Our long term goal is to identify and characterize genetic mutations involved in the pathogenesis of keratoconus (KC). KC is a bilateral, asymmetric corneal degeneration characterized by localized thinning and protrusion of the thinned cornea. KC leads to high myopia, irregular astigmatism, and cornea scarring. Although genetic factors contribute to KC pathogenesis, its genetic causes remain to be identified. Only mutations in the VSX1 and MIR184 genes are known to cause KC, but they account for <10% KC cases. KC is typically inherited through autosomal dominant patterns, though autosomal recessive patterns have been reported. It affects males and females similarly and is detected in all ethnic groups worldwide. Our productive collaborations with others amassing DNA samples from more than 600 KC individuals and their families have led to the identification of KC-segregating mutations in three genes, including PPIP5K2 (diphosphoinositol pentakisphosphate kinase 2). PPIP5K2 encodes a bifunctional kinase and phosphatase with high affinity to InsP5 / 5-InsP7 and PtdIns(3,4,5)P3 respectively. In two multi-generation families with multiple affected individuals, we have identified two heterozygous mutations affecting amino acids located in the polyphosphoinositide binding domain (PBD) of PPIP5K2. PPIP5K2 is highly expressed in human and mouse cornea tissue. The PPIP5K2-related phosphoinositide-3-kinase (PI-3 kinase) pathway, when inhibited, affects AKT phosphorylation and keratocyte survival, leading to the apoptosis of corneal stromal keratocytes in KC patients. We hypothesize that PPIP5K2 mutations alter TGF?/AKT pathways, leading to degeneration of corneal epithelial and stromal cells with subsequent thinning/bulging of the affected cornea. We will determine how the identified mutations affect the cellular function of PPIP5K2 in vitro using primary human epithelial and stromal cells in Aim 1. We will determine the KC-related corneal phenotypes in Ppip5k2-knockout mice using comprehensive approaches including optical coherence tomography, functional vision screening, and slit lamp exams followed by morphological examinations in Aim 2. On the other hand, we will screen PPIP5K2 mutations in additional familial and sporadic patients using whole exome sequencing. PPIP5K2-negative multiplex families will be further examined with whole exome sequencing to identify novel mutations in Aim 3. Upon successful completion, we will have a validated animal model of KC and potential novel targets for future research directed at KC diagnosis and clinical therapy.

Public Health Relevance

This project aims to identify and characterize genetic mutations for a common corneal disorder ? keratoconus, using human patient-derived corneal cell culture and mouse models. The identification and characterization of these mutations for keratoconus will significantly improve our understanding of its pathophysiology, and ultimately promote new treatments and development to prevent vision loss from this disease.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY023242-05A1
Application #
9661734
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Mckie, George Ann
Project Start
2019-05-01
Project End
2024-04-30
Budget Start
2019-05-01
Budget End
2020-04-30
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Augusta University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
City
Augusta
State
GA
Country
United States
Zip Code
30912
Khawaja, Anthony P; Cooke Bailey, Jessica N; Wareham, Nicholas J et al. (2018) Genome-wide analyses identify 68 new loci associated with intraocular pressure and improve risk prediction for primary open-angle glaucoma. Nat Genet 50:778-782
Keller, Kate E; Bhattacharya, Sanjoy K; BorrĂ¡s, Theresa et al. (2018) Consensus recommendations for trabecular meshwork cell isolation, characterization and culture. Exp Eye Res 171:164-173
King, Rebecca; Struebing, Felix L; Li, Ying et al. (2018) Genomic locus modulating corneal thickness in the mouse identifies POU6F2 as a potential risk of developing glaucoma. PLoS Genet 14:e1007145
Bonnemaijer, Pieter W M; Iglesias, Adriana I; Nadkarni, Girish N et al. (2018) Genome-wide association study of primary open-angle glaucoma in continental and admixed African populations. Hum Genet 137:847-862
Khaled, Mariam Lofty; Bykhovskaya, Yelena; Yablonski, Sarah E R et al. (2018) Differential Expression of Coding and Long Noncoding RNAs in Keratoconus-Affected Corneas. Invest Ophthalmol Vis Sci 59:2717-2728
Drewry, Michelle D; Challa, Pratap; Kuchtey, John G et al. (2018) Differentially expressed microRNAs in the aqueous humor of patients with exfoliation glaucoma or primary open-angle glaucoma. Hum Mol Genet 27:1263-1275
Iglesias, Adriana I; Mishra, Aniket; Vitart, Veronique et al. (2018) Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases. Nat Commun 9:1864
Fan, Bao Jian; Chen, Xueli; Sondhi, Nisha et al. (2018) Family-Based Genome-Wide Association Study of South Indian Pedigrees Supports WNT7B as a Central Corneal Thickness Locus. Invest Ophthalmol Vis Sci 59:2495-2502
Khaled, Mariam Lotfy; Helwa, Inas; Drewry, Michelle et al. (2017) Molecular and Histopathological Changes Associated with Keratoconus. Biomed Res Int 2017:7803029
Kalantan, Hatem; Kondkar, Altaf A; Sultan, Tahira et al. (2017) Polymorphism rs13334190 in zinc finger protein 469 (ZNF469) is not a risk factor for keratoconus in a Saudi cohort. BMC Res Notes 10:652

Showing the most recent 10 out of 25 publications