Expression of the cell adhesion molecule axonin-1 in neuromeres of the chicken diencephalon.
Axonin-1/TAG-1, a member of the immunoglobulin (Ig) superfamily of adhesion molecules, has been shown to be selectively expressed by a subset of neurons and fiber tracts in the developing nervous system of vertebrates. Axonin-1/TAG-1 is thought to play a role in the outgrowth, guidance, and fasciculation of neurites. In the present study, we map the expression of axonin-1 in the diencephalon of the chicken brain at early and intermediate stages of development [2-8 days of incubation; embryonic day (E)2-E8] by immunohistochemical methods. Results show that axonin-1 is first expressed at about E2.5 by postmitotic neurons scattered throughout most of the diencephalon. During the neuromeric stage of brain development (about E3-E5), axonin-1+ nerve cell bodies are predominantly found in two neuromeric subdivisions: 1) in the alar plate of the precommissural pretectum and dorsal thalamus and 2) in the posterior preoptic region of the hypothalamus. The axonin-1+ fiber bundles emerging from these areas grow across segmental boundaries. For example, axonin-1+ neurites originating in the dorsal thalamus cross the zona limitans intrathalamica at a right angle to project to the striatum. Later, the axonin-1+ neuromere areas give rise to particular axonin-1+ gray and white matter structures. Most of these structures correspond to the structures described to express TAG-1 in rodents. In conclusion, axonin-1 can be used as a marker to study aspects of the transition from the early neuromeric structure to the mature anatomy of the chicken brain.
Redies
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Institute of Biology III, University of Freiburg, Germany. redies@sun1.biologie.uni-freiburg.de
Arndt
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K
Ast
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D000818:Animals; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism*; D002642:Chick Embryo; D004027:Diencephalon / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D009474:Neurons / Q000378:metabolism*
D015816:Cell Adhesion Molecules, Neuronal