Xenbase Image ID: 159512
Figure S2. Neurogenetic Timing in Xenopus Embryonic Retina
To investigate the cell birth date (that is the time of exit from the cell cycle) of different retinal cells, we labeled dividing retinal progenitors by BrdU intrabdominal injections  from st. 30, st. 34, and st. 37, and analyzed their differentiation fates at st. 42 (mature embryonic retina). As the generation of the Xenopus Müller glia, which is the last retinal cell type to exit from the cell cycle, was extensively investigated both in terms of cell birth date and at the molecular level , we focused our attention on retinal neurons.
(A–C) Examples of st. 42 retinal sections immunostained for BrdU (green signal). Dashed lines enclose the central part of retina that was considered for statistical analysis.
(D–F) Magnifications of st. 42 retinal sections in which BrdU (green) was co-detected with specific retinal markers (Fast Red mRNA detection). White arrows point to double-labeled cells. The following markers were used to identify different cell types: hermes  for ganglion cells (D), prox1  for horizontal cells (not shown), amacrine antibodies panel (anti-5-HT, anti-GABA, anti-tyrosine hydroxilase) as in Figure 1 (not shown), IRBP  for the external segment of photoreceptors (E), Xvsx1 (F), and Xotx2 (not shown) for bipolar cells. ONL: outer nuclear layer; INL: inner nuclear layer; GCL: ganglion cell layer.
(G) Bars show the proportion of each cell type that was still dividing at the time of BrdU injection. Error bars show standard error of the mean. We classified the BrdU-positive cells according to their morphology, position in the retinal layers, and expression of markers. The cell birth dates of the different Xenopus retinal neurons are partially overlapping. Nonetheless, rods among photoreceptors  and bipolar cells show the latest cell birth dates. A substantial proportion of their progenitors are still dividing (being BrdU-positive) at st. 34 (24% photoreceptors and 63% bipolar). At this stage, only a few ganglion, horizontal, and amacrine progenitors are still dividing (6%, 5%, and 12%, respectively). Bipolar cells are the latest neurons, as the majority of them (63%) are still dividing at st. 34.
Image published in: Decembrini S et al. (2006)
Image downloaded from an Open Access article in PubMed Central. Copyright: © 2006 Decembrini et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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