Glia Development in the Embryonic Cns of Drosophila

Ephrin/Eph signalling is crucial for axonal pathfinding in vertebrates and invertebrates. We identified the Drosophila ephrin orthologue, Dephrin, and describe for the first time the role of ephrin/Eph signalling in the embryonic central nervous system (CNS). Dephrin is a transmembrane ephrin with a unique N terminus and an ephrinB-like cytoplasmic tail. Dephrin binds and interacts with DEph, the Drosophila Eph-like receptor, and Dephrin and DEph are confined to different neuronal compartments. Loss of Dephrin or DEph causes the abberant exit of interneuronal axons from the CNS, whereas ectopic expression of Dephrin halts axonal growth. We propose that the longitudinal tracts in the Drosophila CNS are moulded by a repulsive outer border of Dephrin expression.

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Commissure formation in the embryonic CNS of Drosophila

Development ◽

10.1242/dev.126.4.771 ◽

1999 ◽

Vol 126 (4) ◽

pp. 771-779 ◽

Cited By ~ 2

Author(s):

T. Hummel ◽

K. Schimmelpfeng ◽

C. Klambt

Keyword(s):

Nervous System ◽

Glial Cells ◽

Ventral Nerve Cord ◽

Growth Cones ◽

Cellular Functions ◽

Detailed Model ◽

Present Evidence ◽

Embryonic Nervous System ◽

Dependent Signal ◽

Embryonic Cns

Most of the neurons of the ventral nerve cord send out long projecting axons which cross the midline. In the Drosophila central nervous system (CNS) cells of the midline give rise to neuronal and glial lineages with different functions during the establishment of the commissural pattern. Here we present evidence that beside the previously known NETRIN/FRAZZLED (DCC) signalling system an additional attractive system(s) is operating in the developing embryonic nervous system of Drosophila. Attractive cues appear to be provided by the midline neurons. We show that the glial cells present repulsive signals to the previously described ROUNDABOUT receptor in addition to a permissive contact-dependent signal helping commissural growth cones across the midline. A novel repulsive component is encoded by the karussell gene. Furthermore the midline glial cells separate anterior and posterior commissures. By genetic criteria we demonstrate that some of the genes we have identified are acting in the midline glia whereas other genes are required in the midline neurons. The results lead to a detailed model relating different cellular functions to axonal patterning at the midline.

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Targeted neuronal ablation: the role of pioneer neurons in guidance and fasciculation in the CNS of Drosophila

Development ◽

10.1242/dev.124.17.3253 ◽

1997 ◽

Vol 124 (17) ◽

pp. 3253-3262 ◽

Cited By ~ 11

Author(s):

A. Hidalgo ◽

A.H. Brand

Keyword(s):

Temporal Profile ◽

Pioneer Neurons ◽

Longitudinal Axon ◽

Pioneer Neuron ◽

Embryonic Cns

Although pioneer neurons are the first to delineate the axon pathways, it is uncertain whether they have unique pathfinding abilities. As a first step in defining the role of pioneer neurons in the Drosophila embryonic CNS, we describe the temporal profile and trajectory of the axons of four pioneer neurons and show that they differ from previously published reports. We show, by targeted ablation of one, two, three or four pioneer neurons at a time, that (1) no single pioneer neuron is essential for axon tract formation, (2) the interaction between two pioneers is necessary for the establishment of each fascicle and (3) pioneer neurons function synergistically to establish the longitudinal axon tracts, to guide the fasciculation of follower neurons along specific fascicles and to prevent axons from crossing the midline.

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