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Transcriptional Corepressors HIPK1 and HIPK2 Control Angiogenesis via TGF-b-TAK1-depdendent Mechanism

ABSTRACT: Transforming growth factor-b (TGF-b) regulates various aspects of vascular development, yet the signaling mechanisms of TGF-b in the control of angiogenesis remain poorly characterized. Here we show that homeodomain interacting protein kinases, HIPK1 and HIPK2, are transcriptional corepressors that regulate TGF-b-depednent angiogenesis during embryonic development. Loss of HIPK1 and HIPK2 leads to marked up-regulations of several potent angiogenic genes, including Vegf and Mmp10, which result in excessive endothelial proliferation and poor adherens junction formation. This robust phenotype can be recapitulated by siRNA knock down of Hipk1 and Hipk2 in human umbilical vein endothelial cells, as well as in endothelial cell-specific TGF-b type II receptor (TbRII) conditional mutants. The effects of HIPK proteins are mediated through its interaction with MEF2C and HDAC7, and this interaction can be further enhanced by TGF-b and TAK1. Remarkably, TGF-b-TAK1 signaling activates HIPK2 by phosphorylating a highly conserved tyrosine residue Y-361 within the kinase domain. Point mutation in this tyrosine completely eliminates the effect of HIPK2 in the transcriptional suppression of target genes. Together, these results reveal a previously unrecognized role of HIPK proteins in connecting TGF-b signaling pathway with the transcriptional programs for angiogenesis in early embryonic development.

ORGANISM(S): Mus musculus

PROVIDER: GSE39253 | GEO | 2013/06/01

SECONDARY ACCESSION(S): PRJNA170389

REPOSITORIES: GEO

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Project description:Background: Cardiac kinases play a critical role in the development of heart failure, and represent potential tractable therapeutic targets. However, only a very small fraction of the cardiac kinome has been investigated. To identify novel cardiac kinases involved in heart failure, we employed an integrated transcriptomics and bioinformatics analysis and identified Homeodomain-Interacting Protein Kinase 2 (HIPK2) as a novel candidate kinase. The role of HIPK2 in cardiac biology is unknown. Methods: We used the Expression2Kinase algorithm for the screening of kinase targets. To determine the role of HIPK2 in the heart, we generated cardiomyocyte-specific HIPK2 knockout (CM-KO) and heterozygous (CM-Het) mice. Heart function was examined by echocardiography and related cellular and molecular mechanisms were examined. Adeno-associated virus serotype 9 (AAV9) carrying cardiac-specific constitutively active MEK1 (TnT-MEK1-CA) were administrated to rescue cardiac dysfunction in CM-KOs. Results: To our knowledge, this is the first study to define the role of HIPK2 in cardiac biology. Using multiple HIPK2 loss-of-function mouse models, we demonstrated that reduction of HIPK2 in cardiomyocytes leads to cardiac dysfunction—suggesting a causal role in heart failure. Importantly, cardiac dysfunction in HIPK2 KOs developed with advancing age, but not during development. In addition, CM-KO and CM-Het exhibited a gene dose-response relationship of cardiomyocyte HIPK2 on heart function. HIPK2 expression in the heart was significantly reduced in human end-stage ischemic cardiomyopathy compared to non-failing myocardium, suggesting a clinical relevance of HIPK2 in cardiac biology. In vitro studies with neonatal rat ventricular cardiomyocytes corroborated the in vivo findings. Specifically, adenovirus-mediated overexpression of HIPK2 suppressed the expression of heart failure markers, NPPA and NPPB, at basal condition and abolished phenylephrine-induced pathological gene expression. An array of mechanistic studies revealed impaired ERK1/2 signaling in HIPK2 deficient hearts. In vivo rescue experiment with AAV9 TnT-MEK1-CA nearly abolished the detrimental phenotype of KOs suggesting that impaired ERK signaling mediated apoptosis as the key factor driving the detrimental phenotype in CM-KO hearts. Conclusions: Taken together, these findings suggest that cardiomyocyte HIPK2 is required to maintain normal cardiac function via ERK signaling

Project description:Primary murine fetal liver cells were freshly isolated from day e14.5 livers and then sorted for successive differentiation stages by Ter119 and CD71 surface expression (ranging from double-negative CFU-Es to Ter-119 positive enucleated erythrocytes) [Zhang, et al. Blood. 2003 Dec 1; 102(12):3938-46]. RNA isolated from each freshly isolated, stage-sorted population was reverse-transcribed, labelled, and then hybridized onto 3' oligo Affymetrix arrays. Important erythroid specific genes as well as the proteins that regulate them were elucidated through this profiling based on coexpression and differential expression patterns as well as by extracting specific GO categories of genes (such as DNA-binding proteins). Abstract (submitted paper): rationale for expression profiling Gene-targeting experiments report that the homeodomain-interacting protein kinases 1 and 2, Hipk1 and Hipk2, are essential but redundant in hematopoietic developmentâbecause Hipk1/Hipk2 double-deficient animals exhibit severe defects in hematopoiesis and vasculogenesis while the single knockouts do not. These serine-threonine kinases phosphorylate, and consequently modify the functions of, several important hematopoietic transcription factors and cofactors. Here we show that Hipk2 knockdown alone plays a significant role in terminal fetal liver erythroid differentiation. Hipk1 and Hipk2 are highly induced during primary mouse fetal liver erythropoiesis. Specific knockdown of Hipk2 inhibits terminal erythroid cell proliferationâexplained in part by impaired cell cycle progression as well as increased apoptosisâand terminal enucleation as well as the accumulation of hemoglobin. Hipk2 knockdown also reduces the transcription of many genes involved in proliferation and apoptosis as well as important, erythroid-specific genes involved in hemoglobin biosynthesisâsuch as alpha-globin and mitoferrin 1âdemonstrating that Hipk2 plays an important role in some but not all aspects of normal terminal erythroid differentiation.

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Transcriptional Corepressors HIPK1 and HIPK2 Control Angiogenesis via TGF-b-TAK1-depdendent Mechanism

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