Project description:Several transcription factors are known to be expressed in discrete regions of the otic vesicle and Dlx5 is one of those that is expressed highly in the presumptive dorsal vestibular region. Mice lacking Dlx5 have vestibular defects. Specifically, they fail to form the endolymphatic duct (a defect visible as early as E10) as well as the anterior and posterior semi-circular canals. The lateral canal does form but is smaller, whereas the saccule, the utricle and the cochlea appear relatively normal. The goal of this study was to use microarrays to identify differentially expressed genes between wild-type and Dlx5-null otic vesicles microdissected from E10 and 10.5 and identify downstream targets of Dlx5 by searching the immediate 3kb promoter regions of the differentially expressed genes for homeodomain binding sites followed by chromatin immunoprecipitation in an otic vesicle-derived cell line over-expressing Dlx5. Normal vestibular morphogenesis is compromised in mice lacking Dlx5, a member of the Distal-less family of homeobox transcription factors. We identified its direct downstream targets in the developing mouse inner ear by gene expression profiling wild-type and Dlx5 null otic vesicles from embryonic stages E10 and E10.5. Four hundred genes were differentially expressed in mutants when compared to wild-type in at least one of the two stages. To further constrain the list of likely direct targets of Dlx5, we examined the genomic DNA sequences in the 3kb promoter regions immediately proximal to the transcriptional start sites of these genes. We searched for (i) one or more previously described binding site for Dlx5, (ii) one or more novel 12bp-long motifs with a canonical homeodomain response element (HDRE) shared by promoters of two or more genes, and (iii) 100% conservation of the 12bp-long HDRE-containing motifs in promoter regions of human orthologs. Forty genes passed one or more of these filters, 12 of which are known to be expressed in the developing otic vesicle in domains that at least partially overlap with that of Dlx5 in one or both stages that we examined. Chromatin immunoprecipitation using a Dlx5 antibody confirmed direct binding of Dlx5 to promoter regions of seven of these genes (Atbf1, Bmper, Large, Lrrtm1, and Msx1, all of which were down-regulated in mutants, and Ebf1 and Lhx1, both of which were up-regulated in mutants) in an otic vesicle-derived cell line over-expressing Dlx5. Gene expression profiling of this cell line showed that Bmper and Lrrtm1 transcripts were up-regulated, further supporting their identification as direct targets of Dlx5 activity. Otic vesicles from wild-type and Dlx5-null embryos were microdissected from mouse developmental stages E10 and E10.5 and expression profiled in duplicate for each stage and genotype. Dlx5-transfected and empty vector-transfected 2B1 cell line samples were also profiled in duplicate (independent cell cultures).

Project description:Several transcription factors are known to be expressed in discrete regions of the otic vesicle and Dlx5 is one of those that is expressed highly in the presumptive dorsal vestibular region. Mice lacking Dlx5 have vestibular defects. Specifically, they fail to form the endolymphatic duct (a defect visible as early as E10) as well as the anterior and posterior semi-circular canals. The lateral canal does form but is smaller, whereas the saccule, the utricle and the cochlea appear relatively normal. The goal of this study was to use microarrays to identify differentially expressed genes between wild-type and Dlx5-null otic vesicles microdissected from E10 and 10.5 and identify downstream targets of Dlx5 by searching the immediate 3kb promoter regions of the differentially expressed genes for homeodomain binding sites followed by chromatin immunoprecipitation in an otic vesicle-derived cell line over-expressing Dlx5. Normal vestibular morphogenesis is compromised in mice lacking Dlx5, a member of the Distal-less family of homeobox transcription factors. We identified its direct downstream targets in the developing mouse inner ear by gene expression profiling wild-type and Dlx5 null otic vesicles from embryonic stages E10 and E10.5. Four hundred genes were differentially expressed in mutants when compared to wild-type in at least one of the two stages. To further constrain the list of likely direct targets of Dlx5, we examined the genomic DNA sequences in the 3kb promoter regions immediately proximal to the transcriptional start sites of these genes. We searched for (i) one or more previously described binding site for Dlx5, (ii) one or more novel 12bp-long motifs with a canonical homeodomain response element (HDRE) shared by promoters of two or more genes, and (iii) 100% conservation of the 12bp-long HDRE-containing motifs in promoter regions of human orthologs. Forty genes passed one or more of these filters, 12 of which are known to be expressed in the developing otic vesicle in domains that at least partially overlap with that of Dlx5 in one or both stages that we examined. Chromatin immunoprecipitation using a Dlx5 antibody confirmed direct binding of Dlx5 to promoter regions of seven of these genes (Atbf1, Bmper, Large, Lrrtm1, and Msx1, all of which were down-regulated in mutants, and Ebf1 and Lhx1, both of which were up-regulated in mutants) in an otic vesicle-derived cell line over-expressing Dlx5. Gene expression profiling of this cell line showed that Bmper and Lrrtm1 transcripts were up-regulated, further supporting their identification as direct targets of Dlx5 activity.

Project description:The Dlx homeobox genes have central roles in controlling patterning and differentiation of the brain and craniofacial primordia. In the brain, loss of Dlx function results in defects in the production, migration and differentiation of GABAergic neurons, that can lead to epilepsy. In the branchial arches, loss of Dlx function leads to craniofacial malformations that include trigeminal axon pathfinding defects. To determine how these genes function, we wish to identify the transcriptional circuitry that lies downstream of these transcription factors by comparing gene expression in wild type with Dlx mutant CNS and craniofacial tissues. 1) Compare gene expression in the maxillay branch of the first branchial arch (BA) of E10.5 wild type and Dlx2 -/- mutants. 2) Compare gene expression in the maxillary branch of the first BA of E10.5 wild type and Dlx1/2 -/- mutants. 3) Compare gene expression in wild type maxillary and mandibular branchial arches. 4) Compare gene expressionin mandibular branch of Dlx5/6 -/- mutants with wild type mandibular branch. The Dlx transcription factors are essential for controlling patterning of the brain and craniofacial primordia. In the brain, they control differentiation of GABAergic neurons of the basal ganglia. In the branchial arches, they control regional patterning. I hypothesize that there will be some conserved and some divergent mechanisms that the Dlx genes use in controlling brain and craniofacial development. We have already performed array analyses on Dlx function in the developing basal ganglia (with TGEN) by comparing expressed genes in wild type and Dlx1/2 mutants. Here we will compare gene expression in the brachial arches of wild type and Dlx mutant mice. 1) Generate E10.5 mouse embryos that are either wild type, Dlx2-/-, Dlx1/2 -/- or Dlx5/6 -/-. 2) Determine genotype by PCR. 3) Dissect branchial arches from the different genotypes. 4) Separate maxillary and mandibular branch of each branchial arch. 5) Prepare total RNA from the specimens. Obtain sufficient tissue to obtain 10 ug of total RNA - based on previous experience we anticipate that this will require ~ 10 branchial arches. We will pool the tissue from different embryos of the same genotype. 6) Send total RNA to TGEN for probe preparation, hybridization and array result analysis.

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Genome-wide binding profile of Dlx5 in mouse T cell lymphoma

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