Inhibitory neuron migration and IPL formation in the developing zebrafish retina.
Bottom Line: All RINs then transition to a less directionally persistent multipolar phase of migration.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.
Affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.Show MeSH
Mentions: Our finding that multipolar dACs migrate basally through a pre-formed proto-IPL (Fig. 4C; supplementary material Fig. S3) does not support current hypotheses on IPL formation (supplementary material Fig. S2). To gain further insights into how the IPL originates, we examined the formation of the IPL across the wave of retinal differentiation in SoFa1 (Almeida et al., 2014) embryos (Fig. 8A). We observed that RINs can first be visualized in the centre of the retina at times when RGCs are still migrating and that RGCs and RINs are initially interdigitated in the GCL. However, consistent with our previous work (Almeida et al., 2014), we find that this interdigitation is lost as development proceeds and the unevenness of the apical side of the RGC layer decreases to a minimum before the first signs of a continuous RGC dendritic plexus (Fig. 8A,B). Shortly after a sharp boundary is formed between RGCs and RINs, a BC (Crx-positive) axonal plexus forms at the interface between RGCs and RINs (Fig. 8A,C), and it is only after the BC plexus begins to form that dACs migrate to their positions within the GCL (Fig. 8A,C). Our analysis also shows that late-arriving RGCs can migrate basally past ACs to take up residence in the GCL (n=4 RGCs; Fig. 8D), arguing against the idea that ACs arrive at a pre-formed GCL (Godinho et al., 2005).Fig. 8.
Affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK.