| Cytochrome P450 4V2 (CYP4V2) is a gene linked to the ocular disease Bietti's Crystalline Dystrophy (BCD). Sequence analysis of CYP4V2 in BCD patients identified potentially disruptive exonic and intronic mutations. Patients with BCD have characteristic crystalline deposits in the cornea and retina, retinal pigmented epithelium degeneration and sclerosis of the choroidal capillaries. Visual defects progress from nyctalopia to eventual blindness. In addition to vision loss, BCD patients exhibit crystalline deposits in fibroblasts and lymphocytes and alterations in plasma fatty acids. CYP4 family enzymes are associated with metabolism of endogenous substrates, including omega-hydroxylation of fatty acids; CYP4V2 is also an omega-hydroxylase of fatty acids, including docosanoids. While progress has been made in determining the activity and function of CYP4V2, regulation of its expression has not been well-examined. Amongst the 57 CYP genes in humans, CYP4V2 stands out with regard to the length of the transcript 3' UTR, extending over 2.8 kb in comparison to 1.6 kb of coding sequence. This led to the hypothesis that CYP4V2 may be subject to epigenetic regulation by microRNAs. To test this, we selected human liver samples from the UW Liver Bank that had highest and lowest CYP4V2 mRNA and subjected them to microRNA microarray analysis (n=6 per group). We identified miR-146b-5p to be over-expressed in liver samples with lower CYP4V2 mRNA, a miRNA that has a potential binding site in the CYP4V2 mRNA 3'UTR. Western blot data showed CYP4V2 mRNA expression correlated with CYP4V2 protein expression (R2 = 0.472, p = 0.0282) and CYP4V2 protein expression was negatively correlated with miR-146b-5p expression (R2 = 0.4254, p = 0.041). Interestingly, miR-146b expression has been found to be up-regulated by Resolvin D1, a docosanoid signaling molecule involved in acute inflammation. This raises the question of what role CYP4V2 may have in docosanoid signaling pathways in healthy individuals and the effects of CYP4V2 mutations in BCD patients. |
