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M. Tsujikawa, J. Malicki; ovl is Essential for Differentiation and Survival of Vertebrate Sensory Neurons . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1017.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Mutation in the zebrafish oval (ovl) locus causes photoreceptor cell loss and kidney cysts by 3 days after fertilization. This phenotype is very reminiscent of the human Bardet–Biedl Syndrome. Our purpose is to identify and characterize ovl gene. Methods: Positional candidate cloning was followed by biochemical assays. Results:Using a positional candidate approach, we succeeded in identifying the gene affected in ovl. ovl encodes an 824 amino acid–polypeptide and the ovl tz288b mutation causes a truncation of two thirds of its sequence. The injection of anti–ovl morpholinos reproduces the ovl phenotype in wild–type embryos and ovl mRNA injection rescues the defects . These results indicate that we cloned the correct locus. Immunostaining revealed that ovl is concentrated in connecting cilia. To investigate ovl function further, we examined whether cilia and basal bodies are present in mutant photoreceptors by immunostaining. This experiment indicates that the loss of ovl affects either the assembly or the maintenance of photoreceptor cilia but leaves the basal body intact at 3 dpf. The lack of cilia could be due to the lack of cilia maintenance or to the absence of cilia formation. To test which of the above is the case, we performed staining with anti–acetylated–alpha–tubulin antibodies at earlier stages of development. In the retina of the ovl mutant homozygotes, acetylated–alpha–tubulin staining reveals the presence of cilia in neuroepithelial cells at 30 hpf. The staining is indistinguishable from the wild type. These results indicate that ovl function is not necessary for cilia formation in sensory organs but is required for their maintenance. Because cilia are also found in sensory cells of the vertebrate auditory and olfactory systems, we investigated the generation and maintenance of cilia in these sensory organs. The immunostaining experiments revealed that cilia are also generated but not maintained also in other sensory organs. Moreover, the loss of cilia is followed by the loss of sensory neurons in the sense organs. Conclusions: We conclude that ovl function is not necessary for cilia formation in sensory organs but is required for their maintenance and for the survival of sensory neurons.
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