The long term goal of this laboratory is to enhance the ability of the human nervous system, particularly the retina and/or optic nerve, to regenerate. This proposal, if funded, would determine the role of two factors, bone morphogenetic protein 7 (BMP7) and sonic hedgehog (SHH), in increasing the development of a particularly detrimental cell state known as reactive gliosis. Reactive glia are present in many eye diseases, including glaucoma, age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy and retinopathy of prematurity. The cells that transform into reactive glia arise from the region that becomes the optic nerve, and in the normal uninjured or non-diseased eye, the astrocytes perform essential supportive functions for the ganglion cell neurons of the retina. However, upon injury to or in the diseased eye, these cells become reactive, whereupon they begin expressing molecules that are unfavorable to the regeneration of the optic nerve. This proposal focuses on determining the mechanism(s) whereby BMP7 and SHH regulate the expression of PAX2, a DNA- binding protein that is essential for the development of optic nerve astrocytes. This application proposes a novel mechanism in which both SHH and BMP7 modulate the expression of Pax2 during development by altering the association of an inhibitor of PAX2 expression. This application will test if this novel mechanism drives the development of reactive astrocytes in vitro and in vivo. The studies proposed in this application use a multi-disciplinary approach, including 1) in vitro assays to determine interactions of BMP and SHH pathway members with other regulatory DNA-binding proteins such as co-immunoprecipitation, chromatin immunoprecipitation, and luciferase assays, 2) in vitro and in vivo manipulations of BMP pathways following optic nerve injury to determine the role of BMP7 in reactive gliosis, 3) in vivo and in vitro antisense technology to test BMP7 as potential target for reducing reactive astrocytes, and 4) characterization of the phenotypic properties of optic nerve astrocytes in vitro and in vivo using immunohistochemistry, Western blots, in situ hybridization, quantitative polymerase chain reaction and image analysis. Information derived from these studies will further our understanding of the mechanisms necessary for the development of reactive astrocytes and may also provide therapeutic targets for decreasing reactive gliosis in optic nerve injury and disease.
The focus of this proposal is the study of the astrocytes in the optic nerve and their response to injury. By studying the role of growth factors in the regulation of genes that are necessary for the development of normal and reactive astrocytes, we hope to increase the therapeutic targets for diseases such as glaucoma, diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration, and retinitis pigmentosa.
|Dharmarajan, Subramanian; Fisk, Debra L; Sorenson, Christine M et al. (2017) Microglia activation is essential for BMP7-mediated retinal reactive gliosis. J Neuroinflammation 14:76|
|Dharmarajan, Subramanian; Gurel, Zafer; Wang, Shoujian et al. (2014) Bone morphogenetic protein 7 regulates reactive gliosis in retinal astrocytes and Müller glia. Mol Vis 20:1085-108|
|Tiwari, Sarika; Dharmarajan, Subramanian; Shivanna, Mahesh et al. (2014) Histone deacetylase expression patterns in developing murine optic nerve. BMC Dev Biol 14:30|
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|Wilson, Jonathan M; Martinez-De Luna, Reyna I; El Hodiri, Heithem M et al. (2010) RNA helicase Ddx39 is expressed in the developing central nervous system, limb, otic vesicle, branchial arches and facial mesenchyme of Xenopus laevis. Gene Expr Patterns 10:44-52|
|Sehgal, Rachna; Sheibani, Nader; Rhodes, Simon J et al. (2009) BMP7 and SHH regulate Pax2 in mouse retinal astrocytes by relieving TLX repression. Dev Biol 332:429-43|
|Sehgal, Rachna; Karcavich, Rachel; Carlson, Scott et al. (2008) Ectopic Pax2 expression in chick ventral optic cup phenocopies loss of Pax2 expression. Dev Biol 319:23-33|