Date of Award
Level of Access Assigned by Author
Doctor of Philosophy (PhD)
Kerry L. Tucker
Second Committee Member
Third Committee Member
Additional Committee Members
Elimination of primary cilia in cardiac neural crest cell (CNCC) progenitors is hypothesized to cause a variety of congenital heart defects (CHDs), including atrioventricular septal defects, and malformations of the developing cardiac outflow tract. We present an in vivo model of CHD resulting from the conditional elimination of primary cilia from CNCC using multiple, Wnt1:Cre-loxP, neural crest-specific systems, targeting two distinctive, but critical, primary cilia structural genes: Intraflagellar transport protein 88 (Ift88) or kinesin family member 3A (Kif3a). CNCC loss of primary cilia leads to widespread CHD, where homozygous mutant embryos (MUT) display a variety of outflow tract malformations, septation defects and impaired maturation of the myocardium, resulting in early perinatal lethality. Noncompaction of the MUT ventricular myocardium coincides with widespread ventricular arrhythmias, measured using a method for noninvasive neonatal mutant pup electrocardiography developed by our lab. Near-global CNCC primary cilia loss was observed by E11.5, and by E12.5, the MUT displayed fewer cardiomyocytes, but increased cardiomyocyte proliferation when compared to controls. Flow cytometry was used to explore ErbB signaling-mediated mechanisms of ventricular noncompaction and revealed a downregulation in ErbB2/4 expression in MUT hearts. Analysis of Hh signaling using qPCR and immunofluorescence revealed that loss of CNCC primary cilia led to a paradoxical upregulation of Sonic Hedgehog, Patched-1, Smoothened, and Gli1 in both the OFT and ventricular components of the MUT heart. Further analysis suggested that increased Hh signaling protein expression was likely originating from non-CNCC cells.Thus, CNCC loss of primary cilia and subsequent loss/reduction of CNCC Hh signaling in the developing outflow tract likely promotes increased cardiomyocyte proliferation, possibly enabled by disruptions to ErbB2/4 signaling in the ventricular myocardium.Taken together, these data support a causal role for primary cilia of CNCC in the pathogenesis of CHD, likely mediated by disruptions to both Hedgehog and ErbB signaling pathways.
Fitzsimons, Lindsey A., "Primary Cilia of the Cardiac Neural Crest & Hedgehog-Mediated Mechanisms of Congenital Heart Disease" (2022). Electronic Theses and Dissertations. 3582.
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