Title of Abstract

The Effect of Axon Guidance Molecule Semaphorin 3A on Different Aged Chick Retinal Ganglion Cells

Faculty Mentor

One WU mentor: Eric Birgbauer, Ph.D.; birgbauere@winthrop.edu

College

College of Arts and Sciences

Department

Biology

Faculty Mentor

Eric Birgbauer, Ph.D.

Abstract

During embryonic development, axons grow from the retina of the eye to the tectum of the brain which allows for visual information transfer. Axons travel to the tectum via axon pathfinding, which is influenced by axon guidance cues, such as our area of interest: Semaphorin 3A (Sema 3A). Axon guidance molecules interact with retinal ganglion cells (RGCs), which contain growth cones- a crucial feature of the developing visual system. Growth cones are extensions of growing or regenerating axons supported by microfilaments growing to their synaptic target, in this case the brain. Some inhibitory axon guidance molecules are known to cause growth cone collapse and Sema 3A is one of them. When growth cones collapse, they cease growth and then retract, never making it to their target. While Sema 3A’s importance is known in the nervous system, a previous study demonstrated that Sema 3A causes growth cone collapse of chick embryo dorsal root ganglion cells (DRGs) but not growth cone collapse in chick retinal ganglion cells (RGCs). We have found significant evidence that Sema 3A does indeed cause growth cone collapse when it comes in contact with embryonic chick retinal ganglion cells, which is inconsistent with the published findings. After further investigation of this experiment, we have found that RGC’s have the ability to regenerate from collapse after a 15-20 minute time window, thus giving the illusion to the previous report that Sema 3A does not affect RGC’s because of the 60-minute allotted time window they used. We are currently investigating the effect of Sema 3A on different embryonic ages (E5, E6, E7, E8). We have found preliminary data that suggests that Sema 3A causes growth cone collapse of retinal neurites at all ages examined.

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Honors Thesis Committee

Eric Birgbauer, Ph.D., Michael Lipscomb, Ph.D., Daniel Stovall, Ph.D., Kathryn Kohl, Ph.D., and Victoria Frost, Ph.D.

Honors Thesis Committee

Eric Birgbauer, Ph.D., Michael Lipscomb, Ph.D., Daniel Stovall, Ph.D., Kathryn Kohl, Ph.D., and Victoria Frost, Ph.D.

Course Assignment

HONR 450H – Birgbauer & HONR 451H - Lipscomb

Other Presentations/Performances

SYNAPSE Conference, High Point University, April 2019; INBRE Conference, University of South Carolina, January 2020

Grant Support

INBRE Grant

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The Effect of Axon Guidance Molecule Semaphorin 3A on Different Aged Chick Retinal Ganglion Cells

During embryonic development, axons grow from the retina of the eye to the tectum of the brain which allows for visual information transfer. Axons travel to the tectum via axon pathfinding, which is influenced by axon guidance cues, such as our area of interest: Semaphorin 3A (Sema 3A). Axon guidance molecules interact with retinal ganglion cells (RGCs), which contain growth cones- a crucial feature of the developing visual system. Growth cones are extensions of growing or regenerating axons supported by microfilaments growing to their synaptic target, in this case the brain. Some inhibitory axon guidance molecules are known to cause growth cone collapse and Sema 3A is one of them. When growth cones collapse, they cease growth and then retract, never making it to their target. While Sema 3A’s importance is known in the nervous system, a previous study demonstrated that Sema 3A causes growth cone collapse of chick embryo dorsal root ganglion cells (DRGs) but not growth cone collapse in chick retinal ganglion cells (RGCs). We have found significant evidence that Sema 3A does indeed cause growth cone collapse when it comes in contact with embryonic chick retinal ganglion cells, which is inconsistent with the published findings. After further investigation of this experiment, we have found that RGC’s have the ability to regenerate from collapse after a 15-20 minute time window, thus giving the illusion to the previous report that Sema 3A does not affect RGC’s because of the 60-minute allotted time window they used. We are currently investigating the effect of Sema 3A on different embryonic ages (E5, E6, E7, E8). We have found preliminary data that suggests that Sema 3A causes growth cone collapse of retinal neurites at all ages examined.