Abstract
Background Axial length is determined by genetic and environmental influences. Disorders of axial length encompass both myopia and microphthalmia, accounting for significant visual impairment and blindness worldwide. Despite the ocular morbidity, genetic determinants of microphthalmia and early onset (pre-school) high myopia remain very poorly understood. This study aimed to identify key shared pathways influencing axial length in early eye development.
Methods Three fully characterised induced pluripotent stem cell (iPSC) lines from (i) a patient with bilateral microphthalmia (BM), (ii) early onset high myopia (MY) and (iii) normal ocular phenotype (WT) were differentiated into optic vesicles until day 20 and day 35. Organoid morphology, gene and protein expression were assessed through bulk RNA-seq (Total RNA was sequenced from two clones per line and four independent rounds per condition per time point [n=8]), qRT-PCR and immunohistochemistry.
Results BM, MY and WT optic vesicles demonstrated similar macroscopic morphology with key differentiation markers (SOX2, PAX6, VSX2, BRN3, RAX) identified equally at both timepoints. RNA-seq enrichment analysis highlighted membrane transport and adhesion, cell proliferation, apoptosis, and extracellular matrix as overrepresented gene ontologies in a pairwise analysis at both timepoints. Differential expression analysis revealed extracellular matrix and cellular adhesion as inverse directional targets shared between the two conditions relative to WT.
Conclusions This study reports the first use of optic vesicles to model the axial length disorders myopia and microphthalmia. Key pathways regulating cellular proliferation and extracellular matrix are playing a counter role in each disease subtype in eye morphogenesis. These early molecular changes may determine future eye growth and refractive error. Further exploration will be of utmost importance in understanding the development of early-onset high myopia and the identification of potential therapeutic targets.
