RETINAL DIFFERENTIATION FROM MULTIPOTENTIAL PINEAL CELLS OF THE EMBRYONIC QUAIL

Pineal cells of the embryonic quail are multipotent stem cells which a re able to differentiate in vitro into pigmented epithelial cells, len s cells and skeletal muscle fibers. Neuronal expression was added in t his study in the repertory of differentiating potency of pineal cells. We used immunohistochemical methods to characterize neuronal properti es with antibodies against serotonin, GABA, tyrosine hydroxylase and n euron-specific antigen (HPC-1) in addition to the enzyme histochemistr y for acetylcholinesterase activity. Cells in the culture were found t o be positively stained with these methods, suggesting that embryonic pineal cells are neuropotent to differentiate various types of neurona l cells. We have studied the culture conditions which favor increment of neuronal cells with extension of neuritic processes, and we have fo und that neuronal cells are maintained for quite a long period under s uppressive conditions of DNA synthesis and under the effect of basic f ibroblast growth factor (FGF). Suppression of DNA synthesis was achiev ed by the addition of aphidicolin, an inhibitor of DNA polymerase alph a, in the medium. Time lapse videograph revealed two different cell ty pes participated in neurogenesis; a minor population of small round ce lls and a major one of flat epithelial cells. Since embryonic quail pi neal cells have been shown to differentiate into two types of photorec eptors, the present results show wider retinal potency of cell differe ntiation by embryonic pineal cells. The cessation of DNA synthesis as well as growth factor(s) may be positively involved in the mechanisms of determination and differentiation of pineal neurons.