Screening for Novel and Variants in Keratoconus Patients from Brazil.

PURPOSE

To investigate the presence of the variants of lysyl oxygenase () and superoxide dismutase 1 () genes in Brazilian patients with advanced keratoconus.

METHODS

Donor genomic DNA extracted from blood samples was screened for 5'UTR, exonic and variants in a subset of 26 patients presenting with advanced keratoconus (KISA 1000% and I-S 2.0) by Sanger sequencing. The impact of non-synonymous amino acid changes was evaluated by SIFT, PMUT, and PolyPhen algorithms. The Mutation Taster tool was used to evaluate the potential impact of formation of new donor and acceptor splice sites in the promoter region of affected volunteers carrying sequence variants. A 7-base deletion (IVS2 + 50del7bp) previously associated with keratoconus was screened in 140 patients presenting classical keratoconus by gel fragment analysis, and positive samples were sequenced for confirmation.

RESULTS

We found an unreported missense variant in exon 6 in one heterozygous patient, leading to substitution of proline with threonine at residue 392 (p. Thr392Pro) of protein sequence. This mutation was predicted to be potentially damaging to protein. Another variant, Arg158Gln, was also detected in another patient but predicted to be non-pathogenic. Two additional new polymorphisms in 5'UTR region (-116C T and -58C T) were found in two patients presenting with advanced keratoconus and were predicted to modulate or create donor/acceptor splice sites in transcripts. Additionally, deletion was detected in one patient presenting with severe keratoconus, not in control samples.

CONCLUSION

We described three novel LOX polymorphisms identified for the first time in Brazilian patients with advanced keratoconus, as well as a previously described deletion strongly associated with keratoconus. A possible role of these variants in modulating transcript levels in the cornea of affected individual requires further investigation.