title: Oculomotor deficits in aryl hydrocarbon receptor null mouse.
abstract: The Aryl hydrocarbon Receptor or AhR, a ligand-activated transcription factor, is known to mediate the toxic and carcinogenic effects of various environmental pollutants such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). Recent studies in Caenorhabditis elegans and Drosophila melanogaster show that the orthologs of the AhR are expressed exclusively in certain types of neurons and are implicated in the development and the homeostasis of the central nervous system. While physiological roles of the AhR were demonstrated in the mammalian heart, liver and gametogenesis, its ontogenic expression and putative neural functions remain elusive. Here, we report that the constitutive absence of the AhR in adult mice (AhR-/-) leads to abnormal eye movements in the form of a spontaneous pendular horizontal nystagmus. To determine if the nystagmus is of vestibular, visual, or cerebellar origin, gaze stabilizing reflexes, namely vestibulo-ocular and optokinetic reflexes (VOR and OKR), were investigated. The OKR is less effective in the AhR-/- mice suggesting a deficit in the visuo-motor circuitry, while the VOR is mildly affected. Furthermore, the AhR is expressed in the retinal ganglion cells during the development, however electroretinograms revealed no impairment of retinal cell function. The structure of the cerebellum of the AhR-/- mice is normal which is compatible with the preserved VOR adaptation, a plastic process dependent on cerebellar integrity. Finally, intoxication with TCDD of control adults did not lead to any abnormality of the oculomotor control. These results demonstrate that the absence of the AhR leads to acquired central nervous system deficits in the adults. Given the many common features between both AhR mouse and human infantile nystagmus syndromes, the AhR-/- mice might give insights into the developmental mechanisms which lead to congenital eye disorders.
authors.affiliation: INSERM UMR-S 747, Toxicologie Pharmacologie et Signalisation Cellulaire, Centre universitaire des Saints-Pères, Paris, France ; Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
authors.forename: Aline
authors.initials: A
authors.lastname: Chevallier
authors.forename: Antoine
authors.initials: A
authors.lastname: Mialot
authors.forename: Jean-Maurice
authors.initials: JM
authors.lastname: Petit
authors.forename: Pedro
authors.initials: P
authors.lastname: Fernandez-Salguero
authors.forename: Robert
authors.initials: R
authors.lastname: Barouki
authors.forename: Xavier
authors.initials: X
authors.lastname: Coumoul
authors.forename: Mathieu
authors.initials: M
authors.lastname: Beraneck
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D002531:Cerebellum / Q000378:metabolism; D004596:Electroretinography; D005133:Eye Movements; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009759:Nystagmus, Pathologic / Q000235:genetics* / Q000473:pathology; D009801:Oculomotor Muscles / Q000473:pathology*; D015840:Oculomotor Nerve Diseases / Q000235:genetics*; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics*; D012027:Reflex, Vestibulo-Ocular; D012160:Retina / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; C484722:Ahr protein, mouse