Gene regulation of the P2Y-like receptor GPR17, a key player in oligodendroglial differentiation

The P2Y-like receptor GPR17 is a G protein-coupled receptor regulating oligodendrogliogenesis. Under physiological conditions, it is expressed in early oligodendrocyte precursor cells (OPCs) that also express the neural marker NG2, and its expression seems necessary to address their differentiation to mature oligodendrocytes. However, before terminal maturation, GPR17 has to be turned off. We have previously demonstrated that GPR17 is activated by uracil nucleotides and cysteinyl-leukotrienes, but the molecular mechanisms at the basis of its gene regulation are still unknown. To identify candidate factors involved in induction/repression of GPR17 we have developed a reporter assay. First, we cloned two putative promoter regions of the human GPR17 gene into a reporter vector upstream to a gene encoding for an engineered firefly luciferase and we have transfected these constructs in different types of oligodendroglial cell lines. Then, we evaluated the bioluminescence produced in response to an array of stimuli, including nucleotides, hormones and growth factors. Results demonstrate that treatment with 10µM forskolin induced a 2-fold increase of GPR17 promoter activity in the murine oligodendroglial cell line Oli-neu, suggesting regulation via cAMP-responsive elements. Moreover, incubation of cells with conditioned medium from cortical neurons was able to significantly induce GPR17 promoter activity, even if we still don’t know which is the released factor responsible of this effect. Understanding how the expression of GPR17 is finely regulated will not only advance basic knowledge in oligodendrogliogenesis, but will also help developing new strategies to stimulate the reparative potential of the quiescent OPCs that are still present in the adult brain.