Abstract
ABSTRACTGene 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.
Highlights
The insect brain contains a large number of neurons with distinct identities
In the Drosophila ventral nerve cord (VNC), spatial and temporal factors converge to activate the expression of transcription factors that function as terminal selectors of neuronal subtype identity: these factors regulate the lifelong expression of effector genes that together bring about all features of the differentiated cell type (Allan and Thor, 2015; Hobert and Kratsios, 2019)
Analysis of GFP fluorescence in Tribolium adult brains led to the identification of the line G10011 in which the CX is heavily labeled
Summary
The insect brain contains a large number of neurons with distinct identities. Cell identity is manifest in specific structural and functional features which together define a neuronal subtype. Neuronal subtypes express distinct sets of differentiation genes which together bring about all the characteristic features of the cell. The early regulatory cascades which govern neuronal subtype specification have been intensively investigated in the insect model Drosophila melanogaster, reviewed in (Skeath and Thor, 2003; Lin and Lee, 2012; Crews, 2019). In the Drosophila ventral nerve cord (VNC), spatial and temporal factors converge to activate the expression of transcription factors that function as terminal selectors of neuronal subtype identity: these factors regulate the lifelong expression of effector genes that together bring about all features of the differentiated cell type (Allan and Thor, 2015; Hobert and Kratsios, 2019)
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