PDF(Pubmed)
Abstract：
Endoplasmic reticulum (ER) membrane protein complex (EMC) is required for the co-translational insertion of newly synthesized multi-transmembrane proteins. Compromised EMC function in different cell types has been implicated in multiple diseases. Using inducible genetic mouse models, we revealed defects in retinal vascularization upon endothelial cell (EC) specific deletion of Emc1, the largest subunit of EMC. Loss of Emc1 in ECs led to reduced vascular progression and vascular density, diminished tip cell sprouts, and vascular leakage. We then performed an unbiased transcriptomic analysis on human retinal microvascular endothelial cells (HRECs) and revealed a pivotal role of EMC1 in the β-catenin signaling pathway. Further in-vitro and in-vivo experiments proved that loss of EMC1 led to compromised β-catenin signaling activity through reduced expression of Wnt receptor FZD4, which could be restored by lithium chloride (LiCl) treatment. Driven by these findings, we screened genomic DNA samples from familial exudative vitreoretinopathy (FEVR) patients and identified one heterozygous variant in EMC1 that co-segregated with FEVR phenotype in the family. In-vitro expression experiments revealed that this variant allele failed to facilitate the expression of FZD4 on the plasma membrane and activate the β-catenin signaling pathway, which might be a main cause of FEVR. In conclusion, our findings reveal that variants in EMC1 gene cause compromised β-catenin signaling activity, which may be associated with the pathogenesis of FEVR.
摘要：
内质网（ER）膜蛋白复合物（EMC）是新合成的多跨膜蛋白的共翻译插入所必需的。不同细胞类型的EMC功能受损与多种疾病有关。使用诱导型遗传小鼠模型，我们揭示了EMC1（EMC的最大亚基）的内皮细胞（EC）特异性缺失后视网膜血管形成的缺陷。ECs中Emc1的丢失导致血管进展和血管密度降低，尖端细胞芽减少，和血管渗漏。然后，我们对人类视网膜微血管内皮细胞（HRECs）进行了无偏转录组学分析，并揭示了EMC1在β-catenin信号通路中的关键作用。进一步的体外和体内实验证明，EMC1的缺失通过降低Wnt受体FZD4的表达而导致β-连环蛋白信号活性受损，这可以通过氯化锂（LiCl）处理来恢复。在这些发现的推动下，我们筛选了家族性渗出性玻璃体视网膜病变(FEVR)患者的基因组DNA样本,并鉴定了EMC1中的一个杂合变异体,该变异体在家族中与FEVR表型共分离.体外表达实验表明，该变异等位基因未能促进FZD4在质膜上的表达，并激活β-catenin信号通路，这可能是FEVR的主要原因。总之,我们的发现表明，EMC1基因的变异导致β-连环蛋白信号活性受损，这可能与FEVR的发病机制有关。
