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Publication - Dr Lucia Marucci

    Cross-talk between Hippo and Wnt signalling pathways in intestinal crypts

    insights from an agent-based model

    Citation

    Ward, D, Fletcher, AG, Homer, M & Marucci, L, 2018, ‘Cross-talk between Hippo and Wnt signalling pathways in intestinal crypts: insights from an agent-based model’. bioRxiv.

    Abstract

    Intestinal crypts are responsible for the total cell renewal of the lining of the intestines, occurring every 4-7 days in humans. This rapid turnover is governed by the complex interplay between signalling pathways and the cell cycle within individual cells in the crypts. The role of Wnt signalling in governing cell proliferation and differentiation in the intestinal crypt has been extensively studied, with increased signalling found towards the lower regions of the crypt. Recent studies have shown that the Wnt signalling gradient found within the crypt may arise as a result of division-based spreading from a Wnt ‘reservoir’ at the crypt base. The discovery of the Hippo pathway’s involvement in maintaining crypt homeostasis is more recent; a mechanistic understanding of Hippo pathway dynamics, and its possible cross-talk with the Wnt pathway, remains lacking. To explore how the interplay between these pathways may control crypt homeostasis and dysplasia we developed and analysed a mathematical model coupling an ordinary differential equation description of Wnt and Hippo signalling with a cell-based description of cell movement, proliferation and contact inhibition. Furthermore, we compared an imposed Wnt gradient with a division-based Wnt gradient model. Our results suggest that Hippo signalling affects the Wnt pathway by reducing the presence of free cytoplasmic β-catenin, causing cell cycle arrest. This process slows the rate of crypt turnover, previously attributed only to mutations in Wnt pathway components commonly observed in colorectal cancers. We also show that a division-based spreading of Wnt can form a Wnt gradient, resulting in proliferative dynamics comparable to imposed-gradient models. This suggests that imposed-gradient models are a reasonable approximation of experimentally observed Wnt gradients, however they provide little insight into the source of Wnt. Finally, a simulated APC double mutant, with misregulated Wnt and Hippo signalling activity, is predicted to be capable of completing a more rapid monoclonal conversion of the crypt than a Wnt-only mutant.

    Full details in the University publications repository