Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior axis. Required for induction of E-selectin and VCAM-1, on the endothelial cells surface at sites of inflammation. Transiently interacts with PRMT5 in TNF-alpha stimulated endothelial cells. Methylated on Arg-140 by PRMT5; methylation is critical for E-selectin induction. A chromosomal aberration involving HOXA9 is found in a form of acute myeloid leukemia. Translocation t(7;11)(p15;p15) with NUP98 (PubMed:8563753). The chimera includes NUP98 intrinsic disordered regions which contribute to aberrant liquid-liquid phase separation puncta of the chimera in the nucleus. This phase-separation enhances the chimera genomic targeting and induces organization of aberrant three-dimensional chromatin structures leading to tumourous transformation (PubMed:34163069). A chromosomal aberration involving HOXA9 may contribute to disease progression in chronic myeloid leukemia. Translocation t(7;17)(p15;q23) with MSI2. Belongs to the Abd-B homeobox family.