Eric H. Schroeter
Ph.D., 2001, Washington University School of Medicine
The complexity of the developing vertebrate nervous system makes it one of the most challenging places to understand the relationships between form and function. Delineating the numerous and intricate connections that must be made, and understanding the mechanisms controlling their development is a daunting task. My research focuses on using the zebrafish retina as a model system to understand these processes.
The vertebrate retina is a highly organized neural structure where the basic identity and function of individual cell types have been established. Although much is known about the basic structure and function of the retina, much less is known about the events that influence how its neurons differentiate and find their synaptic partners. The zebrafish is an excellent model system to study these events. Embryos develop rapidly and their transparency enables direct visualization of retinal neurons from their birth to maturity. Furthermore, the genetics of this model organism, and the ability to easily manipulate the embryo, allow probing of the molecular mechanisms behind observed cellular behaviors.
My approach is to observe and manipulate the retina as it develops in vivo. To do this transgenic fish are created where specific retinal neurons are labeled with fluorescent proteins. Using advanced optical methods we can perform in vivo time-lapse imaging to observe cellular behavior during development. These observations then provide a baseline for comparison with retinas where genes important for development and signaling have been perturbed.
In addition we have created a method to conditionally ablate specific cells in transgenic zebrafish. This technology permits modeling of cell loss at any stage of development and can be used to mimic degenerative disease states. These transgenic fish will show how loss of a single cell type affects the developing retina. This system will also inform us about differentiation and circuit assembly during regeneration. Unlike mammals, zebrafish can extensively regenerate damaged tissue. Using this technology will allow us to monitor differentiation and synapse formation during regeneration of the vertebrate nervous system. Understanding how this process occurs in fish may eventually help us modulate regenerative capacity in human neural degenerative diseases.
- One Day Old Zebrafish Embryo Expressing Fluorescent Protein (20 MB QuickTime movie)
Curado, S., Anderson, R.M., Jungblut, B., Mumm, J., Schroeter, E., and Stainier, D.Y. (2007) Conditional targeted cell ablation in zebrafish: A new tool for regeneration studies. Dev. Dyn. 236(4):1025-1035.
Schroeter, E.H., Wong, R.O., and Gregg, R.G. (2006) In vivo development of retinal ON-bipolar cell axonal terminals visualized in nyx::MYFP transgenic zebrafish. Vis. Neurosci.. 23(5):833-843.
Godinho, L., Mumm, J.S., Williams, P.R., Schroeter, E.H., Koerber, A., Park, S.W., Leach, S.D., and Wong, R.O. (2005) Targeting of amacrine cell neurites to appropriate synaptic laminae in the developing zebrafish retina. Development. 132(22):5069-5079.
Morris, A.C., Schroeter, E.H., Bilotta, J., Wong, R.O., and Fadool, J.M. (2005) Cone Survival Despite Rod Degeneration in XOPS-mCFP Transgenic Zebrafish. Invest. Ophthalmol. Vis. Sci.. 46(12):4762-4771.
Schroeter, E.H., Ilagan M.X., Brunkan A.L., Hecimovic S., Li Y.M., Xu M., Lewis H.D., Saxena M.T., De Strooper B., Coonrod A., Tomita T., Iwatsubo T., Moore C.L., Goate A.M., Wolfe M.S., Shearman M., and R. Kopan. (2003) A presenilin dimer at the core of the gamma-secretase enzyme: insights from parallel analysis of Notch 1 and APP proteolysis. Proc. Nat.l Acad. Sci. USA. 100(22): 13075-80.
Saxena, M. T., Schroeter, E.H., Mumm, J. S., and R. Kopan. (2001). Murine notch homologs (N1-4) undergo presenilin-dependent proteolysis. J Biol Chem 276, 40268-40273.
Hadland B.K., Manley, N.R., Su, D.M., Longmore, G.D., Moore, C.L., Wolfe, M.S., Schroeter, E.H., R. Kopan. (2001) Gamma-secretase inhibitors repress thymocyte development. Proc. Natl. Acad. Sci. USA, 98(13):7487-7491.
Mumm, J.S., Schroeter, E.H., Saxena, M.T., Tian, X., Griesemer, A., Ray W.J., Pan D.J., and R. Kopan. (2000) A Ligand Induced Extracellular Cleavage Regulates gamma-secretase-like Proteolytic Activation of Notch 1. Molecular Cell, 5: 197-206.
Huppert, S.S., Le, A., Schroeter, E.H., Mumm, J.S., Saxena, M.T., Milner, L..A., and R. Kopan. (2000) Embryonic lethality in mice homozygous for a processing-deficient allele of Notch1. Nature, 405: (6789) 966-977.
De Strooper, B., Annaert W., Cupers P., Saftig P., Craessaerts K., Mumm J.S., Schroeter E.H., Schrijvers V., Wolfe M.S., Ray W.J., Goate A., and R. Kopan. (1999) A Presenilin-1-dependent gamma-secretase-like Protease Mediates Release of Notch Intracellular domain. Nature, 398: (6727) 518-522.
Schroeter, E.H., Kisslinger, J.A., and R. Kopan. (1998) Notch-1 signaling requires ligand-induced proteolytic release of intracellular domain. Nature, 393: (6683) 382-386.
Figure (A) Living transgenic zebrafish expressing Yellow Fluorescent Protein (YFP) in the retina and in the pineal gland (arrow) (B) Confocal images of the retina of a developing zebrafish embryo showing Bipolar Cells (yellow) and Cone photoreceptors (blue) expressing different color fluorescent proteins.