Αναπτυξιακοί μηχανισμοί κατά τη μορφογένεση της παρεγκεφαλίδας στον οργανισμό μοντέλο Gallus domesticus ; Developmental mechanisms during cerebellum morphogenesis in the animal model Gallus domesticus

In the present thesis the parameters involved in the architectural configuration of the cerebellar cortex were studied. Our results showed that the proliferation rate of granule cells in the external granule layer zone (EGL, the main zone of cell proliferation in the developing cerebellum) constitutes the key mechanism for fissures’ formation. Specifically, the higher proliferation rate of granule cells in the apex compared to that of the base of the developing lobe, accounts for the inward foliation of the cerebellar cortex. Moreover, the layer of Purkinje cells was found to involve in the morphogenesis of the lobes with a simultaneous change in the morphology (elongation) of the granule cells and their accumulation in the 'anchoring centers'. Furthermore, the involvement of certain proteins (eg growth factors, transmembrane proteins) in the foliation of the cerebellar cortex was also studied. Participation of the growth factor pleiotrophin in the proliferation, maturation and migration of granule cells of the EGL zone, especially in the apices of the developing lobules, was observed. In addition, integrin, a transmembrane receptor, showed a different expression pattern in the apices compared to that of the walls and bases of the developing lobe, while the spatiotemporal expression pattern of the intermediate filament vimentin, throughout development, indicates that radial glial cells play a key role in organizing the layered structure of the cerebellar cortex, as radial glia provides a scaffold for the migration of granule cells of the proliferative zone (EGL). Finally, the involvement of glutamate and the neuromodulator nitric oxide (NO) in the formation of the cerebellar cortex was investigated. Pharmacological inhibition of AMPA receptors of glutamate using the inhibitor CNQX did not show any significant effect on the proliferation rate of granule cells of the EGL zone. Whereas, pharmacological inhibition of neuronal synthase (nNOS) of nitric oxide, using L-NAME, revealed that nitric oxide (NO), depending ...