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Supplementary Figure Legends 1-4 from HEXIM1 Regulates 17β-Estradiol/Estrogen Receptor-α–Mediated Expression of Cyclin D1 in Mammary Cells via Modulation of P-TEFb

Supplementary Tables 3-4 from HEXIM1 Regulates 17β-Estradiol/Estrogen Receptor-α–Mediated Expression of Cyclin D1 in Mammary Cells via Modulation of P-TEFb

Supplementary Figures 1-4 from HEXIM1 Regulates 17β-Estradiol/Estrogen Receptor-α–Mediated Expression of Cyclin D1 in Mammary Cells via Modulation of P-TEFb

Supplementary Methods and Materials from HEXIM1 Regulates 17β-Estradiol/Estrogen Receptor-α–Mediated Expression of Cyclin D1 in Mammary Cells via Modulation of P-TEFb

Background Despite decades of public education about dire consequences of prenatal alcohol exposure, drinking alcohol during pregnancy remains prevalent. As high as 40% of live-born infants exposed to alcohol during gestation and diagnosed with Fetal Alcohol Syndrome have congenital heart defects that can be life-threatening. In animal models, the methyl donor betaine, found in foods such as wheat bran, quinoa, beets and spinach, ameliorated neurobehavioral deficits associated with prenatal alcohol exposure (PAE) but effects on heart development are unknown. Methods Previously we modeled a binge drinking episode during the first trimester in avian embryos. Here we investigated whether betaine could prevent adverse effects of alcohol on heart development. Embryos exposed to ethanol with and without an optimal dose of betaine (5 μM) were analyzed at late developmental stages. Cardiac morphology parameters were rapidly analyzed and quantified using optical coherence tomography. DNA methylation at early stages was detected by immunofluorescent staining for 5-methylcytosine in sections of embryos treated with ethanol or co-treated with betaine. Results Compared to ethanol-exposed embryos, betaine-supplemented embryos had higher late-stage survival rates and fewer gross head and body defects than seen after alcohol exposure alone. Betaine also reduced the incidence of late-stage cardiac defects such as absent vessels, abnormal atrio-ventricular (AV) valves, and hypertrophic ventricles. Furthermore, betaine co-treatment brought measurements of great vessel diameters, interventricular septum (IVS) thickness, and AV leaflet volumes in betaine-supplemented embryos close to control values. Early-stage 5-methycytosine staining revealed that DNA methylation levels were reduced by ethanol exposure and normalized by co-administration with betaine. Conclusions This is the first study demonstrating efficacy of the methyl donor betaine in alleviating cardiac defects associated with PAE. These findings highlight the therapeutic potential of low-concentration betaine doses in mitigating PAE induced birth defects and has implications for prenatal nutrition policies, especially for women who may not be responsive to folate supplementation. This article is protected by copyright. All rights reserved.

Background The most commonly used method to analyze congenital heart defects involves serial sectioning and histology. However, this is often a time-consuming process where the quantification of cardiac defects can be difficult due to problems with accurate section registration. Here we demonstrate the advantages of using optical coherence tomography, a comparatively new and rising technology, to phenotype avian embryo hearts in a model of Fetal Alcohol Syndrome where a binge-like quantity of alcohol/ethanol was introduced at gastrulation.

Over 500,000 women per year in the United States drink during pregnancy, and 1 in 5 of this population also binge drink. Up to 40% of live-born children with prenatal alcohol exposure (PAE) present with congenital heart defects (CHDs) including life-threatening outflow and valvuloseptal anomalies. Previously we established a PAE model in the avian embryo and used optical coherence tomography (OCT) imaging to assay looping-stage (early) cardiac function/structure and septation-stage (late) cardiac defects. Early-stage ethanol-exposed embryos had smaller cardiac cushions (valve precursors) and increased retrograde flow, while late-stage embryos presented with gross head/body defects, and exhibited smaller atrio-ventricular (AV) valves, interventricular septae, and aortic vessels. However, supplementation with the methyl donor betaine reduced gross defects, prevented cardiac defects such as ventricular septal defects and abnormal AV valves, and normalized cardiac parameters. Immunofluorescent staining for 5-methylcytosine in transverse embryo sections also revealed that DNA methylation levels were reduced by ethanol but normalized by co-administration of betaine. Furthermore, supplementation with folate, another methyl donor, in the PAE model appeared to normalize retrograde flow levels which are typically elevated by ethanol exposure. Studies are underway to correlate retrograde flow numbers for folate with associated cushion volumes. Finally, preliminary findings have revealed that glutathione, a key endogenous antioxidant which also regulates methyl group donation, is particularly effective in improving alcohol-impacted survival and gross defect rates. Current investigations will determine whether glutathione has any positive effect on PAE-related CHDs. Our studies could have significant implications for public health, especially related to prenatal nutrition recommendations.

Alcohol-induced congenital heart defects are frequently among the most life threatening and require surgical correction in newborns. The etiology of these defects, collectively known as fetal alcohol syndrome, has been the focus of much study, particularly involving cellular and molecular mechanisms. Few studies have addressed the influential role of altered cardiac function in early embryogenesis because of a lack of tools with the capability to assay tiny beating hearts. To overcome this gap in our understanding, we used optical coherence tomography (OCT), a nondestructive imaging modality capable of micrometer-scale resolution imaging, to rapidly and accurately map cardiovascular structure and hemodynamics in real time under physiological conditions. In this study, we exposed avian embryos to a single dose of alcohol/ethanol at gastrulation when the embryo is sensitive to the induction of birth defects. Late-stage hearts were analyzed using standard histological analysis with a focus on the atrio-ventricular valves. Early cardiac function was assayed using Doppler OCT, and structural analysis of the cardiac cushions was performed using OCT imaging. Our results indicated that ethanol-exposed embryos developed late-stage valvuloseptal defects. At early stages, they exhibited increased regurgitant flow and developed smaller atrio-ventricular cardiac cushions, compared with controls (uninjected and saline-injected embryos). The embryos also exhibited abnormal flexion/torsion of the body. Our evidence suggests that ethanol-induced alterations in early cardiac function have the potential to contribute to late-stage valve and septal defects, thus demonstrating that functional parameters may serve as early and sensitive gauges of cardiac normalcy and abnormalities.

Over 500,000 women per year in the United States drink during pregnancy, and 1 in 5 of this population also binge drink. As high as 20-50% of live-born children with prenatal alcohol exposure (PAE) present with congenital heart defects including outflow and valvuloseptal anomalies that can be life-threatening. Previously we established a model of PAE (modeling a single binge drinking episode) in the avian embryo and used optical coherence tomography (OCT) imaging to assay early-stage cardiac function/structure and late-stage cardiac defects. At early stages, alcohol/ethanol-exposed embryos had smaller cardiac cushions and increased retrograde flow. At late stages, they presented with gross morphological defects in the head and chest wall, and also exhibited smaller or abnormal atrio-ventricular (AV) valves, thinner interventricular septae (IVS), and smaller vessel diameters for the aortic trunk branches. In other animal models, the methyl donor betaine (found naturally in many foods such as wheat bran, quinoa, beets and spinach) ameliorates neurobehavioral deficits associated with PAE but the effects on heart structure are unknown. In our model of PAE, betaine supplementation led to a reduction in gross structural defects and appeared to protect against certain types of cardiac defects such as ventricular septal defects and abnormal AV valvular morphology. Furthermore, vessel diameters, IVS thicknesses and mural AV leaflet volumes were normalized while the septal AV leaflet volume was increased. These findings highlight the importance of betaine and potentially methylation levels in the prevention of PAE-related birth defects which could have significant implications for public health.

The role of hemodynamics in early heart development is poorly understood. In order to successfully assess the impact of hemodynamics on development, we need to monitor and perturb blood flow, and quantify the resultant effects on morphology. Here, we have utilized cardiac optical pacing to create regurgitant flow in embryonic hearts and OCT to quantify regurgitation percentage and resultant morphology. Embryonic quail in a shell-less culture were optically paced at 3 Hz (well above the intrinsic rate or 1.33-1.67 Hz) on day 2 of development (3-4 weeks human) for 5 minutes. The pacing fatigued the heart and led to a prolonged period (> 1 hour) of increased regurgitant flow. Embryos were kept alive until day 3 (cardiac looping - 4-5 weeks human) or day 8 (4 chambered heart - 8 weeks human) to quantify resultant morphologic changes with OCT. All paced embryos imaged at day 3 displayed cardiac defects. The extent of regurgitant flow immediately after pacing was correlated with cardiac cushion size 24-hours post pacing (p-value < 0.01) with higher regurgitation leading to smaller cushions. Almost all embryos (16/18) surviving to day 8 exhibited congenital heart defects (CHDs) including 11/18 with valve defects, 5/18 with ventricular septal defects and 5/18 with hypoplastic right ventricles. Our data suggests that regurgitant flow leads to smaller cushions, which develop into abnormal valves and septa. Our model produces similar phenotypes as found in our fetal alcohol syndrome and velo-cardio-facial/DiGeorge syndrome models suggesting that hemodynamics plays a role in these syndromes as well. Utilizing OCT and optical pacing to understand hemodynamics in development is an important step towards determining CHD mechanisms and ultimately developing earlier treatments.

The role of hemodynamics in early heart development is poorly understood. In order to successfully assess the impact of hemodynamics on development, we need to monitor and perturb blood flow, and quantify the resultant effects on morphology. Here, we have utilized cardiac optical pacing to create regurgitant flow in embryonic hearts and OCT to quantify regurgitation percentage and resultant morphology. Embryonic quail in a shell-less culture were optically paced at 3 Hz (well above the intrinsic rate or 1.33-1.67 Hz) on day 2 of development (3-4 weeks human) for 5 minutes. The pacing fatigued the heart and led to a prolonged period (> 1 hour) of increased regurgitant flow. Embryos were kept alive until day 3 (cardiac looping - 4-5 weeks human) or day 8 (4 chambered heart - 8 weeks human) to quantify resultant morphologic changes with OCT. All paced embryos imaged at day 3 displayed cardiac defects. The extent of regurgitant flow immediately after pacing was correlated with cardiac cushion size 24-hours post pacing (p-value < 0.01) with higher regurgitation leading to smaller cushions. Almost all embryos (16/18) surviving to day 8 exhibited congenital heart defects (CHDs) including 11/18 with valve defects, 5/18 with ventricular septal defects and 5/18 with hypoplastic right ventricles. Our data suggests that regurgitant flow leads to smaller cushions, which develop into abnormal valves and septa. Our model produces similar phenotypes as found in our fetal alcohol syndrome and velo-cardio-facial/DiGeorge syndrome models suggesting that hemodynamics plays a role in these syndromes as well. Utilizing OCT and optical pacing to understand hemodynamics in development is an important step towards determining CHD mechanisms and ultimately developing earlier treatments.

We report on the role of hexamethylene-bis-acetamide-inducible protein 1 (HEXIM1) as an inhibitor of metastasis. HEXIM1 expression is decreased in human metastatic breast cancers when compared with matched primary breast tumors. Similarly we observed decreased expression of HEXIM1 in lung metastasis when compared with primary mammary tumors in a mouse model of metastatic breast cancer, the polyoma middle T antigen (PyMT) transgenic mouse. Re-expression of HEXIM1 (through transgene expression or localized delivery of a small molecule inducer of HEXIM1 expression, hexamethylene-bis-acetamide) in PyMT mice resulted in inhibition of metastasis to the lung. Our present studies indicate that HEXIM1 downregulation of HIF(-)1α protein allows not only for inhibition of vascular endothelial growth factor-regulated angiogenesis, but also for inhibition of compensatory pro-angiogenic pathways and recruitment of bone marrow-derived cells (BMDCs). Another novel finding is that HEXIM1 inhibits cell migration and invasion that can be partly attributed to decreased membrane localization of the 67 kDa laminin receptor, 67LR, and inhibition of the functional interaction of 67LR with laminin. Thus, HEXIM1 re-expression in breast cancer has therapeutic advantages by simultaneously targeting more than one pathway involved in angiogenesis and metastasis. Our results also support the potential for HEXIM1 to indirectly act on multiple cell types to suppress metastatic cancer.

We have previously shown that estrogen receptor β (ERβ)-mediated up-regulation of quinone reductase (QR) is involved in the protection against estrogen-induced mammary tumorigenesis. Our present study provides evidence that the ERβ agonist, 2,3-bis-(4-hydroxy-phenyl)-propionitrile (DPN), and the selective estrogen receptor modulator tamoxifen (Tam), inhibit estrogen-induced DNA damage and mammary tumorigenesis in the aromatase transgenic (Arom) mouse model. We also show that either DPN or Tam treatment increases QR levels and results in a decrease in ductal hyperplasia, proliferation, oxidative DNA damage (ODD), and an increase in apoptosis. To corroborate the role of QR, we provide additional evidence in triple transgenic MMTV/QR/Arom mice, wherein the QR expression is induced in the mammary glands via doxycycline, causing a decrease in ductal hyperplasia and ODD. Overall, we provide evidence that up-regulation of QR through induction by Tam or DPN can inhibit estrogen-induced ODD and mammary cell tumorigenesis, representing a novel mechanism of prevention against breast cancer. Thus, our data have important clinical implications in the management of breast cancer; our findings bring forth potentially new therapeutic strategies involving ERβ agonists. Krishnamurthy, N., Hu, Y., Siedlak, S., Doughman, Y. Q., Watanabe, M., Montano, M. M. Induction of quinone reductase by tamoxifen or DPN protects against mammary tumorigenesis.

Background: The trajectory to heart defects may start in tubular and looping heart stages when detailed analysis of form and function is difficult by currently available methods. We used a novel method, Doppler optical coherence tomography (OCT), to follow changes in cardiovascular function in quail embryos during acute hypoxic stress. Chronic fetal hypoxia is a known risk factor for congenital heart diseases (CHDs). Decreased fetal heart rates during maternal obstructive sleep apnea suggest that studying fetal heart responses under acute hypoxia is warranted. Results: We captured responses to hypoxia at the critical looping heart stages. Doppler OCT revealed detailed vitelline arterial pulsed Doppler waveforms. Embryos tolerated 1 hr of hypoxia (5%, 10%, or 15% O2), but exhibited changes including decreased systolic and increased diastolic duration in 5 min. After 5 min, slower heart rates, arrhythmic events and an increase in retrograde blood flow were observed. These changes suggested slower filling of the heart, which was confirmed by four-dimensional Doppler imaging of the heart itself. Conclusions: Doppler OCT is well suited for rapid noninvasive screening for functional changes in avian embryos under near physiological conditions. Analysis of the accessible vitelline artery sensitively reflected changes in heart function and can be used for rapid screening. Acute hypoxia caused rapid hemodynamic changes in looping hearts and may be a concern for increased CHD risk. Developmental Dynamics 241:534–544, 2012. © 2012 Wiley Periodicals, Inc.

Light has been used to noninvasively alter the excitability of both neural and cardiac tissue 1–10. Recently, pulsed laser light has been shown to be capable of eliciting action potentials in peripheral nerves and in cultured cardiomyocytes 7–10. Here, we demonstrate for the first time optical pacing (OP) of an intact heart in vivo. Pulsed 1.875 μm infrared laser light was employed to lock the heart rate to the pulse frequency of the laser. A laser Doppler velocimetry (LDV) signal was used to verify the pacing. At low radiant exposures, embryonic quail hearts were reliably paced in vivo without detectable damage to the tissue, indicating that OP has great potential as a tool to study embryonic cardiac dynamics and development. In particular, OP can be utilized to control the heart rate, and thereby alter stresses and mechanically transduced signaling.

The adult heart has been reported to have an extensive lymphatic system, yet the development of this important system during cardiogenesis is still largely unexplored. The nuclear-localized transcription factor Prox-1 identified a sheet of Prox-1-positive cells on the developing aorta and pulmonary trunk in avian and murine embryos just prior to septation of the four heart chambers. The cells coalesced into a branching lymphatic network that spread within the epicardium to cover the heart. These vessels eventually expressed the lymphatic markers LYVE-1, VEGFR-3, and podoplanin. Before the Prox-1-positive cells were detected in the mouse epicardium, LYVE-1, a homologue of the CD44 glycoprotein, was primarily expressed in individual epicardial cells. Similar staining patterns were observed for CD44 in avian embryos. The proximity of these LYVE-1/CD44-positive mesenchymal cells to Prox-1-positive vessels suggests that they may become incorporated into the lymphatics. Unexpectedly, we detected LYVE-1/PECAM/VEGFR-3-positive vessels within the embryonic and adult myocardium which remained Prox-1/podoplanin-negative. Lymphatic markers were surprisingly found in adult rat and embryonic mouse epicardial cell lines, with Prox-1 also exhibiting nuclear-localized expression in primary cultures of embryonic avian epicardial cells. Our data identified three types of cells in the embryonic heart expressing lymphatic markers: (1) Prox-1-positive cells from an extracardiac source that migrate within the serosa of the outflow tract into the epicardium of the developing heart, (2) individual LYVE-1-positive cells in the epicardium that may be incorporated into the Prox-1-positive lymphatic vasculature, and (3) LYVE-1-positive cells/vessels in the myocardium that do not become Prox-1-positive even in the adult heart.

Disrupted ERK1/2 ( MAPK3 / MAPK1 ) MAPK signaling has been associated with several developmental syndromes in humans; however, mutations in ERK1 or ERK2 have not been described. We demonstrate haplo-insufficient ERK2 expression in patients with a novel ≈1 Mb micro-deletion in distal 22q11.2, a region that includes ERK2 . These patients exhibit conotruncal and craniofacial anomalies that arise from perturbation of neural crest development and exhibit defects comparable to the DiGeorge syndrome spectrum. Remarkably, these defects are replicated in mice by conditional inactivation of ERK2 in the developing neural crest. Inactivation of upstream elements of the ERK cascade ( B-Raf and C-Raf, MEK1 and MEK2 ) or a downstream effector, the transcription factor serum response factor resulted in analogous developmental defects. Our findings demonstrate that mammalian neural crest development is critically dependent on a RAF/MEK/ERK/serum response factor signaling pathway and suggest that the craniofacial and cardiac outflow tract defects observed in patients with a distal 22q11.2 micro-deletion are explained by deficiencies in neural crest autonomous ERK2 signaling.

Lung maturation at the terminal sac stage of lung development is characterized by a coordinated increase in terminal sac formation and vascular development in conjunction with the differentiation of alveolar type I and type II epithelial cells. The Cited2-Tcfap2a/c complex has been shown to activate transcription of Erbb3 and Pitx2c during mouse development. In this study, we show that E17.5 to E18.5 Cited2-null lungs had significantly reduced terminal sac space due to an altered differentiation of type I and type II alveolar epithelial cells. In addition, E17 Cited2-null lungs exhibited a decrease in the number of apoptotic cells, contributing to the loss in airspace. Consistent with the phenotype, genes associated with alveolar cell differentiation and survival were differentially expressed in Cited2-null fetal lungs compared to those of wild-type littermates. Moreover, expression of Cebpa, a key regulator of airway epithelial maturation, was significantly decreased in Cited2-null fetal lungs. Cited2 and Tcfap2c were present on the Cebpa promoter in E18.5 lungs to activate Cebpa transcription. We propose that the Cited2-Tcfap2c complex controls lung maturation by regulating Cebpa expression. Understanding the function of this complex may provide novel therapeutic strategies for patients with respiratory distress syndromes.

Tissue hypoxia plays a critical role in normal development, including cardiogenesis. Previously, we showed that oxygen concentration, as assessed by the hypoxia indicator EF5, is lowest in the outflow tract (OFT) myocardium of the developing chicken heart and may be regulating events in OFT morphogenesis. In this study, we identified additional areas of the embryonic chicken heart that were intensely positive for EF5 within the myocardium in discrete regions of the atrial wall and the interventricular septum (IVS). The region of the IVS that is EF5-positive includes a portion of the developing central conduction system identified by HNK-1 co-immunostaining. The EF5 positive tissues were also specifically positive for nuclear-localized hypoxia inducible factor 1α (HIF-1α), the oxygen-sensitive component of the hypoxia inducible factor 1 (HIF-1) heterodimer. The pattern of the most intensely EF5-stained myocardial regions of the atria and IVS resemble the pattern of the major coronary vessels that form in later stages within or immediately adjacent to these particular regions. These vessels include the sinoatrial nodal artery that is a branch of the right coronary artery within the atrial wall and the anterior/posterior interventricular vessels of the IVS. These findings indicate that a portion of the developing central conduction system and the patterning of coronary vessels may be subject to a level of regulation that is dependent on differential oxygen concentration within cardiac tissues and subsequent HIF-1 regulation of gene expression. Developmental Dynamics 235:115–123, 2006. © 2005 Wiley-Liss, Inc.

The outflow tract (OFT) is abnormal in many congenital heart defects. One critical mechanism for morphogenesis of this complex structure is apoptosis. Chicken embryos (stages 19-38; ED4-10) stained with a fluorescent supravital lysosomal dye (LysoTracker Red; LTR) revealed the three-dimensional relationship between structural changes and apoptosis. The LTR staining peaked in the OFT myocardium at stages 27-32, consistent with our previous analyses using other apoptosis assays. While LTR stained under both the pulmonary artery and the aorta, it was most prevalent in the subaortic myocardium before its elimination. Furthermore, LTR staining was most abundant in the myocardium under intensely cytokeratin-positive, thick epicardium. These data support the hypothesis that temporally and spatially restricted apoptosis in the OFT myocardium allows the aorta and pulmonary artery to dock at the appropriate angle and level with the proper ventricle. These data also support a relationship between the differentiating epicardium and cardiomyocyte apoptosis.

The most commonly used method to analyze congenital heart defects involves serial sectioning and histology. However, this is often a time-consuming process where the quantification of cardiac defects can be difficult due to problems with accurate section registration. Here we demonstrate the advantages of using optical coherence tomography, a comparatively new and rising technology, to phenotype avian embryo hearts in a model of fetal alcohol syndrome where a binge-like quantity of alcohol/ethanol was introduced at gastrulation.The rapid, consistent imaging protocols allowed for the immediate identification of cardiac anomalies, including ventricular septal defects and misaligned/missing vessels. Interventricular septum thicknesses and vessel diameters for three of the five outflow arteries were also significantly reduced. Outflow and atrioventricular valves were segmented using image processing software and had significantly reduced volumes compared to controls. This is the first study to our knowledge that has 3D reconstructed the late-stage cardiac valves in precise detail to examine their morphology and dimensions.We believe, therefore, that optical coherence tomography, with its ability to rapidly image and quantify tiny embryonic structures in high resolution, will serve as an excellent and cost-effective preliminary screening tool for developmental biologists working with a variety of experimental/disease models.

Purpose Cited2 (CBP/p300-interacting transactivators with glutamic acid (E) and aspartic acid (D)-rich tail 2) is a member of a new family of transcriptional modulators. Cited2 null embryos exhibit hyaloid hypercellularity consisting of aberrant vasculature in the eye. The purpose of the study is to address whether abnormal lenticular development is a primary defect of Cited2 deletion and whether deletion of hypoxia inducible factor (HIF)-1α or an HIF-1α target gene, vascular endothelial growth factor (VEGF), could rescue abnormal hyaloid vascular system (HVS) in Cited2 deficient adult eyes. Methods Le-Cre specific Cited2 knockout (Cited2CKO) mice with or without deletion of HIF-1α or VEGF were generated by standard Cre-Lox methods. Eyes collected from six-eight weeks old mice were characterized by Real Time PCR and immunohistological staining. Results Cited2CKO mice had smaller lenses, abnormal lens stalk formation, and failed regression of the HVS in the adult eye. The eye phenotype had features similar to persistent hyperplastic primary vitreous (PHPV), a human congenital eye disorder leading to abnormal lenticular development. Deletion of HIF-1α or VEGF in Cited2 knockout eyes partially rescued the abnormal HVS but had no effect on the smaller lens and abnormal lens stalk differentiation. Intravitreal injection of Topotecan (TPT), a compound that inhibits HIF-1α expression, partially eliminated HVS defects in Cited2CKO lenses. Conclusions Abnormal HVS is a primary defect in Cited2 knockout mice, resulting in part from dysregulated functions of HIF-1 and VEGF. The Cited2CKO mouse line could be used as a novel disease model for PHPV and as an in vivo model for testing potential HIF-1 inhibitors.

Notch1 is an important regulator of intercellular interactions in cardiovascular development. We show that the nuclear-localized, cleaved and active form of Notch1, the Notch1 intracellular domain (N1ICD), appeared in mesothelial cells of the pro-epicardium during epicardial formation at looped heart stages. N1ICD was also present in mesothelial cells and mesenchymal cells specifically within the epicardium at sulcus regions. N1ICD-positive endothelial cells were detected within the nascent vessel plexus at the atrioventricular junction and within the compact myocardium (Hamburger and Hamilton stage [HH] 25-HH30). The endothelial cells expressing N1ICD were surrounded by N1ICD-positive smooth muscle cells after coronary orifice formation (HH32-HH35), while N1ICD expression was absent in the mesenchymal and mesothelial cells surrounding mature coronary vessels. We propose that differential activation of the hypoxia/HIF1-VEGF-Notch pathway may play a role in epicardial cell interactions that promote epicardial epithelial/mesenchymal transition and coronary progenitor cell differentiation during epicardial development and coronary vasculogenesis in particularly hypoxic sulcus regions.

Background : Angiotensin II (A-II) causes pathologic remodeling of the heart and vasculature through gene-regulatory pathways that are incompletely understood. We and others have identified Kruppel-Like Factor 15 (KLF15) as a transcription factor that may exert beneficial effects in the cardiovascular system, however, its role in A-II signaling remains unknown. We hypothesize that KLF15 can modulate the deleterious effects of A-II on the heart and blood vessel. Methods and Results : A-II downregulates KLF15 expression in heart and vascular tissues in vitro and in vivo . Mice with systemic KLF15 deficiency (male, age 10 wks) have baseline abnormalities of the heart (increased cardiac mass, LV thickness, fetal gene expression) and vasculature (thickened aortic media with elastin breakdown). In response to chronic A-II infusion (1.4 mg/kg/D x 14D), KLF15 KO mice develop severe degenerative changes in both the heart and vessel compared to wild-type controls. In the heart, KLF15 KO mice develop pronounced heart failure characterized by augmented cardiac mass, eccentric LV remodeling, profound LV systolic dysfunction, increased fibrosis, enhanced fetal gene expression and apoptotic cell loss. Dramatic degenerative changes also occur in the aorta of KLF15 KO mice including medial destruction with elastin degradation, outward remodeling with vessel dilation, augmented inflammatory gene expression, and foci of severe smooth muscle apoptosis. Mechanistically, there is exaggerated accumulation of p53 and its direct pro-apoptotic targets in the heart (Bax) and aorta (Bax, p21) of KLF15 KO mice. As p53-mediated degradation of HIF1α has been implicated in cardiac decompensation, we show that KLF15 KO hearts have decreased HIF1α levels and fail to mount an angiogenic response to A-II. Finally, we provide evidence that KLF15 can directly inhibit p53 protein accumulation in a proteasome-dependent manner. Conclusion : KLF15 deficiency renders the cardiovascular system exquisitely sensitive to A-II stimulation and leads to degenerative remodeling of the heart and blood vessel with exaggerated p53 accumulation in these tissues. These findings suggest that manipulation of KLF15 function may provide novel approaches to inhibit the pathologic effects of A-II.

The transcriptional modulator Cited2 is induced by various biological stimuli including hypoxia, cytokines, growth factors, lipopolysaccharide (LPS) and flow shear. In this study, we report that Cited2 is required for mouse fetal liver development. Cited2(-/-) fetal liver displays hypoplasia with higher incidence of cell apoptosis, and exhibits disrupted cell-cell contact, disorganized sinusoidal architecture, as well as impaired lipid metabolism and hepatic gluconeogenesis. Furthermore, we demonstrated the physical and functional interaction of Cited2 with liver-enriched transcription factor HNF4alpha. Chromatin immunoprecipitation (ChIP) assays further confirmed the recruitment of Cited2 onto the HNF4alpha-responsive promoters and the reduced HNF4alpha binding to its target gene promoters in the absence of Cited2. Taken together, this study suggests that fetal liver defects in mice lacking Cited2 result, at least in part, from its defective coactivation function for HNF4alpha.

Apoptosis occurs at high frequency in the myocardium of the developing avian cardiac outflow tract (OFT). Up- or down-regulating apoptosis results in defects resembling human conotruncal heart anomalies. This finding suggested that regulated levels of apoptosis are critical for normal morphogenesis of the four-chambered heart. Recent evidence supports an important role for hypoxia of the OFT myocardium in regulating cell death and vasculogenesis. The purpose of this study was to determine whether apoptosis in the outflow tract myocardium occurs in the mouse heart during developmental stages comparable to the avian heart and to determine whether differential hypoxia is also present at this site in the murine heart. Apoptosis was detected using a fluorescent vital dye, Lysotracker Red (LTR), in the OFT myocardium of the mouse starting at embryonic day (E) 12.5, peaking at E13.5-14.5, and declining thereafter to low or background levels by E18.5. In addition, high levels of apoptosis were detected in other cardiac regions, including the apices of the ventricles and along the interventricular sulcus. Apoptosis in the myocardium was detected by double-labeling with LTR and cardiomyocyte markers. Terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) and immunostaining for cleaved Caspase-3 were used to confirm the LTR results. At the peak of OFT apoptosis in the mouse, the OFT myocardium was relatively hypoxic, as indicated by specific and intense EF5 staining and HIF1alpha nuclear localization, and was surrounded by the developing vasculature as in the chicken embryo. These findings suggest that cardiomyocyte apoptosis is an evolutionarily conserved mechanism for normal morphogenesis of the outflow tract myocardium in avian and mammalian species.

Optical pacing has been demonstrated to be a viable alternative to electrical pacing in embryonic hearts. In this study, the feasibility of optically pacing an adult rabbit heart was explored. Hearts from adult New Zealand White rabbits (n = 9) were excised, cannulated and perfused on a modified Langendorff apparatus. Pulsed laser light (λ = 1851 nm) was directed to either the left or right atrium through a multimode optical fiber. An ECG signal from the left ventricle and a trigger pulse from the laser were recorded simultaneously to determine when capture was achieved. Successful optical pacing was demonstrated by obtaining pacing capture, stopping, then recapturing as well as by varying the pacing frequency. Stimulation thresholds measured at various pulse durations suggested that longer pulses (8 ms) had a lower energy capture threshold. To determine whether optical pacing caused damage, two hearts were perfused with 30 µM of propidium iodide and analyzed histologically. A small number of cells near the stimulation site had compromised cell membranes, which probably limited the time duration over which pacing was maintained. Here, short-term optical pacing (few minutes duration) is demonstrated in the adult rabbit heart for the first time. Future studies will be directed to optimize optical pacing parameters to decrease stimulation thresholds and may enable longer-term pacing.