Genetic control of sensory connections in Drosophila

Abstract

The function of the nervous system depends on the formation of a net of appropriate connections. This process must be at least partly under genetic control, yet the genetic analysis of the development of specific nerve connections has so far made little progress (reviewed in ref. 1). This is in part because of the immense complexity of the connective net. The problem is simpler in the case of insect secondary neurones which are derived from the epidermis and send their axons centripetally towards the central nervous system². The arrangement of sense organs on the body surface is very reproducible in many cases, so that given neurones can be recognized unambiguously in different individuals. In Drosophila, the genetic analysis of development has so far concentrated on the epidermis. The genetic control of segmentation is relatively well understood^3,4 and it has been found that segments are progressively subdivided in smaller developmental units called compartments⁵. This led to the speculation that sensory neurones belonging to different compartments might have different properties⁶. Here we show that the stimulation of mechanoreceptor bristles at different positions on the notum and legs of Drosophila specifically evoke different behavioural responses. This specificity depends on the segmental and in some cases on the compartmental identity of the bristle, but not on the site of entry of the axon into the central nervous system.