Molecular pathogenesis of pseudoexfoliation syndrome/glaucoma: from genes to mechanisms

• Applicants: Privatdozentin Dr. Francesca Pasutto; Professorin Dr. Ursula Schlötzer-Schrehardt
• Subject Area: Ophthalmology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449642544

Pseudoexfoliation (PEX) syndrome, one of the most frequent causes of chronic open-angle glaucoma, represents a complex, genetically determined, fibrotic disorder, which leads to progressive accumulation of abnormal fibrillar aggregates in intra- and extraocular tissues. LOXL1 (lysyl oxidase-like 1), coding for a cross-linking matrix enzyme, has been conclusively confirmed as the major effect locus in PEX disease (OR: 3-20). However, all PEX-associated common variants at LOXL1 show allele effect reversal in different populations, casting doubt on their causative role in pathogenesis, and even large-scale genome-wide association studies identified not more than a fraction of specific co-modulating loci. Albeit, our previous LOXL1 re-sequencing efforts revealed a spectrum of >60 rare genetic missense variants at LOXL1, mostly conferring protection against PEX. Based on their strong effect size and functional impact, these rare variants represent promising candidates for modelling of pathomechanisms and beneficial effects.Based on our preliminary data, we hypothesize that 1.) Rare missense genetic variants at LOXL1 provide information on LOXL1-dependent pathomechanisms and potential mechanisms of protection against PEX by impacting on enzyme function and extracellular matrix synthesis and assembly.2.) PEX as a complex disease is caused by additional not yet identified genes disrupting more than one biological pathway that may interact with LOXL1-dependent mechanisms.To test these hypotheses, this interdisciplinary research project seeks to achieve two specific aims:1.) Experimental validation and functional characterization of a subset of three prioritized rare, protein-altering, protective variants, predicted to affect LOXL1 function, in vitro and in vivo, with regard to enzyme function and extracellular matrix synthesis and assembly.2.) Identification of additional differentially expressed genes in PEX followed by pathway and gene network analyses through next-generation RNA sequencing on disease-relevant tissues of PEX and control subjects. Analyses will be performed both at bulk and single cell level ex vivo as well as following LOXL1 knockdown in vitro, with subsequent integration of existing GWAS data.These functional analyses of genetic data will not only increase our understanding of the molecular genetic etiology of PEX pathogenesis, but may also provide valuable, naturally occurring therapeutic opportunities for one of the most frequent and severe causes of glaucoma.

• DFG Programme: Research Grants