Functional analysis of LOXL1 gene polymorphisms in the pathogenesis of pseudoexfoliation syndrome/glaucoma

• Applicant: Professorin Dr. Ursula Schlötzer-Schrehardt
• Subject Area: Ophthalmology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 226809164

Pseudoexfoliation (PEX) syndrome, one of the most frequent causes of chronic open-angle glaucoma, represents a genetically determined, fibrotic matrix process, which leads to progressive accumulation of an abnormal elastotic material in intra- and extraocular tissues. Genetic studies identified a highly significant association between two coding and several non-coding polymorphisms in the LOXL1 gene on chromosome 15q24.1 with PEX syndrome and PEX glaucoma. Since these LOXL1 risk variants were found to occur in almost 100% of PEX patients in all geographical populations worldwide, LOXL1 appears to represent a major risk factor which is absolutely necessary, though not sufficient, for manifestation of the PEX phenotype. In view of the key role of LOXL1 (lysyl oxidase-like 1) in elastogenesis, the working hypothesis of this research project postulates that the PEX-associated LOXL1 risk variants are essentially involved in the pathogenesis of the elastotic PEX process through functional and/or regulatory effects. The growth factor TGF-ß1, which is considered a central mediator of the fibrotic PEX process and a key regulator of lysyl oxidase expression and activity, may act as a comodulating external factor. On the basis of substantial preliminary work on establishing stable LOXL1-expression systems in HEK193 cells, E.coli bacteria, and primary human fibroblasts, the aims of this project include: 1) a comparative functional characterization of the recombinantly expressed LOXL1 missense variants with regard to expression, secretion, processing, catalytic activity, protein interactions, and substrate binding properties; 2) a comparative analysis of the effect of the LOXL1 missense variants on extracellular matrix synthesis and assembly and 3) on the TGF-ß1 signal transduction in a fibroblast cell culture model in vitro; and 4) a comparative analysis of the effect of the non-coding LOXL1 variants on the regulation of LOXL1 expression. These functional analyses will not only increase our understanding of the molecular pathomechanisms underlying the fibrotic PEX process, but may also open up new rational therapeutic strategies for one of the most frequent causes of glaucoma.

• DFG Programme: Research Grants
• Participating Person: Dr. Matthias Zenkel