Abstract
Drosophila uses 50 different olfactory receptor neuron (ORN) classes that are clustered within distinct sensilla subtypes to decipher their chemical environment. Each sensilla subtype houses 1–4 ORN identities that arise through asymmetric divisions of a single sensory organ precursor (SOP). Despite a number of mutational studies investigating the regulation of ORN development, a majority of the transcriptional programs that lead to the different ORN classes in the developing olfactory system are unknown. Here we use transcriptional profiling across the time series of antennal development to identify novel transcriptional programs governing the differentiation of ORNs. We surveyed four critical developmental stages of the olfactory system: 3rd instar larval (prepatterning), 8 hours after puparium formation (APF, SOP selection), 40 hrs APF (neurogenesis), and adult antennae. We focused on the expression profiles of olfactory receptor genes and transcription factors—the two main classes of genes that regulate the sensory identity of ORNs. We identify distinct clusters of genes that have overlapping temporal expression profiles suggesting they have a key role during olfactory system development. We show that the expression of the transcription factor distal antenna (dan) is highly similar to other prepatterning factors and is required for the expression of a subset of ORs.
Highlights
With different and restricted differentiation potentials[13,14,15,16]
Of the >29,000 transcripts that were analyzed only 17 had a correlation coefficient >0.1 for PC1 (Table S1). Three of these transcripts were annotated as having metabolic functions, three as odorant binding proteins (Obps), one as involved in lateral inhibition and 10 had no known function. 21 transcripts had correlation coefficients >0.1 for PC2 (Table S2), and of these 10 were involved in cuticle/chitin development, 8 had no known function and one each were involved in wing disc morphogenesis, lateral inhibition, and metabolism
We identified transcription factor programs in the developing olfactory system with stage specific functions corresponding to different processes in ORN development
Summary
With different and restricted differentiation potentials[13,14,15,16]. Each field gives rise to the precursors that will generate different combinations of ORNs. The SOPs undergo asymmetric cell division, mediated by Notch signaling, to generate all of the cells (both the neuronal and supporting cells) that make up each sensillum[21,22] During these final divisions, genes that directly regulate olfactory receptor expression act as terminal selectors to determine the final fate of the ORNs23–27. This study is a unique, in-depth analysis of the olfactory tissue transcriptome across development These data provide a broad and unbiased view into the genes that govern and shape diversification of ORNs. We followed the expression profiles of two main classes of genes that can regulate the sensory identity of ORNs: olfactory receptor genes, and transcription factors. These studies revealed distinct clusters of genes with overlapping temporal expression profiles that we interpret in light of the events set to occur during olfactory system development
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