In study IV, we performed a proteomic analysis of the core Wnt/PCP receptor Ror2, and discovered several novel binding partners which were verified in m DA cells and in the developing ventral midbrain. rerio, we found that the Ror2-Sor CS2 receptor complex is required during embryogenesis to regulate convergent extension, somitogenesis and brain development.
We selected Sor CS2, a proneurotrophin receptor from the VPS10-domain containing sortilin receptor family, as a top candidate because of its specific expression in the mouse midbrain floorplate and its functional involvement in m DA neuron wiring. We also suggest that Sor CS2 has the capacity to internalize Ror2 and its other co-receptors in a Wnt/PCP-dependent manner in vitro and in vivo, via an unknown pathway.
In study II, we investigated the expression of mammalian Wnts in developing choroid plexi.
We discovered that biologically active Wnt5a is secreted to the cerebral spinal fluid (CSF) by the epithelial cells of the hindbrain, but not the telencephalic choroid plexus, in both mouse and in human embryos.
In study V, we investigated whether Leucine-rich repeat kinase 2 (Lrrk2), the protein product of the park8 gene, which is mutated in more than 40% of patients with inherited PD, can interact with the Wnt/PCP pathway by using a proteomic screening.
We describe that Lrrk2 interacts with a number of Wnt/PCP components in dopaminergic cells, in the VM of E18.5 mice embryos, and in a human cell line.A proteomic analysis of LRRK2 binding partners reveals interactions with multiple signaling components of the WNT/PCP pathway. Wnt/Planar Cell Polarity (PCP) signaling is involved in many cellular processes throughout the development of the embryo.Analysis of Wnt5a-/-, Wnt5a overexpressing, Wnt5a-/-; Ror2-/- and Ror2-/-; Vangl2-/- mice identified a function of the Wnt5a-Ror2/Vangl2 signaling axis in the VM morphogenesis and in m DA neuron development.Our study shows that correct Wnt5a expression levels are crucial for VM morphogenesis, m DA neurogenesis and m DA neuron maturation.These data reveal that the two pathways previously considered to be independent, Wnt/PCP and proneurotrophin receptor signaling, functionally interact.Moreover, our results identify Sor CS2 as a novel regulator of Wnt/PCP signaling in vertebral embryogenesis.Moreover, we found a novel phenotype of bilateral asymmetry in Ror2-/-; Vangl2-/- animals which suggests that Vangl2 alone or in a complex with Ror2 controls the correct position, proliferation and differentiation of m DA progenitors into m DA neuroblasts and neurons.Our results additionally identify a novel role of Wnt/PCP signaling in controlling m DA neurogenesis, which may be of interest for the development of novel regenerative approaches to treat neurodegenerative diseases which affect m DA neurons, such as Parkinson's disease.These produce signals that influence the fate, histogenic organisation and growth of adjacent tissues, resulting in spatial patterning.Members of the Wnt gene family are among few secreted proteins expressed in patterning centers of the developing CNS, such as the pallial-subpallial boundary (PSB) and the cortical hem.