In stage 8 embryos, reporter expression is observed in the stomodeal opening, posterior midgut, and proctodeum. At stage 11, expression is observed in the two rows of cells at the midline of the prospective foregut and hindgut epithelium. Similar rows of cells are seen in the primordium of the posterior region of the midgut. No expression is seen in the visceral muscles or their precursors that overlie the epithelial foregut and hindgut, indicating that sim reporter expression is in the ectodermal and endodermal gut but not in mesodermal tissues. The cells expressing sim reporter in the embryonic gut do not delaminate from the ectodermal layer and remain among the epithelial cells of the gut.

sim reporter expression is observed in stage 8 embryos in the stomodeum, posterior midgut, and proctodeum. Staining is observed in two rows of cells at the midline of the prospective foregut and hindgut epithelium and in similar cells in the primordium of the posterior region of the midgut. Expression was found to be in the ectoderm of these organs and not in the muscle layers. While ventral midline cells delaminate at stage 11 to translocate to the proper position in the CNS, the sim expressing cells in the gut do not delaminate but remain among the epithelial cells of the gut.