Project description:Previous studies have suggested that Bmp4 is a key Msx1-dependent mesenchymal odontogenic signal for driving tooth morphogenesis through the bud-to-cap transition. Whereas the bud stage tooth developmental arrest in Msx1-/- mutant mice was accompanied by reduction in mesenchymal Bmp4 mRNA expression, we show that depleting functional Bmp4 mRNAs in the tooth mesenchyme, through neural crest-specific gene inactivation in Bmp4f/f;Wnt1Cre mice, caused mandibular molar developmental arrest at the bud stage but allowed maxillary molars and incisors to develop to mineralized teeth. We show that the Wnt inhibitors Dkk2 and Wif1 were much more abundantly expressed in the mandibular than maxillary molar mesenchyme in wildtype embryos and that Dkk2 expression was significantly unregulated in the tooth mesenchyme in Bmp4f/f;Wnt1Cre embryos. In addition, expression of Osr2, which encodes a zinc finger protein that antagonizes Msx1-mediated activation of odontogenic mesenchyme, is significantly upregulated in the molar mesenchyme in Bmp4f/f;Wnt1Cre embryos. Msx1 heterozygosity enhanced maxillary molar developmental defects whereas Osr2 heterozygosity rescued mandibular first molar morphogenesis in Bmp4f/f;Wnt1Cre mice. Moreover, in contrast to complete lack of supernumerary tooth initiation in Msx1-/-Osr2-/- mutant mice, Osr2-/-Bmp4f/f;Wnt1Cre compound mutant mice exhibit formation and subsequent arrest of supernumerary tooth germs that correlated with down regulation of Msx1 expression in the tooth mesenchyme. Taken together, our data indicate that, while reduction in mesenchymal Bmp4 expression alone could not account for the tooth bud arrest phenotype in Msx1-/- mutant mice, Bmp4 signaling synergizes with Msx1 and antagonizes Osr2 to activate mesenchymal odontogenic activity to drive tooth morphogenesis and sequential tooth formation. E13.5 mouse embryos tooth germs were microdissected by laser capture microdissection (LCM), and the mandibular molar and maxillary molar were separated. 3 pairs of control and mutant samples were pooled for the RNA extraction.

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.

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. Keywords: other

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