hbn transcript expression begins at embryonic stage 4 as a U-shaped pattern in the dorsal head region. During embryonic stage 5 the hbn expression domain retracts from the ventro-lateral side of the presumptive head. A second hbn expression domain, dorso-lateral to the first domain, becomes visible on each side of the embryo during embryonic stages 6-7, and the U-shaped pattern resolves into two distinct domains, a weakly-expressed dorsal domain and a strongly-expressed dorso-lateral domain. During embryonic stages 9-10, transcript expression is detected in three domains on each side of the dorsal posterior head and in a dorsal-anterior spot. When the germband is fully extended at stage 11, a few cells in each neuromere of the ventral nerve cord express hbn transcript. Shortly afterwards each of the three dorso-lateral expression domains in the head split, resulting in six dorso-lateral patches of expression. hbn transcript is expressed in the developing hindgut at the boundary with the midgut during germband retraction. Discrete localized expression domains in the brain and in the ventral nerve cord are detected until the end of embryogenesis.

hbn is expressed in subsets of neuroblasts in stage 16 embryos. It is also observed in mushroom body neuroblasts. In type II neuroblasts, it is expressed in the PDM and DL clusters. It is also expressed in many type 1 neuroblasts.