Energy profiles and statistics of spontaneous T1 transitions in confluent tissues

Cellular rearrangements play a vital role in several morphogenetic processes. T1 transitions are an important type of such cellular rearragements that are observed in biological foam structures like morphogenesis of developing embryos and in unjammed epithelial cells. We use a multi phase field model to study spontaneously generated T1 transitions under different regimes of cell deformability and cell-cell interaction. We have found an universal profile of energy evolution at the site of T1 transitions that indicates a slow buildup of energy followed by a fast decay. This profile is remisniscent of avalanches in granular matter and energy release in earthquakes. We have also studied how cell shape deformability and intercellular interactions affect properties of T1 transitions including rate of T1 transitions, their durations and the amount of energy build up during them. We also show that in confleunt tissues, large deformations only happen when there are T1 transitions provided there is no apoptosis or cell division.