Dataset Information

Identification of a direct Dlx homeodomain target in the developing mouse forebrain and retina by optimization of chromatin immunoprecipitation.

ABSTRACT: Understanding homeobox gene specificity and function has been hampered by the lack of proven direct transcriptional targets during development. Dlx genes are expressed in the developing forebrain, retina, craniofacial structures and limbs. Dlx1/Dlx2 double knockout mice die at birth with multiple defects including abnormal forebrain development and decreased Dlx5 and Dlx6 expression. We have successfully applied chromatin immunoprecipitation (ChIP) to identify a direct transcriptional target of DLX homeoproteins from embryonic tissues in vivo. We optimized cross-linking conditions to enrich for protein-DNA complexes, then using specific high affinity DLX antibodies captured immunoenriched DLX genomic DNA transcriptional targets. DLX homeobox proteins bind differentially to the Dlx5/Dlx6 intergenic enhancer in newborn retina (DLX2) and embryonic striatum (DLX1, DLX2) in situ. Reporter gene assays demonstrated the functional significance of the binding of DLX proteins to this regulatory element, confirmed in vitro by electrophoretic mobility shift assays, using tissue extracts or recombinant DLX proteins. ChIP provides the best approach to identify direct Dlx homeoprotein targets from developing tissues in situ. The use of this technology will advance our understanding of Dlx gene function in the vertebrate in vivo and can be applied to examine targets of other homeobox genes and other classes of transcription factors.

SUBMITTER: Zhou QP

PROVIDER: S-EPMC373381 | biostudies-literature | 2004

REPOSITORIES: biostudies-literature

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Identification of a direct Dlx homeodomain target in the developing mouse forebrain and retina by optimization of chromatin immunoprecipitation.

Zhou Qing-Ping QP Le Trung Ngoc TN Qiu Xiangguo X Spencer Virginia V de Melo Jimmy J Du Guoyan G Plews Margot M Fonseca Mario M Sun Jian Min JM Davie James R JR Eisenstat David D DD

Nucleic acids research 20040209 3

Understanding homeobox gene specificity and function has been hampered by the lack of proven direct transcriptional targets during development. Dlx genes are expressed in the developing forebrain, retina, craniofacial structures and limbs. Dlx1/Dlx2 double knockout mice die at birth with multiple defects including abnormal forebrain development and decreased Dlx5 and Dlx6 expression. We have successfully applied chromatin immunoprecipitation (ChIP) to identify a direct transcriptional target of ...[more]

PMID: 14769946

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Project description:Pax6 encodes a specific DNA-binding transcription factor that regulates the development of multiple organs, including the eye, brain and pancreas. Previous studies have shown that Pax6 regulates the entire process of ocular lens development. In the developing forebrain, Pax6 is expressed in ventricular zone precursor cells and in specific populations of neurons; absence of Pax6 results in disrupted cell proliferation and cell fate specification in telencephalon. In the pancreas, Pax6 is essential for the differentiation of ?-, ?- and ?-islet cells. To elucidate molecular roles of Pax6, chromatin immunoprecipitation experiments combined with high-density oligonucleotide array hybridizations (ChIP-chip) were performed using three distinct sources of chromatin (lens, forebrain and ?-cells). ChIP-chip studies, performed as biological triplicates, identified a total of 5,260 promoters occupied by Pax6. 1,001 (133) of these promoter regions were shared between at least two (three) distinct chromatin sources, respectively. In lens chromatin, 2,335 promoters were bound by Pax6. RNA expression profiling from Pax6?/? lenses combined with in vivo Pax6-binding data yielded 76 putative Pax6-direct targets, including the Gaa, Isl1, Kif1b, Mtmr2, Pcsk1n, and Snca genes. RNA and ChIP data were validated for all these genes. In lens cells, reporter assays established Kib1b and Snca as Pax6 activated and repressed genes, respectively. In situ hybridization revealed reduced expression of these genes in E14 cerebral cortex. Moreover, we examined differentially expressed transcripts between E9.5 wild type and Pax6?/? lens placodes that suggested Efnb2, Fat4, Has2, Nav1, and Trpm3 as novel Pax6-direct targets. Collectively, the present studies, through the identification of Pax6-direct target genes, provide novel insights into the molecular mechanisms of Pax6 gene control during mouse embryonic development. In addition, the present data demonstrate that Pax6 interacts preferentially with promoter regions in a tissue-specific fashion. Nevertheless, nearly 20% of the regions identified are accessible to Pax6 in multiple tissues.

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

Identification of a direct Dlx homeodomain target in the developing mouse forebrain and retina by optimization of chromatin immunoprecipitation.

Publications

Identification of a direct Dlx homeodomain target in the developing mouse forebrain and retina by optimization of chromatin immunoprecipitation.

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