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The Hippo-TEAD pathway regulates cellular proliferation and function. The existing paradigm is that TEAD co-activators, YAP and TAZ, and co-repressor, VGLL4, bind to the pocket region of TEAD1 to enable transcriptional activation or repressive function. Here we demonstrate a pocket-independent transcription repression mechanism whereby TEAD1 controls cell proliferation in both non-malignant mature differentiated cells and in malignant cell models. TEAD1 overexpression can repress tumor cell proliferation in distinct cancer cell lines. In pancreatic β cells, conditional knockout of TEAD1 led to a cell-autonomous increase in proliferation. Genome-wide analysis of TEAD1 functional targets via transcriptomic profiling and cistromic analysis revealed distinct modes of target genes, with one class of targets directly repressed by TEAD1. We further demonstrate that TEAD1 controls target gene transcription in a motif-dependent and orientation-independent manner. Mechanistically, we show that TEAD1 has a pocket region-independent, direct repressive function via interfering with RNA polymerase II (POLII) binding to target promoters. Our study reveals that TEAD1 target genes constitute a mutually restricted regulatory loop to control cell proliferation and uncovers a novel direct repression mechanism involved in its transcriptional control that could be leveraged in future studies to modulate cell proliferation in tumors and potentially enhance the proliferation of normal mature cells.

Bromocriptine is approved as a diabetes therapy, yet its therapeutic mechanisms remain unclear. Though bromocriptine's actions have been mainly attributed to the stimulation of brain dopamine D

Introduction: Mammalian cardiomyocyte (CM) proliferation peaks in the embryonic and neonatal periods. TEAD1, a key transcription factor regulated by the Hippo pathway, is critical for early embryonic CM proliferation. But mid gestation lethality of Tead1 germline deletion precluded the study of its role in CMs at later developmental stages. We recently generated Tead1 floxed (Tead1 F/F ) mice which allows the study of TEAD1 function in CMs at later stages. The objective of this study was to determine requirement of TEAD1 for neonatal CM proliferation. Hypothesis: TEAD1 remains critical for CM proliferation in late embryonic and early neonatal periods through transcriptional regulation of cell cycle promoting genes. Methods and Results: We observed that TEAD1 cardiac expression peaks in the perinatal period. Using Myh6-Cre deletor mice, we knocked out Tead1 in CMs at E10.5 (referred as cKO). cKO pups were born in expected Mendelian frequency, but survived only till day of life (DOL) 9. Systolic dysfunction was evident by ECHO in DOL1 cKO pups and progressed to frank heart failure (HF) by DOL9. Histological exam showed decreased myocardial mass with increased intercellular fibrosis. Ventricles of DOL1 cKO pups demonstrated increased expression of Acta1, Nppa, and Nppb, consistent with HF but showed decreased expression of Myh7, suggesting an impairment in the typical fetal gene program activated in HF. Myocardial immunostaining showed reduction in Ki67 (G1/S/G2/M phase marker) (Fig 1) and PH3-S10 (M phase marker) positive CMs by 82% and 46% respectively in DOL1 cKO hearts, indicating significantly reduced CM proliferation. The expression of essential cell cycle proteins showed a significant decrease in the levels of G1/S regulating proteins, CDK4, CDK6, ppRB S807/811 and S/G2 and G2/M regulating proteins, pWEE1 S642 and Cyclin B1 in cKO hearts (Fig 2). Similar results in ex vivo and in vitro Tead1 knockout models in CMs using neonatal Tead1 F/F CMs and HL1 cells validated the cell autonomous regulation of CM cell cycle by TEAD1. Conclusions: TEAD1 is required for embryonic and neonatal CM proliferation and its loss at mid gestation leads to neonatal HF associated with impaired fetal gene program activation and decreased expression of cell cycle promoting genes.

Metabolic abnormalities underlying diabetes are primarily the result of the lack of adequate insulin action and the associated changes in protein phosphorylation and gene expression. To define the full set of alterations in gene expression in skeletal muscle caused by diabetes and the loss of insulin action, we have used Affymetrix oligonucleotide microarrays and streptozotocin-diabetic mice. Of the genes studied, 235 were identified as changed in diabetes, with 129 genes up-regulated and 106 down-regulated. Analysis revealed a coordinated regulation at key steps in glucose and lipid metabolism, mitochondrial electron transport, transcriptional regulation, and protein trafficking. mRNAs for all of the enzymes of the fatty acid β-oxidation pathway were increased, whereas those for GLUT4, hexokinase II, the E1 component of the pyruvate dehydrogenase complex, and subunits of all four complexes of the mitochondrial electron transport chain were all coordinately down-regulated. Only about half of the alterations in gene expression in diabetic mice could be corrected toward normal after 3 days of insulin treatment and euglycemia. These data point to as of yet undefined mechanisms for highly coordinated regulation of gene expression by insulin and potential new targets for therapy of diabetes mellitus.

The insulin/IGF-1 (insulin-like growth factor 1) signalling pathway promotes adipocyte differentiation via complex signalling networks. Here, using microarray analysis of brown preadipocytes that are derived from wild-type and insulin receptor substrate (Irs) knockout animals that exhibit progressively impaired differentiation, we define 374 genes/expressed-sequence tags whose expression in preadipocytes correlates with the ultimate ability of the cells to differentiate. Many of these genes, including preadipocyte factor-1 (Pref-1) and multiple members of the Wnt signalling pathway, are related to early adipogenic events. Necdin is also markedly increased in Irs knockout cells that cannot differentiate, and knockdown of necdin restores brown adipogenesis with downregulation of Pref-1 and Wnt10a expression. Insulin receptor substrate proteins regulate a necdin-E2F4 interaction that represses peroxisome-proliferator-activated receptor gamma (PPARgamma) transcription via a cyclic AMP response element binding protein (CREB)-dependent pathway. Together these define a key signalling network that is involved in brown preadipocyte determination.

Although there is a well-recognized association between thymic hyperplasia and benign thyroid disorders, the prevalence of thymic hyperplasia in patients with malignant thyroid diseases has not been previously reported. We performed this study to determine the prevalence and morphologic features of thymic hyperplasia on CT scans of thyroid cancer patients.Thymic hyperplasia is commonly observed on CT scans of thyroid cancer patients and almost always demonstrates a characteristic pyramidal configuration. This characteristic appearance should not be mistaken for metastatic disease.

Obesity is a major risk factor for diabetes and heart disease. We previously reported that the inactivation of the gene for perilipin (plin), an adipocyte lipid droplet surface protein, produced lean and obesity-resistant mice. To dissect the underlying mechanisms involved, we used oligonucleotide microarrays to analyze the gene-expression profile of white adipose tissue (WAT), liver, heart, skeletal muscle, and kidney of plin(-/-) and plin(+/+) mice. As compared with wild-type littermates, the WAT of plin(-/-) mice had 270 and 543 transcripts that were significantly up- or downregulated. There was a coordinated upregulation of genes involved in beta-oxidation, the Krebs cycle, and the electron transport chain concomitant with a downregulation of genes involved in lipid biosynthesis. There was also a significant downregulation of the stearoyl CoA desaturase-1 gene, which has been associated with obesity resistance. Thus, in response to the constitutive activation of lipolysis associated with absence of perilipin, WAT activated pathways to rid itself of the products of lipolysis and activated pathways of energy expenditure that contribute to the observed obesity resistance. The biochemical pathways involved in obesity resistance in plin(-/-) mice identified in this study may represent potential targets for the treatment of obesity.