SPI1 is a pioneer transcription factor that controls hematopoietic cell fate by decompacting stem cell heterochromatin and enabling access to otherwise inaccessible genomic regions 12. It binds the PU-box DNA sequence (5'-GAGGAA-3') via its ETS domain and transcriptionally activates genes crucial for myeloid and lymphoid differentiation, often cooperatively with other factors like GATA1 23. SPI1 is essential for the pro- to pre-B cell transition and can recruit transcription factors such as interferon regulatory factors to regulate gene expression 2. In hematopoietic development, SPI1 is one of seven transcription factors sufficient to convert haemogenic endothelium into functional hematopoietic stem and progenitor cells capable of multilineage engraftment 4. Beyond hematopoiesis, SPI1 functions as a transcriptional regulator in multiple disease contexts: it regulates interleukin-8 and interleukin-10 expression in tumor-associated macrophages within lung adenocarcinoma 5, serves as a transcriptional factor for complement pathway genes in atherosclerotic plaques 6, and contributes to immune signatures in triple-negative breast cancer subtypes 7. Notably, SPI1 negatively regulates METTL14 in the SPI1-METTL14-MYB/MYC signaling axis governing myelopoiesis and leukemogenesis 8. Mutations in SPI1 cause autosomal dominant agammaglobulinemia, underscoring its critical role in B lymphocyte development.