Dysregulation of Fas-Fasl in chordoma and implications on zebrafish notochord development/regression

Chordoma is a rare malignant tumor of embriogenetic origin arising from notochord remnants. As the apoptotic pathway mediated by FAS-FASL was found to be involved in mouse notochord regression, we studied the expression pattern of these genes in 34 chordomas in comparison to that of the normal adult tissue, nucleus pulposus. Since we found FAS-FASL dysregulation in most tumors, we hypothesized that this apoptotic pathway might be affected during notochord development leading to tumorigenesis. To better define the notochord developmental steps we started an in vivo study on zebrafish (Danio rerio), firstly investigating fas-fasl homologue genes expression by RT-PCR in embryos and larvae. While fas was maternally and zigotycally expressed, fasl showed a stage-specific expression. Following microinjection of a GFP-construct activated by the twhh promoter, we specifically sorted by FACS the GFP-positive notochordal cells in which we studied fas-fasl expression by means of RT-PCR at 24 and 48 hours post fertilization (hpf). fas was found to be expressed at both stages, while fasl at 48 hpf; further stages will be analyzed to better define fas-fasl expression profile in notochord cells. Immunohistochemical experiments showed fasl expression in the notochord at 48 hpf, 3 and 5 days post fertilization (dpf) and at 9 mm. We will perform functional studies to silence both fas and fasl by means of morpholinos injections. The appearance of aberrant phenotypes will be studied and it will be verified whether the reactivation of fas-fasl pathway might rescue the normal phenotype.