Epigenetic Silencing of HSA21 in Down Syndrome

总结 唐氏综合征是由21号染色体上的一个基因子集（HSA21）的三倍体引起的。人士 DS均表现出一定程度的智力迟钝（MR）。MR已被归因于 脑发育（即神经发生）受损以及细胞进行性死亡， 突触发生（即神经变性）。三条HSA21染色体之一的沉默拯救了DS 但是这种治疗方法实际上受到基因组编辑的效率和能力的限制。 专门针对单个HSA21染色体。我们的初步研究表明， 改良的CRISPR方法大大增强了基因组材料在HSA 21上的整合， 还设计了一种特异性靶向单个HSA21拷贝的方法。我们现建议 实验以评估这些方法在人DS iPSC系中的效率，并遵循其结果。 分化成神经和少突胶质细胞状态。我们还将讨论这些干预措施的程度 与其同基因对应物相比，使DS系内的遗传和表观遗传表达正常化 以及DS细胞是否从功能角度（增殖、细胞死亡、线粒体损伤）被拯救。 功能和氧化应激）。总的来说，如果成功，这些研究将克服两个基本障碍 需要从表观遗传学的方法来治疗DS（和其他染色体异常）， 潜在动物研究的基础。

Summary Down syndrome arises from the triplication of a subset of genes on chromosome 21 (HSA21). Individuals with DS uniformly demonstrate some degree of mental retardation (MR). The MR has been attributed to impairments in brain development (i.e. neurogenesis) as well as progressive cell death with altered synaptogenesis (i.e. neurodegeneration). Silencing of one of the three HSA21 chromosomes rescues the DS phenotype but such a therapeutic approach is limited practically by the efficiency of genomic editing and ability to specifically target a single HSA21 chromosome. Our preliminary studies show the feasibility of a novel modified CRISPR approach which greatly enhances the integration of genomic material on HSA21 and we have also devised a means with which to specifically target a single HSA21 copy. We now propose experiments to assess the efficiency of these approaches in human DS iPSC lines and following their differentiation into neural and oligodendrocyte states. We will also address to what extent these interventions normalize both genetic and epigenetic expression within the DS lines compared to their isogenic counterparts and whether the DS cells are rescued from a functional perspective (proliferation, cell death, mitochondrial function and oxidative stress). Overall, if successful, these studies will overcome two fundamental hurdles needed to treat DS (and other chromosomal abnormalities) from an epigenetic approach and lay the foundation for potential animal studies.