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Lawrence J. Rizzolo, Ph.D.
Associate Professor of Anatomy & Experimental Surgery
Associate Professor of Ophthalmology & Visual Science
Phone: 203 785-6277
FAX: 203 737-2825
lawrence.rizzolo@yale.edu
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Research Interests:
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The retinal pigment epithelium (RPE) plays a central role in retinal physiology by forming the outer blood-retinal barrier and supporting the function of the photoreceptors. Many retinopathies involve a disruption of the epithelium's interactions with the neural retina or its uncontrolled proliferation. Surgical interventions limit the progression of disease, but fail to restore function. Although encouraging progress has been made with RPE transplantation, it remains unclear how to restore RPE-retinal interactions or re-establish a blood-retinal barrier. To examine these interactions, We study a developmental model of chick RPE. We observed that the RPE develops gradually under the influence of the neighboring tissues. Because different interactions appear at different times of development, we are able to identify and investigate them.
We devised several primary cell and organ culture systems that model different aspects of development. We have shown that: 1) As the neural retina matures, it secretes factors that induce the RPE to form the outer blood-retinal barrier by decreasing the permeability of RPE junctions. 2) At the RPE/neural retina interface, extracellular matrix or cell-cell interactions regulate the distribution of certain integrins. These integrins are redistributed when the neural retina and its extracellular matrix mature. 3) Initially, diffusible factors produced by the neural retina maintain the apical polarity of the Na,K-ATPase. These retinal factors differ from those that decrease the permeability of the monolayer, and may act indirectly through effects on the structure of the apical microvilli.
Our current research focuses on the development and regulation of RPE tight junctions. Tight junctions are an integral part of any blood-tissue barrier, because they regulate diffusion across the paracellular spaces of an epithelial monolayer. Tight junctions form a network of anastomosing strands that encircles each cell and binds it to its neighbors in the monolayer. In the photo above, the RPE monolayer is viewed en face with the tight junctions illuminated by fluorescent tags for the tight junction protein, ZO-1, and the subadjacent circumferential band of actin. During embryonic development, the RPE and junctional functions develop gradually. Development is coordinated with the neural retina by two-way communications between the tissues. We continue to document changes in the expression of tight junctional proteins during development and wish to understand how the neural retina regulates the composition and function of the junction. To accomplish this, we established a unique culture model of development that has already led us to propose a refinement of the classical "pore" model of tight junctions. We partially characterized the retinal factors that regulate the permeability of tight junctions, and found at least two factors that act at different stages of development. Our interest is in how these factors regulate two modes of tight junction function that were revealed by our culture model. We recently cloned the avian form of the tight junction protein, ZO-2. Some regions of this protein are remarkably conserved among species, and we are using this insight to create dominant negative mutations for use in our culture system. Preliminary data indicate that different PDZ domains within ZO-2 have different regulatory functions. We are also pursuing the observation that the RPE expresses several isoforms of the tight junction protein, claudin, and that claudin expression is developmentally regulated. This is especially exciting, because the claudins are thought to lend specificity to tight junction function.
These studies address fundamental issues about tissue interactions, cell polarity and the regulation of barrier function. Understanding these interactions will help us understand the proliferative retinopathies that result when these interactions are altered, and help us develop methods that insure these interactions are reestablished upon RPE or retinal transplantation. |
Selected Publications:
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1. Ban Y, Rizzolo LJ: (1997) A Culture Model of Development Reveals Multiple Properties of RPE Tight Junctions. Mol. Vis. 3: 18, http://www.emory.edu/molvis/v3/ban.
2. Rizzolo LJ: (1997) Polarity and the Development of the Outer Blood-Retinal Barrier. Histol. Histopath. 12:1057-1067.
3. Collins JR, Rizzolo LJ: (1998) Protein-binding domains of the tight junction protein, ZO-2, are highly conserved between avian and mammalian species. Bioch. Biophys. Res. Comm. 252:617-622.
4. Ban Y, Rizzolo LJ: (2000) Regulation of glucose transporters during development of the retinal pigment epithelium. Brain Res. Dev. Brain Res.121:89-95, .
5. Ban Y, Wilt SD, Rizzolo LJ: (2000) Two secreted retinal factors regulate different stages of development of the outer blood-retinal barrier. Brain Res. Dev. Brain Res. 119:259-267.
6. Ban Y, Rizzolo LJ: (2000) Differential regulation of tight junction permeability during development of the retinal pigment epithelium. Am. J. Physiol. 279: C744-C750, .
7. Wilt SD, Rizzolo LJ: (2001 Unique aspects of the blood-brain barrier. In Tight Junctions, Ed. M. Cereijido and J.M. Anderson, CRC Press, 415-443,.
8. Kojima S, Rahner C, Peng S, and Rizzolo LJ. (2002) Claudin 5 is transiently expressed during the development of the retinal pigment epithelium. J Membr Biol 15;186:81-88.
9. Rizzolo, L.J ., Aden , M. and Stewart, W.B. (2002) Correlation of Web Usage and Exam Performance in a Human Anatomy and Development Course. Clinical Anatomy 15:351–355.
10. Rizzolo, L.J. (2002) Human Dissection: An approach to interweaving the traditional and humanistic goals of medical education. Anat Rec. (New Anat.) 269:242-248
11. Peng S, Rahner C and Rizzolo LJ. (2003) Apical and basal regulation of the permeability of the retinal pigment epithelium. Invest. Opthalmol. Vis. Sci. 44:808-817.
12. Rahner C, Fukuhara M., Peng S., Kojima S. and Rizzolo LJ (2004) The apical and basal environments of the retinal pigment epithelium regulate the formation of tight junctions during
development. J. Cell Science, 117:3307-3318.
13. Rizzolo, L.J., Stewart W.B., O’Brien, M, Haims, A, Rando, W., Abrahams J, Dunne, S, Wang, S. and Aden , M. (2006) Design principles for developing an efficient clinical anatomy course. Medical Teacher, in press.
14. Luo, Y, Zhuo, Y, Fukuhara M. and Rizzolo LJ (2006) Effects of culture conditions on heterogeneity and the apical junctional complex of the ARPE-19 cell line.Submitted
15. Luo, Y, Downard M, Weitzman, M. and Rizzolo LJ (2006) Putative assembly proteins and the assembly and remodeling of RPE tight junctions. Submitted
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