Project description:Dioxins are ubiquitous environmental poisons that are developmentally toxic. Exposure of mouse E14 tooth germs to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to reduced tooth size and deformation of cuspal morphology implying the induction of a variety of biological responses on both cellular and molecular levels. To verify such responses at the gene level, mouse embryonic cap staged tooth germs were cultured for 24 h with/without 1 ÂµM TCDD. Experiment Overall Design: Organ culture: Mandibular molar tooth regions from E14 mouse embryos (NMRI X NMRI; the day of vaginal plug = E0) were dissected under a stereomicroscope and transferred to an organ culture. The tissue explants were supported by polycarbonate Nuclepore filters [pore size, 0.1 Âµm; Corning Inc., New York] placed on a stainless steel grid. The basal culture medium was Dulbeccoâs modified Eagleâs medium (DMEM) containing Glutamax-1 (Gibco BRL, Paisley, Scotland) supplemented with 10% fetal calf serum (FCS; Gibco BRL). TCDD (from the Department of Chemistry, University of JyvÃ¤skylÃ¤, JyvÃ¤skylÃ¤, Finland) was dissolved in dimethylsulfoxide (DMSO) at a concentration of 50 Âµg/ml. TCDD at the concentration of 1 ÂµM, or DMSO, was added to the basal culture medium from the start of culture. The culture dishes were kept in a humidified incubator at 37 ÂºC in an atmosphere of 5% CO2. The tissue explants were cultured for 24 hours, after which they were snap frozen in liquid nitrogen. Explants from several experiments were collected and kept in liquid nitrogen. In a single experiment, 15â29 explants were included in each experimental group. Experiment Overall Design: Microarray analysis: Experiment Overall Design: Three separate experiments were combined for each replicate sample. About 60 explants each were pooled and homogenized while still frozen in liquid nitrogen. Total RNA was isolated using the RNeasy Mini Kit (Qiagen). cDNA was synthesized from the total RNA by using a GeneChip T7-Oligo(dT)24 Promoter Primer Kit (Affymetrix) and Superscript II Choice System (Invitrogen Life Sciences). The double stranded cDNA was cleaned-up with the GeneChip Sample Cleanup Module (Affymetrix). Biotin-labelled cRNA was synthesized by in vitro transcription usin a RNA labelling kit from Enzo Life Sciences, Inc. The labelling time was 5 h in 37ÂºC waterbath. All syntheses were done according to the manufacturers instructions. Unincorporated NTPs were removed with the GeneChip Sample Cleanup kit and the concentration of the labelled cRNA was mesured by spectrophotometric analysis and quantificated. 15 or 16 Âµg of labelled cRNA was fragmented by incubation at 94 ÂºC for 35 min in the fragmentation buffer supplied in the GeneChip Sample Cleanup kit. The cRNA was hybridized to a murine U74v2A array (Affymetrix) for 16 h at 45 ÂºC, washed and stained with streptavidine-phycoerythrin. The arrays were scanned in a Genechip System confocal scanner (Aligent) and Affymetrix Microarray Suite 5.0 was used to scan and analyze the relative abundance of each gene. The target signal scaling was set to 100.

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.

Dataset Information

Mus musculus

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets