Abstract

Embryonic hematopoiesis is essential for establishing lifelong blood and immune system function. During development, hematopoietic stem and progenitor cells (HSPCs) acquire intrinsic programs that persist into adulthood and can influence disease susceptibility, yet the molecular signals governing these early-life decisions remain poorly understood. Here, we investigated the role of developmental Transforming Growth Factor-{beta} (TGF-{beta}) signaling in regulating HSPC lineage bias and long-term hematopoietic outcomes. Using the zebrafish model, we found that transient embryonic TGF-{beta} signaling inhibition during the HSPC specification window altered their frequency and migration after emergence from the hemogenic endothelium and movement into the key secondary maturation and expansion niche. Single-cell transcriptomic analysis of embryonic HSPCs revealed repression of migration- and cytoskeleton-associated genes alongside dampened expression of myeloid/macrophage-related genes following ALK5 inhibition. Functionally, early ALK5 blockade reduced macrophage numbers and promoted an M2-like immunosuppressive transcriptional profile. These developmental perturbations produced sustained effects on hematopoietic and immune function into adulthood, including diminished inflammatory gene expression, reduced clonal complexity, and impaired regenerative capacity. Together, our findings identify embryonic TGF-{beta} signaling as a key developmental regulator of HSPC fate and immune programming, with potential implications for immune dysfunction and susceptibility to inflammatory-related disease later in life.