FOXO3B is a forkhead box transcription factor located on chromosome 17 that functions as a DNA-binding regulator of RNA polymerase II-dependent transcription 1. Unlike its highly homologous paralog FOXO3A, FOXO3B is cytosolically localized and does not translocate in response to Akt signaling 1. In zebrafish models, foxo3b regulates hematopoietic development by suppressing the transcriptional activity of gata1 and spi1 through protein-protein interactions, with the eaf1-foxo3b-gata1/spi1 pathway potentially relevant to leukemogenesis 2. FOXO3B also modulates hypoxia signaling by upregulating the von Hippel-Lindau gene (VHL), and foxo3b-null zebrafish exhibit impaired hypoxic tolerance 3. Additionally, FOXO3B expression is regulated by exon junction complex-dependent nonsense-mediated decay, controlling protein levels during development 4. In erythroid differentiation, FOXO3B knockdown reduces globin and gata1 expression 5. Recent evidence suggests FOXO3B participates in anti-aging mechanisms, with topical formulations upregulating FOXO3B alongside telomere length maintenance and collagen stimulation 6. Genetic studies of FOXO3B require careful methodology due to 99% sequence homology with FOXO3A 7.