Browsing by Subject "Tricuspid Atresia"

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    Hand2 function within non-cardiomyocytes regulates cardiac morphogenesis and performance
    (2014) VanDusen, Nathan J.; Firulli, Anthony B.; Herbert, Brittney-Shea; Mayo, Linda D.; Shou, Weinian
    The heart is a complex organ that is composed of numerous cell types, which must integrate their programs for proper specification, differentiation, and cardiac morphogenesis. During cardiac development the basic helix-loop-helix transcription factor Hand2 is dynamically expressed within the endocardium and extra-cardiac lineages such as the epicardium, cardiac neural crest cells (cNCCs), and NCC derived components of the autonomic nervous system. To investigate Hand2 function within these populations we utilized multiple murine Hand2 Conditional Knockout (H2CKO) genetic models. These studies establish for the first time a functional requirement for Hand2 within the endocardium, as several distinct phenotypes including hypotrabeculation, tricuspid atresia, aberrant septation, and precocious coronary development are observed in endocardial H2CKOs. Molecular analyses reveal that endocardial Hand2 functions within the Notch signaling pathway to regulate expression of Nrg1, which encodes a crucial secreted growth factor. Furthermore, we demonstrate that Notch signaling regulates coronary angiogenesis via Hand2 mediated modulation of Vegf signaling. Hand2 is strongly expressed within midgestation NCC and endocardium derived cardiac cushion mesenchyme. To ascertain the function of Hand2 within these cells we employed the Periostin Cre (Postn-Cre), which marks cushion mesenchyme, a small subset of the epicardium, and components of the autonomic nervous system, to conditionally ablate Hand2. We find that Postn-Cre H2CKOs die shortly after birth despite a lack of cardiac structural defects. Gene expression analyses demonstrate that Postn-Cre ablates Hand2 from the adrenal medulla, causing downregulation of Dopamine Beta Hydroxylase (Dbh), a gene encoding a crucial catecholaminergic biosynthetic enzyme. Electrocardiograms demonstrate that 3-day postnatal Postn-Cre H2CKO pups exhibit significantly slower heart rates than control littermates. In conjunction with the aforementioned gene expression analyses, these results indicate that loss of Hand2 function within the adrenal medulla results in a catecholamine deficiency and subsequent heart failure.
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    HAND2 Mutation Detection in Tricuspid Atresia Patients
    (Office of the Vice Chancellor for Research, 2013-04-05) Barry, Elijah H.; VanDusen, Nathan; Firulli, Anthony B.
    Tricuspid Atresia (TA) is a congenital heart disease in which the tricuspid valve is missing or abnormally developed. The defect blocks blood in the right atrium from flowing directly into the right ventricle. It is an uncommon form of congenital heart disease that affects about 5 in every 100,000 live births. While the cause of TA is unknown, the lab data shows that in mice loss of transcription factor Hand2 function within a population of cells that line the inside of the heart (the endocardium) results in a TA phenotype. Hand2 is a protein that belongs to the basic helix-loop-helix family of transcription factors, and has been shown to play many different roles in embryonic development. To test whether loss of Hand2 function in humans results in TA, sequencing the HAND2 gene in 25 TA patients. Polymerase Chain Reaction (PCR) was used to amplify the TA patient Hand2 alleles. A TOPO reaction was then performed to insert the amplicons into a sequencing plasmid, followed by a transformation and minipreps to isolate individual clones. Isolated Hand2 alleles within the TOPO sequencing plasmid were sent to a sequencing core facility. In this manner the Hand2 DNA sequence for several patients was obtained and analyzed for mutations. This project will shed light on the cause of TA. Further research is currently in progress in Dr. Firulli’s Lab.