Screening of the Seed Region of MIR184 in Keratoconus Patients from Saudi Arabia

Abstract

Micro-RNAs (miRNAs) are regulators of gene expression that control various biological processes. The role of many identified miRNAs is not yet resolved. Recent evidence suggests that miRNA mutations and/or misexpression may contribute to genetic disorders. Point mutations in the seed region of MIR184 have been recently identified in Keratoconus (KC) patients with or without other corneal and lens abnormalities. We investigated mutations within MIR184 in KC patients from Saudi Arabia and examined the relative expression of miR-184 and miR-205 in human cornea. Ethnically matched KC cases (n = 134) were recruited and sequencing was performed using PCR-based Sanger sequencing and analyzed using the Sequencher 5.2 software. Expression of miR-184 and miR-205 was profiled in postmortem unaffected ocular tissues obtained from donors with no history of ocular diseases. miR-184 expression was 15-fold higher than that of miR-205 in cornea samples. No mutation(s) within the screened genomic region of MIR184 in KC cases was detected. This suggests that mutation in MIR184 is a rare cause of KC alone and may be more relevant to cases of KC associated with other ocular abnormalities. The increased expression of miR-184 versus miR-205 in normal cornea samples implies a possible role of miR184 in cornea development and/or corneal diseases.

Figure 1

Chromosomal map showing the primers used in our study using UCSC genome browser. The figure shows that there are no common SNPs located in either the forward primer or reverse primer. Two common (rs12903401 and rs41280052) SNPs are located in the PCR amplicon.

Figure 2

Representative sequence chromatograms showing no substitution mutations in five KC patients from the Saudi Arabian group. Sequences were compared to the reference coding sequence MIR184.

Figure 3

The relative expression level of miR-184 and miR-205 in different human ocular tissues (cornea, trabecular meshwork (TM), ciliary body, and retina) using miRNA sequencing with Illumina MiSeq Personal Sequencing System. (Y-axis logarithmic scale of 10).