title: An Expression Refinement Process Ensures Singular Odorant Receptor Gene Choice.
abstract: Odorant receptor (OR) gene choice in mammals is a paradigmatic example of monogenic and monoallelic transcriptional selection, in which each olfactory sensory neuron (OSN) chooses to express one OR allele from over 1,000 encoded in the genome [1-3]. This process, critical for generation of the circuit from nose to brain [4-6], is thought to occur in two steps: a slow initial phase that randomly activates a single OR allele, followed by a rapid feedback that halts subsequent expression [7-14]. Inherent in this model is a finite failure rate wherein multiple OR alleles may be activated prior to feedback suppression [15, 16]. Confronted with more than one receptor, the neuron would need to activate a refinement mechanism to eliminate multigenic OR expression and resolve unique neuronal identity [16], critical to the generation of the circuit from nose to olfactory bulb. Here we used a genetic approach in mice to reveal a new facet of OR regulation that corrects adventitious activation of multiple OR alleles, restoring monogenic OR expression and unique neuronal identity. Using the tetM71tg model system, in which the M71 OR is expressed in >95% of mature OSNs and potently suppresses the expression of the endogenous OR repertoire [10], we provide clear evidence of a post-selection refinement (PSR) process that winnows down the number of ORs. We further demonstrate that PSR efficiency is linked to OR expression level, suggesting an underlying competitive process and shedding light on OR gene switching and the fundamental mechanism of singular OR choice.
authors.affiliation: Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar.
authors.forename: Ishmail
authors.initials: I
authors.lastname: Abdus-Saboor
authors.affiliation: Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar.
authors.forename: Mohammed J
authors.initials: MJ
authors.lastname: Al Nufal
authors.affiliation: Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar.
authors.forename: Maha V
authors.initials: MV
authors.lastname: Agha
authors.affiliation: Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR 7241, and INSERM U1050, Paris 75005, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Ruinart de Brimont
authors.affiliation: Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS UMR 7241, and INSERM U1050, Paris 75005, France.
authors.forename: Alexander
authors.initials: A
authors.lastname: Fleischmann
authors.affiliation: Weill Cornell Medical College in Qatar, Qatar Foundation - Education City, Doha 24144, Qatar. Electronic address: ben.shykind@meiragtx.com.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Shykind
mesh_terms: D000483:Alleles; D000818:Animals; D005786:Gene Expression Regulation; D051379:Mice; D009830:Olfactory Bulb / Q000378:metabolism*; D018034:Olfactory Receptor Neurons / Q000378:metabolism*; D018035:Receptors, Odorant / Q000235:genetics* / Q000378:metabolism
chemical_list: D018035:Receptors, Odorant