Inhibition of the wnt canonical signalling by retinoic acid in ntera/d1 cellswnts involved in the early stages of neuronal differentiation

Zusammenfassung

Different processes like cell proliferation and differentiation are regulated by Wnts, secreted glycoproteins that act through canonical (ß-catenin-Tcf signalling) and non-canonical pathways (activation of JNK or Rho GTPases or calcium release from intracellular stores). The role of Wnts in neurogenesis can be studied using as a model system NTERA-2/D1 (NT2/D1) embryonal carcinoma cells, which display characteristics of neuroepithelium in the undifferentiated state and differentiate into neurons when treated with retinoic acid (RA). The aim of the present thesis was to study the expression pattern of the different WNTs in the early phase of neuronal differentiation of NT2/D1 cells, characterizing RA effect on Wnt signalling pathway during this period, and how these Wnts could affect neurogenesis. From these studies it was observed that RA induced the expression of non-canonical and canonical WNTs, although it effectively repressed endogenous and induced canonical signalling in NT2/D1 cells. Interestingly, the upregulation of non-canonical WNTs like WNT4 and WNT11, preceded the onset of neurogenesis, characterized by the expression of transcription factors such as ASCL1, HOXC5 and NEUROD1. The action of Wnt4 seems to be important for certain populations of neuronal progenitors and together with Wnt11 may be involved in the increase of survival of these progenitors