CADMIUM EXPOSURE ALTERS GENE EXPRESSION OF LENS, RETINA, AND EYE-RELATED GENES IN ZEBRAFISH AND HUMAN LENS EPITHELIAL CELLS

Abstract

Vision is a crucial aspect of life for humans and animals. Impaired vision can lead to reduced quality of life along with other complications. Cataracts are a leading cause of impaired vision and blindness worldwide. Cataracts develop as a process of aging, although several environmental and lifestyle factors increase the risk of this disease. The toxic metal cadmium (Cd) has been associated with cataract formation and other ocular diseases such as macular degeneration. Cadmium exposure experiments were conducted to investigate potential pathways or mechanisms by which Cd may contribute to cataract formation and ocular disease. Zebra fish larvae (72, 96, and 120 hours post fertilization), adult zebra sh (6-month male, 10-month male, and 10-month female) and the B3 human lens epithelial (HLE) cell line were acutely exposed to varying concentrations of Cd. Transcriptomic changes relative to control (0 μM Cd) were determined using microarray analysis for zebra sh larvae and RNA sequencing (RNA-Seq) for adult zebra sh and HLE cells. Gene Ontology (GO) enrichment analysis for the zebra sh larvae exposure (50 μM Cd for 4 or 8 hours) enriched the "retina development in camera-type eye" term, and genes involved in enrichment (dnmt1, ccna2, fen1, mcm3 and slbp) were down-regulated. Gene set enrichment analysis (GSEA) for the 10-month male zebra sh exposure (50 μM Cd for 4 hours) enriched the "embryonic eye morphogenesis" gene set and signi ficant genes involved in enrichment (tcf7l1a, pitx2, fzd8a, sfrp5, lmx1bb, mfap2, six3b, lum, phactr4b, and foxc1a) were down-regulated. GSEA for the 10-month female zebra sh (50 μM Cd for 4 hours) enriched the "photoreceptor cell differentiation" gene set and signi cant genes involved in enrichment (odc1, thrb, and ush2a) were up-regulated. GO enrichment analysis for up-regulated genes in the HLE cell exposure (10 μM Cd for 4 hours) enriched the terms "eye development" (22 genes) and "lens development in camera-type eye" (CITED2, SKIL, CRYAB, SLC7A11, TGFB2, EPHA2, BCAR3, WNT5B, and BMP4). These results show cadmium is capable of altering transcription of eye-related genes in both zebra sh and human models, which may contribute to the formation of ocular disease. Many of these genes are involved in lens and retina development, yet they are also associated with diseases in these eye structures. Future studies could assess the consequences of altered transcription of these genes which could help elucidate the mechanisms of these changes and the overall effect of cadmium exposure on ocular disease. Ultimately, our study characterized the regulation of eye-related genes in response to Cd exposure and provided valuable knowledge laying the foundation for identi fication of the molecular mechanisms contributing to ocular diseases.