Plasticity and Differentiation of Embryonic Retinal Cells After Terminal Mitosis

Abstract

The relation between terminal mitosis and the events that determine the developmental fate of embryonic precursor cells is not well understood. This relation has now been investigated with [3H]thymidine autoradiography to determine the time of cell birth and with a culture system that allows the testing of the developmental potential of cells isolated from the chick embryo retina. Contrary to the situation in vivo, where neuronal differentiation always precedes photoreceptor differentiation, photoreceptor differentiation occurs prematurely and precedes neuronal differentiation when precursor cells are isolated from the retina at early embryonic stages. Thus, cells born by embryonic day 5 (ED-5) give rise predominantly to photoreceptors when isolated for culture on ED-6 but develop mainly as neurons when isolated on ED-8. This suggests that retinal precursor cells retain after terminal mitosis the capacity to develop either as neurons or as photoreceptors. Moreover, photoreceptor differentiation appears to represent a constitutive or "default" pathway that precursor cells follow in the absence of neuron-inducing signals.

The nitric oxide-cGKII system relays death and survival signals during embryonic retinal development via AKT-induced CREB1 activation

“…Cell composition and characterization in E6 and E8 purified cultures has been described previously. 31 In E6 cultures, the cell composition was 25-30% neurons (amacrine-like cells) to 75-80% cone photoreceptors and in E8 20-30% cone photoreceptors to 70-80% amacrine like-cells. 31 Counting of viable cells was performed as previously described.…”

“…31 In E6 cultures, the cell composition was 25-30% neurons (amacrine-like cells) to 75-80% cone photoreceptors and in E8 20-30% cone photoreceptors to 70-80% amacrine like-cells. 31 Counting of viable cells was performed as previously described. 27 Cells in vitro for 2 h (C0) or 24 h (C1) were treated with different drugs at the indicated concentrations.…”

“…Since in E6 cultures there is a high proportion of cone photoreceptors in relation to MNs, 31 one could regard that only cone photoreceptors would be responsive to SNAP in E6, but this is not the case. Interestingly, in E8 cultures, MNs are more numerous than photoreceptors, and SNAP does not regulate the size of cone photoreceptor population but only MNs survival.…”

Rod-derived cone viability factor : un espoir de thérapie des dégénérescences rétiniennes ?

“…Pour identifier les RdCVF, nous avons développé une approche systématique par clonage d'expression fondée sur un test de viabilité des cônes (Figure 1) [8]. Le modèle utilisé est une culture de cellules rétiniennes d'embryons de poulet, cultivées à faible densité et en l'absence d'agents inducteurs, ce qui conduit à une différenciation en photorécepteurs par défaut de signal [9]. Ces photorécep-teurs sont majoritairement des cônes, contrairement à ce qui est observé dans des cultures de cellules de mammifères.…”

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cours du développement [7][8][9]. Les analyses phénotypiques des souris invalidées pour CDK4/6 et les cyclines D ayant été réalisées à des stades tardifs du développement, des phénomènes compensatoires ont pu se produire.

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