Program: Oral and Poster Abstracts
Session: 501. Hematopoietic Stem and Progenitor Biology: Poster II
Methods: The Tomato gene, coding a red fluorescent protein, was knock-in to the coding region of endogenous Satb1 gene. The heterozygous SATB1/Tomato knock-in mice in which one Satb1 allele was replaced with the Tomato were used to sort HSCs in adult BM. The sorted cells were evaluated for the differentiation potential with methylcellulose colony assays and co-cultures with MS5 stromal cells. Further, the long-term reconstitution ability was evaluated by transplantation to lethally irradiated mice. To obtain transcriptome information, total RNA was isolated from SATB1/Tomato- and SATB1/Tomato+HSCs, and then next-generation sequencing was performed. The data were analyzed with the Ingenuity Pathway Analysis software.
Results: We defined Lin- Sca1+ c-KitHi (LSK) CD150+ Flt3- cells as HSCs, especially adopting FLT3- to exclude FLT3+ lymphoid-primed multipotent progenitors from our functional analyses. We found that the LSK CD150+ Flt3- fraction contains substantial number of SATB1/Tomato+ cells. While both SATB1/Tomato- and SATB1/Tomato+ HSCs produced numerous CFU-Mix and CFU-GM/G/M colonies, the latter were less potent to produce BFU-E. In co-culture with MS5 stromal cells that support B and myeloid lineages, the output of B lineage cells from SATB1+ HSCs was more robust than that of SATB1- HSCs. Upon transplantation, enhanced B-lineage engraftment was observed in the SATB1+ HSC-transplanted recipients. Interestingly, while the two types of HSCs showed obvious difference in the differentiation potential toward lymphoid or myeloid lineage, both HSCs reconstituted the LSK CD150+ Flt3- fraction that similarly contained SATB1/Tomato- and SATB1/Tomato+ cells. With the RNA-sequencing data of SATB1- and SATB1+ HSCs, biological pathway analyses revealed that the “Hematological System Development and Function” pathway was remarkably up-regulated in the SATB1+HSCs. Among subcategories of the “Hematological System Development and Function” pathway, the “quantity of lymphocytes” pathway was increased whereas “quantity of myeloid cells” and “quantity of granulocytes” pathways were decreased.
Conclusion: We have developed a new mouse system that can be used to identify and isolate viable lymphoid-biased HSCs in the most primitive hematopoietic cell fraction of adult BM. While the SATB1- and SATB1+ HSCs differ genetically and functionally, both subtypes have displayed a self-renewal activity with mutual interconversion in transplanted recipients. These findings suggest that functional heterogeneity and variability within the HSC population is, at least in part, a manifestation of SATB1 expression.
Disclosures: Yokota: SHIONOGI & CO., LTD.: Research Funding .
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