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Microphthalmia is a congenital ocular disorder resulting from abnormal morphogenesis during early eye development. It affects approximately 17 in every 100,000 live births and accounts for up to 11% of childhood blindness worldwide. Unfortunately, there’s currently no treatment available. Clinical data shows that gene mutations are associated with the development of microphthalmia. Here, we particularly focus on FNBP4 (formin binding protein 4). Whole-genome sequencing identified a homozygous FNBP4 mutation in microphthalmia patients. Despite its identification, research on FNBP4 and its role in eye development remains limited. Preliminary study in our lab revealed that CRISPR knockout of FNBP4 results in microphthalmia in zebrafish embryos. Additionally, FNBP4 knockout leads to increased apoptosis and an expansion of phospho-Smad1/5/8 staining in the embryonic eye implicating alterations in cellular dynamics and BMP signalling as a potential mechanism underlying microphthalmia conditions. Therefore, this project aims to explore the molecular mechanism of FNBP4 in eye development by identifying binding partners and investigating FNBP4 regulation of the BMP-SMAD signalling pathway in retinal cell-lines and iPSC-derived organoids. Western blot analysis revealed that FNBP4 knockdown in RPE-1 cells increases phosphorylated Smad (p-Smad1/5/8) levels in response to BMP4 stimulation, suggesting a conserved role for FNBP4 in inhibiting or attenuating BMP signalling. To further investigate the cellular pathways regulated by FNBP4, we will employ RNA-seq and Co-IP in RPE cell lines and generate wild-type and FNBP4 CRISPR-knockout hiPSC-derived retinal organoids to examine its role in ocular development.