Widely Interspaced Zinc Finger Motifs, Wiz, binds active promoters and CTCF-binding sites and is required for normal neural function in the mouse

Mice heterozygous for a null mutation in Widely-interspaced zinc finger, Wiz, were produced in a screen for modifiers of epigenetic reprogramming; expression of the GFP reporter transgene decreased in mutants, suggesting a role in transcriptional activation (Daxinger et al., 2013). These mice are viable and fertile, with no overt abnormalities and homozygosity for the mutation is embryonic lethal (Daxinger et al, 2013). Wiz is expressed at high levels in the brain, both in the embryo and in the adult, but there have been no reports of its role in neural tissue. To address this, ChIP-seq, using an anti-Wiz antibody, was carried out in adult cerebellum. Wiz peaks were found at tens of thousands of sites across the genome, many of which are gene promoters that show enrichment for the pioneer transcription factor CTCF. RNA-seq, using WizMommeD30/+ and Wiz+/+ mice, revealed that some genes were affected by haploinsufficiency of Wiz; ~30 in the brains of mid-gestation embryos and ~80 in adult cerebellum. Most genes that were deregulated in embryonic brain of heterozygous mutants decreased in expression and include a group of clustered protocadherin genes that were also down-regulated in adult cerebellum. The enhancer of this gene cluster has a strong Wiz peak in the ChIP-seq data and has been reported, by others, to be activated by CTCF in neurons. Examination of Wiz binding using ChIP sequencing and the result of Wiz haploinsufficiency using RNA sequencing, in mouse neural tissues.为筛选表观遗传重编程的调控因子，我们构建了携带广泛间隔锌指（Widely-interspaced zinc finger, Wiz）基因无效突变的杂合小鼠。突变体中GFP报告转基因的表达水平下调，提示Wiz在转录激活过程中发挥作用（Daxinger等，2013）。该杂合小鼠可正常存活并具有生育能力，无明显表型异常；而该突变的纯合子则会导致胚胎致死（Daxinger等，2013）。 Wiz在胚胎和成年小鼠的脑组织中均呈高表达，但目前尚无其在神经组织中功能的相关报道。 为探究这一科学问题，我们使用抗Wiz抗体对成年小鼠小脑组织开展了染色质免疫共沉淀测序（ChIP-seq）实验。全基因组范围内共鉴定到数万个Wiz结合峰，其中大部分位于基因启动子区域，且这些位点富集先锋转录因子CCCTC结合因子（CTCF）。 我们使用WizMommeD30/+杂合突变小鼠与Wiz+/+野生型小鼠开展了RNA测序（RNA-seq）实验，结果显示部分基因的表达受Wiz单倍体不足的影响：在妊娠中期胚胎的脑组织中约有30个差异表达基因，在成年小脑中则约有80个。杂合突变小鼠胚胎脑组织中大多数表达失调的基因呈现表达下调，其中包含一组成簇原钙粘蛋白基因，该组基因在成年小脑中同样呈现表达下调。该基因簇的增强子区域在ChIP-seq数据中存在显著的Wiz结合峰，且已有研究报道其在神经元中可被CTCF激活。 本数据集通过染色质免疫共沉淀测序分析了Wiz在小鼠神经组织中的结合特征，并通过RNA测序揭示了Wiz单倍体不足对小鼠神经组织基因表达的影响。