Targeted expression ofshibirets andsemaphorin 1areveals critical periods for synapse formation in the giant fiber ofDrosophila

Abstract

In order to determine the timing of events during the assembly of a neural circuit in Drosophila we targeted expression of the temperature-sensitive shibire gene to the giant fiber system and then disrupted endocytosis at various times during development. The giant fiber retracted its axon or incipient synapses when endocytosis was blocked at critical times, and we perceived four phases to giant fiber development: an early pathfinding phase, an intermediate phase of synaptogenesis, a late stabilization process and, finally, a mature synapse. By co-expressing shibire ts and semaphorin 1a we provided evidence that Semaphorin 1a was one of the proteins being regulated by endocytosis and its removal was a necessary part of the program for synaptogenesis. Temporal control of targeted expression of the semaphorin 1a gene showed that acute excess Semaphorin 1a had a permanent disruptive effect on synapse formation.

Chondroitin sulfates and their binding molecules in the central nervous system

“…Initially being identified as repulsive guidance molecules, several studies in the last decades have reported a chemoattractive role of semaphorins [138–140]. Semaphorins guide the development of peripheral nerve projection and involved in synaptogenesis in the CNS [141, 142]. The persistence of their expression in adulthood suggests a role in the maintenance of pre-established connections and cerebral homeostasis [143].…”

Light-Induced Structural and Functional Plasticity in Drosophila Larval Visual System

“…To manipulate the level of synaptic activity, we either increased the BO excitability by expressing the heat-activated Drosophila transient-receptor-potential A1 (dTrpA) channel (23) or reduced transmitter release from BN through a temperature-sensitive form of the dominant-negative dynamin, Shibire ts ( Shi ts ) (24). These manipulations eliminated light-induced modification of LN(v) dendrites at 29°C (Fig.…”

A Mechanism Distinct from Highwire for theDrosophilaUbiquitin Conjugase Bendless in Synaptic Growth and Maturation

“…Previous anatomical studies have delineated the various developmental stages of the GFS (Allen et al, 1998; Phelan et al, 1996) (Fig. 4A) and have also identified critical periods for synapse formation (Murphey et al, 2003). We utilized the TARGET system (McGuire et al, 2004a; McGuire et al, 2004b) to regulate UAS- ben expression during different stages of GF development.…”