Morphogen gradients play a crucial role in defining epithelial patterning during development. Despite variations in morphogen gradients, pattern readout is remarkably consistent across different embryos. Here, Dagmar Iber and colleagues extend their existing mathematical model of gradient variability to investigate the importance of cell size during patterning. They predict that reduced cell surface area in the developing epithelium should lead to increased gradient precision. Indeed, a literature search reveals that epithelial tissues patterned by morphogen gradients tend to exhibit smaller cell surface areas than tissues with no known morphogen gradient. The authors postulate that this apparent advantage of small cell surface areas could explain the evolution of pseudostratified epithelia. Their model also shows that the positional error is also affected by gradient decay length (with this error predicted to increase as the tissue grows) and by the size of the morphogen source. Using data from the developing Drosophila wing disc, they demonstrate that the effect of tissue growth can be buffered by an increase in morphogen source size and a decrease in epithelial cell surface area. Overall, this work provides new insight into how such precise patterning is achieved during development.
