San Pin Wu

Cysteine-Rich LIM-Only Proteins CRP1 and CRP2 Are Potent Smooth Muscle Differentiation Cofactors

Cysteine-rich LIM-only proteins, CRP1 and CRP2, expressed during cardiovascular development act as bridging molecules that associate with serum response factor and GATA proteins. SRF-CRP-GATA complexes strongly activated smooth muscle gene targets. CRP2 was found in the nucleus during early stages of coronary smooth muscle differentiation from proepicardial cells. A dominant-negative CRP2 mutant blocked proepicardial cells from differentiating into smooth muscle cells. Together with SRF and GATA proteins, CRP1 and CRP2 converted pluripotent 10T1/2 fibroblasts into smooth muscle cells, while muscle LIM protein CRP3 inhibited the conversion. Thus, LIM-only proteins of the CRP family play important roles in organizing multiprotein complexes, both in the cytoplasm, where they participate in cytoskeletal remodeling, and in the nucleus, where they strongly facilitate smooth muscle differentiation.

COUP-TFII inhibits TGF-β-induced growth barrier to promote prostate tumorigenesis

Mutations in phosphatase and tensin homologue (PTEN) or genomic alterations in the phosphatidylinositol-3-OH kinase-signalling pathway are the most common genetic alterations reported in human prostate cancer. However, the precise mechanism underlying how indolent tumours with PTEN alterations acquire metastatic potential remains poorly understood. Recent studies suggest that upregulation of transforming growth factor (TGF)-β signalling triggered by PTEN loss will form a growth barrier as a defence mechanism to constrain prostate cancer progression, underscoring that TGF-β signalling might represent a pre-invasive checkpoint to prevent PTEN-mediated prostate tumorigenesis. Here we show that COUP transcription factor II (COUP-TFII, also known as NR2F2), a member of the nuclear receptor superfamily, serves as a key regulator to inhibit SMAD4-dependent transcription, and consequently overrides the TGF-β-dependent checkpoint for PTEN-null indolent tumours. Overexpression of COUP-TFII in the mouse prostate epithelium cooperates with PTEN deletion to augment malignant progression and produce an aggressive metastasis-prone tumour. The functional counteraction between COUP-TFII and SMAD4 is reinforced by genetically engineered mouse models in which conditional loss of SMAD4 diminishes the inhibitory effects elicited by COUP-TFII ablation. The biological significance of COUP-TFII in prostate carcinogenesis is substantiated by patient sample analysis, in which COUP-TFII expression or activity is tightly correlated with tumour recurrence and disease progression, whereas it is inversely associated with TGF-β signalling. These findings reveal that the destruction of the TGF-β-dependent barrier by COUP-TFII is crucial for the progression of PTEN-mutant prostate cancer into a life-threatening disease, and supports COUP-TFII as a potential drug target for the intervention of metastatic human prostate cancer.

Estrogen Receptor β Modulates Apoptosis Complexes and the Inflammasome to Drive the Pathogenesis of Endometriosis

Alterations in estrogen-mediated cellular signaling play an essential role in the pathogenesis of endometriosis. In addition to higher estrogen receptor (ER) β levels, enhanced ERβ activity was detected in endometriotic tissues, and the inhibition of enhanced ERβ activity by an ERβ-selective antagonist suppressed mouse ectopic lesion growth. Notably, gain of ERβ function stimulated the progression of endometriosis. As a mechanism to evade endogenous immune surveillance for cell survival, ERβ interacts with cellular apoptotic machinery in the cytoplasm to inhibit TNF-α-induced apoptosis. ERβ also interacts with components of the cytoplasmic inflammasome to increase interleukin-1β and thus enhance its cellular adhesion and proliferation properties. Furthermore, this gain of ERβ function enhances epithelial-mesenchymal transition signaling, thereby increasing the invasion activity of endometriotic tissues for establishment of ectopic lesions. Collectively, we reveal how endometrial tissue generated by retrograde menstruation can escape immune surveillance and develop into sustained ectopic lesions via gain of ERβ function.

Atrial Identity Is Determined by A COUP-TFII Regulatory Network

Atria and ventricles exhibit distinct molecular profiles that produce structural and functional differences between the two cardiac compartments. However, the factors that determine these differences remain largely undefined. Cardiomyocyte-specific COUP-TFII ablation produces ventricularized atria that exhibit ventricle-like action potentials, increased cardiomyocyte size, and development of extensive T tubules. Changes in atrial characteristics are accompanied by alterations of 2,584 genes, of which 81% were differentially expressed between atria and ventricles, suggesting that a major function of myocardial COUP-TFII is to determine atrial identity. Chromatin immunoprecipitation assays using E13.5 atria identified classic atrial-ventricular identity genes Tbx5, Hey2, Irx4, MLC2v, MLC2a, and MLC1a, among many other cardiac genes, as potential COUP-TFII direct targets. Collectively, our results reveal that COUP-TFII confers atrial identity through direct binding and by modulating expression of a broad spectrum of genes that have an impact on atrial development and function.

Androgen deprivation–induced NCoA2 promotes metastatic and castration-resistant prostate cancer

A major clinical hurdle for the management of advanced prostate cancer (PCa) in patients is the resistance of tumors to androgen deprivation therapy (ADT) and their subsequent development into castration-resistant prostate cancer (CRPC). While recent studies have identified potential pathways involved in CRPC development, the drivers of CRPC remain largely undefined. Here we determined that nuclear receptor coactivator 2 (NCoA2, also known as SRC-2), which is frequently amplified or overexpressed in patients with metastatic PCa, mediates development of CRPC. In a murine model, overexpression of NCoA2 in the prostate epithelium resulted in neoplasia and, in combination with Pten deletion, promoted the development of metastasis-prone cancer. Moreover, depletion of NCoA2 in PTEN-deficient mice prevented the development of CRPC. In human androgen-sensitive prostate cancer cells, androgen signaling suppressed NCoA2 expression, and NCoA2 overexpression in murine prostate tumors resulted in hyperactivation of PI3K/AKT and MAPK signaling, promoting tumor malignance. Analysis of PCa patient samples revealed a strong correlation among NCoA2-mediated signaling, disease progression, and PCa recurrence. Taken together, our findings indicate that androgen deprivation induces NCoA2, which in turn mediates activation of PI3K signaling and promotes PCa metastasis and CRPC development. Moreover, these results suggest that the inhibition of NCoA2 has potential for PCa therapy.

Estrogen receptor–α in medial amygdala neurons regulates body weight

Estrogen receptor-α (ERα) activity in the brain prevents obesity in both males and females. However, the ERα-expressing neural populations that regulate body weight remain to be fully elucidated. Here we showed that single-minded-1 (SIM1) neurons in the medial amygdala (MeA) express abundant levels of ERα. Specific deletion of the gene encoding ERα (Esr1) from SIM1 neurons, which are mostly within the MeA, caused hypoactivity and obesity in both male and female mice fed with regular chow, increased susceptibility to diet-induced obesity (DIO) in males but not in females, and blunted the body weight-lowering effects of a glucagon-like peptide-1-estrogen (GLP-1-estrogen) conjugate. Furthermore, selective adeno-associated virus-mediated deletion of Esr1 in the MeA of adult male mice produced a rapid body weight gain that was associated with remarkable reductions in physical activity but did not alter food intake. Conversely, overexpression of ERα in the MeA markedly reduced the severity of DIO in male mice. Finally, an ERα agonist depolarized MeA SIM1 neurons and increased their firing rate, and designer receptors exclusively activated by designer drug-mediated (DREADD-mediated) activation of these neurons increased physical activity in mice. Collectively, our results support a model where ERα signals activate MeA neurons to stimulate physical activity, which in turn prevents body weight gain.

Tbx18 regulates development of the epicardium and coronary vessels

The epicardium and coronary vessels originate from progenitor cells in the proepicardium. Here we show that Tbx18, a T-box family member highly expressed in the proepicardium, controls critical early steps in coronary development. In Tbx18(-/-) mouse embryos, both the epicardium and coronary vessels exhibit structural and functional defects. At E12.5, the Tbx18-deficient epicardium contains protrusions and cyst-like structures overlying a disorganized coronary vascular plexus that contains ectopic structures resembling blood islands. At E13.5, the left and right coronary stems form correctly in mutant hearts. However, analysis of PECAM-1 whole mount immunostaining, distribution of SM22α(lacZ/+) activity, and analysis of coronary vascular casts suggest that defective vascular plexus remodeling produces a compromised arterial network at birth consisting of fewer distributing conduit arteries with smaller lumens and a reduced capacity to conduct blood flow. Gene expression profiles of Tbx18(-/-) hearts at E12.5 reveal altered expression of 79 genes that are associated with development of the vascular system including sonic hedgehog signaling components patched and smoothened, VEGF-A, angiopoietin-1, endoglin, and Wnt factors compared to wild type hearts. Thus, formation of coronary vasculature is responsive to Tbx18-dependent gene targets in the epicardium, and a poorly structured network of coronary conduit vessels is formed in Tbx18 null hearts due to defects in epicardial cell signaling and fate during heart development. Lastly, we demonstrate that Tbx18 possesses a SRF/CArG box dependent repressor activity capable of inhibiting progenitor cell differentiation into smooth muscle cells, suggesting a potential function of Tbx18 in maintaining the progenitor status of epicardial-derived cells.

Increased COUP-TFII expression in adult hearts induces mitochondrial dysfunction resulting in heart failure

Mitochondrial dysfunction and metabolic remodelling are pivotal in the development of cardiomyopathy. Here, we show that myocardial COUP-TFII overexpression causes heart failure in mice, suggesting a causal effect of elevated COUP-TFII levels on development of dilated cardiomyopathy. COUP-TFII represses genes critical for mitochondrial electron transport chain enzyme activity, oxidative stress detoxification and mitochondrial dynamics, resulting in increased levels of reactive oxygen species and lower rates of oxygen consumption in mitochondria. COUP-TFII also suppresses the metabolic regulator PGC-1 network and decreases the expression of key glucose and lipid utilization genes, leading to a reduction in both glucose and oleate oxidation in the hearts. These data suggest that COUP-TFII affects mitochondrial function, impairs metabolic remodelling and has a key role in dilated cardiomyopathy. Last, COUP-TFII haploinsufficiency attenuates the progression of cardiac dilation and improves survival in a calcineurin transgenic mouse model, indicating that COUP-TFII may serve as a therapeutic target for the treatment of dilated cardiomyopathy.

Chapter 9. Development of coronary vessels.

This chapter summarizes experimental techniques used to study coronary vessel development from its origins in the proepicardium (PE) to the final assembled network of arteries, veins, and capillaries present in the mature heart. Methods are described for microdissection and culture of the PE and embryonic epicardial cells, isolation of total RNA from single PE primordia and analysis by RT-PCR, imaging of the epicardium and coronary vessels by whole-mount confocal microscopy and by scanning electron microscopy, and the preparation of coronary vascular corrosion casts to visualize the entire coronary artery network structure. These techniques form the basic tools to study the cellular and molecular pathways that guide development and remodeling of coronary vessels.

Endometrial Expression of Steroidogenic Factor 1 Promotes Cystic Glandular Morphogenesis

Epigenetic silencing of steroidogenic factor 1 (SF1) is lost in endometriosis, potentially contributing to de novo local steroidogenesis favoring inflammation and growth of ectopic endometrial tissue. In this study, we examine the impact of SF1 expression in the eutopic uterus by a novel mouse model that conditionally expresses SF1 in endometrium. In vivo SF1 expression promoted the development of enlarged endometrial glands and attenuated estrogen and progesterone responsiveness. Endometriosis induction by autotransplantation of uterine tissue to the mesenteric membrane resulted in the increase in size of ectopic lesions from SF1-expressing mice. By integrating the SF1-dependent transcriptome with the whole genome binding profile of SF1, we identified uterine-specific SF1-regulated genes involved in Wingless and Progesterone receptor-Hedgehog-Chicken ovalbumin upstream promoter transcription factor II signaling for gland development and epithelium-stroma interaction, respectively. The present results indicate that SF1 directly contributes to the abnormal uterine gland morphogenesis, an inhibition of steroid hormone signaling and activation of an immune response, in addition to previously postulated estrogen production.