Unknown,Transcriptomics,Genomics,Proteomics

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Pbx and Prdm1a transcription factors differentially regulate subsets of the fast skeletal muscle program in zebrafish

ABSTRACT: The basic helix-loop-helix factor Myod initiates skeletal muscle differentiation by directly and sequentially activating sets of muscle differentiation genes, including those encoding muscle contractile proteins. We hypothesize that Pbx homeodomain proteins direct Myod to a subset of its transcriptional targets, in particular fast twitch muscle differentiation genes, thereby regulating the competence of muscle precursor cells to differentiate. We have previously shown that Pbx proteins bind with Myod on the promoter of the zebrafish fast muscle gene mylpfa and that Pbx proteins are required for Myod to activate mylpfa expression and the fast-twitch muscle-specific differentiation program in zebrafish embryos. Here we have investigated the interactions of Pbx with another muscle fiber-type regulator, Prdm1a, a SET-domain DNA-binding factor that directly represses mylpfa expression and fast muscle differentiation. The prdm1a mutant phenotype, early and increased fast muscle differentiation, is the opposite of the Pbx-null phenotype, delayed and reduced fast muscle differentiation. To determine whether Pbx and Prdm1a have opposing activities on a common set of genes, we used RNA-seq analysis to globally assess gene expression in zebrafish embryos with single- and double-losses-of-function for Pbx and Prdm1a. We find that the levels of expression of certain fast muscle genes are increased or approximately wild type in pbx2/4-MO;prdm1a-/- embryos, suggesting that Pbx activity normally counters the repressive action of Prdm1a for a subset of the fast muscle program. However, other fast muscle genes require Pbx but are not regulated by Prdm1a. Thus, our findings reveal that subsets of the fast muscle program are differentially regulated by Pbx and Prdm1a. Our findings provide an example of how Pbx homeodomain proteins act in a balance with other transcription factors to regulate subsets of a cellular differentiation program. Total RNA samples were genotyped and pooled for 4 sample types: control-MO;prdm1+/+; control-MO;prdm1-/-; pbx2/4-MO;prdm1+/+; and pbx2/4-MO;prdm1-/- embryos at the 10 somite (s) stage from three independent sets of egg collections/injections.

ORGANISM(S): Danio rerio

SUBMITTER: Zizhen yao

PROVIDER: E-GEOD-45532 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The zebrafish u-boot (ubo) gene encodes the transcription factor Prdm1, which is essential for the specification of the primary slow twitch muscle fibres that derive from adaxial cells. Here we show that Prdm1 executes this function by acting as a transcriptional repressor. Expression of the slow twitch isoform of the myosin heavy chain in adaxial cells is achieved by Prdm1 mediated repression of the transcriptional repressor Sox6. Using Chromatin immuno precipitation (ChIP) we found that genes encoding fast specific isoforms of sarcomeric proteins are direct targets of Prdm1. These genes are ectopically expressed in the adaxial cells of ubotp39 mutant embryos, suggesting that Prdm1 promotes slow twitch fibre differentiation by acting both as a global repressor of fast fibre specific genes as well as of a repressor of slow specific genes. Keywords: ChIP-chip Genomic array design. Microarrays were designed as described below and manufactured by Agilent Technologies (www.agilent.com). We have previously described the ChIP-chip technique in zebrafish and the design of promoter microarrays which cover a 2kb region around the transcription start sites (TSSs) of 11,512 zebrafish genes based on Zv4 (Wardle et al, 2006. Genome Biology 7:R71). In order to capture additional regulatory information further from the basal promoter region we also designed an expanded set of 60mer probes that cover 9kb upstream and 3kb downstream of the TSS of these genes using the same parameters as for the 2kb microarrays. These probe sequences were re-mapped to Zv6 over the course of the project and the coordinates given are for Zv6. We also incorporated several sets of control probes, both positive and negative. On each array there are 769 negative probes designed against zebrafish gene desert regions and Arabidopsis thaliana genes. In addition we included duplicates of promoter probes for several genes that we anticipated may be bound by factors of interest for this and other studies (tnnt3a, mylz2, myhz2, wnt11, flh, vent, msgn1, myod, fgf8, pcdh8) and these probes are arrayed on both slides slide. Finally on each array there are 1804 controls added by Agilent. The final design contained 352,490 probes divided between two microarray slides. Further information on design and manufacture of the microarrays can be found at the Agilent Technologies website.

Project description:Two critical events that are required for normal transition from fetal to extrauterine life are development of the alveoli that allow for efficient gas exchange in the lung and relaxation of the pulmonary vascular smooth muscle. Patients with congenital diaphragmatic hernia (CDH) have abnormal lung and pulmonary vascular development that results in a lethal combination of lung hypoplasia and pulmonary hypertension. To better understand the mechanisms responsible for abnormal lung and pulmonary vascular development and function we generated Pbx1/2 conditional knockout mice that lack Pbx1 and Pbx2 expression in the lung mesenchyme. Pbx1 has previously been shown to be required for normal diaphragm development, however its role in alveologenesis, and the mechanisms responsible for pulmonary hypertension, has not been studied. We found that Pbx1/2 CKO mice have failure of alveologenesis and die of severe pulmonary hypertension by 2 to 3 weeks of age. In order to better understand the downstream genetic mis-regulation caused by deletion of Pbx1/2, and identify their potential transcriptional targets, we carried out transcriptional profiling of Pbx1/2 CKO and control mice starting at postnatal day 3 (P3), when a histological phenotype first becomes apparent, and then working back to the time of birth (P0), and embryonic day 14 (E14) when the pulmonary vascular smooth muscle is developing. In this dataset are the expression data obtained from dissected embryonic and early postnatal lungs of Pbx1/2 CKO and control mice. Pbx1/2 CKO mice are homozygous null for Pbx2 with conditional deletion of Pbx1 in the lung mesenchyme directed by Tbx4 Cre (Tbx4 Cre/wild-type; Pbx1 flox/flox; Pbx2 delta/delta). Control mice are homozygous null for Pbx2 and are heterozygous for Pbx1 in the lung mesenchyme (Tbx4 Cre/wild-type; Pbx1 flox/wild-type; Pbx2 delta/delta). These data are used to identify the transcriptional targets and down-stream effectors of PBX transciptional regulation in the lung.

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Pbx and Prdm1a transcription factors differentially regulate subsets of the fast skeletal muscle program in zebrafish

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