Ordered patterning of the sensory system is susceptible to stochastic features of gene expression

Sensory neuron numbers and positions are precisely organized to accurately map environmental signals in the brain. However, this precision must emerge from biochemical processes within and between cells that are stochastic. We measured intrinsic noise in senseless protein output, a key determinant of sensory fate, during Drosophila development. Perturbing microRNA regulation or genomic locus of senseless transcription produced distinct noise signatures. Genomic location altered protein stochasticity in an allelic-pairing dependent manner (transvection). This generated sensory pattern disorder without perturbing protein abundance. In contrast, loss of microRNA repression of senseless increased protein abundance but not sensory pattern disorder. This suggests that gene expression stochasticity is a critical feature that must be constrained during development to allow rapid yet accurate cell fate resolution. One Sentence Summary Life on the Margin: balancing speed and accuracy during animal development.