Critical Periods of Eye Development in Vertebrates with Special Reference to Humans

Abstract

This review highlights similarities in human, rodent and avian eye development, focusing on morphogenesis, proliferative activity, apoptosis and mechanistic aspects during the development of the retina, the iris and the cornea. Retinal morphogenesis encompasses four stages: (1) appearance of the ganglion cell layer, (2) formation of the outer plexiform layer separating the inner and outer nuclear layers, (3) formation of immature photoreceptor segments and (4) development of outer photoreceptor segments. The first two stages occur very early during development, i.e. within the first 10 days of incubation in chickens, during the first postnatal week in rodents and until 28 weeks of gestation in humans. In contrast, the formation of receptor inner and outer segments takes considerably less time, i.e. about another 4 days in chickens, 7 days in rodents and 12 weeks in humans. Lesion experiments in chickens and rodents indicate that catecholaminergic input is a prerequisite for proper photoreceptor development, whereas synaptic contact of retinal ganglion cells with higher CNS centers is not necessary. Although already observed very early during the development of the human retina, apoptotic cell death only becomes significant after 23 weeks of gestation and further increases during late gestation. The majority of dying cells in the human and avian retina represent bipolar cells, and the number of apoptotic cells is highest during the formation of inner and outer photoreceptor segments. The similarities outlined in the present review indicate that the basic developmental mechanisms are the same in the primate, rodent and avian retina.

Morphogenesis of the different types of photoreceptors of the chicken (Gallus domesticus) retina and the effect of amblyopia in neonatal chicken

“…Our findings are in good agreement with recent gene expression studies in the chicken retina, indicating commencement of visual cell differentiation, at around 6 days of incubation (Chen and Cepko, 2002). Early photoreceptor cell morphogenesis in the chicken is thus very similar to that found in other vertebrate species (Lorke and Winking, 1986;Usukura and Obata, 1995;Wu et al, 2003).…”

“…It is interesting to note that biochemical analyses of chicken retinal lightsensitive pigments indicate that at least four different types of cones exist, each characterized by an opsin with different spectral absorbance (Hart, 2001;Mey and Thanos, 2000). Our observation, that photoreceptor maturation is essentially completed on day 19 of incubation, is consistent with the electrophysiological analyses, showing that the chicken retina becomes light sensitive shortly before the time of hatching (Mey and Thanos, 2000;Wu et al, 2003).…”

“…The chicken retina is frequently used as a model system to study fundamental aspects of neuronal and retinal development (Mey and Thanos, 2000;Wu et al, 2003), but also to investigate the development of refractive abnormalities (Stone et al, 2003). Despite numerous similarities, the chicken retina is, however, far more complex than that of mammals.…”

Progenitor Cells from Human Embryonic Retina – Proliferation and Preferential Differentiation into Ganglion Cells

“…It remains unclear whether the various capacities in differentiation simply reflect different progenitors isolated from different stages of the retinal development [2]. Based on our preliminary data, observations of GFAP immunoreactivity in our cultures using progenitors from fetuses of comparable ages (12 weeks) support the view of such a cellular heterogeneity in progenitor cell isolation from later stages of the retinal development.…”

“…The formation of the ganglion cell layer is followed in overlapping phases by the graduate differentiation of horizontal and amacrine cells as well as cone receptors. Towards the end of retinogenesis, rod receptors, bipolar cells and Müller cells are generated, again in an overlapping and yet strictly time-related sequence that is generally conserved across all vertebrate species [1,2]. Cell lineage studies in mammals and amphibian revealed that retinal progenitors are multipotent, and subsets of progenitors can give rise to more than one or two cell types [3].…”