We then went on to demonstrate that proliferation perfectly scales when different amounts of tissue are removed by amputation, so that the probability of proliferation depends only on fraction of tissue that has regenerated.
To understand how this scaling is encoded, we turned our attention to Fgf/Erk pathway as it has a well established role in controlling growth in many contexts, including fin regeneration. To characterize the spatiotemporal dynamics of the pathway, we use the Erk biosensor to measure activity.
By quantifying Erk activity and proliferation in all osteoblasts of the regenerate, we found that Erk activity is predictive of the probability of cells to proliferate independently of the amount of tissue removed
This led us to ask how Erk activity is controlled in space and time. We realized that Erk activity can be described mathematically throughout the entire regeneration process as the product of two functions, one describing time-dependency (left) and one spatial-dependency (right)
This framework has several interesting consequences, implying that average Erk activity is what encodes memory of tissue size, while the Erk gradients have invariant properties, i.e. the ratio of Erk activity at the tip vs the amputation plane is the same for all rays at all times.
Comments