RT Journal Article
SR Electronic
T1 Photoreceptor progenitor dynamics in the zebrafish embryo retina and its modulation by primary cilia and N-cadherin
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.02.13.947663
DO 10.1101/2020.02.13.947663
A1 Gonzalo Aparicio
A1 Magela Rodao
A1 José L. Badano
A1 Flavio R. Zolessi
YR 2020
UL http://biorxiv.org/content/early/2020/02/14/2020.02.13.947663.abstract
AB Background Photoreceptors of the vertebrate neural retina are originated from the neuroepithelium, and like other neurons, must undergo cell body translocation and polarity transitions to acquire their final functional morphology, which includes features of neuronal and epithelial cells.Methods We analyzed this process in detail on zebrafish embryos using in vivo confocal microscopy and electron microscopy. Photoreceptor progenitors were labeled by the transgenic expression of EGFP under the regulation of the photoreceptor-specific promoter crx, and genes of interest were knocked-down using morpholino oligomers.Results Photoreceptor progenitors detached from the basal retina at pre-mitotic stages, rapidly retracting a short basal process as the cell body translocated apically. They remained at an apical position indefinitely to form the outer nuclear layer (ONL), initially extending and retracting highly dynamic neurite-like processes, tangential to the apical surface. Many photoreceptor progenitors presented a short apical primary cilium. The number and length of these cilia was gradually reduced until nearly disappearing around 60 hpf. Their disruption by knocking-down IFT88 and Elipsa caused a notorious defect on basal process retraction. Time-lapse analysis of N-cadherin knock-down, a treatment known to cause a severe disruption of the ONL, showed that the ectopic photoreceptor progenitors initially migrated in an apparent random manner, profusely extending cell processes, until they encountered other cells to establish cell rosettes in which they stayed acquiring the photoreceptor-like polarity.Conclusion Altogether, our observations indicate a complex regulation of photoreceptor progenitor dynamics to form the retinal ONL, previous to the post-mitotic maturation stages.aPKCatypical protein kinase C;Crxcone-rod homeobox transcription factor;hpfhours post-fertilization;ONLouter nuclear layer;RGCretinal ganglion cell;TEMtransmission electron microscopy.