Expression of EphB receptors and EphrinB ligands in the developing chick auditory brainstem.
Nucleus magnocellularis (NM) in the avian auditory brainstem receives auditory input from nerve the VIIIth and projects bilaterally to nucleus laminaris (NL). This projection preserves binaural segregation in that ipsilateral NM projects to dorsal dendrites of NL and contralateral NM projects to ventral dendrites of NL. We have begun to examine the molecular signals that influence segregation of inputs onto discrete regions of NL cells. We previously showed that the Eph receptor, EphA4, is expressed selectively in the dorsal NL neuropil from embryonic day (E) 9 to E11, when NM axons grow into the NL neuropil. This asymmetric distribution suggests that EphA4 acts as a guidance molecule during binaural segregation. We report here on the developmental changes in the expression of two other Eph receptors, EphB2 and EphB5, and two ligands, ephrin-B1 and ephrin-B2, in the chick auditory brainstem. These proteins are expressed in the auditory nuclei during the maturation of the NM-NL projection. EphB2, EphB5, and ephrin-B1 are expressed in dorsal and ventral NL neuropil and at the midline of the brainstem at E10-E12. At this age, ephrin-B2, a ligand for EphB receptors and for EphA4, is expressed in NL cell bodies and NM-NL axons. The expression of these proteins diminishs in the posthatch ages examined. These results suggest that several members of the Eph family are involved in maturation of the nuclei and their projections. Moreover, ephrin-B2 in growing axons may interact with the asymmetrically expressed EphA4 during the establishment of binaural segregation.
Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington 98195, USA. kcramer@u.washington.edu
Karina S
KS
Cramer
Sana D
SD
Karam
Mark
M
Bothwell
Douglas Pat
DP
Cerretti
Elena B
EB
Pasquale
Edwin W
EW
Rubel
D000818:Animals; D015153:Blotting, Western; D002642:Chick Embryo / Q000033:anatomy & histology / Q000254:growth & development*; D017626:Cochlear Nucleus / Q000196:embryology*; D036387:Ephrin-B1; D036388:Ephrin-B2; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000096:biosynthesis*; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis*; D036183:Receptor, EphB2
D036387:Ephrin-B1; D036388:Ephrin-B2; D008565:Membrane Proteins; D020794:Receptor Protein-Tyrosine Kinases; D036183:Receptor, EphB2