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Roser Gonzalez-Duarte, Alejandro Garanto, Javier Vicente-Tejedor, Marina Riera, Pedro de la Villa, Roman Blanco, Gemma Marfany; Cerkl Knockdown Murine Model Shows Mild Affectation Of The Retinal Ganglion Cell Layer. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1620.
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© ARVO (1962-2015); The Authors (2016-present)
The function of CERKL, a RP/CRD causative gene, has remained elusive since its identification in 2004. Mutations in this gene account for a large number of cases in the Spanish population. We have recently shown that CERKL displays an unexpected transcriptional complexity, which further hampers genotype-phenotype correlations. In order to shed light on CERKL function and contribution to retinal dystrophies, we generated and performed the initial characterization of a novel Cerkl-/- mouse model.
The knockout model was generated by the cre-mediated excision of a 2.3 kb genomic region encompassing the proximal promoter, first exon and a segment of the first intron in a C57BL/6J background. The Cerkl-/- retinas were characterized at the transcriptional, morphological, immunohistological and electroretinographic levels. Specific protein markers were used to assess retinal disfunction and stress at the molecular level. All procedures were performed according to the ARVO statement for the use of animals in ophthalmic and vision research.
The Cerkl-/- mice were viable and fertile. Although the deletion was successful, some remnant Cerkl expression was unexpectedly driven by adjacent and internal alternative promoters. This residual expression (35%) of Cerkl in the KO was moderate in photoreceptors and weak in ganglion and inner nuclear layers as supported by in situ hybridization and immunohistochemical analyses. Morphological studies did not show any gross changes even at 12 moths of age or after light damage. A significant decrease of the ganglion cell marker Brn3a, as well as the increase of the retinal stress marker GFAP indicated alterations at the molecular and cellular levels. Notably, the oscillatory potentials (OPs) were significantly reduced in the electroretinographic recordings at all ages.
The targeted Cerkl deletion resulted in a knockdown rather than a full knockout model, with retention of some Cerkl transcription (35%) from alternative promoters. A mild retinal phenotype in the Cerkl-/- retinas was supported by: i) the increase of the GFAP levels, ii) the decrease of Brn3a marker levels and iii) the consistent non-progressive perturbation of the OPs in the ERGs, although no gross morphological differences were observed. Taken together, these results strongly point to a disfunction of the ganglion and/or amacrine rather than photoreceptor cells, challenging the role of CERKL in human versus mouse retinas.
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