Zellweger syndrome disorders (ZSD) affect an estimated 1/10.000 – 1/50.000 live births, where affected children usually do not live long into adulthood. However, the spectrum of disease severity is wide and life expectancy ranges from a few days old babies to patients who live into their 30s. Therapeutic options for these patients are scarce and the disease is poorly understood. This makes it clear that a research project aiming at both progressing in our understanding of the disease and concomitantly developing improved therapeutic approaches is timely and relevant. We will tackle these objectives by mimicking both severe and mild forms of ZSD in the model organism Danio rerio (zebrafish) and by searching for drugs that can potentially help patients with a milder disease within the spectrum to get a treatment that targets the origin of the disease instead of only the symptoms. For that, we will work on drugs that we have previously identified in a large screening effort aimed at finding compounds that improve the function of lipid metabolizing structures, the peroxisomes, which are the cellular compartments that do not function correctly in ZSDs. To further validate these drugs as potential therapeutic agents for ZSD patients, we will measure their effects on the levels of lipids that are normally degraded by healthy peroxisomes and on the localization of proteins that are normally found within healthy peroxisomes. These experiments will be performed on skin cells derived from ZSD patients. In addition, we will apply sophisticated methodologies to better understand how the studied compounds act on the molecular level to exert their beneficial effects on patient cells. This is important to develop potentially even more efficient drugs in the future.

Concerning our planned work in zebrafish, we will use a model that we have already generated using ‘genetic scissors’ (CRISPR/Cas9 system), to cut out one gene that is crucial for peroxisome function in many living organisms and that is often mutated in ZSD patients (PEX1). We found that the zebrafish lacking PEX1 mimic symptoms of the human disease with notably abnormal lipid accumulation in various organs. We will extend this work by generating another zebrafish model mimicking a milder form of ZSD. Both models will be used in the project to further progress in understanding how the disease develops since the earliest stages of life and to test the effect of the above described therapeutic drug candidates in the complexity of a living vertebrate organism. Such ‘preclinical’ studies provide crucial information to decide whether drug candidates can be taken forward for clinical trials in patients.