The P19 embryonal carcinoma cells differentiate into neurons, astrocytes, and fibroblast-like cells following induction with retinoic acid. The cells mature into functional neurons, as determined by their ability to release neurotransmitters in a Ca2+- and depolarization-dependent manner. P19 neurons in culture represent a mixed population in terms of their neurotransmitter phenotype. The cholinergic phenotype of these neurons is modulated by culture density. Cholinergic markers, such as the vesicular acetylcholine transporter, acetyl cholinesterase, and choline acetyltransferase, are expressed in about 85% of the cells in sparse cultures and are largely suppressed at high cell densities. In contrast, glutamate release is enhanced in dense P19 neuronal cultures. The factor mediating the density effect is concentrated exclusively on the cell membrane of P19 neurons and not on the nonneuronal cells, which also differentiate from P19 embryonal carcinoma cells. This membrane-associated component retains its functionality, even after membrane fixation. The downregulation of the cholinergic properties in dense cultures is paralleled by a downregulation of the α subunit of the ciliary neurotrophic factor (GNTF) receptor. Thus, it is suggested that the membrane-associated factor, which mediates the density effect, downregulates the cholinergic phenotype by inhibiting the responsiveness of these neurons to CNTF. We further suggest that the P19 cell line can serve as a model system for the study of neurotransmitter phenotype acquisition and plasticity throughout neuronal differentiation.
Bibliographical noteFunding Information:
We are grateful to M.-F. Diebler (Gif-sur-Yvette, France) for the v-AChT antibodies, to Alomone Labs (Israel) for CNTF supply, and to Regeneron Pharmaceuticals (New York) for the CNTFR~ clone. We would like to thank the Smith Laboratory in the Hebrew University for the use of their facilities. This work was partially supported by the German-Israeli Foundation (I-299-023) and by the Israel Science Foundation (152/93). D. P. is supported by the L. Eshkol scholarship.
- Cholinergic phenotype
- Embryonal carcinoma
- Neuronal cell line
- Neurotransmitter release
- Neurotrophic factors
- Synaptic proteins