Horizontal Cells in the Zebrafish Retina
In the image above, cell nuclei (cyan) were stained with BODIPY while the outer plexiform layer is pseudo-colored in red. In yellow are the Cx55.5:M-YFP-labeled horizontal cell precurors.
Symmetric cell divisions have been proposed to rapidly increase neuronal number late in neurogenesis, but how critical this mode of division is to establishing a specific neuronal layer is unknown. Through in vivo time-lapse imaging methods, Leanne Godinho et al. discovered that in the laminated zebrafish retina, the horizontal cell layer forms quickly during embryonic development upon division of a precursor cell population. These precursors undergo nonapical symmetric division at the laminar location where mature horizontal cells contact photoreceptors. Strikingly, the observed precursor cell type (yellow) exclusively generates horizontal cells.
Image by Leanne Godinho and Philip Williams, courtesy of Rachel Wong, University of Washington.