Thesis Defense of Mathilde Poulet

The laboratory is pleased to announce that Mathilde Poulet will defend her thesis, entitled “PRL-2, a novel component of the angiogenesis network” on the 15th December 2017 at 1.30pm in the ampitheatre of building B6 (Talence University Campus). 

PRL-2, a novel component of the angiogenesis network

The three Phosphatase of Regenerative Liver (PRL-1, -2, -3) represent an intriguing group of protein tyrosine phosphatases that has been implicated in a number of diseases. They have gained much attention in the context of cancer. Indeed, they have been constantly associated with metastasis, cell proliferation, cell invasion and migration. To date, however, little is known about their physiological function and no biological substrates have been clearly identified. All three PRLs are highly conserved among mammals, underscoring the idea that they might have important roles in cellular functions. Characterization of the PRL-2 knockout mouse indicates that this phosphatase is likely involved throughout development. Protein phosphorylation is implicated in angiogenesis by playing critical and reversible functions in cell signaling pathways. This prompted us, in the frame of this thesis, to investigate the role of PRL-2 in vascular morphogenesis using both in vitro models and genetic loss-of-function mouse models. In the retinal angiogenesis mouse model, we found that PRL-2 deletion leads to delay in the formation of the retinal vascular plexus with a reduction of the advancing vasculature across the vitreal surface. Furthermore, excessive angiogenesis and branching at the leading edge in 6 day old pups is observed. Indeed, the growing front of PRL-2 KO mouse retinas showed a higher vascular density due to active, multidirectional hypersprouting of the vasculature. This data introduces PRL-2 as a potential component of the complex signaling network that orchestrates neo-angiogenesis. Based on these findings, we have examined whether the absence of PRL-2 can modify the behavior of endothelial cells in vitro. We showed an altered migration in various assays. In particular, sprouting in in vitro angiogenesis assays is altered, which is in agreement with the in vivo data. By using several siRNA, we showed that the signaling pathway of PRL-2 is dependent to VEGF/VEGFR signaling. Indeed, the stimulation of endothelial cells by VEGF is dependant of the presence or absence of PRL-2. Furthermore, other targets altered by PRL-2 downregulation, are Notch and the Hey2 transcription factor, which is consistent with in vivo data as we showed a strikingly effect on arteriovenous differentiation. Taken together, these data introduce PRL-2 as a novel component of the complex signaling network that orchestrates developmental and, possibly, pathological angiogenesis.

We wish her good luck!