A Multi-Omics Approach to Study Retinal Pigment Epithelium (RPE)-Secreted Factors in Postnatal Mouse Eye Size Determination

Human eye size is determined by genetic factors and modulated by environmental factors. Given the complex structure of the human eye, eye size determination cannot be accomplished by a single ocular tissue; rather, it is a synchronized process that involves cross-tissue signaling. Previous research, including our own study, suggests that the retinal pigment epithelium (RPE) plays a crucial role in eye size determination. The RPE is the source of various growth factors and is involved in influencing the sclera, the outer structural layer of the eye globe. However, there is a gap in our knowledge regarding the specific signaling molecules that mediate communications between the RPE and the sclera.In a preliminary study, we conducted an RNA-seq analysis of the RPE in neonatal mice during the first month of postnatal development. This period is significant because it marks a transition from rapid to slower eye growth in size. Our findings revealed that Wnt2, a canonical Wnt ligand, is specifically expressed in the RPE of neonatal mouse eyes and that its expression decreases rapidly from birth to one month of age. Adenoassociated virus (AAV)-mediated Wnt2 overexpression in the RPE led to increased eye size in mice. The enlarged eye was primarily attributed to an expansion of the vitreous chamber, while the retinal structure remained relatively normal. In this proposed study, we will test the hypothesis that RPE-derived Wnt2 acts on the sclera to promote eye growth during normal animal development and in the progression of myopia. To demonstrate that the sclera is the target of Wnt2, we will directly activate downstream signaling pathways of Wnt in the sclera and examine the effects of Wnt2 on the recipient scleral tissue using proteomic analyses. In addition, this proposal will take an unbiased approach to characterize the RPE-to-sclera secretome in mice to identify other eye size-regulating signaling proteins for further investigation. Overall, we believe that this proposed study will provide valuable insights into the role of RPE-derived Wnt2 in determining eye size and help uncover additional signaling proteins involved in regulating eye size.