in-vivo-imaging-transgenic-gene-expression-individual-retinal

<em>In Vivo </em>Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

The genetic and technical strengths have made the zebrafish vertebrate a key model organism in which the consequences of gene manipulations can be traced ...

The University of Melbourne

Monash University

Unlike mammals, zebrafish exhibits extensive neural regeneration after injury in adult stages of its lifetime due to the neurogenic activity of the radial glial cells. However, the genes involved in the regenerative neurogenesis response of the zebrafish brain are largely unknown. Thus, understanding the underlying principles of this regeneration capacity of the zebrafish brain is an interesting research realm that may offer vast clinical ramifications.

The chemokine receptor cxcr5 regulates the regenerative neurogenesis response in the adult zebrafish brain.

Contrairement aux mammif&egrave;res, zebrafish expose une vaste r&eacute;g&eacute;n&eacute;ration neuronale apr&egrave;s une blessure dans les stades adultes de sa dur&eacute;e de vie en raison de l&#39;activit&eacute; neurog&egrave;ne des cellules gliales radiales. Toutefois, les g&egrave;nes impliqu&eacute;s dans la r&eacute;ponse r&eacute;g&eacute;n&eacute;ratrice de la neurogen&egrave;se du cerveau chez le poisson z&egrave;bre sont largement inconnus. Ainsi, comprendre les principes sous-jacents de cette capacit&eacute; de r&eacute;g&eacute;n&eacute;ration du cerveau chez le poisson z&egrave;bre est un domaine de recherche int&eacute;ressant qui peut offrir de vastes ramifications cliniques.

Le cxcr5 de r&eacute;cepteur de chimiokine r&eacute;gule la r&eacute;ponse r&eacute;g&eacute;n&eacute;ratrice neurogen&egrave;se du cerveau adulte chez le poisson z&egrave;bre.

A differenza dei mammiferi, zebrafish esibisce vasta rigenerazione neurale dopo l&#39;infortunio nella fase adulte della sua vita a causa dell&#39;attivit&agrave; neurogena delle cellule gliale radiali. Tuttavia, i geni coinvolti nella risposta rigenerativa neurogenesi del cervello zebrafish sono in gran parte sconosciuti. Quindi, comprendere i principi di questa capacit&agrave; di rigenerazione del cervello zebrafish &egrave; un regno di ricerca interessante che pu&ograve; offrire vaste conseguenze cliniche.

Il chemokine recettore cxcr5 regola la risposta rigenerativa neurogenesi nel cervello adulto zebrafish.

The adult zebrafish brain, unlike mammalian counterparts, can regenerate after injury owing to the neurogenic capacity of stem cells with radial glial character. We hypothesized that injury-induced regenerative programs might be turned on after injury in zebrafish brain and enable regenerative neurogenesis. Here we identify one such gene-the transcription factor gata3-which is expressed only after injury in different zebrafish organs. Gata3 is required for reactive proliferation of radial glia cells, subsequent regenerative neurogenesis, and migration of the newborn neurons. We found that these regeneration-specific roles of Gata3 are dependent on the injury because Gata3 overexpression in the unlesioned adult zebrafish brain is not sufficient to induce neurogenesis. Thus, gata3 acts as a specific injury-induced proregenerative factor that is essential for the regenerative capacity in vertebrates.

Regenerative neurogenesis from neural progenitor cells requires injury-induced expression of Gata3.

Le cerveau du poisson-z&egrave;bre adulte, contrairement &agrave; des homologues chez les mammif&egrave;res, peut se r&eacute;g&eacute;n&eacute;rer apr&egrave;s une blessure en raison de la capacit&eacute; neurog&egrave;ne de caract&egrave;re glial radial des cellules souches. Nous avons suppos&eacute; que les programmes r&eacute;g&eacute;n&eacute;ratrices induite par blessure peuvent &ecirc;tre activ&eacute;s apr&egrave;s une blessure au cerveau de poisson-z&egrave;bre et activez la neurogen&egrave;se r&eacute;g&eacute;n&eacute;ratrice. Ici, nous identifions une telle transcription g&eacute;nique, la facteur gata3-ce qui est exprim&eacute; seulement apr&egrave;s une blessure dans le poisson-z&egrave;bre diff&eacute;rents organes. Gata3 est requise pour la prolif&eacute;ration r&eacute;active des cellules gliales radiales, neurogen&egrave;se r&eacute;g&eacute;n&eacute;ratrice ult&eacute;rieure et migration des neurones nouveau-n&eacute;s. Nous avons constat&eacute; que ces r&ocirc;les de r&eacute;g&eacute;n&eacute;ration propres de Gata3 reposent sur la blessure car Gata3 surexpression dans le cerveau du poisson-z&egrave;bre adulte unlesioned n&#39;est pas suffisante pour induire la neurogen&egrave;se. Ainsi, gata3 agit comme un facteur de sp&eacute;cifiques proregenerative induite par la blessure qui est essentiel pour la capacit&eacute; de r&eacute;g&eacute;n&eacute;ration chez les vert&eacute;br&eacute;s.

Neurogen&egrave;se r&eacute;g&eacute;n&eacute;ratrice des cellules prog&eacute;nitrices neurales requiert expression induite par la blessure de Gata3.

Il cervello di zebrafish adulto, a differenza delle controparti dei mammiferi, pu&ograve; rigenerare dopo l&#39;infortunio a causa neurogena capacit&agrave; delle cellule staminali con carattere gliali radiali. Abbiamo ipotizzato che indotta da lesioni rigenerative programmi potrebbero essere attivate dopo l&#39;infortunio nel cervello di zebrafish e abilitare la neurogenesi rigenerativa. Qui ci identifichiamo una tale trascrizione genica, il fattore gata3, che si esprime solo dopo l&#39;infortunio in zebrafish diversi organi. Gata3 &egrave; necessaria per la proliferazione reattiva di cellule della glia radiali, successiva neurogenesi rigenerativa e migrazione dei neuroni neonati. Abbiamo trovato che questi ruoli specifici di rigenerazione di Gata3 dipendono le lesioni perch&eacute; Gata3 iperespressione del cervello di zebrafish adulto di unlesioned non &egrave; sufficiente a indurre neurogenesi. Cos&igrave;, gata3 agisce come un fattore specifico indotta da lesioni proregenerative che &egrave; essenziale per la capacit&agrave; rigenerativa nei vertebrati.

Neurogenesi rigenerativa da cellule progenitrici neurali richiede espressione indotta da lesioni di Gata3.

Early retinal progenitor cells (RPCs) in vertebrates produce lineages that vary greatly both in terms of cell number and fate composition, yet how this variability is achieved remains unknown. One possibility is that these RPCs are individually distinct and that each gives rise to a unique lineage. Another is that stochastic mechanisms play upon the determinative machinery of equipotent early RPCs to drive clonal variability. Here we show that a simple model, based on the independent firing of key fate-influencing transcription factors, can quantitatively account for the intrinsic clonal variance in the zebrafish retina and predict the distributions of neuronal cell types in clones where one or more of these fates are made unavailable.

The Independent Probabilistic Firing of Transcription Factors: A Paradigm for Clonal Variability in the Zebrafish Retina.

During neurogenesis, progenitors balance proliferation and cell cycle exit together with expression of fate determinant genes to ensure that the correct number of each of these neuron types is generated. Although intrinsic gene expression acting cell autonomously within each progenitor drives these processes, the final number of neurons generated is also influenced by extrinsic cues, representing a potential avenue to direct neurogenesis in developmental disorders or regenerative settings without the requirement to change intrinsic gene expression. Thus, it is important to understand which of these stages of neurogenesis are amenable to such extrinsic influences. Additionally, all types of neurons are specified in a highly conserved histogenic order, although its significance is unknown. This study makes use of conserved patterns of neurogenesis in the relatively simple yet highly organized zebrafish retina model, in which such histogenic birth order is well characterized. We directly visualize and quantify birth dates and cell fate determinant expression in WT vs. environments lacking different neuronal populations. This study shows that extrinsic feedback from developing retinal neurons is important for the temporal expression of intrinsic fate determinants but not for the timing of birth dates. We found no changes in cell cycle exit timing but did find a significant delay in the expression of genes driving the generation only of later- but not earlier-born cells, suggesting that the robustness of this process depends on continuous feedback from earlier-formed cell types. Thus, extrinsic cues selectively influence cell fate determinant progression, which may explain the function of the retinal histogenic order observed. J. Comp. Neurol. 524:2553-2566, 2016. © 2016 Wiley Periodicals, Inc.

Stefanie Dudczig

School of Biosciences

The University of Melbourne

In Vivo Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

Stefanie Dudczig

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The University of Melbourne

In Vivo Imaging of Transgenic Gene Expression in Individual Retinal Progenitors in Chimeric Zebrafish Embryos to Study Cell Nonautonomous Influences

School of Biosciences