Epigenetic Reprogramming of Retinal Neurons

描述（由申请人提供）：视网膜变性每年影响世界各地数百万人。在过去的十年里，我的实验室研究了视网膜发育中增殖和分化的协调，以及视网膜增殖性疾病，如视网膜母细胞瘤。最近，我们有了一个惊人的发现，从根本上改变了我们对视网膜发育的分子和细胞机制的理解，也可能对一些视网膜变性患者恢复视力的努力产生重大影响。我们发现单个视网膜母细胞瘤肿瘤细胞同时表达多种发育程序。这是通过由RB 1蛋白直接或间接调节的表观遗传程序的失调而发生的。为了进一步探索这一令人兴奋的发现，我们开发了一种新的实验系统，通过使用4个因子（Oct 4，Klf 4，Sox 2和Myc）和体细胞核移植来量化单个视网膜神经元的表观遗传重编程。我们发现，视网膜细胞类型之间重编程的表观遗传障碍存在显着差异，并且它们具有发育阶段特异性。此外，我们使用Sasai三维培养系统首次显示小鼠iPSCs可以形成视杯和分化的视网膜。来自这些实验的最令人兴奋的结果之一是，我们的源自视网膜神经元的iPSC系通过前神经外胚层特化绕过正常过渡。相反，它们保留视网膜表观遗传记忆，并专门形成分化成层状视网膜的视网膜祖细胞。来自视网膜神经元的iPSC保留其表观遗传视网膜记忆至少50代，而从遗传上相同的MEF产生的iPSC很少在该系统中产生视网膜。我们现在已经证明，来自视网膜iPSC的感光细胞前体可以整合到视网膜中;因此，从成熟的视网膜神经元产生的iPSC可以为细胞替代疗法提供感光细胞前体的可再生来源，以恢复患有视网膜变性的人的视力。这项创新的研究提案将促进我们对表观遗传学在视网膜发育中的作用的理解，并开始阐明参与该过程的分子机制和细胞类型特异性靶基因。它还将为未来的光受体替代疗法治疗视网膜变性的临床试验提供关于使用视网膜衍生iPSC的关键临床前数据。

DESCRIPTION (provided by applicant): Retinal degeneration affects millions of people around the world each year. For the past decade, my lab has studied the coordination of proliferation and differentiation in the developing retina and in proliferative diseases of the retna such as retinoblastoma. Recently, we made a startling discovery that has fundamentally altered our understanding of the molecular and cellular mechanisms of retinal development and may also have a major impact on efforts to restore vision in some patients with retinal degeneration. We discovered that individual retinoblastoma tumor cells express multiple developmental programs simultaneously. This occurs through deregulation of the epigenetic programs that are directly or indirectly regulated by the RB1 protein. To explore this exciting finding further, we developed a novel experimental system to quantify the epigenetic reprogramming of individual retinal neurons by using 4 factors (Oct4, Klf4, Sox2, and Myc) and somatic cell nuclear transfer. We discovered that the epigenetic barriers to reprogramming dramatically differ across retinal cell types, and they are developmental stage-specific. Moreover, we have used the Sasai 3-dimensional culture system to show for the first time that mouse iPSCs can form the optic cup and differentiated retinae. One of the most exciting results from these experiments is that our iPSC lines derived from retinal neurons bypass the normal transition through anterior neuroectodermal specification. Instead, they retain retinal epigenetic memory and form exclusively retinal progenitor cells that differentiate into laminated retinae. The iPSCs derived from retinal neurons retain their epigenetic retinal memory for at least 50 passages, whereas iPSCs generated from genetically identical MEFs rarely produce retinae in this system. We have now shown that the photoreceptor precursors derived from retinal iPSCs can integrate into the retina; thus, iPSCs generated from mature retinal neurons may provide a renewable source of photoreceptor precursors for cell-replacement therapies to restore vision in those who suffer from retinal degeneration. This innovative research proposal will advance our understanding of the role of epigenetics in retinal development and begin to elucidate the molecular mechanisms and cell type-specific target genes involved in that process. It will also provide crucial preclinial data on the use of retinal-derived iPSCs for future clinical trials of photoreceptor-replacement therapy to treat retinal degeneration.