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N. Cuenca, G.C. Martinez–Navarrete, A. Angulo, J. Esteve–Rudd, J. Martin–Nieto; Pax6 And Chx10 Transcription Factors Expression In Retinal Progenitors And Neuronal Differentiation In Adult Primates . Invest. Ophthalmol. Vis. Sci. 2006;47(13):165.
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© ARVO (1962-2015); The Authors (2016-present)
CHX10 and PAX6 are retinogenic, homeobox transcription factors coexpressed in embryonic retinal progenitor cells of mammals. In this work we have used them as molecular markers to identify retinal precursor cells in adult primates. As well, we show the existence of cells differentiating into cone and rod photoreceptors in the far peripheral retina of monkeys and humans.
Cryostat vertical sections of the far peripheral retina from macaques and humans were subjected to single and double immunostaining with antibodies to PAX6 and CHX10, together with nestin (a neural stem–cell marker) and PCNA (a proliferating–cell marker). Hoechst 33248 staining and TUNEL labeling were used to test for degenerating cells. The expression of photoreceptor markers, such as arrestin and opsins, was also analyzed, and images were obtained by means of immunofluorescence confocal microscopy. Transmission electron microscopy studies were carried out on ultrathin retinal sections.
Cells coexpressing PAX6 and CHX10, together with cells displaying single labelings, were identified in both the human and monkey non–laminated peripheral retinal margin. In contrast, segregation of these transcription factors was found in the inner nuclear layer of the laminated peripheral retina. Colocalization was also observed between nestin and CHX10 or PCNA in cells in the far peripheral retina. No evidence of pyknotic nuclei was found upon Hoechst 33258 staining, or of apoptotic cells using the TUNEL technique. Instead, a gradient of morphological differentiation of immature cells into cones and rods was evident in this zone in parallel to the establishment of correct synaptic contacts. Ultrastructurally, formation of outer segment discs was observed close to the nucleus of immature cells in the retinal margin lying underneath the outer limiting membrane. In advancing towards the laminated retina, outer segments increased in size and evaginated off the outer nuclear layer, till reaching their adequate size and location in fully–developed photoreceptors.
Stem/progenitor cells exist in the far peripheral retina of adult monkeys and humans together with cells undergoing active neuronal differentiation. This zone constitutes the site where genesis of novel retinal circuitries takes place through life in primates.
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