Hippo-YAP signaling controls lineage differentiation of mouse embryonic stem cells through modulating the formation of super-enhancers

Abstract

Hippo-YAP signaling pathway functions in early lineage differentiation of pluripotent stem cells, but the detailed mechanisms remain elusive. We found that knockout (KO) of Mst1 and Mst2, two key components of the Hippo signaling in mouse embryonic stem cells (ESCs), resulted in a disruption of differentiation into mesendoderm lineage. To further uncover the underlying regulatory mechanisms, we performed a series of ChIP-seq experiments with antibodies against YAP, ESC master transcription factors and some characterized histone modification markers as well as RNA-seq assays using wild type and Mst KO samples at ES and day 4 embryoid body stage respectively. We demonstrate that YAP is preferentially co-localized with super-enhancer (SE) markers such as Nanog, Sox2, Oct4 and H3K27ac in ESCs. The hyper-activation of nuclear YAP in Mst KO ESCs facilitates the binding of Nanog, Sox2 and Oct4 as well as H3K27ac modification at the loci where YAP binds. Moreover, Mst depletion results in novel SE formation and enhanced liquid-liquid phase-separated Med1 condensates on lineage associated genes, leading to the upregulation of these genes and the distortion of ESC differentiation. Our study reveals a novel mechanism on how Hippo-YAP signaling pathway dictates ESC lineage differentiation.

YAP1 Regulates the Self-organized Fate Patterning of hESCs-Derived Gastruloids

“…Lineage-specific YAP1 KO mutants have revealed specific roles of YAP1 in the cell-fate decisions of the zygote 19 and specification of the trophectoderm and epiblast-cells [20][21][22] . Similarly, we and others have described important roles of YAP1 during differentiation of epiblast-like cells (hESCs and mESCs) [23][24][25][26][27][28] . For instance, YAP1 represses mesoendodermal (ME) differentiation in hESCs 24,25,29 by regulating the activity of the NODAL and WNT3 pathways 24,26 .…”

Context-dependent roles of YAP/TAZ in stem cell fates and cancer

“…During differentiation, Rassf1a promotes the phosphorylation of Yap1, which causes it to switch binding partners from Tead2 and β-catenin to p73 and initiate lineage-specific transcriptional programs [57]. However, not all three germ layers are equally favored, and it seems that in mice, Yap1 favors the ectoderm lineage [58]. Mechanistically, activation of Yap1 (for example, via KO of upstream Hippo kinases Mst1/2) leads to the formation of novel phase-separated Med1-positive super-enhancers that promote the expression of ectoderm markers [55] while downregulating mesendoderm markers [58].…”

“…However, not all three germ layers are equally favored, and it seems that in mice, Yap1 favors the ectoderm lineage [58]. Mechanistically, activation of Yap1 (for example, via KO of upstream Hippo kinases Mst1/2) leads to the formation of novel phase-separated Med1-positive super-enhancers that promote the expression of ectoderm markers [55] while downregulating mesendoderm markers [58]. In humans, YAP appears to inhibit the cardiac fate as culturing YAP -/-hESCs in Activin A results in the spontaneous derivation of beating cardiomyocytes.…”

Super-enhancers: a new frontier for epigenetic modifiers in cancer chemoresistance

“…Insulated by the strong boundaries with lower chromatin interaction frequencies, SEs can only target genes within the SDs, thus preventing abnormal SE-promoter interactions and transcriptional activation [80,82]. In addition, mediated by lowcomplexity disordered regions or intrinsically disordered regions, SEs can form membraneless phase-separated structures, which concentrate biologically and physically similar proteins or other molecules, thus enabling efficient transcription [83]. The transcriptional coactivators BRD4 and mediator of RNA Pol-II transcription subunit 1 (MED1) were found to form condensates at SEs, thereby compartmentalizing and concentrating the transcription apparatus [84].…”