Education

B.S., Biology, Haverford College, Haverford, PA, 1991
Ph.D., Molecular Biology, Princeton University, Princeton, NJ, 1999
FIRST Postdoctoral Fellow, Department of Cell Biology, Emory University School of Medicine, 2000-2003

Research Interests

(1) The role of the hedgehog genes in retinal differentiation: Drosophila eye development has served as an excellent model system for studying cellular signaling interactions as one mechanism for cell fate specification. During the establishment of the fly’s visual system, undifferentiated cells are set aside as an eye primordium (the eye disc), cells communicate with their neighbors through specific molecular signals and ultimately, distinct cell types are formed that can then coordinate their functions to allow for visual perception. Retinal pattern formation is progressive and associated with a moving indentation in the developing eye disc called the morphogenetic furrow. The furrow functions as a moving boundary that separates posteriorly localized differentiating photoreceptor neurons from the undifferentiated cells that lie anterior to it. The movement of the furrow thus, directs a “wave of neural differentiation” and a propagation of information that specifies photoreceptor cells. The hedgehog gene (hh) acts as a key molecular signal in the developing eye to produce the progressive propagation of retinal development. Despite the differences between invertebrate and vertebrate adult eyes, it is becoming increasingly evident that many of the same molecules are involved in making both types of structures. Recent work has shown that vertebrate homologues of hh (particularly sonic hedgehog) are also crucial for the patterning of the vertebrate retina. In the lab, we are interested in understanding the role of hh genes in the "wave of neural differentiation" that occurs during Xenopus eye development. We are focused on studying the regulation of hh gene expression during eye development and how this contributes to retinal patterning. We are also looking at the functions of hhs throughout eye development in Xenopus.

(2) Understanding how the eyes connect to the brain: One fascinating example of cell migration guidance is found during the wiring of the visual system (through the neural retina) to a specific area of the brain (the optic tectum) to allow for visual sensory perception to occur. The retinal ganglion cells (RGCs) occupy one of the innermost layers of the vertebrate retina and they represent the only neuronal cells that actually leave the eye. RGC axons are responsible for conveying all visual information from beyond the retina to the brain and they do so by following a stereotypical, “retinotectal” migratory pathway. The retinal ganglion cells, once differentiated, extend their axons from the optic nerve, upward through the diencephalon, where they then turn to continue migration to their final destination – the optic tectum of the midbrain. The precision with which these axons must travel and the determination of their proper destination is critical to the ability to see; yet the molecular nature of this process is largely unknown. We are interested in using the embryonic Xenopus as an experimental system to identify components of the extracellular environment that are required for normal retinotectal pathfinding and guidance.

Grant Support

NIH Career Development Award for Diversity in Neuroscience
National Institute of Neurological Disorders and Stroke
Grant Number: 1K01NS052551-01A1
Project Title: Understanding Directed Retinal Cell Axon Guidance
Project Period: August 01, 2007 - July 31, 2012

The research plan reflects the value of a mentored career development opportunity and has two main objectives. The first is to characterize the expression patterns of Xenopus sonic hedgehog signaling pathway components in the embryonic brain during visual system development. The second research objective is to determine whether sonic hedgehog signaling is required for proper retinal axon guidance along the optic tract in Xenopus. Collectively, these goals will contribute to a broader understanding of mechanisms of axon guidance during vertebrate development. (www.haverford.edu/news/stories/861/51)

Recent Publications

Rogers, E.M., Brennan, C.A., Mortimer, N.T., Cook, S., Morris, A.R., Moses, K. (2005) Pointed regulates an eye-specific transcriptional enhancer in the Drosophila hedgehog gene, which is required for the movement of the morphogenetic furrow.  Development. 132(21):4833-43.

Morris, A., Drawbridge, J and Steinberg, M.S. (2003). Axolotl pronephric duct migration requires an epidermally-derived, laminin-1-containing extracellular matrix and the integrin receptor alpha-6-beta-1. Development,130(23):5601-5608.

Aduonum. A., Crater, D., Haftel, V., Morris, A. and Morris, L. Redefining Postdoctoral Education. (2003). (Manuscript in preparation for the Journal of College Science Teaching)

Haverford College
Department of Biology
370 Lancaster Ave.
Haverford, PA 19041
Tel: 610.896.1306
Email: armorris@haverford.edu
Link: www.haverford.edu/biology/Morris/