Novel approach to quantitative spatial gene expression uncovers genetic stochasticity in the developingDrosophilaeye

Abstract

25Robustness in development allows for the accumulation of cryptic variation, and this largely neutral 26 variation is potentially important for both evolution and complex disease phenotypes. However, it has 27 generally only been investigated as variation in the response to large genetic perturbations. Here we 28 use newly developed methods to quantify spatial gene expression patterns during development of the 29Drosophila eye disc, and uncover cryptic variation in wildtype developmental systems. We focus on 30 four conserved morphogens, hairy, atonal, hedgehog, and Delta, that are involved in specifying 31 ommatidia in the developing eye. We find abundant cryptic variation within and between species, 32 genotypes, and sexes, as well as cryptic variation in the regulatory logic between atonal and hairy and 33 their regulators, Delta and hedgehog. This work paves the way for a synthesis between population 34 and quantitative genetic approaches with that of developmental biology.