During neural development, growing axons come to sites where they must negotiate changes in course. Using the developing mouse visual system as a model, the proposed research will examine the growth and directionality of retinal axons in the optic chiasm, a classic example of a site where axons redistribute, some remaining on the same side of the brain and others crossing. This plan results in the formation topographic maps that subserve binocular vision. First, the detailed morphology of retinal ganglion cell axon growth cones will be examined in fixed preparations within the retinofugal pathway after labeling with the labels HRP or Di-I. Emphasis will be placed on defining the trajectory and growth cone shape of ipsi- and contralaterally projecting axons within the optic chiasm. Identified dye-labeled axons will be studied ultrastructurally to investigate the neuronal and non- neuronal cellular relationships within the chiasm. Second, dye-labeled axons will be viewed in semi-intact tissue slices with conventional fluorescent optics and SIT camera or with a confocal microscope and image analysis. This will allow analysis of the dynamics of growth cone behavior within the optic chiasm in real time. Third, an in vitro assay system will be developed by which to test factors responsible for fiber rearrangement and changes in directionality within the optic chiasm. Such an assay will test whether guidance cues are associated with intrinsic cells of the optic chiasm, and whether they are membrane-bound. Retinal explants will be cocultured with cells from the chiasm, or grown on membranes derived from parts of the chiasm. The behavior of growth cones, including advance, retraction and turning behavior, will be documented with video time-lapse microscopy. These experiments aim to define the factors responsible for guidance of axons towards targets during the formation of specific topographic connections. The in vitro assay will be used in the future to test for molecular mechanisms of growth cone guidance.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS027615-03
Application #
3413963
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1989-08-01
Project End
1992-07-31
Budget Start
1991-08-01
Budget End
1992-07-31
Support Year
3
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Columbia University (N.Y.)
Department
Type
Schools of Medicine
DUNS #
064931884
City
New York
State
NY
Country
United States
Zip Code
10027
Marcus, R C; Matthews, G A; Gale, N W et al. (2000) Axon guidance in the mouse optic chiasm: retinal neurite inhibition by ephrin ""A""-expressing hypothalamic cells in vitro. Dev Biol 221:132-47
Marcus, R C; Shimamura, K; Sretavan, D et al. (1999) Domains of regulatory gene expression and the developing optic chiasm: correspondence with retinal axon paths and candidate signaling cells. J Comp Neurol 403:346-58
Mason, C A; Wang, L C (1997) Growth cone form is behavior-specific and, consequently, position-specific along the retinal axon pathway. J Neurosci 17:1086-100
Wang, L C; Rachel, R A; Marcus, R C et al. (1996) Chemosuppression of retinal axon growth by the mouse optic chiasm. Neuron 17:849-62
Marcus, R C; Wang, L C; Mason, C A (1996) Retinal axon divergence in the optic chiasm: midline cells are unaffected by the albino mutation. Development 122:859-68
Marcus, R C; Blazeski, R; Godement, P et al. (1995) Retinal axon divergence in the optic chiasm: uncrossed axons diverge from crossed axons within a midline glial specialization. J Neurosci 15:3716-29
Marcus, R C; Mason, C A (1995) The first retinal axon growth in the mouse optic chiasm: axon patterning and the cellular environment. J Neurosci 15:6389-402
Wang, L C; Dani, J; Godement, P et al. (1995) Crossed and uncrossed retinal axons respond differently to cells of the optic chiasm midline in vitro. Neuron 15:1349-64
Wang, L C; Baird, D H; Hatten, M E et al. (1994) Astroglial differentiation is required for support of neurite outgrowth. J Neurosci 14:3195-207
Baird, D H; Baptista, C A; Wang, L C et al. (1992) Specificity of a target cell-derived stop signal for afferent axonal growth. J Neurobiol 23:579-91

Showing the most recent 10 out of 11 publications