Collagen synthesis disruption and downregulation of core elements of TGF-β, Hippo, and Wnt pathways in keratoconus corneas

Abstract

To understand better the factors contributing to keratoconus (KTCN), we performed comprehensive transcriptome profiling of human KTCN corneas for the first time using an RNA-Seq approach. Twenty-five KTCN and 25 non-KTCN corneas were enrolled in this study. After RNA extraction, total RNA libraries were prepared and sequenced. The discovery RNA-Seq analysis (in eight KTCN and eight non-KTCN corneas) was conducted first, after which the replication RNA-Seq experiment was performed on a second set of samples (17 KTCN and 17 non-KTCN corneas). Over 82% of the genes and almost 75% of the transcripts detected as differentially expressed in KTCN and non-KTCN corneas were confirmed in the replication study using another set of samples. We used these differentially expressed genes to generate a network of KTCN-deregulated genes. We found an extensive disruption of collagen synthesis and maturation pathways, as well as downregulation of the core elements of the TGF-β, Hippo, and Wnt signaling pathways influencing corneal organization. This first comprehensive transcriptome profiling of human KTCN corneas points further to a complex etiology of KTCN.

Differential Expression of Coding and Long Noncoding RNAs in Keratoconus-affected Corneas

“…Importantly, loss of CTGF impairs efficient corneal wound healing 53 . We have found that CTGF was significantly down-regulated in KC-affected corneas, which is consistent with previous studies 24,32 . EPPK1 encodes a cytoskeletal linker protein called epiplakin, which maintains the integrity of intermediate filaments networks in epithelial cells 54,55 .…”

“…PIK3IP1 has been suggested to suppress AKT activity by inhibiting the expression of PI3K 78 . PIK3IP1 has previously been reported to be down-regulated in KCaffected corneas 32 . IGFBPs belong to a family of six structurally similar proteins which antagonize the binding of insulin growth factors to their receptors, thus, controlling cell survival, mitogenesis, and differentiation 79 .…”

“…Extracellular matrix (ECM) regulatory pathways are important for corneal integrity; however dysregulation in these pathways have been reported with KC progression 24,45 . Previous studies have shown an up-regulation of ECM degradative enzymes (such as matrix metalloproteinases and cathepsin) and/or down-regulation of their inhibitors (such as α1-protease inhibitor, α2-macroglobulin, secretory Leukocyte Peptidase Inhibitor, and TIMPs) 32,39,71 . Our data shows significant down-regulation in proteinases inhibitors (TIMP-1, TIMP-3, and A2M, and SLPI), but interestingly no significant change with ECM proteinases.…”

Accumulation of sequence variants in genes of Wnt signaling and focal adhesion pathways in human corneas further explains their involvement in keratoconus

“…All patients with KTCN underwent a complete ophthalmic evaluation in the Department of Ophthalmology, Medical University of Warsaw, Poland. The KTCN diagnosis was made based on the criteria previously described (Kabza et al, 2017;Karolak et al, 2016). The study protocol was approved by the Institutional Review Board at Poznan University of Medical Sciences (453/14; 755/19).…”

Genética de ceratocone: Estudo genético e molecular de uma família brasileira

“…Cada elemento na matriz contém exemplos de técnicas e tecnologias que podem ser usadas para estudar aspectos biológicos particulares. MS), Cromatografia gasosa (GC), Cromatografia líquidaespectrometria de massa (LC-MS).EmKabza (2017), foram identificados por RNA-Seq (transcriptoma) as seguintes proteínas alteradas em córnea com ceratocene, relacionadas à formação das fibras de colágeno:…”