Browsing by Subject "Hand2"

Now showing 1 - 5 of 5
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    Hand Factors in Cardiac Development
    (Wiley, 2019-01) George, Rajani M.; Firulli, Anthony B.; Pediatrics, School of Medicine
    Congenital heart defects account for 1% of infant mortality and 10% of in utero deaths. As the vertebrate embryo develops, multiple tissue types develop in tandem to morphologically pattern the functional heart. Underlying cardiac development is a network of transcription factors known to tightly control these morphological events. Members of the Twist family of basic helix–loop–helix transcription factors, Hand1 and Hand2, are essential to this process. The expression patterns and functional role of Hand factors in neural crest cells, endocardium, myocardium, and epicardium is indicative of their importance during cardiogenesis; however, to date, an extensive understanding of the transcriptional targets of Hand proteins and their overall mechanism of action remain unclear. In this review, we summarize the recent findings that further outline the crucial functions of Hand factors during heart development and in post‐natal heart function.
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    Hand2 elevates cardiomyocyte production during zebrafish heart development and regeneration
    (The Company of Biologists, 2014-08) Schindler, Yocheved L.; Garske, Kristina M.; Wang, Jinhu; Firulli, Beth A.; Firulli, Anthony B.; Poss, Kenneth D.; Yelon, Deborah; Department of Pediatrics, IU School of Medicine
    Embryonic heart formation requires the production of an appropriate number of cardiomyocytes; likewise, cardiac regeneration following injury relies upon the recovery of lost cardiomyocytes. The basic helix-loop-helix (bHLH) transcription factor Hand2 has been implicated in promoting cardiomyocyte formation. It is unclear, however, whether Hand2 plays an instructive or permissive role during this process. Here, we find that overexpression of hand2 in the early zebrafish embryo is able to enhance cardiomyocyte production, resulting in an enlarged heart with a striking increase in the size of the outflow tract. Our evidence indicates that these increases are dependent on the interactions of Hand2 in multimeric complexes and are independent of direct DNA binding by Hand2. Proliferation assays reveal that hand2 can impact cardiomyocyte production by promoting division of late-differentiating cardiac progenitors within the second heart field. Additionally, our data suggest that hand2 can influence cardiomyocyte production by altering the patterning of the anterior lateral plate mesoderm, potentially favoring formation of the first heart field at the expense of hematopoietic and vascular lineages. The potency of hand2 during embryonic cardiogenesis suggested that hand2 could also impact cardiac regeneration in adult zebrafish; indeed, we find that overexpression of hand2 can augment the regenerative proliferation of cardiomyocytes in response to injury. Together, our studies demonstrate that hand2 can drive cardiomyocyte production in multiple contexts and through multiple mechanisms. These results contribute to our understanding of the potential origins of congenital heart disease and inform future strategies in regenerative medicine.
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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.
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    Loss of Hand2 in a population of Periostin lineage cells results in pronounced bradycardia and neonatal death
    (Elsevier, 2014-04-15) VanDusen, Nathan J.; Vincentz, Joshua W.; Firulli, Beth A.; Howard, Marthe J.; Rubart, Michael; Firulli, Anthony B.; Department of Pediatrics, IU School of Medicine
    The Periostin Cre (Postn-Cre) lineage includes endocardial and neural crest derived mesenchymal cells of the cardiac cushions, neural crest-derived components of the sympathetic and enteric nervous systems, and cardiac fibroblasts. In this study, we use the Postn-Cre transgenic allele to conditionally ablate Hand2 (H2CKO). We find that Postn-Cre H2CKOs die shortly after birth despite a lack of obvious cardiac structural defects. To ascertain the cause of death, we performed a detailed comparison of the Postn-Cre lineage and Hand2 expression at mid and late stages of embryonic development. Gene expression analyses demonstrate that Postn-Cre ablates Hand2 from the adrenal medulla as well as the sphenopalatine ganglia of the head. In both cases, Hand2 loss-of-function dramatically reduces expression of Dopamine Beta Hydroxylase (Dbh), a gene encoding a crucial catecholaminergic biosynthetic enzyme. Expression of the genes Tyrosine Hydroxylase (Th) and Phenylethanolamine N-methyltransferase (Pnmt), which also encode essential catecholaminergic enzymes, were severely reduced in postnatal adrenal glands. Electrocardiograms demonstrate that 3-day postnatal Postn-Cre H2CKO pups exhibit sinus bradycardia. In conjunction with the aforementioned gene expression analyses, these results strongly suggest that the observed postnatal lethality occurs due to a catecholamine deficiency and subsequent heart failure.