Doctor of Philosophy (Ph.D.)
Degree Granting Department
Thomas McDonald, Ph.D.
Derek Wildman, Ph.D.
Sami Noujaim, Ph.D.
Thomas Taylor-Clark, Ph.D.
Lamin A/C, dilated cardiomyopathy, connexin 43, extracellular matrix
Mutations in the LMNA gene (encoding lamin A/C) are the second most common cause of familial arrhythmogenic cardiomyopathy. Diverse LMNA variants in cardiomyocytes have been associated with cardiac phenotypes. Moreover, cardiac fibroblasts make up a large fraction of the myocardium's non-myocyte component, intrinsically linked to extracellular matrix synthesis and turnover as well as secreting large amounts of bioactive metabolites. However, our understanding of how different mutation sites and the non-myocyte niche mediate cardiomyocyte function is limited. To fill this gap, in this thesis I investigated the hypothesis that variable LMNA mutations have significant effects on the genetic, structure and electrophysiological properties of cardiomyocytes and cardiac fibroblasts.
I differentiated iPSC-derived cardiomyocytes (iCMs) and cardiac fibroblasts (iCFs) from seven different patients carrying LMNA mutation: M1I, R216C/R399H, R216C-male (R216C.m), R216C-female (R216C.f), R335Q, R377H and R541C. LMNA expression and extracellular signal-regulated kinase pathway activation were perturbed to varying degrees in both iCMs and iCFs from the different lines. Enhanced apoptosis occurred in iCMs but not in iCFs. Markedly diverse irregularities of nuclear membrane morphology were present in iCFs but not iCMs, while iCMs demonstrated variable sarcomere disarray. Heterogenous electrophysiological aberrations assayed by calcium indicator imaging and multi-electrode array suggest differing substrates for arrhythmias that were accompanied by variable ion channel gene expression in the iCMs. Direct contact iCM-iCF co-cultures suggest enhancement of the LMNA mutation effects on electrophysiological function exerted by iCFs, possibly linked to the disturbed location and quantity of connexin 43. RNA sequencing demonstrated remarkable enrichment terms associated with extracellular matrix constituents and organization both in iCMs and iCFs derived from various LMNA mutation carriers.
This work supports the growing understanding of the use of patient-specific iPSCs in modeling and deciphering cardiovascular diseases. Cardiac fibroblasts play a fundamental role in supporting and regulating cardiomyocyte electrophysiology function. Given that the molecular pathways to disease differ with specific mutations, one therapeutic option is not likely to suit every patient unless the specific genotype is considered (i.e., one size will not fit all).
Scholar Commons Citation
Yang, Jiajia, "Phenotypic Variability in iPSC-Induced Cardiomyocytes and Cardiac Fibroblasts Carrying Diverse LMNA Mutations" (2022). USF Tampa Graduate Theses and Dissertations.