Direct Sequencing of miR-184 and miR-205 in Sporadic Keratoconus

Abstract

Purpose: : Targeted sequence capture and next generation sequencing of a 5.5 Mb region on chr15q22 linked to keratoconus and congenital cataract (MIM# 614303) recently identified a disease causing mutation (r.57c> t) in the seed region of miR-184 (MIM# 613146). miR-184 is highly expressed in the cornea and is known to rescue INPPL1 production by competitive inhibition of the binding of miR-205. The purpose of this study was to sequence miR-184 and miR-205 in a keratoconus cohort of mixed ethnicity.

Methods: : All patients had a full ophthalmic examination and the diagnosis of keratoconus was made on the basis of clinical examination, a history of penetrating keratoplasty for keratoconus and corneal topography. DNA extraction, PCR amplification, and direct sequencing of the miR-184 and miR-205 gene were performed in 250 unrelated patients of mixed ethnicity.

Results: : The pathogenic mutation r.57c> t in the seed region of miR-184 previously found in a large northern Irish family affected by combined clinically severe keratoconus and early onset anterior polar cataract was not found in any of the 250 sporadic keratoconus patients analysed. Furthermore, direct sequencing of miR-205 in the same panel did not reveal any pathogenic variants.

Conclusions: : The r.57c> t mutation found in the seed region of miR-184 is a private mutation. Mutations in miR-184 and miR-205 do not play a significant role in the development of keratoconus. However, understanding the important function of micro RNAs in the cornea could aid identification of other keratoconus susceptibility genes and new therapeutic targets for treatment.

Keywords: keratoconus • mutations • genetics