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

Abstract

Sensory neuron numbers and positions are precisely organized to accurately map environmental signals in the brain. This precision emerges from biochemical processes within and between cells that are inherently stochastic. We investigated impact of stochastic gene expression on pattern formation, focusing on <i>senseless</i> (<i>sens</i>), a key determinant of sensory fate in <i>Drosophila</i>. Perturbing microRNA regulation or genomic location of <i>sens</i> produced distinct noise signatures. Noise was greatly enhanced when both <i>sens</i> alleles were present in homologous loci such that each allele was regulated in trans by the other allele. This led to disordered patterning. In contrast, loss of microRNA repression of <i>sens</i> 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.