Human RUNX1 Synthetic Peptide. RUNX1 belongs to the mammalian RUNX family of DNA binding proteins that regulate the expression of genes involved in cellular differentiation and cell cycle progression. RUNX1 is essential for hematopoietic stem cell generation in the vascular regions of the aorta, vitelline and umbilical arteries, yolk sac and placenta. RUNX1 is expressed in all tissues except brain and heart, with highest levels in thymus, bone marrow and peripheral blood.