Transcription factor NKX3-1 is required for reprogramming to pluripotency and can replace OCT4 in mouse and human iPSC induction [ATAC-seq]

Resolution of early molecular events preceding endogenous OCT4 activation is critical to understanding the mechanism of reprogramming somatic cells to induced pluripotent stem cells (iPSCs), yet capturing transient regulators at the onset of reprogramming is difficult in heterogeneous populations of asynchronously reprogramming fibroblasts following four-factor transduction. To address this need, we used a heterokaryon system to identify an early and transiently expressed homeobox transcription factor, NKX3-1. Upon knockdown of NKX3-1, iPSC reprogramming is abrogated. Further, we identify that NKX3-1 functions downstream of the IL6-STAT3 regulatory network to activate endogenous OCT4. Importantly, we show that NKX3-1 can substitute for exogenous OCT4 to reprogram both mouse and human fibroblasts at comparable efficiencies generate fully pluripotent stem cells. Our findings establish an essential role for NKX3-1, previously known as a prostate-specific tumor suppressor, in iPSC reprogramming. ATAC-seq timecourse of heterokaryon reprogramming

解析内源性OCT4激活前的早期分子事件，是阐明体细胞重编程为诱导多能干细胞（iPSCs）机制的核心前提；但在经四因子转导后处于异步重编程状态的异质性成纤维细胞群体中，捕获重编程起始阶段的瞬时调控因子仍存在极大挑战。为应对这一科研需求，本研究借助异核体系统，鉴定出一种早期瞬时表达的同源盒转录因子NKX3-1。敲低NKX3-1会导致iPSC重编程过程完全受阻。进一步研究表明，NKX3-1在IL6-STAT3调控网络的下游发挥功能，从而激活内源性OCT4。尤为重要的是，本研究证实NKX3-1可替代外源性OCT4，以相近的重编程效率将小鼠和人类成纤维细胞重编程为完全多能干细胞。本研究结果明确了此前被认定为前列腺特异性肿瘤抑制因子的NKX3-1在iPSC重编程中的必需作用。异核体重编程的ATAC-seq时序数据集