ARID1A and PI3-Kinase pathway mutations in the endometrium drive epithelial transdifferentiation and collective invasion [12Z_ATAC-seq]. ARID1A and PI3-Kinase pathway mutations in the endometrium drive epithelial transdifferentiation and collective invasion [12Z_ATAC-seq]

ARID1A and PI3-Kinase (PI3K) pathway alterations are common in neoplasms originating from the uterine endometrium. Here we show that monoallelic loss of ARID1A in the mouse endometrial epithelium is sufficient for vaginal bleeding when combined with PI3K activation. Sorted mutant epithelial cells display gene expression and promoter chromatin signatures associated with epithelial-to-mesenchymal transition (EMT). We further show that ARID1A is bound to promoters with open chromatin, but ARID1A loss leads to increased promoter chromatin accessibility and the expression of EMT genes. PI3K activation partially rescues the mesenchymal phenotypes driven by ARID1A loss through antagonism of ARID1A target gene expression, resulting in partial EMT and invasion. We propose that ARID1A normally maintains endometrial epithelial cell identity by repressing mesenchymal cell fates, and that coexistent ARID1A and PI3K mutations promote epithelial transdifferentiation and collective invasion. Broadly, our findings support a role for collective epithelial invasion in the spread of abnormal endometrial tissue. Overall design: 12Z endometriotic epithelial cells transfected with either siARID1A or non-targeting siRNA control were assayed 48 hours post-transfection for genome-wide chromatin accessibility via ATAC.

ARID1A与磷脂酰肌醇3-激酶（PI3-Kinase, PI3K）通路异常在子宫内膜来源的肿瘤中较为常见。本研究证实，小鼠子宫内膜上皮中ARID1A的单等位基因缺失联合PI3K激活即可引发阴道出血。分选获得的突变上皮细胞呈现出与上皮间质转化（epithelial-to-mesenchymal transition, EMT）相关的基因表达及启动子染色质特征。我们进一步发现，ARID1A可结合开放染色质状态的启动子，而ARID1A缺失会导致启动子染色质开放性升高，并上调EMT相关基因的表达。PI3K激活可通过拮抗ARID1A靶基因的表达，部分挽救ARID1A缺失所诱导的间质表型，进而引发部分上皮间质转化及侵袭行为。我们提出，ARID1A通常通过抑制间质细胞命运来维持子宫内膜上皮细胞的身份特征，而ARID1A与PI3K的共突变会促进上皮转分化及集体侵袭。总体而言，本研究结果支持集体上皮侵袭在异常子宫内膜组织播散中的作用。实验设计：将12Z子宫内膜异位上皮细胞分别转染siARID1A或非靶向siRNA对照，于转染48小时后通过ATAC实验检测全基因组染色质开放性。