Mapping mRNA Expression of Glaucoma Genes in the Healthy Mouse Eye

Many genes have been associated with primary open-angle glaucoma (POAG). Knowing exactly where they are expressed in the eye helps to unravel POAG pathology and to select optimal targets for intervention. We investigated whether RNA <i>in situ</i> hybridization (RNA-ISH) is a convenient technique to obtain detailed pan-ocular expression data of these genes. We tested this for four diverse candidate POAG genes, selected because of unclear ocular distribution (<i>F5</i> and <i>Dusp1)</i> and relevance for potential new therapies (<i>Tnf, Tgfβr3</i>). <i>Optn</i>, a POAG gene with well-known ocular expression pattern served as control. We made a list of candidate glaucoma genes reported in genetic studies. A table of their ocular expression at the tissue level was compiled using publicly available microarray data (the ocular tissue database). To add cellular detail we performed RNA-ISH for <i>Optn, Tnf, Tgfβr3, F5</i>, and <i>Dusp1</i> on eyes of healthy, 2-month-old, pigmented, and albino mice. Expression of the <i>Optn</i> control matched with published immunohistochemistry data. Ocular expression of <i>Tnf</i> was generally low, with patches of higher <i>Tnf</i> expression, superficially in the corneal epithelium. <i>F5</i> had a restricted expression pattern with high expression in the nonpigmented ciliary body epithelium and moderate expression in the peripapillary region. <i>Tgfβr3</i> and <i>Dusp1</i> showed ubiquitous expression. RNA-ISH is a suitable technique to determine the ocular expression pattern of POAG genes, adding meaningful cellular detail to existing microarray expression data. For instance, the high expression of <i>F5</i> in the nonpigmented ciliary body epithelium suggests a role of this gene in aqueous humor dynamics and intraocular pressure. In addition, the ubiquitous expression of <i>Tgfβr3</i> has implications for designing TGF-β-related glaucoma therapies, with respect to side effects. Creating pan-ocular expression maps of POAG genes with RNA-ISH will help to identify POAG pathways in specific cell types and to select targets for drug development.