Abstract

Comparative ground pattern analysis suggests that brains of distantly related animals such as insects and vertebrates are organized similarly but the underlying mechanisms remain elusive. Here we identify a character identity network for the Drosophila deutocerebral-tritocerebral boundary (DTB) comprising genes homologous to those governing vertebrate midbrain-hindbrain boundary (MHB) formation. We show the DTB gives rise to Drosophila adult midbrain circuits that mediate body posture and motor control comparable to vertebrate MHB -derived midbrain-cerebellar circuitry. DTB /midbrain-specific gene expression and function is mediated by cis-regulatory elements of inv/En2, sv/Pax2, Dachshund/Dach1, Msx, Vnd/Nkx2.1, Emx, Wnt, FGF8 -like, Ptf1a, Zinc finger of the cerebellum, and Purkinje cell protein homologs. The DTB -specific regulatory elements exhibit sequence similarities to human regulatory elements that direct MHB -specific expression in mouse. We propose these gene regulatory networks predate the radiation of the insect and vertebrate-specific DTB and MHB region-derived circuits and morphologies, and possibly of the bilaterian cephalic nervous systems.