Pax6 regulation of Sox9 in the mouse retinal pigmented epithelium controls its timely differentiation and choroid vasculature development

Yamit Cohen-Tayar, Hadar Cohen, Yulia Mitiagin, Zohar Abravanel, Carmit Levy, Masha Idelson, Benjamin Reubinoff, Shalev Itzkovitz, Shaul Raviv, Klaus H. Kaestner, Pablo Blinder, Ran Elkon, Ruth Ashery-Padan

The synchronized differentiation of neuronal and vascular tissues is crucial for normal organ development and function, although there is limited information about the mechanisms regulating the coordinated development of these tissues. The choroid vasculature of the eye serves as the main blood supply to the metabolically active photoreceptors, and develops together with the retinal pigmented epithelium (RPE). Here, we describe a novel regulatory relationship between the RPE transcription factors, Pax6 and Sox9, which control the timing of RPE differentiation, and the adjacent choroid maturation. We used a novel machine learning algorithm tool to analyze high resolution imaging of the choroid in Pax6 and Sox9 conditional mutant mice. Additional unbiased transcriptomic analyses in mutant mice and RPE cells generated from human embryonic stem cells, as well as chromatin immunoprecipitation and high throughput analyses, revealed secreted factors that are regulated by Pax6 and Sox9. These factors may be involved in choroid development and in the pathogenesis of the common blinding disease, age-related macular degeneration (AMD).