title: Photoreceptor morphology is severely affected in the beta,beta-carotene-15,15'-oxygenase (bcox) zebrafish morphant.
abstract: The retinoic acid molecule, a vitamin A derivative, is of key importance for eye and photoreceptor development in vertebrates. Several studies have provided evidence that the ventral part of the retina is particularly susceptible to impairment in retinoid signalling during the period of its development. In zebrafish, targeted gene knockdown of beta,beta-carotene-15,15'-oxygenase (bcox), the key enzyme for vitamin A formation, provokes a loss of retinoid signalling during early eye development that results in microphthalmia at larval stages. Using this model, we analysed the consequences of this for the retinal morphology of the fish larvae in structural details. Our analyses revealed that rods and cones do not express photoreceptor specific proteins (rhodopsin, peanut agglutinin, zpr1) in the peripheral retina. The photoreceptors in the central retina showed shortened outer segments, and electron dense debris in their intermembranal space. The number of phagosomes was increased, and cell death was frequently observed in the outer nuclear layer. Furthermore, the number of Muller cells was significantly reduced in the inner nuclear layer. Thus, we found that the lack of retinoid signalling strongly effects photoreceptor development in the ventral and dorsal retina. In addition, shortened outer segments and cell death of the remaining photoreceptors in the central retina indicate that there is an ongoing need for retinoid signalling for photoreceptor integrity and survival at later developmental stages.
authors.affiliation: Experimental Ophthalmology, University Eye Hospital, Roentgenweg 11, 72076 Tuebingen, Germany. konrad.kohler@uni-tuebingen.de
authors.forename: Oliver
authors.initials: O
authors.lastname: Biehlmaier
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Lampert
authors.forename: Johannes
authors.initials: J
authors.lastname: von Lintig
authors.forename: Konrad
authors.initials: K
authors.lastname: Kohler
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002452:Cell Count / Q000379:methods; D016923:Cell Death / Q000235:genetics; D004625:Embryo, Nonmammalian; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D020287:In Situ Nick-End Labeling / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D020419:Photoreceptor Cells, Vertebrate / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure*; D011975:Receptors, Mitogen / Q000276:immunology / Q000378:metabolism; D012160:Retina / Q000196:embryology / Q000378:metabolism* / Q000648:ultrastructure*; D012243:Rhodopsin / Q000378:metabolism; D015027:Zebrafish
chemical_list: D011975:Receptors, Mitogen; C038223:peanut agglutinin receptor; D012243:Rhodopsin; D010105:Oxygenases; D005974:Glutamate-Ammonia Ligase