Hoxa9/hoxb3/hoxb4 compound null mice display severe hematopoietic defects

These findings demonstrate overlapping functions of hoxa9, hoxb3, and hoxb4 in hematopoietic cells, and emphasize an important role for these transcription factors for regulation of HSC proliferation. However, none of these hox proteins is absolutely essential for generation or maintenance of all major blood lineages.