Dataset Information

Runx+ HSPC, kdrl+ endothelial, and negative cells sorted from DMSO- or Lycorine-treated 3 dpf zebrafish embryos

ABSTRACT: The zebrafish is a powerful model for the study of hematopoietic stem and progenitor cells (HSPC). We have developed a novel HSPC-specific transgenic line (Runx1+23:GFP). We have used this line in time-lapse live imaging studies to track the migration of HSPC during development. We have also performed a chemical genetic screen to find small molecules that modulate HSPC numbers during development. Treating embryos from 2-3 days post fertilization (2-3 dpf) then fixing for in situ staining with HSPC probes cmyb and runx1, we found the compound lycorine increased HSPC numbers. Applying this compound during time-lapse live imaging showed increased accumulation of Runx+ HSPC in the caudal hematopoietic tissue (CHT). Treatment from 2-3 dpf, then washing off the compound, had a sustained effect on the size of the HSPC with Runx+ numbers higher at 5 and 7 dpf. We have performed microarray analysis to elucidate the molecular changes within HSPC and endothelial cells after Lycorine treatment. We treated Runx1+23:GFP;kdrl:DsRed2 embryos from 2-3 dpf with 75 uM lycorine in 1% DMSO. We then dissociated the embryos and sorted the Runx+ GFP cells, the kdrl+ DsRed2 cells, and the non-fluorescent negative cells from the total embryo as a comparator population. Total RNA was amplified and biotin labled for hybridization on Affymetrix microarrays.

ORGANISM(S): Danio rerio

PROVIDER: GSE56015 | GEO | 2015/01/15

SECONDARY ACCESSION(S): PRJNA242226

REPOSITORIES: GEO

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Project description:Runx1 and Runx3 function redundantly in early T-development, and together drive T-lineage developmental progression by regulating distinct sets of genes in different stages. Context-specific Runx target genes are particularly enriched near Runx binding sites that dynamically shift from pre-T-commitment stages (Phase 1) to post-T-commitment stages (Phase 2). As total Runx activities (Runx1+Runx3) are maintained stably throughout early T-development stages, yet Runx factors physically interact with multiple collaborators, we hypothesized that different Runx-collaborating transcription factors compete to recruit a limited pool of Runx transcription factors. To test whether increasing Runx availability can alter Runx DNA-binding site choices, Runx1 overexpression vectors were introduced to two different systems. First, we increased Runx1 expression in a DN3-like cell line (representing a post-commitment, Phase 2 stage) in the presence or absence of exogenous Phase 1 co-factor, PU.1. Second, we increased Runx1 expression in Phase 1 primary cells which naturally express PU.1 and other Phase 1 collaborators. Then, Runx1 binding behaviors were measured using ChIP-seq or CUT&RUN (C&R). A modest increase of Runx1 levels (about 2-3 fold increase) substantially increased the number of Runx binding sites seen and the intensity of occupancy in both systems. When Runx expression was at physiological levels, PU.1 dominated Runx1 site choice before T commitment by recruiting Runx1 to PU.1 sites. The Phase 2 cell line system showed that it did this while depleting Runx1 from alternative high quality Runx motif sites. However, when Runx1 was overexpressed, Runx1 was still recruited to PU.1 sites, but this recruitment did not evacuate Runx1 occupancy from default preferred sites. Notably, Runx1 overexpression in primary Phase 1 cells caused precocious occupancy of post-commitment, Phase 2-specific sites. We found that these are often co-occupied with TCF1, E2A, and HEB, but have minimal co-binding with PU.1. In addition, Runx1 overexpression resulted in new binding sites that were not normally observed in pro-T cells, which are mostly sequestered by closed chromatin normally although they harbor more numerous Runx motifs. Thus, these data suggest that Runx DNA binding site choices are sensitive to Runx concentration and co-factors during early T-development.

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Runx+ HSPC, kdrl+ endothelial, and negative cells sorted from DMSO- or Lycorine-treated 3 dpf zebrafish embryos

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