Crossing the midline: roles and regulation of Robo receptors.
In the Drosophila CNS, the midline repellent Slit acts at short range through its receptor Robo to control midline crossing. Longitudinal axons express high levels of Robo and avoid the midline; commissural axons that cross the midline express only low levels of Robo. Robo levels are in turn regulated by Comm. Here, we show that the Slit receptors Robo2 and Robo3 ensure the fidelity of this crossing decision: rare crossing errors occur in both robo2 and robo3 single mutants. In addition, low levels of either Robo or Robo2 are required to drive commissural axons through the midline: only in robo,robo2 double mutants do axons linger at the midline as they do in slit mutants. Robo2 and Robo3 levels are also tightly regulated, most likely by a mechanism similar to but distinct from the regulation of Robo by Comm.
Rajagopalan
S
S
Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, A-1030, Vienna, Austria.
Nicolas
E
E
Vivancos
V
V
Berger
J
J
Dickson
B J
BJ
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D002490:Central Nervous System / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004330:Drosophila; D029721:Drosophila Proteins; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism / Q000494:pharmacology; D008648:Mesoderm / Q000473:pathology; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D000097905:Roundabout Proteins
D029721:Drosophila Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D000097905:Roundabout Proteins; C421243:Robo2 protein, Drosophila; C110665:comm protein, Drosophila; C421244:robo3 protein, Drosophila