Effects of Imposed Defocus on Inhibitor of DNA-Binding Gene Expression in Chick Posterior Ocular Tissues

Inhibitors of DNA-binding genes (<i>Id</i>s) are key downstream targets of bone morphogenetic proteins (BMPs), gene expression of which is differentially regulated in the chick retinal pigment epithelium (RPE) during altered eye growth. The current study examined the effects of optical defocus on the gene expression of <i>Id1-4</i> in chick retina, RPE, and choroid after 2 or 48 h of monocular +10 or -10 D lens wear. Defocus-induced differential <i>Id</i> gene expression was observed in all three tissues, with defocus sign and treatment duration-related differences. In the choroid, 2 h of +10 D (myopic) defocus induced upregulation of all four of the <i>Id</i>s, with this effect also seen with 48 h exposure, for both <i>Id3</i> and <i>Id4</i> genes. Two hours of +10 D defocus also induced upregulation of both <i>Id2</i> and <i>Id3</i> in RPE, while 48 h of -10 D (hyperopic) defocus induced downregulation of <i>Id1</i>. Gene expression changes in the retina were less predictable. The significant myopic defocus-induced upregulation of expression for all four <i>Id</i> genes in the choroid is consistent with previously observed increased <i>Bmp</i> gene expression in chick RPE under the same conditions, and offers further supporting evidence for important roles for BMPs and downstream signaling pathways in defocus-driven eye growth regulation.