Abstract
Gene regulatory mechanisms that specify subtype identity of central complex (CX) neurons are the subject of intense investigation. The CX is a compartment within the brain common to all insect species and functions as a 'command center' that directs motor actions. It is made up of several thousand neurons, with more than 60 morphologically distinct identities. Accordingly, transcriptional programs must effect the specification of at least as many neuronal subtypes. We demonstrate a role for the transcription factor Shaking hands (Skh) in the specification of embryonic CX neurons in Tribolium. The developmental dynamics of skh expression are characteristic of terminal selectors of subtype identity. In the embryonic brain, skh expression is restricted to a subset of neurons, many of which survive to adulthood and contribute to the mature CX. skh expression is maintained throughout the lifetime in at least some CX neurons. skh knockdown results in axon outgrowth defects, thus preventing the formation of an embryonic CX primordium. The previously unstudied Drosophila skh shows a similar embryonic expression pattern, suggesting that subtype specification of CX neurons may be conserved.