HA epitope detects Meis1 protein expression. (A) HA epitope–tagged MEIS1 protein is detectable in sorted GFP⁺ BM cells from C57BL/6N-Meis1^em1Bcca mice. (B) An IP for HA-tagged MEIS1 using mouse anti-HA beads with Lin⁻-enriched BM cells from a homozygous C57BL/6N-Meis1^em1Bcca mouse can be detected by a rabbit anti-HA antibody as well as an anti-MEIS1 antibody.