Yap Regulates Müller Glia Reprogramming in Damaged Zebrafish Retinas.

Vertebrates such as zebrafish have the outstanding ability to fully regenerate their retina upon injury, while mammals, including humans, do not. In zebrafish, upon light-induced injury, photoreceptor regeneration is achieved through reprogramming of Müller glia cells, which proliferate and give rise to a self-renewing population of progenitors that migrate to the lesion site to differentiate into the new photoreceptors. The Hippo pathway effector YAP was recently implicated in the response to damage in the retina, but how this transcription coactivator is integrated into the signaling network regulating Müller glia reprogramming has not yet been explored. Here, we show that Yap is required in Müller glia to engage their response to a lesion by regulating their cell cycle reentry and progenitor cell formation, contributing to the differentiation of new photoreceptors. We propose that this regulation is accomplished through a lin28a-ascl1a-dependent mechanism, bona fide Müller glia-reprogramming factors. Overall, this study presents Yap as a key regulator of zebrafish Müller glia reprogramming and consequently retina regeneration upon injury.

Usefulness of zebrafish larvae to evaluate drug-induced functional and morphological renal tubular alterations.

Prediction and management of drug-induced renal injury (DIRI) rely on the knowledge of the mechanisms of drug insult and on the availability of appropriate animal models to explore it. Zebrafish (Danio rerio) offers unique advantages for assessing DIRI because the larval pronephric kidney has a high homology with its human counterpart and it is fully mature at 3.5 days post-fertilization. Herein, we aimed to evaluate the usefulness of zebrafish larvae as a model of renal tubular toxicity through a comprehensive analysis of the renal alterations induced by the lethal concentrations for 10% of the larvae for gentamicin, paracetamol and tenofovir. We evaluated drug metabolic profile by mass spectrometry, renal function with the inulin clearance assay, the 3D morphology of the proximal convoluted tubule by two-photon microscopy and the ultrastructure of proximal convoluted tubule mitochondria by transmission electron microscopy. Paracetamol was metabolized by conjugation and oxidation with further detoxification with glutathione. Renal clearance was reduced with gentamicin and paracetamol. Proximal tubules were enlarged with paracetamol and tenofovir. All drugs induced mitochondrial alterations including dysmorphic shapes ("donuts", "pancakes" and "rods"), mitochondrial swelling, cristae disruption and/or loss of matrix granules. These results are in agreement with the tubular effects of gentamicin, paracetamol and tenofovir in man and demonstrate that zebrafish larvae might be a good model to assess functional and structural damage associated with DIRI.