Hbxip (Lamtor5) is essential for embryogenesis and regulates embryonic stem cell differentiation through activating mTORC1

Hbxip, also named Lamtor5, has been well characterized as a transcriptional coactivator in various cancers. However, the role of Hbxip in normal development remains unexplored. Here, we demonstrated that homozygous knockout of Hbxip leads to embryonic lethality, with retarded growth around E7.5. Using Hbxip knockout embryonic stem cells (ESCs), we showed that depletion of Hbxip compromises the self-renewal of ESCs, with reduced expression of pluripotency genes, reduced cell proliferation, and decreased colony forming capacity. In addition, Hbxip-/- ESCs are defective in differentiation, particularly ectodermal and mesodermal differentiation. Consistently, Hbxip-/- epiblast fails to differentiate properly, indicated by sustained expression of Oct4 in E8.5 Hbxip-/- epiblast. Mechanistically, in ESCs, Hbxip interacts with other components of the Ragulator complex, which is required for mTORC1 activation by amino acids. Importantly, ESCs depleted of Ragulator subunits, Lamtor3 or Lamtor4, display differentiation defects similar to those of Hbxip-/- ESCs. Moreover, Hbxip-/-, p14-/-, and p18-/- mice, lacking subunits of the Ragulator complex, also share similar phenotypes, embryonic lethality and retarded growth around E7-8. Thus, we conclude that Hbxip plays a pivotal role in the development and differentiation of the epiblast, as well as the self-renewal and differentiation of ESCs, through activating mTORC1 signaling.

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Murine embryonic stem cell differentiation is promoted by SOCS-3 and inhibited by the zinc finger transcription factor Klf4

Blood ◽

10.1182/blood-2004-07-2681 ◽

2005 ◽

Vol 105 (2) ◽

pp. 635-637 ◽

Cited By ~ 167

Author(s):

Yanjun Li ◽

Jeanette McClintick ◽

Li Zhong ◽

Howard J. Edenberg ◽

Mervin C. Yoder ◽

...

Keyword(s):

Cell Function ◽

Embryoid Body ◽

Es Cells ◽

Embryonic Stem ◽

Stem Cell Differentiation ◽

Northern Blotting ◽

Cytokine Signaling ◽

Embryonic Stem Cell Differentiation ◽

Es Cell ◽

Self Renewal

Abstract Embryonic stem (ES) cells homozygous for a Shp-2 mutation (Shp-2Δ46-110) demonstrate leukemia inhibitory factor (LIF) hypersensitivity and increased LIF-stimulated phosphorylation of signal transducer and activator of transcription (STAT3). We hypothesized that LIF-responsive genes in Shp-2Δ46-110 cells would represent potential candidates for molecules vital for ES cell self-renewal. Using microarray analysis, we detected 41 genes whose expression was modified by LIF in Shp-2Δ46-110 ES cells. Induction of 2 significantly up-regulated genes, suppressor of cytokine signaling–3 (SOCS-3) and Krüppel-like factor 4 (Klf4), was verified using Northern blotting. ES cells overexpressing SOCS-3 had an increased capacity to differentiate to hematopoietic progenitors, rather than to self-renew. In contrast, ES cells overexpressing Klf4 had a greater capacity to self-renew based on secondary embryoid body (EB) formation. Klf4-transduced d6 EBs expressed higher levels of Oct-4, consistent with the notion that Klf4 promotes ES cell self-renewal. These findings verify the negative role of SOCS-3 on LIF signaling and provide a novel role for Klf4 in ES cell function.

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ARID4B is critical for mouse embryonic stem cell differentiation towards mesoderm and endoderm, linking epigenetics to pluripotency exit

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.015534 ◽

2020 ◽

Vol 295 (51) ◽

pp. 17738-17751

Author(s):

Nihal Terzi Cizmecioglu ◽

Jialiang Huang ◽

Ezgi G. Keskin ◽

Xiaofeng Wang ◽

Idil Esen ◽

...

Keyword(s):

Gene Expression ◽

Stem Cells ◽

Embryonic Stem Cells ◽

Critical Role ◽

Embryonic Stem ◽

Stem Cell Differentiation ◽

Specific Gene ◽

Embryonic Stem Cell Differentiation ◽

Self Renewal ◽

Cell Fate Decisions

Distinct cell types emerge from embryonic stem cells through a precise and coordinated execution of gene expression programs during lineage commitment. This is established by the action of lineage specific transcription factors along with chromatin complexes. Numerous studies have focused on epigenetic factors that affect embryonic stem cells (ESC) self-renewal and pluripotency. However, the contribution of chromatin to lineage decisions at the exit from pluripotency has not been as extensively studied. Using a pooled epigenetic shRNA screen strategy, we identified chromatin-related factors critical for differentiation toward mesodermal and endodermal lineages. Here we reveal a critical role for the chromatin protein, ARID4B. Arid4b-deficient mESCs are similar to WT mESCs in the expression of pluripotency factors and their self-renewal. However, ARID4B loss results in defects in up-regulation of the meso/endodermal gene expression program. It was previously shown that Arid4b resides in a complex with SIN3A and HDACS 1 and 2. We identified a physical and functional interaction of ARID4B with HDAC1 rather than HDAC2, suggesting functionally distinct Sin3a subcomplexes might regulate cell fate decisions Finally, we observed that ARID4B deficiency leads to increased H3K27me3 and a reduced H3K27Ac level in key developmental gene loci, whereas a subset of genomic regions gain H3K27Ac marks. Our results demonstrate that epigenetic control through ARID4B plays a key role in the execution of lineage-specific gene expression programs at pluripotency exit.

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