EMBRYONIC GLIA AND FOREBRAIN NEUROGENESIS; in vitro generation and differentiation of telencephalic neurons

Abstract: The current thesis is aimed to increase our understanding of the generation and differentiation of telencephalic neurons, with emphasis on the role of glial cells in these processes. Using in vitro methods we have studied the role of glial cells in neurogenesis, inheritance of genetic regional specification, and influence on differentiation of neurons. We demonstrate that expanded cell cultures exhibiting glial characteristics produce neurons when EGF and serum is removed from the culture medium. At least some of the neurons are generated by GFAP expressing progenitor cells. Proliferating (i.e. undifferentiated) progenitor cells expanded under different culture conditions exhibit distinct expression profiles of region specific genes. LGE precursor cells expanded as attached cultures are most similar to LGE subventricular zone cells, while progenitor cells within LGE neurospheres resemble LGE ventricular zone cells. Despite the differences in gene expression in the proliferating cell cultures, the neurons generated by expanded LGE attached or neurosphere cultures, in vitro, are comparable. Furthermore, expanded glial cultures from the LGE produce retinoic acid after 4 passages (at P4), but not at P9. MGE glial cultures do not produce retinoic acid. In co-culture with glial cultures maturation of primary LGE neurons is influenced. LGE neurons co-cultured with LGE glia grow long neurites, while they develop short processes on MGE glia. Furthermore, twice as many DARPP-32 positive neurons are produced in co-culture with retinoic acid producing P4 LGE glia, as compared to on non-retinoic acid producing P9 LGE glia or P5 MGE glia.