TY  - GEN
ID  - heidok34630
N2  - The sinoatrial node (SAN) is the primary pacemaker of the heart, where the pulse necessary for cardiac
contraction arises to be propagated to the cardiac chambers via the cardiac conduction system. The
transcription factor short stature homeobox 2 ( SHOX2 ) is essential for the development and function
of the SAN, activating a transcriptional program for pacemaker development while suppressing
differentiation towards working myocardium during cardiogenesis. Variants in the SHOX2 gene have
been associated with atrial fibrillation (AF), the most common cardiac arrhythmia. However, the
pathomechanisms behind SHOX2 dependent AF and the SHOX2 regulatory genetic network have not
been fully understood. Until now, the impact of Shox2 deficiency has only been investigated in mouse
or zebrafish animal models. Therefore, the aim of this thesis was to gain new insights from a human
background and to investigate whether data obtained via animal models can be transferred to a human
model system. At the beginning of this work, two induced pluripotent stem cell (iPSC) lines from two
different patients with early onset AF were available, carrying a heterozygous single nucleotide variant
either in the 3?UTR or in the coding region of SHOX2. A targeted correction of these variants had already
been performed to generate isogenic control lines.
First, I generated two homozygous SHOX2 KO iPSC lines from the available cell lines and validated them
using several methods. Furthermore, I established and adapted previously published differentiation
protocols to generate pacemaker and atrial cardiomyocytes (CMs) from iPSCs. To uncover variant specific changes in the two patient lines that contribute to the disease phenotype, I performed comparative profiling with their isogenic controls using gene expression analysis, single cell RNA
sequencing and electrical phenotyping. Gene expression profiling of iPSC derived CMs confirmed several deregulated gene expression patterns known from animal models and uncovered additional dysregulation. Data from Single cell RNA sequencing revealed a possibly impaired differentiation
capability and disturbed mitochondrial function in the patient cells. In CMs of the 3?UTR variant patient
line, changed action potential characteristics were discovered, which notably could be attributed to
differential ion channel expression. M ost strikingly, upregulation of the Na+ channel SCN5A led to an
increased action potential upstroke velocity and amplitude, and upregulation of several K+ channels
caused a shortened repolarization time observed in the patient line. Thus, novel disease mechanisms
causing SHOX2 dependent AF as well as underlying molecular mechanisms and potential targets for
adapted treatment strategies could be uncovered. Overall, the established human iPSC model and the
differentiated cardiac cell types provide a valuable tool to further dissect the detailed molecular
mechanisms of SHOX2 dependent AF in the future.
TI  - Elucidating the role of SHOX2 in atrial fibrillation using a patient-derived human induced pluripotent stem cell model
Y1  - 2025///
A1  - Rädecke, Kristin
CY  - Heidelberg
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/34630/
AV  - public
ER  -