Required for mesoderm development, including specification of muscle and coelomocyte precursors. Nuclear localization most obvious in the 8 embryonic cells derived from the MS blastomere. Expressed in the early embryo, in the mesodermal lineage derived from the MS blastomere. RNAi-mediated knockdown on an hlh-1 mutant background causes embryos to become paralyzed and arrested at the 2-fold stage. Belongs to the NK-2 homeobox family.