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Transcription factor HESX1 enhances mesendodermal commitment of human embryonic stem cells by modulating ERK1/2 signaling

ABSTRACT: Transcription factors are key determinants of lineage commitment during mammalian development. However, the function and molecular mechanism for the transcription factors in the formation of three primary germ layers during human embryonic development are not fully elucidated. Here, we report that homeobox-containing transcription factor HESX1 plays a critical role in mesendodermal (ME) commitment of human embryonic stem cells (hESCs). Our results show that expression of HESX1 in hESCs is regulated by OCT4 and NANOG, and that its expression level changes with hESC differentiation. We find that knockdown of HESX1 does not disrupt the undifferentiated state of hESCs, in terms of cell morphology and expression levels of pluripotency- associated genes. However, HESX1 deficiency in hESCs impairs their ME commitment, whereas forced expression of HESX1 significantly enhances ME marker expression during ME commitment. Interestingly, HESX1 knockdown in hESCs represses ERK1/2 signaling activated by ME induction, while overexpression of HESX1 markedly enhances ERK1/2 activity during ME commitment of hESCs. Of note, MEK inhibitor PD0325901 weakens or even eliminates HESX1 overexpression- mediated promotive effects on ME induction in a dosage- dependent manner. Together, this study identifies a novel role of HESX1 in hESC commitment to ME cells and establishes the functional link between a transcription factor and lineage- associated signaling. These findings would help to better understand early human development and develop more efficient protocols to induce hESC differentiation to desired lineages.

ORGANISM(S): Homo sapiens

PROVIDER: GSE199196 | GEO | 2022/06/10

REPOSITORIES: GEO

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Project description:The MLL-AF4 fusion gene is a hallmark genomic aberration in high-risk acute lymphoblastic leukemia in infants. Although it is well-established that MLL-AF4 arises pre-natally during human development, its effects on hematopoietic development in utero remains unexplored. We have created a human-specific in vitro system to study early hemato-endothelial development in MLL-AF4-expressing human embryonic stem cells (hESCs). Differentiation and functional studies as well as clonal analyses and gene expression profiling reveal that expression of MLL-AF4 in hESCs has a phenotypic, functional and gene expression impact. It enhances the specification of hemogenic precursors from hESCs and impairs further hematopoietic commitment of these precursors in favour of the endothelial cell fate. Similar to that reported in cord blood CD34+ hematopoietic stem/progenitor cells (HSPCs), MLL-AF4 expression is not sufficient to transform hESC-derived hematopoietic cells in vitro or in vivo, indicating that additional events may be required to initiate leukemogenesis or that embryonic hematopoiesis is not the appropriate human cellular target for MLL-AF4-mediated leukemogenesis. This work illustrates how hESCs can provide unique insights into human development and further our understanding of how leukemic fusion genes known to arise pre-natally regulate human embryonic hematopoietic specification. MLL is involved in transcriptional regulation and most MLL translocations appear to result in increased expression of Hox genes and hematopoietic genes. We therefore assessed the impact of MLL-AF4 expression on the transcriptome of hESCs. Gene expression profiling performed in MLL-AF4 hESCs revealed that MLL-AF4 preferentially activates transcription. 1826 out of the 3001 genes (61%) expressed were up-regulated in MLL-AF4 hESCs. Human ESC samples were collected during the exponential cell growth phase and stabilized in RNA later. 500 ng of each total RNA sample was labelled with Cy3 using the Quick-Amp Labelling kit and hybridized with the Gene Expression Hybridization kit to a Whole Human Genome Oligo Microarray (Agilent Technologies) following the Manufacturer’s instructions. Each cell line was analyzed as independent duplicates. NEO-expressing (empty lentivector) hESC line was used as the baseline.

Project description:Recent advances in the study of human embryonic stem cells (hESCs) and induced-pluripotent stem cells (iPS) highlight their importance as both model systems for basic research and avenues for therapeutic applications. To gain better insight into these cells, a clearer understanding of their molecular properties is crucial. In this study, we analyze changes in the expression profile of microRNAs (miRNAs) and mRNAs in nine different, National Institutes of Health (NIH)-approved hESC lines. By examining both undifferentiated hESCs and cells exposed to an undirected differentiation scheme at early stages, we found those miRNAs and mRNAs enriched in the hESC lines, and those miRNAs and mRNAs initially regulated upon commitment. In comparing these profiles with those of an embryonal carcinoma (EC) cell line, NTera-2, we observed distinct patterns of miRNA expression in hESCs. Furthermore, we identify several new hESC-enriched miRNAs that respond rapidly to differentiation cues, in addition to miRNAs from a large cluster of hESC-enriched miRNAs located on chromosome 19, and miRNAs from the miR-302 cluster and the miR-17~92 family of clusters. We show that key miRNAs in the chromosome 19 cluster are highly enriched in hESCs in comparison to NTera-2, and might therefore serve as future diagnostic markers for stem cell capacity. Examination of changes in mRNA expression during early commitment further reveals that many differentiation-regulated genes are possible candidates for regulation by these hESC-enriched miRNAs. A set of 9 different NIH-approved hESC lines were treated with conditions to promote either maintenance of an undifferentiated state (mouse embryonic fibroblast- conditioned media) or undirected differentiation of the hESCs into various cell lineages (DMEM + 20% FBS). RNA was harvested from the cells and subjected to miRNA microarray analysis. An embryonal carcinma cell line, NTera-2, which shows similar growth characteristics to hESCs was used an additional comparative sample. Additionally, human placental RNA samples were used as internal controls for miRNA microarray slide (Agilent Technologies). The miRNA expression data was used to analyze differential miRNA expression in each specific cell line, as well as large-scale comparisons of the undifferentiated and differentiated hESC lines.

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Transcription factor HESX1 enhances mesendodermal commitment of human embryonic stem cells by modulating ERK1/2 signaling

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