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 (OTX2), paired box 6 gene (PAX6), and SRY-box transcription factor 2 gene (SOX2) 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 OTX2, PAX6, and SOX2 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. OTX2, PAX6, and SOX2 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.