Álvarez-Hernán G , Bejarano-Escobar R , Morona R , González A , Martín-Partido G , Francisco-Morcillo J .

	Figure 1. Stereomicroscope images of selected lateral views of Xenopus laevis tailbud embryos ((a)–(f)) and a dorsal view of a free-swimming tadpole (g) according to developmental stages (St) of Nieuwkoop and Faber [37]. Scale bars: 1 mm.
	Figure 2. Morphological features and expression patterns of Isl1 and other cell differentiation markers in the St53 Xenopus laevis central retina. (a)–(c) DAPI fluorescence combined with Isl1 immunofluorescence. DAPI staining showed well-organized retinal layers. Isl1 expressing cells in the INL could be characterized morphologically and topographically as horizontal (arrowheads), bipolar (arrows), or amacrine cells (double arrows). Notice that not all cells located in the GCL expressed Isl1 (asterisks). (d)–(f) A few Isl1-positive bipolar cells also expressed CB (arrows). (g)–(i) Subpopulations of Isl1-positive horizontal (arrowheads), bipolar (arrows), and ganglion cells (double arrowheads) also expressed CR. GCL: ganglion cell layer; INL: inner nuclear layer; ONL: outer nuclear layer. Scale bars: 100 μm.
	Figure 3. Morphological features and expression patterns of Isl1 in the St29/30 ((a), (b)) and St31 ((c), that Isl1 is also expressed by undi (d)) Xenopus laevis retina. ((a), (c)) Toluidine blue-stained transverse retinal resin sections showed that the neural retina had the structure of pseudostratified columnar epithelium. Notice that during these early stages abundant dark-stained granules were observed in the cytoplasm of the neuroepithelial cells. (b),(d) Isl1 immunoreactivity was present in sparse nuclei mainly located near the vitreal surface (arrowheads). L: lens; NbL: neuroblastic layer. Scale bar: 50 μm.
	Figure 4. Morphological features and expression patterns of Isl1 and other cell differentiation markers in the St35/36 Xenopus laevis retina. (a) Toluidine blue-stained transverse retinal resin sections showed that neural retina remained undifferentiated during this stage. (b) Although no plexiform layers were observed, many Isl1-positive nuclei were mainly located near the inner surface of the neuroretina. (c) Immunoreactive ganglion cell axons for SV2 were observed in the vitreal surface of the retina (asterisks). Furthermore, immunoreactivity was also detected near the scleral surface of the undifferentiated retina (arrowheads). (d)–(f) CERN-922 antibody revealed that sparse photoreceptors were differentiating by this stage in the scleral surface of the central nonlayered retina ((d), (F)). L: lens; NbL: neuroblastic layer. Scale bars: 50 μm.
	Figure 5. Morphological features and expression patterns of Isl1 and other cell differentiation markers in the St37/38 Xenopus laevis retina. (a) Toluidine blue-stained transverse retinal resin sections showed that the plexiform layers were observed across the central to mid-peripheral extent of the retina (asterisks). An immature GCL, 2-3 cells in depth, was also observed at this stage. (b) SV2 immunoproducts were observed in the OFL (double arrows), IPL, and ONL. (c) Abundant nuclei were immunoreactive for Isl1 in the GCL, but also in the INL. Thus, nuclei located in the amacrine cell layer (double arrowheads), bipolar cell layer (arrows), and horizontal cell layer (arrowheads) were detected with this antibody. (d)–(g) Incipient plexiform layers were also clearly distinguishable with the DAPI nucleic acid stain (asterisks in (d)). CERN-922 immunoreactivity paralleled the expression of Isl1 and extended towards the more mid-peripheral region of the retina. GCL: ganglion cell layer; INL: inner nuclear layer; L: lens; ONL: outer nuclear layer. Scale bars: 50 μm.
	Figure 6. Morphological features and expression patterns of Isl1 and other cell differentiation markers in the St40 Xenopus laevis retina. (a) Toluidine blue-stained transverse retinal resin sections revealed that the typical multilayered structure was clearly distinguishable, showing morphological features of maturation. The CMZ was visible in the peripheralmost region. (b) Isl1 immunoreactivity was clearly established in abundant nuclei located in the GCL, whereas the INL contained Isl1 labeling that corresponded to horizontal (arrowhead), bipolar (arrow), and amacrine cells (double arrowhead). (c) SV2 expression in the plexiform layers extended to more peripheral regions. (d)–(f) The CERN-922 labeling in the ONL coursed in parallel with Isl1 immunoreactivity and reached the periphery by this stage. CMZ: ciliary marginal zone; GCL: ganglion cell layer; INL: inner nuclear layer; L: lens; ONH: optic nerve head; ONL: outer nuclear layer. Scale bars: 100 μm.
	Figure 7. Schematic drawings of the Isl1 positive cells in the developing retina of Xenopus laevis. Black nuclei represent Isl1-immunostained cells. (a) Isl1 immunoreactivity during St29–31 was restricted to nuclei located near the vitreal surface of the NbL. (b) Although the retinal lamination was absent in the St35-36, cell differentiation was detected immunohistochemically. Abundant Isl1-positive cells were located in the vitreal half of the NbL. (c) At St37-38, retinal layering was completed in the central retina with the emergence of the plexiform layers. Isl1 immunoreactivity was detected in the GCL and in cell subpopulations located in the INL. (d) From St40 onwards Isl1 immunoreactivity was confined to subpopulations of ganglion, amacrine, bipolar, and horizontal cells. Ac: amacrine cell; bc: bipolar cell; gc: ganglion cell; GCL: ganglion cell layer; hc: horizontal cell; INL: inner nuclear layer; IPL: inner plexiform layer; L: lens; mc: Müller cell; NbL: neuroblastic layer; ONL: outer nuclear layer; OPL: outer plexiform layer; ph: photoreceptor.

Austin, Vertebrate retinal ganglion cells are selected from competent progenitors by the action of Notch. 1995, Pubmed

Austin, Vertebrate retinal ganglion cells are selected from competent progenitors by the action of Notch. 1995, Pubmed
Bejarano-Escobar, Cell differentiation in the retina of an epibenthonic teleost, the Tench (Tinca tinca, Linneo 1758). 2009, Pubmed
Bejarano-Escobar, Macrophage and microglia ontogeny in the mouse visual system can be traced by the expression of Cathepsins B and D. 2011, Pubmed
Bejarano-Escobar, Retinal histogenesis and cell differentiation in an elasmobranch species, the small-spotted catshark Scyliorhinus canicula. 2012, Pubmed
Bejarano-Escobar, Light-induced degeneration and microglial response in the retina of an epibenthonic pigmented teleost: age-dependent photoreceptor susceptibility to cell death. 2012, Pubmed
Bejarano-Escobar, Eye development and retinal differentiation in an altricial fish species, the senegalese sole (Solea senegalensis, Kaup 1858). 2010, Pubmed
Bergmann, Developmental expression of dynamin in the chick retinotectal system. 1999, Pubmed
Bilitou, Spatial and temporal expressions of prune reveal a role in Müller gliogenesis during Xenopus retinal development. 2012, Pubmed , Xenbase
Blanchart, Synaptogenesis in the mouse olfactory bulb during glomerulus development. 2008, Pubmed
Boije, Temporal and spatial expression of transcription factors FoxN4, Ptf1a, Prox1, Isl1 and Lim1 mRNA in the developing chick retina. 2008, Pubmed
Boije, Horizontal cell progenitors arrest in G2-phase and undergo terminal mitosis on the vitreal side of the chick retina. 2009, Pubmed
Candal, Patterns of cell proliferation and cell death in the developing retina and optic tectum of the brown trout. 2005, Pubmed
Cepko, The patterning and onset of opsin expression in vertebrate retinae. 1996, Pubmed
Chang, Sequential genesis and determination of cone and rod photoreceptors in Xenopus. 1998, Pubmed , Xenbase
Cheng, The Iroquois homeobox gene, Irx5, is required for retinal cone bipolar cell development. 2005, Pubmed
Chow, Control of late off-center cone bipolar cell differentiation and visual signaling by the homeobox gene Vsx1. 2004, Pubmed
Chung, The structural and functional development of the retina in larval Xenopus. 1975, Pubmed , Xenbase
Cima, Ontogeny of the retina and optic nerve of Xenopus laevis. IV. Ultrastructural evidence of early ganglion cell differentiation. 1980, Pubmed , Xenbase
Dorsky, Regulation of neuronal diversity in the Xenopus retina by Delta signalling. 1997, Pubmed , Xenbase
Edqvist, Early identification of retinal subtypes in the developing, pre-laminated chick retina using the transcription factors Prox1, Lim1, Ap2alpha, Pax6, Isl1, Isl2, Lim3 and Chx10. 2006, Pubmed
Edqvist, Axon-bearing and axon-less horizontal cell subtypes are generated consecutively during chick retinal development from progenitors that are sensitive to follistatin. 2008, Pubmed
Elshatory, Expression of the LIM-homeodomain protein Isl1 in the developing and mature mouse retina. 2007, Pubmed
Elshatory, Islet-1 controls the differentiation of retinal bipolar and cholinergic amacrine cells. 2007, Pubmed
Ericson, Early stages of motor neuron differentiation revealed by expression of homeobox gene Islet-1. 1992, Pubmed , Xenbase
Ferreiro-Galve, Patterns of cell proliferation and rod photoreceptor differentiation in shark retinas. 2010, Pubmed
Fischer, Heterogeneity of horizontal cells in the chicken retina. 2007, Pubmed
Fischer, Exogenous growth factors induce the production of ganglion cells at the retinal margin. 2002, Pubmed
Francisco-Morcillo, Expression of Fgf19 in the developing chick eye. 2005, Pubmed
Francisco-Morcillo, Spatial and temporal patterns of proliferation and differentiation in the developing turtle eye. 2006, Pubmed
Galli-Resta, Mosaics of islet-1-expressing amacrine cells assembled by short-range cellular interactions. 1997, Pubmed
Hirsch, Xenopus Pax-6 and retinal development. 1997, Pubmed , Xenbase
Hirsch, Xenopus Brn-3.0, a POU-domain gene expressed in the developing retina and tectum. Not regulated by innervation. 1997, Pubmed , Xenbase
Hobert, Functions of LIM-homeobox genes. 2000, Pubmed
Hocking, Expression of Bmp ligands and receptors in the developing Xenopus retina. 2007, Pubmed , Xenbase
Holt, A single-cell analysis of early retinal ganglion cell differentiation in Xenopus: from soma to axon tip. 1989, Pubmed , Xenbase
Holt, Cellular determination in the Xenopus retina is independent of lineage and birth date. 1988, Pubmed , Xenbase
Kiyama, Overlapping spatiotemporal patterns of regulatory gene expression are required for neuronal progenitors to specify retinal ganglion cell fate. 2011, Pubmed
Lom, Local and target-derived brain-derived neurotrophic factor exert opposing effects on the dendritic arborization of retinal ganglion cells in vivo. 2002, Pubmed , Xenbase
Ma, Zac1 promotes a Müller glial cell fate and interferes with retinal ganglion cell differentiation in Xenopus retina. 2007, Pubmed , Xenbase
Marquardt, Pax6 is required for the multipotent state of retinal progenitor cells. 2001, Pubmed
Meléndez-Ferro, Early development of the retina and pineal complex in the sea lamprey: comparative immunocytochemical study. 2002, Pubmed
Misgeld, Roles of neurotransmitter in synapse formation: development of neuromuscular junctions lacking choline acetyltransferase. 2002, Pubmed
Moreno, Evidences for tangential migrations in Xenopus telencephalon: developmental patterns and cell tracking experiments. 2008, Pubmed , Xenbase
Moreno, Islet1 as a marker of subdivisions and cell types in the developing forebrain of Xenopus. 2008, Pubmed , Xenbase
Moreno, Subdivisions of the turtle Pseudemys scripta subpallium based on the expression of regulatory genes and neuronal markers. 2010, Pubmed
Moreno, Characterization of the bed nucleus of the stria terminalis in the forebrain of anuran amphibians. 2012, Pubmed , Xenbase
Morona, Comparative analysis of calbindin D-28K and calretinin in the retina of anuran and urodele amphibians: Colocalization with choline acetyltransferase and tyrosine hydroxylase. 2007, Pubmed
Morona, Calbindin-D28k and calretinin as markers of retinal neurons in the anuran amphibian Rana perezi. 2008, Pubmed
Morona, Immunohistochemical localization of calbindin D28k and calretinin in the retina of two lungfishes, Protopterus dolloi and Neoceratodus forsteri: colocalization with choline acetyltransferase and tyrosine hydroxylase. 2011, Pubmed
Mu, Gene regulation logic in retinal ganglion cell development: Isl1 defines a critical branch distinct from but overlapping with Pou4f2. 2008, Pubmed
Okada, Light and electron microscopic analysis of synaptic development in Macaca monkey retina as detected by immunocytochemical labeling for the synaptic vesicle protein, SV2. 1994, Pubmed
Okamoto, Subtype-specific expression of Fgf19 during horizontal cell development of the chicken retina. 2009, Pubmed
Pan, ISL1 and BRN3B co-regulate the differentiation of murine retinal ganglion cells. 2008, Pubmed
Pfaff, Requirement for LIM homeobox gene Isl1 in motor neuron generation reveals a motor neuron-dependent step in interneuron differentiation. 1996, Pubmed
Rapaport, Cellular competence plays a role in photoreceptor differentiation in the developing Xenopus retina. 2001, Pubmed , Xenbase
Stanke, Muscarinic signaling influences the patterning and phenotype of cholinergic amacrine cells in the developing chick retina. 2008, Pubmed
Stiemke, Cell birthdays in Xenopus laevis retina. 1995, Pubmed , Xenbase
Suga, LIM family transcription factors regulate the subtype-specific morphogenesis of retinal horizontal cells at post-migratory stages. 2009, Pubmed
Wang, Requirement for math5 in the development of retinal ganglion cells. 2001, Pubmed
Wang, Developmental restriction of the LIM homeodomain transcription factor Islet-1 expression to cholinergic neurons in the rat striatum. 2001, Pubmed
Whitney, Genetic modulation of horizontal cell number in the mouse retina. 2011, Pubmed
Wu, Onecut 1 and Onecut 2 are potential regulators of mouse retinal development. 2012, Pubmed
Young, Cell proliferation during postnatal development of the retina in the mouse. 1985, Pubmed