Suppression of asthmatic phenotype and altered lipid metabolism in mice lacking zona pellucida binding protein 2

The human chromosomal region 17q12-q21 is associated with childhood asthma. It harbors 5 protein-coding genes, of which ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3) and gasdermin B (GSDMB) are the top causal gene candidates. Emerging evidence suggests that the promoter region of another gene, the zona pellucida binding protein 2 (ZPBP2), located more than 50kb proximal to ORMDL3 may be critical for its transcriptional regulation influencing susceptibility to asthma. To test this hypothesis, we examined the lung phenotypes, liver transcriptomes and lipid metabolism of Zpbp2 knock-out (KO) mice. We found that in comparison to wild type (WT) mice, Zpbp2 KO mice sensitized with allergen ovalbumin (OVA) had reduced bronchial reactivity. The Zpbp2 KO mice also had altered lipid metabolism with a 3-fold decrease in the levels of docosahexaenoic acid (DHA), increased body weight and changes in the expression of the adipocytokine signaling pathway gene peroxisome proliferator activated receptor alpha (Pparα). The Zpbp2 deletion was also associated with increased DNA methylation at the Zpbp2 promoter/enhancer region, reminiscent of the methylation of the orthologous region in humans, and reduced expression of Ormdl3 in liver. The sum of our results implies that the Zpbp2 gene is involved in the regulation of airway hypersensitivity and lipid metabolism, either directly or through a cis-regulatory effect on Ormdl3. RNA-sequencing assays were conducted on RNA from livers of 3 C57BL/6J and 3 B6.Zpbp2-/- males.人类17号染色体q12-q21区域与儿童哮喘相关。该区域包含5个蛋白编码基因，其中鞘磷脂生物合成调节因子3（ORMDL sphingolipid biosynthesis regulator 3，ORMDL3）与焦亡素B（GSDMB）为最主要的致病候选基因。越来越多的研究证据表明，另一个基因——透明带结合蛋白2（ZPBP2）的启动子区域，其位置距ORMDL3近端超过50kb，可能通过转录调控影响哮喘易感性。 为验证这一假说，我们对Zpbp2基因敲除（KO）小鼠的肺部表型、肝脏转录组及脂质代谢进行了检测。结果显示，与野生型（WT）小鼠相比，经过敏原卵清蛋白（OVA）致敏的Zpbp2 KO小鼠支气管反应性降低。Zpbp2 KO小鼠同时存在脂质代谢异常：二十二碳六烯酸（DHA）水平下降3倍，体重增加，且脂肪细胞因子信号通路相关基因过氧化物酶体增殖物激活受体α（Pparα）的表达发生改变。Zpbp2基因敲除还与Zpbp2启动子/增强子区域的DNA甲基化水平升高相关，这与人类同源区域的甲基化特征一致，同时肝脏中Ormdl3的表达水平降低。 综合本研究结果可知，Zpbp2基因可通过直接作用或对Ormdl3的顺式调控作用，参与气道高反应性及脂质代谢的调控。本研究对3只C57BL/6J品系雄性小鼠及3只B6.Zpbp2基因敲除雄性小鼠的肝脏RNA开展了RNA测序（RNA-seq）实验。