title: Ephrin-As play a rhombomere-specific role in trigeminal motor axon projections in the chick embryo.
abstract: In this study, we investigate the possible role of ephrin-Eph signaling in trigeminal motor axon projections. We find that EphA receptors are expressed at higher levels by rhombomere 2 (r2) trigeminal motor neurons than by r3 trigeminal motor neurons in the chick embryo. Mapping of rhombomere-specific axon projections shows that r2 and r3 trigeminal motor neurons project to different muscle targets, including the mandibular adductor and the intermandibularis muscles respectively. Ephrin-A5 is expressed in these muscles, especially in some regions of the intermandibularis muscle, and can cause growth cone collapse of both r2 and r3 motor axons in vitro. We demonstrate that in vivo overexpression of ephrin-A5 in the intermandibularis muscle, or overexpression of dominant-negative EphA receptors in trigeminal motor neurons leads to a reduction in branching of r3-derived motor axons specifically. Overexpression of full-length EphA receptors impairs the formation of r3 projections to the intermandibularis muscle. These findings indicate that ephrins and their Eph receptors play a role in trigeminal motor axon topographic mapping and in rhombomere 3-derived projections in particular.
authors.affiliation: MRC Centre for Developmental Neurobiology, 4th Floor New Hunt's House, King's College, Guy's Campus, London SE1 1UL, United Kingdom.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Prin
authors.forename: Keat-Eng
authors.initials: KE
authors.lastname: Ng
authors.forename: Uma
authors.initials: U
authors.lastname: Thaker
authors.forename: Uwe
authors.initials: U
authors.lastname: Drescher
authors.forename: Sarah
authors.initials: S
authors.lastname: Guthrie
mesh_terms: D000818:Animals; D019521:Body Patterning; D002642:Chick Embryo / Q000033:anatomy & histology / Q000502:physiology*; D036386:Ephrin-A5 / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009024:Morphogenesis / Q000502:physiology; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000196:embryology / Q000294:innervation*; D036081:Receptors, Eph Family / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014276:Trigeminal Nerve / Q000166:cytology / Q000196:embryology*
chemical_list: D036386:Ephrin-A5; D011993:Recombinant Fusion Proteins; D036081:Receptors, Eph Family