Inhibitory neuron migration and IPL formation in the developing zebrafish retina.
Bottom Line: Finally, HCs, iACs and dACs each undergo cell type-specific migration.In contrast to current hypotheses, we find that most dACs send processes into the forming inner plexiform layer (IPL) before migrating through it and inverting their polarity.By imaging and quantifying the dynamics of HCs, iACs and dACs from birth to final position, this study thus provides evidence for distinct and new migration patterns during retinal lamination and insights into the initiation of IPL formation.
Affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.Show MeSH
Mentions: Having analysed apico-basal migration, we next investigated the dynamics of tangential migration in the three types of RIN (Fig. 7), as this is crucial for our understanding of how neurons become properly spaced within their respective layers. To begin to answer this question, we analysed the average values for distance and speed for each phase and found that they are not significantly different from one another. However, whereas only 0.05% of RINs migrated >5 µm tangentially, which is roughly one somal length, during Phase 1, 27% of RINs migrated >5 µm in Phase 2 and 22% of RINs migrated >5 µm in the first 12 h of Phase 3, suggesting that tangential migration occurs mainly during later stages of migration. At all phases of migration, cells were seen to migrate tangentially in one direction, only to reverse direction at a later time. This lack of directional persistence often results in low ratios of displacement over distance travelled (Fig. 7F). Thus, it seems that the first bipolar phase of migration is used primarily for getting RINs to the apico-basal centre of the retina, but that the second and third phases of migration are used to refine the position of the cells into specific layers and establish mosaic arrays within these layers.Fig. 7.
Affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.