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J. Teusner, J.J. Alexander, M.T. McManus, B.D. Harfe, W.W. Hauswirth; Determining the Role of Dicer in the Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3137.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Dicer, an RNaseIII–like nuclease, processes microRNAs into their mature form that can regulate gene expression through inhibition of mRNA translation and mRNA degradation. Recent studies in plants and invertebrates have demonstrated that this processing controls crucial developmental transitions and regulates cell division and cell death. However, little is known about what role, if any, Dicer has in directing tissue development in mammals. The purpose of this work is to investigate the function of Dicer in the mouse retina. Methods: To bypass the requirement of Dicer during early development, a conditional allele of this mouse gene was previously constructed by flanking an exon encoding most of the second RNaseIII domain with loxP sites. Mice homozygous for the floxed Dicer conditional allele are phenotypically wild type. Removal of this exon in the germline by crossing the floxed allele to a germline Cre produced embryos exhibiting arrested development at E7.5, as seen before in the Dicer null mouse. To investigate the effects of specifically knocking out Dicer in the retina, AAV2–CBA–Cre vectors were delivered to one eye of P2 or P30 pups homozygous for the floxed Dicer conditional allele by intravitreal or subretinal injection. Full–field scotopic electroretinography (ERG) was performed on dark–adapted mice followed by photopic ERG analysis. Results: Scotopic and photopic ERGs recorded in age–matched mice 30 days after intravitreal injection showed no significant difference in the a–wave amplitudes of injected eyes compared to control eyes. In contrast, the b–wave signal was significantly reduced in treated eyes relative to controls. ERGs of mice injected subretinally with rAAV–Cre are in progress and histological analysis of these retinas is being done to determine the possible morphological effects of this knock–out. Conclusions: We are currently using a unique mouse conditional allele of Dicer and an AAV–Cre vector to achieve specific Dicer knockdown in the mouse retina. The reduced b–wave amplitudes seen in treated eyes suggest the absence of Dicer leads to a deficiency in post–synaptic signaling between photoreceptors and cells of the inner retina.
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