Whole-Exome Sequencing of 24 Spanish Families: Candidate Genes for Non-Syndromic Pediatric Keratoconus

Abstract

Keratoconus is a corneal dystrophy that is one of the main causes of corneal transplantation and for which there is currently no effective treatment for all patients. The presentation of this disease in pediatric age is associated with rapid progression, a worse prognosis and, in 15-20% of cases, the need for corneal transplantation. It is a multifactorial disease with genetic variability, which makes its genetic study difficult. Discovering new therapeutic targets is necessary to improve the quality of life of patients. In this manuscript, we present the results of whole-exome sequencing (WES) of 24 pediatric families diagnosed at the University Hospital La Paz (HULP) in Madrid. The results show an oligogenic inheritance of the disease. Genes involved in the structure, function, cell adhesion, development and repair pathways of the cornea are proposed as candidate genes for the disease. Further studies are needed to confirm the involvement of the candidate genes described in this article in the development of pediatric keratoconus.

Keywords: non-syndromic pediatric keratoconus; ophthalmogenetics; whole-exome sequencing.

Figure A1

Genetic trees of the 24 families of pediatric probands with keratoconus.

Figure 1

Cascade of molecular processes in the pathophysiology of keratoconus. Summary of the molecular involvement of the corneal layers. The presence of external factors, such as eye rubbing, increased reactive oxygen species (ROS), mitochondrial damage or mutations in certain genes, can lead to the activation of biochemical cascades that first induce the loss of cellular uniformity in the corneal epithelium. The process continues with the inflow of epithelial cells into Bowman’s membrane, leading to its rupture and the accumulation of ferritin in the area, which clinically translates into the clinical sign of Fleischer’s ring. There is an increase in proinflammatory cytokines (IL-6, TNF-alpha) and an exacerbation of the function of metalloproteinases (MMP-1, MMP-2, MMP-9, MMP-13), resulting in the separation of collagen bundles and their abnormal arrangement (clinically perceived as Vogt’s striae), increased apoptosis of keratocytes, leading to a reduction in corneal stromal thickness, and both histological changes and disruption of the extracellular matrix. Created with Biorender.com (accessed on 29 August 2023).

Figure 2

Workflow for the methodology of exome analysis in families of keratoconus patients. Created with Biorender.com (accessed on 29 August 2023).

Figure 3

Pathogenicity of the variants detected in the study. LP, likely pathogenic; VUS, variant of uncertain significance.

Figure 4

Functions of the genes selected as candidates for KC in which variants were detected in the study.