mature olfactory sensory neuron dendrite number

Both function as heteromeric odor-gated ion channels composed of subunits of a ligand-specific (“tuning”) receptor, which is expressed in a unique population of OSNs, and a broadly expressed, family-specific co-receptor (Orco for Ors Ir8a or Ir25a for Irs) ( Clyne et al., 1999b Vosshall et al., 2000 Larsson et al., 2004 Couto et al., 2005 Nakagawa et al., 2005 Benton et al., 2006, 2009 Sato et al., 2008 Abuin et al., 2011 Butterwick et al., 2018 Del Marmol et al., 2021).

Insects have two main olfactory receptor families: odorant receptors (Ors) and ionotropic receptors (Irs) ( Figure 1A). We also make select comparisons with receptor choice in mammals, which relies on a combination of stochastic and deterministic mechanisms ( Dalton and Lomvardas, 2015 Monahan and Lomvardas, 2015), to illustrate convergent or divergent strategies to achieve singular receptor expression. melanogaster and other insect models reveal multiple levels by which selective olfactory receptor expression is achieved and the plasticity of these processes over short and long timescales. Here we discuss recent advances, in which new experimental approaches in D. How the specificity of insect receptor expression is defined has been an unresolved problem for two decades.Įarly work, mainly in adult Drosophila melanogaster, focused on identifying cis-regulatory sequences of olfactory receptor genes as well as transcription factors (TFs) required to promote their correct expression. In insects, as in vertebrates, the majority of individual receptors are expressed in unique populations of olfactory sensory neurons (OSNs), a property critical for the representation of odor-evoked neural activity in the brain. Most animals possess large families of olfactory receptors, which enable detection of diverse chemical signals in their environment. Finally, we describe the mechanisms and potential significance of examples of receptor co-expression. We also consider the plasticity of receptor regulation in response to environmental cues and internal state during the lifetime of an individual, as well as the evolution of novel expression patterns over longer timescales. We discuss how cis-regulatory elements, trans-acting factors, chromatin modifications, and feedback pathways collaborate to activate and maintain expression of the chosen receptor (and to suppress others), highlighting similarities and differences with the mechanisms underlying singular receptor expression in mammals. Focusing on Drosophila melanogaster, where most investigations have been performed, but incorporating recent insights from other insect species, we review the multilevel regulatory mechanisms of olfactory receptor expression. How a receptor gene is selected, from among a large repertoire in the genome, to be expressed in a particular neuron is an outstanding question. The singular expression of insect olfactory receptors in specific populations of olfactory sensory neurons is fundamental to the encoding of odors in patterns of neuronal activity in the brain. Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.

Mature olfactory sensory neuron dendrite number