Investigating the developmental programming of hematopoietic stem and progenitor cells

/Abstract Hematopoietic stem and progenitor cells (HSPCs) reside in a microenvironment that regulates their behavior by interactions with niche support cells. During development of the mammalian embryo HSPCs are born in the dorsal aorta and migrate to the fetal liver, where they expand and differentiate. Fetal liver HSPCs are proliferative and when transplanted have a greater capacity for reconstituting the blood system compared to quiescent adult HSPCs. However, the genetic networks regulating fetal liver HSPCs, and their maturation, are poorly understood. To dissect these networks, we are characterizing a viable integrin α4 (itga4) mutant zebrafish model with perturbed interaction between HSPCs and the mammalian fetal liver equivalent—the caudal hematopoietic tissue (CHT). Preliminary analysis of HSPCs at 5 days post fertilization (dpf), after migration from the CHT to the presumptive adult kidney marrow niche, detected transcriptomic and epigenomic differences between wild-type (WT) and itga4 mutant HSPCs, indicating reprogramming of HSPCs after interaction with the CHT niche. Gene Set Enrichment Analysis (GSEA) of differentially expressed genes between WT and itga4 mutant HSPCs showed enrichment of inflammatory signaling in itga4 mutant HSPCs which did not lodge in the CHT niche. Motif analysis of accessible chromatin regions unique to itga4 mutant HSPCs revealed potential regulatory factors of HSPC reprogramming, such as ets1 and AP-1 factors. We hypothesize that bypass of the CHT niche prevents correct HSPC programming and transition to quiescence, causing itga4 mutant HSPCs to remain in an immature state. In Aim 1, we will analyze the proliferative capacity, inflammatory profile, and stem cell capacity of HSPCs that did (WT) or did not lodge in the CHT niche (itga4 mutant) to characterize the programming event initiated by itga4-mediated interactions between HSPCs and the CHT niche. In Aim 2, we will map the epigenomic landscape and perform multiomic analysis of WT and itga4 mutant HSPCs to determine the gene regulatory networks underlying the developmental switch of HSPCs from proliferation to quiescence. We will utilize our unique zebrafish system and multiomic approaches to dissect the developmental networks of HSPC regulation. By understanding the transitions between proliferative and quiescent HSPC states, our findings could translate into novel approaches for stem cell expansion and improved stem cell therapy. Project Number: 1F31HL176107-01A1 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Nicole Woodhead | Institution: UNIVERSITY OF WISCONSIN-MADISON, MADISON, WI | Award Amount: $37,898 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F10C-B (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1F31HL17610701A1