Abstract
Introduction Choroideremia is an X-linked recessive retinal dystrophy, marked by degeneration of the RPE, photoreceptors and choroid. Choroideremia is caused by loss-of-function variants in the CHM gene, with no genotype-phenotype correlation. The CHM gene encodes REP1 protein, which is involved in intracellular vesicle trafficking. Disruption to melanosome transport, photoreceptor outer segment digestion and phagolysosomal activation is reported in choroideremia models. The pathogenic mechanism of choroideremia is not yet fully characterised.
Aims There is no current animal model that fully recapitulates the choroideremia retinal phenotype. We aim to use patient-derived iPSC-RPE to identify novel disrupted pathways and therapeutic targets.
Methods We generated iPSC-RPE from a CHMS190X patient-derived fibroblast line (n=3), and two wildtype control lines (n=3). Samples were sent off for paired-end RNAseq. Differential gene expression and enrichment analysis were performed (using threshold cut off for the adjusted p value of < 0.05, log2fold change > 2).
Results Significant disruption was seen in 4149 genes of CHMS190X iPSC-RPE, compared to wildtype lines. Disrupted cytokine, cellular senescence, and oxidative stress pathways were seen in CHMS190X iPSC-RPE, suggesting inflammatory pathomechanisms. Disruption of cell adhesion pathways was also highlighted, potentially causative of lymphocyte migration into the retina, as seen in choroideremia patients. Disruption of several ion transport mechanisms was observed, which could be associated with inflammation.
Conclusion To our knowledge, this is the first study to characterise the choroideremia iPSC-RPE transcriptome using RNAseq. Disruption to inflammatory pathways were identified, which may draw parallels to underlying mechanisms in AMD.
