Transdifferentiation of putative neuronal cells of neural retina into lens: A demonstration by chick-quail chimeric cultures

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Abstract
To elucidate the cell-type origin of lens cells, which differentiate in stationary cultures of neural retina, chimeric cultures between chick and quail cells were made to recombine xenoplastically the different cell fractions separated from 8- to 9-day cultures of 3.5-day-old embryonic neural retinal cells by means of centrifugation in Percoll. Extensive lentoidogenesis occurred in the recombination of the N2-fraction (consisting mostly of small round cells) with the E-fraction (containing a number of flattened epithelial cells). Taking advantage of the difference in electrophoretic mobility of chick and quail δ-crystallin, it was shown that this lens-specific protein, synthesized in the chimeric cultures, was mostly of the species-specificity of N2. Microscopic observations of histological sections of cell sheets of quail N2- and chick E-fraction chimeric cultures revealed that most cells with δ-crystallin, as identified by means of immunohistological detection, are provided with a nuclear marker characteristic of quail. By determining the level of activity of choline acetyltransferase and by examining the stainability with a fluorescent dye (Merocyanine-540), it was suggested that cells in the N2-fraction are primitive neuroblast-like cells. Thus, we can conclude that putative neuronal cells in early cultures of avian embryonic neural retina can transdifferentiate into lens cells.