Genetic networks regulating normal development of anterior segment structures are poorly understood. Mice are ideal models for determining the basic mechanisms contributing to normal eye development and for analyzing genetic eye disease. Mutations in the homeobox gene PITX2 result in Axenfeld-Rieger Syndrome (ARS), an autosomal dominant disease causing congenital anterior segment defects and glaucoma. I cloned Pitx2 from mouse and used gene targeting in mice to generate a series of Pitx2 alleles that allow for global or conditional ablation of gene function, and the ability to vary gene dose. Based on published data and our own preliminary results, we hypothesize a central role for Pitx2 in periocular mesenchyme during eye development for differentiation of ocular cell types derived from mesenchyme and for mesenchyme expression of extrinsic factors required for normal development of surface and neural ectoderm in the eye. In the previous grant cycle, we demonstrated early Pitx2 expression in ocular neural crest and mesoderm, established that Pitx2 function in neural crest is required for multiple steps in eye development, and identified a role for PITX2 in regulating Wnt signaling in neural crest that could account for Pitx2 mutant phenotypes. The overall goals of this proposal are to use our series of murine Pitx2 alleles to determine the role(s) of Pitx2 in mesoderm during eye development and to establish the mechanistic and functional relationships between Pitx2 and components of the Wnt signaling pathway.
In Aim 1, we will test the hypothesis that Pitx2 has distinct functions in ocular mesoderm using a conditional targeting strategy.
In Aim 2, we will test a specific Wnt signaling pathway gene as a direct PITX2 target and identify its morphological and molecular roles in eye development to see if this gene accounts for components of the Pitx2 phenotype. We will also screen human patients with specific anterior segment defects and glaucoma for mutations in this gene.
In Aim 3, we will directly test for genetic interactions between Pitx2 and the Wnt pathway gene in mice as a mechanism for modification of the Pitx2 mutant phenotype since phenotypic variability is a key feature of ARS. This multifaceted approach will provide specific mechanistic details about the functions of Pitx2 in eye development and new knowledge into more general fundamental mechanisms of periocular mesenchyme in this process. This basic information is essential for understanding eye disease, including glaucoma.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY014126-08
Application #
7881490
Study Section
Anterior Eye Disease Study Section (AED)
Program Officer
Agarwal, Neeraj
Project Start
2002-09-01
Project End
2011-08-31
Budget Start
2010-07-01
Budget End
2011-08-31
Support Year
8
Fiscal Year
2010
Total Cost
$363,941
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Seo, Seungwoon; Chen, Lisheng; Liu, Wenzhong et al. (2017) Foxc1 and Foxc2 in the Neural Crest Are Required for Ocular Anterior Segment Development. Invest Ophthalmol Vis Sci 58:1368-1377
Benson, Matthew D; Khor, Chiea C; Gage, Philip J et al. (2017) A targeted approach to genome-wide studies reveals new genetic associations with central corneal thickness. Mol Vis 23:952-962
Chen, Lisheng; Martino, Vanessa; Dombkowski, Alan et al. (2016) AP-2? Is a Downstream Effector of PITX2 Required to Specify Endothelium and Establish Angiogenic Privilege During Corneal Development. Invest Ophthalmol Vis Sci 57:1072-81
Chen, Lisheng; Gage, Philip J (2016) Heterozygous Pitx2 Null Mice Accurately Recapitulate the Ocular Features of Axenfeld-Rieger Syndrome and Congenital Glaucoma. Invest Ophthalmol Vis Sci 57:5023-5030
Davis, Shannon W; Mortensen, Amanda H; Keisler, Jessica L et al. (2016) ?-catenin is required in the neural crest and mesencephalon for pituitary gland organogenesis. BMC Dev Biol 16:16
Gage, Philip J; Hurd, Elizabeth A; Martin, Donna M (2015) Mouse Models for the Dissection of CHD7 Functions in Eye Development and the Molecular Basis for Ocular Defects in CHARGE Syndrome. Invest Ophthalmol Vis Sci 56:7923-30
Gage, Philip J; Kuang, Chen; Zacharias, Amanda L (2014) The homeodomain transcription factor PITX2 is required for specifying correct cell fates and establishing angiogenic privilege in the developing cornea. Dev Dyn 243:1391-400
French, Curtis R; Seshadri, Sudha; Destefano, Anita L et al. (2014) Mutation of FOXC1 and PITX2 induces cerebral small-vessel disease. J Clin Invest 124:4877-81
Plageman Jr, Timothy F; Zacharias, Amanda L; Gage, Phillip J et al. (2011) Shroom3 and a Pitx2-N-cadherin pathway function cooperatively to generate asymmetric cell shape changes during gut morphogenesis. Dev Biol 357:227-34
Zacharias, Amanda L; Lewandoski, Mark; Rudnicki, Michael A et al. (2011) Pitx2 is an upstream activator of extraocular myogenesis and survival. Dev Biol 349:395-405

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