Abstract
Morphogen gradients are crucial for the development of organisms, but there is still no agreement on the mechanisms involved in their establishment. The biochemical properties of many morphogens prevent their extracellular free diffusion, indicating the need for an active mechanism for transport. The involvement of filopodial structures (cytonemes) has been proposed for morphogen signaling, although a detailed description of the mechanism is pending. Here, we describe the development of an in silico model based on the main general features of cytoneme-meditated gradient formation and its implementation into an open software tool we named Cytomorph. We have tested the spatial and temporal adaptability of our model experimentally quantifying Hedgehog (Hh) gradient formation in Drosophila and found that Cytomorph is able to reproduce the gradient and explain its scaling between different epithelia. After experimental validation, we studied the predicted impact of a range of features such as length, size, density, dynamics and contact behavior of cytonemes on morphogen distribution. Our results illustrate Cytomorph as an adaptive tool to test and generate hypotheses that are difficult to study experimentally.