Human rare variant and zebrafish CRISPR/Cas9-mediated mutant analyses reveal novel functions for API5, HSPB7, and LMO2 in heart failure

The clinical heterogeneity of heart failure has challenged our understanding of the underlying genetic mechanisms of this disease. To gain further insights into this complex pathophysiology we combined human rare variant analysis and in vivo CRISPR/Cas9-mediated mutant phenotyping in zebrafish to identify and investigate the role of 3 genes. Whole-exome sequencing of patients identified API5 , HSPB7 , and LMO2 as causally associated with heart failure and these genes were further investigated, alongside the positive control gata5 , using CRISPR/Cas9-mediated multi-locus in vivo mutation in zebrafish. Following effective somatic mutation, we observed multiple impacts on cardiovascular development and function in F0 embryos including reductions in ventricle size, pericardial oedema, and chamber malformation. In the case of lmo2 , there was also a significant impact on heart function. Our analysis suggests novel functions for API5 , HSPB7 , and LMO2 in human cardiovascular disease and identifies them as potential drug targets. Our data also supports in vivo CRISPR/Cas9-mediated multi-locus gene mutation analysis in F0 zebrafish as a rapid and effective primary screen for assessing gene function, as part of an integrated multi-level drug target validation strategy. Summary Statement Human rare variant analysis and CRISPR/Cas9-generated mutant phenotyping in zebrafish identifies genes as potential drug targets in cardiovascular disease. ### Competing Interest Statement SR, MB, AW and EM are employees of AstraZeneca PLC. There are no other potential conflicts of interest.