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Abstract

Accounting for nearly a third of global deaths, cardiovascular diseases (CVDs) represent a major health burden to our society. Most CVDs can be prevented with early diagnosis and intervention. Several of the major risk factors, which contribute in a cumulative manner to the onset and development of CVDs, can be regulated. Among the major risk factors, the resting heart rate is a vital indicator that reflects underlying physiology and is a recognised predictor for cardiovascular and overall mortality. Early life-style changes or medical interventions can foster control of modifiable risk factors and in turn, by reducing or preventing CVDs, positively impact on the patient’s longevity and quality of life.

The crucial contribution of genetics to the onset and progression of CVDs has led the discovery of its diagnostic and prognostic genetic determinants utilising human genome-wide association studies (GWAS). These association studies correlate hundreds of genes and CVDs after diagnosis and therefore constitute a valuable resource for potential candidate discovery. However, to date many of these genes remain uncharacterized or without link to heart development or function. Moreover, genes correlated to CVDs, still lack causality and require functional validation in animal models. Due to the lack of rapid gene validation workflows and the pressured demand for mechanistic insights, further focus is mainly directed towards genes with known and established functions rather than novel uncharacterized genes. Consequently, in the realm of functional validation, a negative loop of re-discovery is created.

In this thesis, I addressed this negative loop by targeting and validating an understudied domain of human GWAS candidates with no known connection to the heart. I built on the high conservation of cardiac function and underlying genetics between teleost fish and humans, and developed a sensitive and robust functional gene validation assay using an isogenic strain of the Japanese rice fish medaka. By combining highly efficient CRISPR/Cas9-mediated mutagenesis with high-throughput heart rate phenotyping, I identified novel candidate genes with potential predictive power for human CVDs, and in turn redirected the spotlight onto these genes as putative diagnostic and prognostic CVD genetic markers.