA甲基化的变化与基因表达程序的激活和抑制有关，这些程序发生在早期发育过程中，伴随着体细胞重编程产生诱导多能干细胞。很可能基因组甲基化在关键位置的消除和重建，

DESCRIPTION (provided by applicant): Unlike mammals, zebrafish are able to regenerate a damaged retina and restore lost sight. This regenerative ability depends on Muller glia (MG) that respond to retinal injury by undergoing multiple shifts in identity as they dedifferentiate, proliferate, and finally differentiate to regenerate new neurons and glia. Although MG can be coaxed to proliferate in the injured mammalian retina, they do not exhibit multipotency and only rarely regenerate damaged neurons. Therefore understanding the mechanisms driving zebrafish MG reprogramming to mutlipotency may suggest novel strategies for generating multipotent progenitors from mammalian MG. Recent studies suggest that MG reprogramming is accompanied by activation of gene expression programs that are similar to those acting in embryonic stem cells and retinal progenitors. We hypothesize that genetic programs driving MG dedifferentiation and multipotency are controlled by DNA methylation. In animals, DNA methylation predominantly occurs at CpG dinucleotides and controls transcriptional regulatory processes like imprinting, X-chromosome inactivation, transposon silencing, and stable silencing of gene activity. Methylation of DNA proximal to gene-coding regions is correlated with gene silencing. Importantly, changes in DNA methylation have been correlated with the activation and suppression of gene expression programs that take place during early development and accompany the reprogramming of somatic cells to yield induced pluripotent stem cells. It is likely that erasure and reestablishment of genomic methylation, at key locations, accompanies the gene expression changes that drive MG dedifferentiation and multipotency and subsequently the regeneration of new retinal cell types. Here we propose to identify regions of the MG genome that are undergoing methylation changes during retina regeneration and determine if these changes correlate with gene expression changes that have previously been characterized using microarray technology. In addition, we propose to test the hypothesis that DNA demethylation in dedifferentiating MG is an active process driven by Apobec2a and 2b proteins.