ID1 and CEBPA coordinate epidermal progenitor cell

The regulatory circuits that coordinate epidermal differentiation during development are still not fully understood. Here we report that the transcriptional regulator ID1 is enriched in basal epidermal progenitor cells and find ID1 expression to be diminished upon differentiation. In utero silencing of Id1 impairs progenitor cell proliferation, leads to precocious delamination of targeted progenitor cells and enables differentiated keratinocytes to retain progenitor markers and characteristics. Transcriptional profiling suggests ID1 acts by mediating adhesion to the basement membrane while inhibiting spinous layer differentiation. Co-immunoprecipitation reveals ID1 binding to transcriptional regulators of the class I bHLH family. We localize bHLH Tcf3, Tcf4 and Tcf12 to epidermal progenitor cells during epidermal stratification and established TCF3 as a downstream effector of ID1-mediated epidermal proliferation. Finally, we identify crosstalk between CEBPA, a known mediator of epidermal differentiation, and Id1 and demonstrate that CEBPA antagonizes BMP-induced activation of Id1. Our work establishes ID1 as a key coordinator of epidermal development, acting to balance progenitor proliferation with differentiation and unveils how functional crosstalk between CEBPA and Id1 orchestrates epidermal lineage progression. Comparative gene expression profiling analysis of RNA-seq data for primary epidermal cells comparing control (shScr) with Id1 silenced (shId1) with ID1 overexpression (ID1 dox) as progenitors or upon differentiation.目前学界对发育过程中协调表皮分化的调控环路仍未完全阐明。本研究发现，转录调控因子ID1在表皮基底层祖细胞中富集，且其表达随细胞分化进程下调。宫内沉默Id1基因会损伤祖细胞的增殖能力，导致靶向祖细胞提前脱离基底膜，并使已分化的角质形成细胞保留祖细胞标志物及特性。转录组分析显示，ID1通过介导细胞与基底膜的黏附、同时抑制棘层分化发挥作用。免疫共沉淀（co-immunoprecipitation）实验证实，ID1可与I类bHLH家族的转录调控因子结合。我们发现，在表皮分层过程中，bHLH家族成员Tcf3、Tcf4及Tcf12定位于表皮祖细胞，并确定TCF3是ID1介导的表皮增殖过程的下游效应因子。最后，本研究发现CEBPA——一种已知的表皮分化调控介质——与Id1存在功能性串扰，并证实CEBPA可拮抗BMP诱导的Id1基因激活。本研究确立了ID1作为表皮发育关键调控因子的地位，其通过平衡祖细胞增殖与分化进程发挥功能，并揭示了CEBPA与Id1之间的功能性串扰如何调控表皮谱系的演进。本研究针对原代表皮细胞开展了比较基因表达谱分析，所用RNA-seq数据涵盖三组样本：对照组（shScr）、Id1基因敲低组（shId1）以及ID1诱导过表达组（ID1 dox），分别采集了祖细胞状态及分化诱导后的样本。