Coordination between stochastic and deterministic specification in the Drosophila visual system

Abstract

Retinal neurons play musical chairs As the retina develops in fruit flies, subtypes of certain color photoreceptors, the R7 neurons, are stochastically specified even though the downstream neurons they need to connect to, the Dm8 neurons, are not randomly specified. Courgeon and Desplan find that Dm8 neurons are actually specified in subtypes and are produced in excess. Those Dm8 neurons that connect to an R7 input survive; those that fail to find a match die by apoptosis. The matching is facilitated by a pair of cell adhesion molecules. The stochastic results of R7 differentiation are thus propagated downstream even though those downstream elements are not stochastically determined. Science , this issue p. eaay6727