Analysis of OTX2, PAX6, and SOX2 Gene and Protein Expression Patterns in Ocular Development of Human and Rat Embryos

Transcription factors orthodenticle homeobox 2 gene (<i>OTX2</i>), paired box 6 gene (<i>PAX6</i>), and SRY-box transcription factor 2 gene (<i>SOX2</i>) are key regulators of ocular morphogenesis; however, their comparative embryonic localization across species-and the correspondence between transcript and protein distributions-remain incompletely defined. Chromogenic in situ hybridization (CISH) was employed to detect <i>OTX2</i>, <i>PAX6</i>, and <i>SOX2</i> transcripts, while biotin-streptavidin immunohistochemistry (IHC) was used to assess Otx2, Pax6, and Sox2 protein expression. A semi-quantitative scoring system was applied to evaluate positive structures across ocular compartments. Transcripts were predominantly localized to the retina in both species, with occasional low-level expression in the optic nerve, sclera, and eyelid. Proteins displayed broader distributions: Otx2 was abundant in the retina and eyelid, while Pax6 and Sox2 were detected in multiple tissues, including cornea and extraocular muscles. <i>OTX2</i>, <i>PAX6</i>, and <i>SOX2</i> show retina-predominant transcription and wider protein expression across ocular tissues. These findings highlight spatial differences between transcript and protein localization, supporting a complex regulatory framework underlying vertebrate eye development.