Modelling and understanding SHOX2-associated atrial arrhythmias using human iPSCs

• Applicant: Dr. Sandra Hoffmann
• Subject Area: Human Genetics ; Cardiology, Angiology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 493726818

A specialized cell population in the right atrium of the heart, the so-called sinoatrial node, initiates and coordinates regular heartbeat. Cardiac arrhythmias are pathological abnormalities from the normal heartbeat and are among the most common heart diseases. In recent years, there has been a significant increase in both the frequency and associated mortality. Atrial fibrillation is the most common sustained arrhythmia. Sinus node dysfunction often coexists with atrial fibrillation, however, the underlying molecular mechanisms are not well understood. Shared genetic causes may indicate a common link between both disorders. It is therefore of utmost importance to better understand those genetic mechanisms in order to develop novel therapeutic concepts. The homeodomain transcription factor SHOX2 plays a crucial role in the development of the sinoatrial node and has been thoroughly investigated by various animal models in the past. In humans, mutations in the SHOX2 gene have been identified in patients with atrial fibrillation and sinus node dysfunction. In the proposed study we will use SHOX2 as a molecular tool to elucidate the relationship between both diseases to understand common pathomechnisms and treatment options. We aim to study the role of SHOX2 and SHOX2-dependent gene regulatory networks in a human disease model using induced pluripotent stem cells (iPSCs). iPSCs reprogrammed from atrial fibrillation patients with heterozygous coding and regulatory SHOX2 point mutations, together with genetic knockout iPSC lines (reflecting the sinus node dysfunction phenotype observed in animal models) will be crucial in exploring these connections. To understand how the transcriptional effects underlying those mutations lead to pathogenic phenotypes, we will decipher the relationship between genome structure and changes in global patterns of gene expression at cellular resolution. I expect that single-cell RNA- and single-cell ATAC-sequencing of patient-specific and knockout iPSC-derived subtype-specific cardiomyocytes carrying mutations in the SHOX2 gene, together with isogenic controls, will allow us to understand disease-relevant genetic pathways. Specifically, we will determine the precise transcriptional changes taking place within atrial and nodal iPSC-derived cell populations using 2D and 3D models to better understand complex phenotypes such as atrial fibrillation and sinus node dysfunction. Following an integrated analysis of RNA- and ATAC-sequencing, these data will provide a model of transcriptional and epigenetic regulations that play a role in atrial arrhythmia-associated diseases at single-cell resolution. Modelling atrial arrhythmias with genotype-guided approaches using iPSCs will improve our understanding of the molecular mechanisms by which genomic variation cause those diseases. Moreover, this innovative approach provides a preclinical model for the selection of novel therapeutic targets paving the way to personalized medicine.

• DFG Programme: Research Grants