Analysis of a repulsive axon guidance molecule, draxin, on ventrally directed axon projection in chick early embryonic midbrain

Iftekhar Bin Naser, Yuhong Su, Shahidul M. Islam, Yohei Shinmyo, Sanbing Zhang, Giasuddin Ahmed, Sandy Chen, Hideaki Tanaka

Research output: Contribution to journalArticle

10 Scopus citations


The mesencephalic V neurons and tectobulbar axons in chick embryo project over long distances that appear during the early development of the chick optic tectum. The mesencephalic V neuron and tectobulbar axonal growth begin at Hamburger and Hamilton stage 14 and stage 18, respectively. Both fibers proceed downward from the dorsal to the ventral side of the lateral wall of the optic tectum and then turn caudally and join the medial longitudinal fasciculus. Their axons appear in the most superficial layer of the tectum at early stages and do not cross the dorsal midline of the tectum. Here, we report the role of draxin, a recently identified axon guidance protein, in the formation of the ventrally directed tectum axonal tracts in chicken embryo. draxin is expressed in a high dorsal to low ventral gradient in chick optic tectum. In vitro experiments show that draxin repels neurite outgrowth from dorsal tectum explants. In vivo overexpression resulted in inhibition or misrouting of axon growth in the tectum. Therefore, draxin may be an important member of the collection of repulsive guidance molecules that regulate the formation of the ventrally directed tectum axon tracts.

Original languageEnglish (US)
Pages (from-to)351-359
Number of pages9
JournalDevelopmental Biology
Issue number2
Publication statusPublished - Aug 15 2009
Externally publishedYes



  • Axon guidance
  • Chemorepulsion
  • Draxin
  • Mesencephalic V neuron
  • Tectobulbar tract
  • Tectum

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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