Ventricular cells from the mouse neural plate, stage Theiler 12, transform into different neuronal cell classes in vitro

The rostral parts of the cephalic neural plate and neural crest of mice, stage Theiler 12, were prepared and cultured. At that stage of development they exclusively consist of proliferative ventricular cells, which do not yet display vimentin and neurofilament immunoreactivity. 3H-thymidine autoradiography showed that the progenitor cells of neurons became postmitotic as soon as they were taken into culture. The neurofilament protein (kD 68) was immunocytochemically demonstrable from day 2 in culture, while immunoreactivity to vimentin was never observed. The neurons, prematurely developed from the neuroepithelium of stage Theiler 12-embryos, were identified by their histological and immunocytochemical properties. They gave distinct patterns of immunoreactivity to neuropeptides and anti-serotonin antibodies. Anti-serotonin and anti-somatostatin antibodies reacted from the 3rd day of culture. Antibodies against ACTH, luliberin, substance P and vasopressin gave positive reactions at day 7. Two classes of neurons, the serotonin and the large substance P-immunoreactive ones, were recognized by both immunoreactivity and morphology. The serotonin immunoreactive neurons usually were of a multipolar shape and had a long, varicose axon that was heavily stained, particularly at its distal third. The perikarya appeared in limited areas of the cultured tissue. They grew in the vicinity of each other, but never in densely packed aggregates. The large neurons, reacting heavily with antibodies against substance P and faintly with all the other neuropeptide antibodies applied, were up to 50 micron in diameter and usually occurred in 20-40 cells per preparation of half a neural plate. The results suggest that at least some classes of neurons can develop from the cultured neural plates of stage Th12.