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Spatial transcriptome profiling by MERFISH reveals fetal liver hematopoietic stem cell niche architecture [scRNA-seq]

ABSTRACT: The hematopoietic stem cell (HSC) niche has been extensively studied in bone marrow, yet a more systematic investigation into the microenvironment regulation of hematopoiesis in fetal liver is necessary. Here we investigate the spatial organization and transcriptional profile of individual cells in both wild type and Tet2-/- fetal livers, by multiplexed error robust fluorescence in situ hybridization (MERFISH). We find that specific pairs of fetal liver cell types are preferentially positioned next to each other. Ligand-receptor singling molecule pairs such as Kitl and Kit are enriched in neighboring cell types. The majority of HSCs are directly in contact with endothelial cells (ECs) in both wild type and Tet2-/- fetal livers. Loss of Tet2 increases the number of HSCs, and upregulates Wnt and Notch signaling genes in the HSC niche. Two subtypes of ECs – arterial ECs and sinusoidal ECs – and other cell types contribute distinct signaling molecules to the HSC niche. Collectively, this study provides a comprehensive picture and bioinformatic foundation for HSC spatial regulation in fetal liver.

ORGANISM(S): Mus musculus

PROVIDER: GSE172127 | GEO | 2021/04/16

REPOSITORIES: GEO

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Project description:Hematopoietic stem cells (HSCs) are at the basis of the hematopoietic hierarchy. Their ability to self-renew and differentiate is strictly controlled by molecular signals produced by their surrounding micorenvironments composed of stromal cells. HSCs first emerge in the AGM (Aorta Gonads Mesonephros) region, amplify in the fetal liver (FL) and are maintained in the adult bone marrow (BM). To further characterize the molecular program of the HSC niches, we have compared the global transcriptome of HSC-supportive and non-supportive stromal clones established from the AGM, FL and BM. Hematopoietic stem cells (HSCs) are at the basis of the hematopoietic hierarchy. Their ability to self-renew and differentiate is strictly controlled by molecular signals produced by their surrounding micorenvironments composed of stromal cells. HSCs first emerge in the AGM (Aorta Gonads Mesonephros) region, amplify in the fetal liver (FL) and are maintained in the adult bone marrow (BM). To further characterize the molecular program of the HSC niches, we have compared the global transcriptome of HSC-supportive line from Fetal Calvaria (OP9) and non-supportive stromal clones from fetal liver (BFC). Hematopoietic stem cells (HSCs) are at the basis of the hematopoietic hierarchy. Their ability to self-renew and differentiate is strictly controlled by molecular signals produced by their surrounding micorenvironments composed of stromal cells. HSCs first emerge in the AGM (Aorta Gonads Mesonephros) region, amplify in the fetal liver (FL) and are maintained in the adult bone marrow (BM). To further characterize the molecular program of the HSC niches, we have compared the global transcriptome of HSC-supportive and non-supportive stromal clones established from fetal liver. We took advantage of stromal clones established from the AGM, FL and BM and tested for their ability to support or not HSCs ex vivo. RNA were extracted from confluent stromal cultures or sorted cells and used for hybridization of Affymetrix (mouse gene 1.0 ST) microarrays.

Project description:Haematopoietic stem cells (HSCs) are derived early from embryonic precursor cells, such as haemogenic endothelial cells and pre-HSCs. However, the identity of precursor cells remains elusive due to their rareness, transience, and inability to be isolated efficiently. Here we employed potent surface markers to capture the nascent pre-HSCs at 30% purity, as rigorously validated by single-cell-initiated serial transplantation assay. Then we applied single-cell RNA-Seq technique to analyse five populations closely related to HSC formation: endothelial cells, CD45- and CD45+ pre-HSCs in E11 aorta-gonad-mesonephros (AGM) region, and mature HSCs in E12 and E14 foetal liver. In comparison, the pre-HSCs showed unique features in transcriptional machinery, apoptosis, metabolism state, signalling pathway, transcription factor network, and lncRNA expression pattern. Among signalling pathways enriched in pre-HSCs, the mTOR activation was uncovered indispensable for the emergence of HSCs but not haematopoietic progenitors from endothelial cells in vivo. By comparing with proximal populations without HSC potential, the core molecular signature of pre-HSCs was identified. Collectively, our work paves the way for dissection of complex molecular mechanisms regulating the step-wise generation of HSCs in vivo, informing future efforts to engineer HSCs for clinical application. RNA-Seq of 181 single-cell samples from 8 FACS sorted cell types: 1. endothelial cells (samples E11.0_EC_xxxx. CD31+ VE-cadherin+CD41-CD43-CD45-Ter119-); 2. T1 pre-HSCs (samples E11.0_T1_xxxx. CD31+CD45-CD41low c-Kit+CD201high); 3. T1 CD201- cells (samples E11.0_T1CD201neg_xxxx, CD31+CD45-CD41low c-Kit+CD201low/-) ; 4. T2 pre-HSCs (samples E11.0_T2_35xx. CD31+CD45+c-Kit+CD201high), 5. T2 CD41low (samples E11.0_T2_21xx, E11.0_T2_24xx and E11.0_T2_27xx. CD31+CD45+CD41low); 6. E12 HSCs (samples E12.5_FL_xxxx. Lin-Sca-1+Mac-1lowCD201+); 7. E14 HSCs (samples E14.5_FL_xxxx. CD45+CD150+CD48-CD201+); 8. Adult HSCs (samples Adult_HSC_xxxx. CD45+CD150+CD48-CD201+). ECs, T1 pre-HSCs, T1 CD201- cells, T2 pre-HSCs, T2 CD41low cells were sorted from E11 AGM region. Mature HSCs were sorted from E12 or E14 fetal liver and adult bonemarrow.

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Spatial transcriptome profiling by MERFISH reveals fetal liver hematopoietic stem cell niche architecture [scRNA-seq]

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