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The homeodomain transcription factor Irx5 establishes the mouse cardiac ventricular repolarization gradient.

ABSTRACT: Rhythmic cardiac contractions depend on the organized propagation of depolarizing and repolarizing wavefronts. Repolarization is spatially heterogeneous and depends largely on gradients of potassium currents. Gradient disruption in heart disease may underlie susceptibility to fatal arrhythmias, but it is not known how this gradient is established. We show that, in mice lacking the homeodomain transcription factor Irx5, the cardiac repolarization gradient is abolished due to increased Kv4.2 potassium-channel expression in endocardial myocardium, resulting in a selective increase of the major cardiac repolarization current, I(to,f), and increased susceptibility to arrhythmias. Myocardial Irx5 is expressed in a gradient opposite that of Kv4.2, and Irx5 represses Kv4.2 expression by recruiting mBop, a cardiac transcriptional repressor. Thus, an Irx5 repressor gradient negatively regulates potassium-channel-gene expression in the heart, forming an inverse I(to,f) gradient that ensures coordinated cardiac repolarization while also preventing arrhythmias.

SUBMITTER: Costantini DL

PROVIDER: S-EPMC1480411 | biostudies-literature | 2005 Oct

REPOSITORIES: biostudies-literature

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The homeodomain transcription factor Irx5 establishes the mouse cardiac ventricular repolarization gradient.

Costantini Danny L DL Arruda Eric P EP Agarwal Pooja P Kim Kyoung-Han KH Zhu Yonghong Y Zhu Wei W Lebel Melanie M Cheng Chi Wa CW Park Chong Y CY Pierce Stephanie A SA Guerchicoff Alejandra A Pollevick Guido D GD Chan Toby Y TY Kabir M Golam MG Cheng Shuk Han SH Husain Mansoor M Antzelevitch Charles C Antzelevitch Charles C Srivastava Deepak D Gross Gil J GJ Hui Chi-chung CC Backx Peter H PH Bruneau Benoit G BG

Cell 20051001 2

Rhythmic cardiac contractions depend on the organized propagation of depolarizing and repolarizing wavefronts. Repolarization is spatially heterogeneous and depends largely on gradients of potassium currents. Gradient disruption in heart disease may underlie susceptibility to fatal arrhythmias, but it is not known how this gradient is established. We show that, in mice lacking the homeodomain transcription factor Irx5, the cardiac repolarization gradient is abolished due to increased Kv4.2 potas ...[more]

PMID: 16239150

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Project description:The Dlx homeodomain transcription factors are implicated in regulating the function of inhibitory GABAergic interneurons; therefore understanding their functions will provide insights into disorders such as epilepsy, mental retardation and autism. Identifying genes that are downstream of Dlx1/2 function and are relevant for the differentiation and survival of GABAergic interneurons. During embryonic development, cortical GABAergic interneurons are generated in the proliferative zone of the medial ganglionic eminence (MGE), from where they migrate to reach their final positions in the cortex. The differentiation of these interneuron precursors is dependent on Dlx genes, as shown by Dlx1/Dlx2 double mutants, which have a block in GABAergic cell differentiation and in cell migration. When interneuron progenitors are isolated from the mutant MGE and growth in culture, they are able to proceed along their differentiation program. However, mutant cells growth in vitro show defects in cell morphogenesis and increased cell apoptosis. We hypothesize that Dlx transcription factors regulate important aspects of GABAergic neuron differentiation such as the formation and growth of axon and dendrites, and the formation of inhibitory synapses. We generated E15.5 mouse embryos that are Dlx1/2 -/- or Dlx1/2 +/?. Genotype was confirmed by PCR. A total of 8 litters were used. For each experiment, we pooled tissue from at least 6 different embryos of the same genotype. We dissected the ventricular and subventricular zones of the MGE (rostral part). This area contains ~1 million of progenitor cells per embryo. We isolated total RNA using the Stratagene RNA Miniprep kit (these samples are called MGE+/ and MGE-/- in our proposal). In addition, we used the same area (ventricular and subventricular zones of the rostral MGE) to perform primary neuronal cultures. Cells were maintained 3 days in vitro. After that, we isolated total RNA using the Stratagene RNA Miniprep kit (samples called primary cells+/ and primary cells-/- in our proposal). We would like to perform gene expression comparison between: 1) MGE+/ and MGE-/-, and 2) primary cells+/ and primary cells-/-. Keywords: Dlx mutants, medial ganglionic eminence, neuronal cultures

Dataset Information

The homeodomain transcription factor Irx5 establishes the mouse cardiac ventricular repolarization gradient.

Publications

The homeodomain transcription factor Irx5 establishes the mouse cardiac ventricular repolarization gradient.

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