title: Differential ligand regulation of PlexB signaling in motor neuron axon guidance in Drosophila.
abstract: Plexins (Plexs) are a large family of phylogenetically conserved guidance receptors that bind specifically to semaphorins (Semas), another large family of guidance molecules. In the Drosophila embryonic central nervous system (CNS), the secreted semaphorins Sema-2a and Sema-2b both act as ligands for PlexB, but mediate mutually independent and opposite functions (repulsive and attractive guidance, respectively). PlexB is also known to regulate motor axon guidance in the embryonic peripheral nervous system (PNS). However, it is unclear whether the mechanisms of ligand regulation of PlexB seen in the CNS are similar or the same as those that exist in PNS motor axon guidance. Here, we find that two distinct modes of ligand regulation underlie differential roles of PlexB in PNS motor axon pathfinding during embryonic development. Epistasis analyses in the intersegmental nerve b (ISNb) pathway suggest that PlexB serves as a receptor for both Sema-2a and Sema-2b and integrates their mutually dependent but opposite guidance functions. Furthermore, we present evidence that PlexB mediates not only Sema-2a/2b-dependent guidance functions, but also Sema-2a/2b-independent target recognition in establishing the segmental nerve a (SNa) motor axon pathway. These results demonstrate that a single guidance receptor can elicit diverse effects on the establishment of neuronal connectivity via regulation of its ligands themselves.
authors.affiliation: Department of Molecular Biology, Chonbuk National University, Jeonju, Jeollabukdo, 54896, Republic of Korea.
authors.forename: Seyun
authors.initials: S
authors.lastname: Roh
authors.affiliation: Department of Molecular Biology, Chonbuk National University, Jeonju, Jeollabukdo, 54896, Republic of Korea.
authors.forename: Da-Som
authors.initials: DS
authors.lastname: Yang
authors.affiliation: Department of Molecular Biology, Chonbuk National University, Jeonju, Jeollabukdo, 54896, Republic of Korea. Electronic address: sjeong4@jbnu.ac.kr.
authors.forename: Sangyun
authors.initials: S
authors.lastname: Jeong
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000502:physiology*; D002490:Central Nervous System / Q000166:cytology* / Q000196:embryology; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D009046:Motor Neurons / Q000166:cytology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; C116484:plexB protein, Drosophila
keywords: Axon guidance; Drosophila; Ligand regulation; Plexin B; Semaphorin-2a; Semaphorin-2b