UNDERSTANDING THE MOLECULAR MECHANISMS UNDERLYING THE PATHOGENESIS OF OPITZ G/BBB SYNDROME EXPLOITING THE Mid1 KNOCK-OUT MOUSE MODEL

Opitz G/BBB syndrome (OS) is a multiple congenital anomaly disorder characterized by developmental defects of midline structures. Mutations in the MID1 gene are responsible of the X-linked form of the syndrome and lead to loss-of-function of the protein. MID1 is an E3 ubiquitin ligase of the tripartite motif (TRIM) subfamily of RING proteins and associates with microtubules. The mouse line carrying a nonfunctional ortholog of the human MID1 gene, Mid1, (Mid1-/Y) recapitulates the brain morphological abnormalities observed in patients, i.e. hypoplasia of the anterior cerebellar vermis, although the role of Mid1 in cerebellar development is still unclear. Previous analysis demonstrated that the alteration of the cerebellum in Mid1-/Y mice originates prenatally, delineating the embryonic day (E) 13.5 as the time of the first sign of the cerebellar defect. We started to explore the molecular pathways affected by the lack of Mid1 at E13, thus placing immediately before the appearance of the defect. Starting from an unbiased proteomics study using differential mass spectrometry approach, we explored altered pathways in Mid1-/Y developing cerebella. The network analysis has suggested that Mid1-/Y cerebella might present impairment in vesicular trafficking and intercellular communication, later confirmed by immunoblot experiments. In parallel, the association of Mid1 with some regulators of RNA processing and stability has been investigated in cells upon MID1-overexpression. All the collected results may be helpful in disclosing potential molecular mechanisms involved in the establishment of the neurological defects observed in mouse embryos and in OS patients. Further investigations are required to provide new evidence confirming our data and the results might increase our knowledge of the OS pathogenesis not only in the cerebellar compartments but also in the other midline-affected structures.