Final Report Summary - DOTOS (DOT1L in Osteoarthritis)
Thus, our specific objectives were to decipher the protein and transcriptional network of DOT1L in cartilage, to study the role of DOT1L in vivo in joint development, homeostasis and disease, and to do a translational validation of the previous insights in clinically relevant samples from patients.
Since the beginning of the project, we managed to fulfill the objectives set at the start of the project. Indeed, the in vitro part was perform in primary human chondrocytes extracted from femoral heads. We managed to characterize the DOT1L partners in human chondrocytes in basal conditions or when the Wnt pathway is activated. Moreover, we have gone beyond what was planned, and have found and validated new DOT1L interactors by mass spectrometry. We also performed a microarray in human articular chondrocytes, with provided us in depth insights into the DOT1L molecular network in articular cartilage. The microarray data were analysed with different bioinformatics tools resulting in novel insights into the DOT1L molecular network. We successfully validated all the results obtained in clinically relevant samples.
To study the role of DOT1L in vivo in cartilage development, cartilage specific Dot1l knockout mice were successfully generated, in a series of complex matings combining a Col2 CRE transgenic mice with a mouse strain carrying floxed Dot1l alleles. We managed to arrive at the final genetic model, and the analysis have been performed as planned but in a straightforward way taking into account the results obtained in the in vitro experiments described above, which provided extremely relevant and novel information about the role of DOT1L in cartilage biology. To study the role of DOT1L in vivo in cartilage homeostasis and disease, we performed an alternative strategy to the one that was planned, based in our in vitro success in the optimization for the use of DOT1L inhibitors in chondrocytes. We injected DOT1L inhibitor intra-articularly in the knees of mice, and studied the development of spontaneous osteoarthritis. This change in the workplan allowed us to finish and submit a manuscript to a high-impact journal. However, we are still performing the strategy that was planned to study the role of DOT1L postnatally in cartilage, by generating tamoxifen induced cartilage-specific knockout of Dot1l. We anticipate that this will allow us to obtain further translational insights into DOT1L biology.
Part of the in vitro data were presented in the 35th European Workshop for Rheumatology Research (EWRR) (Budapest, 5-7 March, 2015), and in the Osteoarthritis Research Society International (OARSI) World Congress (Seattle, Washington, from April 30- May 3, 2015). The in vivo data have recently been presented in the 36th EWRR (York, 25-27 February, 2016). We have obtaining an abstract award in two of these conferences (EWRR 2015 and 2016) and the 2015 Celgene Prize in Rheumatology. This highlight the impact of our findings.