Toward Understanding the Role of the Polycomb Complex in Skin Control

项目摘要 毛囊干细胞具有终生生成新毛囊的独特能力。 有机体的。当新的毛囊生长时，hfSCs被激活；它们增殖以促进 产生一个新的卵泡，并迅速恢复静止。虽然这一过渡的手段 静止和激活是受调控的，仍然难以捉摸，识别这些过程至关重要，因为 HFSC的异常激活与脱发、衰老和癌症有关。 多梳抑制复合体(PRC)1和2是重要的染色质转录调节因子 用来维持干细胞的特性。通过进行功能丧失研究，我们发现，在 HfSCs导致hfSCs过早激活并诱导毛发生长，而prc2的缺失则导致 导致HFSC静息时间延长和毛发生长延迟。这些数据显示了关键和对立的角色 多梳复合体对肾小管上皮细胞静止的调节作用。这是一个耐人寻味的观察结果，因为Prc1和 PRC2被认为是共同作用的，在大多数系统中，失去PRC1或PRC2会导致相同的结果 表型。我们假设Prc1和PrC2维持着静止和激活的微妙平衡， 但他们的作用机制与之前报道的不同。 在目标1中，我们将确定PRC2微调HFSC静止的分子机制。通过 进行RNA-seq，我们鉴定了Wnt抑制物Notom和SFRP2，以及BMP受体Bmpr1b 在PRC2中上调-空HFSC。因为已知Wnt抑制和BMP激活可促进肾小管上皮细胞 静止期，我们假设这些基因的表达导致了HFSC激活的延迟。在这里，我们将 分析Notom、SFRP2和/或Bmpr1b的表达是否促进肾小管上皮细胞的静息和重现 PrC2缺失的表型。在目标2中，我们将研究压制性的PRC1和PRC2之间的合作 在控制hfsc方面的功能。我们最近的研究表明，PrC1和PrC2具有相加的基因抑制作用 这两个角色的缺失才会导致Prc1/2靶基因的完全抑制。在这里，我们将消融 HfSCs中PrC1和PrC2复合体的抑制功能，分析其表型，并确定 HfSCs Prc1/2调控的分子机制。在目标3中，我们将研究非规范的基因激活。 Prc1在促进肾小管上皮细胞静止中的作用因为Prc1和PrC2的缺失表现出相反的表型， 我们分别假设PRC1的功能独立于PRC2来促进基因的表达 影响HFSC静止的因素。在这里，我们将通过以下方式确定hfSCs中受prc1控制的基因 进行RNA-SEQ和CHIP-SEQ研究，并测试上述基因下调是否会导致 早熟的HFSC激活。这些研究的完成将确定Polycomb介导的基因如何 调节微调了hfSCs静止和激活之间的微妙平衡。

Project Summary Hair follicle stem cells (HFSCs) have the unique ability to generate new hair follicles throughout the lifetime of an organism. When the growth of a new hair follicle occurs, HFSCs are activated; they proliferate to fuel the production of a new follicle and quickly return to quiescence. While the means by which this transition between quiescence and activation is regulated remain elusive, identification of these processes is critical, because abnormal HFSC activation has implications in hair loss, aging, and cancer. Polycomb repressive complexes (PRC) 1 and 2 are chromatin transcriptional regulators that are essential for maintaining stem cell identity. By performing loss-of-function studies, we showed that loss of PRC1 in HFSCs results in premature activation of HFSCs and the induction of hair growth, whereas loss of PRC2 leads to a prolonged HFSC quiescence and delayed hair growth. These data show the critical and opposing roles of Polycomb complexes in regulation of HFSC quiescence. This is an intriguing observation because PRC1 and PRC2 are thought to act together, and, in most systems, the loss of either PRC1 or PRC2 results in identical phenotypes. We hypothesize that PRC1 and PRC2 maintain the delicate balance of quiescence and activation, but their mechanism of action is different than what was previously reported. In Aim 1, we will determine the molecular mechanisms by which PRC2 fine-tunes HFSC quiescence. By performing RNA-seq, we identified that Wnt inhibitors Notum and Sfrp2, and BMP receptor Bmpr1b are upregulated in the PRC2-null HFSC. Because Wnt inhibition and Bmp activation are known to promote HFSC quiescence, we hypothesize that expression of these genes leads to delayed HFSC activation. Here, we will analyze whether expression of Notum, Sfrp2, and/or Bmpr1b promotes HFSC quiescence and recapitulates the PRC2-null phenotype. In Aim 2, we will examine cooperation between repressive PRC1 and PRC2 functions in control of HFSCs. Our recent studies showed that PRC1 and PRC2 have additive gene-repressive roles and that only loss of both leads to complete de-repression of PRC1/2 target genes. Here, we will ablate repressive functions of both PRC1 and PRC2 complexes in HFSCs, analyze the phenotype, and determine molecular mechanisms of PRC1/2 control of HFSCs. In Aim 3, we will examine noncanonical gene-activating roles of PRC1 in promoting HFSC quiescence. Because loss of PRC1 and PRC2 show opposing phenotypes, respectively, we hypothesize that PRC1 functions independently of PRC2 to promote the expression of genes that influence HFSC quiescence. Here, we will identify genes that are under the control of PRC1 in HFSCs by performing RNA-seq and ChIP-seq studies and test whether downregulation of said genes results in precocious HFSC activation. The completion of these studies will define how Polycomb-mediated gene regulation fine-tunes the delicate balance between quiescence and activation in HFSCs.