Our goal is to identify the genetic networks governing ocular anterior segment development and to understand how disruption of these networks leads to defects in anterior segment structure and function. Our objective is to test the functions of the homeodomain transcription factor PITX2 in anterior segment tissues that are most commonly affected in human patients with PITX2 mutations. Our central hypothesis is that PITX2 regulates genetic networks that are required to specify normal corneal cell fates, exclude blood vessels from the developing and mature cornea, and regulate cell proliferation and lineage specification within the iris and structures of the iridocorneal angle. Our hypothesis was formulated on the basis of preliminary data generated by analysis of temporal knockout mice. The rationale for the proposed research is that knowledge of the genetic networks regulated by PITX2 in normal development of the cornea, iris, and iridocorneal angle will advance our understanding of anterior segment dysgenesis and associated pathologies, including elevated intraocular pressure. We will test our hypothesis by pursuing three specific aims: 1) Test the hypothesis that Pitx2 is required for specification and maintenance of corneal cell fates, 2) Test the hypothesis that Pitx2 is required to prevent vascular growth into the developing and mature cornea, and 3) Test the hypothesis that Pitx2 is required for normal development of the iris and structures of the iridocorneal angle. Under the first two aims, a temporal knockout strategy, which is already feasible in the applicant's hands, will be used to ablate Pitx2 at the beginning of corneal development, after which corneal lineages and vascular growth will be assessed using well-established approaches. Under the third aim, an analogous temporal knockout approach, also established as feasible in the applicant's hands, will be used to ablate Pitx2 at the beginning of iris and iridocorneal angle development and the consequences on development of the structures will be determined. The expected outcome is that essential functions of PITX2 in the development of the cornea, iris, and iridocorneal angle will be identified. The approach is innovative because it utilizes a temporal gene knockout strategy to overcome the limitations of global and tissue-specific Pitx2 knockout animals, thereby permitting us to study important later-forming structures in the anterior segment. The proposed research is significant because it will vertically advance and expand understanding of how anterior segment structures are formed during development. Ultimately, such knowledge will provide insights into how anterior segment dysgenesis contributes to vision loss.
The proposed research is relevant to public health, because understanding the molecular mechanisms governing normal anterior segment development will advance our knowledge of the pathogenesis and vision loss resulting from anterior segment dysgenesis. Thus, the proposed research is relevant to the part of NIH's mission that pertains to developing fundamental knowledge that will ultimately help to reduce the burdens of human disease and disability.
|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) Î²-catenin is required in the neural crest and mesencephalon for pituitary gland organogenesis. BMC Dev Biol 16:16|
|Chen, Lisheng; Martino, Vanessa; Dombkowski, Alan et al. (2016) AP-2Î² Is a Downstream Effector of PITX2 Required to Specify Endothelium and Establish Angiogenic Privilege During Corneal Development. Invest Ophthalmol Vis Sci 57:1072-81|
|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|
|Zacharias, Amanda L; Gage, Philip J (2010) Canonical Wnt/Î²-catenin signaling is required for maintenance but not activation of Pitx2 expression in neural crest during eye development. Dev Dyn 239:3215-25|
|Gage, Philip J; Zacharias, Amanda L (2009) Signaling "cross-talk" is integrated by transcription factors in the development of the anterior segment in the eye. Dev Dyn 238:2149-62|
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