Usp22 controls multiple signaling pathways that are essential for vasculature formation in the mouse placenta

Usp22, a component of the SAGA complex, is over expressed in highly aggressive cancers, but the normal functions of this deubiquitinase are not well defined. We determined that loss of Usp22 in mice results in embryonic lethality due to defects in extra-embryonic placental tissues and failure to establish proper vascular interactions with the maternal circulatory system. These phenotypes arise from abnormal gene expression patterns that reflect defective kinase signaling, including TGFbeta and several receptor tyrosine kinase (RTK) pathways. Usp22 deletion in endothelial cells and pericytes induced from embryonic stem cells also hinders these signaling cascades with detrimental effects on cell survival and differentiation as well as ability to form vessels. Our findings provide new insights to Usp22 functions during development that may offer clues to its role in disease states. To determine changes in gene expression profile upon Usp22 loss in the developing placenta, RNA from day E9.5 placentas from wild-type and Ups22-/- mice was isolated for deep sequencing, in triplicates and duplicates respectively. Key genes identified from RNAseq were validated by qRT-PCR using RNA from the same samples that were used for sequencing.Usp22作为SAGA复合物（SAGA complex）的组成部分，在高侵袭性癌症中呈过表达状态，但目前对该去泛素化酶的正常生理功能尚缺乏明确认知。本研究发现，小鼠体内Usp22缺失会引发胚胎致死，具体诱因是胚外胎盘组织存在发育缺陷，且无法与母体循环系统建立正常的血管交互联系。上述表型源于异常的基因表达模式，该模式反映了激酶信号通路的功能异常，包括转化生长因子β（TGFbeta）通路及多种受体酪氨酸激酶（receptor tyrosine kinase, RTK）通路。在由胚胎干细胞诱导生成的内皮细胞与周细胞中敲除Usp22，同样会阻滞此类信号级联反应，对细胞存活、分化及血管形成能力产生不利影响。本研究结果为Usp22在发育过程中的功能提供了全新见解，或可为揭示其在疾病状态中的作用提供重要线索。为探究发育胎盘中Usp22缺失后基因表达谱的变化，我们分别从野生型与Usp22^-/-小鼠的E9.5天胎盘中提取RNA进行深度测序，其中野生型样本设置三次生物学重复，Usp22敲除型样本设置两次生物学重复。从RNA测序（RNA-seq）结果中鉴定得到的关键基因，采用与测序所用相同的RNA样本，通过qRT-PCR（quantitative real-time reverse transcription PCR）完成了验证。