title: Analysis of a repulsive axon guidance molecule, draxin, on ventrally directed axon projection in chick early embryonic midbrain.
abstract: 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.
authors.affiliation: Division of Developmental Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan.
authors.forename: Iftekhar Bin
authors.initials: IB
authors.lastname: Naser
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Su
authors.forename: Shahidul M
authors.initials: SM
authors.lastname: Islam
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shinmyo
authors.forename: Sanbing
authors.initials: S
authors.lastname: Zhang
authors.forename: Giasuddin
authors.initials: G
authors.lastname: Ahmed
authors.forename: Sandy
authors.initials: S
authors.lastname: Chen
authors.forename: Hideaki
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D002642:Chick Embryo; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008636:Mesencephalon / Q000166:cytology / Q000196:embryology*; D009434:Neural Pathways / Q000033:anatomy & histology / Q000196:embryology; D055495:Neurogenesis / Q000502:physiology; D013477:Superior Colliculi / Q000166:cytology / Q000196:embryology; D046509:Tissue Culture Techniques; D014404:Tubulin / Q000378:metabolism
chemical_list: D015415:Biomarkers; D036341:Intercellular Signaling Peptides and Proteins; D014404:Tubulin