Objective: To investigate the expression of gamma-aminobutyric acid type A receptor beta3 subunit (GABRB3) on cleft palate in C57BL/6J mice induced by 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD). Methods: Sixty C57BL/6J pregnant mice on gestation day (GD) 10.5 were divided into two groups: one group was administered through gastric tubes one dose of 28 μg/kg TCDD (experimental group) and the other group was administered through gastric tubes one dose of 5.6 ml/kg corn oil (control group). Embryos were removed by cesarean section from pregnant mice during the palatal formation stage (GD 13.5-17.5) and the palatal tissue studied in morphological and histological observation. The relative mRNA and protein expression of GABRB3 was measured by real-time quantitative PCR and Western blotting. Localization of GABRB3 protein was measured by immunohistochemistry or immunofluorescence. Results: The incidence of cleft palate at GD17.5 was 100% in experimental group and there was no cleft palate occurred in the control group (0); elevation of palatine processes in experimental group was completed on GD15.5 which was clearly delayed by a day compared with that in control group. On GD14.5-GD17.5, the mRNA expression (0.561±0.073, 0.728±0.104, 0.782±0.137, 0.686±0.145) and protein expression (0.288±0.013, 0.404±0.017, 0.399±0.012, 0.307±0.010) in the experimental group were significantly lower than the control group mRNA expression (0.818±0.088, 0.865±0.086, 1.021±0.054, 1.163±0.179) and protein expression (0.481±0.017, 0.456±0.009, 0.474±0.016, 0.529±0.015)(P<0.05). Immunohistochemistry and immunofluorescence showed that GABRB3 was mainly expressed in the mesenchymal cells and medial edge epithelium. Conclusions TCDD delayed palatal shelf elevation and eventually led to cleft palate may be associated with a decrease in GABRB3. GABRB3 may play an important role in the elevation and fusion phases of the palate development.

Objective:To explore the role of epithelial-mesenchymal transition(EMT) in fusion of the secondary palatal shelves to form the intact secondary palate induced by 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD).Methods:Twelve C57BL/6 J pregnant mice on gestation day (GD) 10.5 were divided into two groups: one group was conducted through gastric tubes with one dose of 28 μg/kg TCDD (experimental group) and the other group was operated through gastric tubes with equal volume corn oil (control group). Embryos were removed by cesarean section from pregnant mice during the palatal formation stage (GD 15.5) and the morphology of palatal tissue was observed. Primary media edge epithelial(MEE) were divided into experimental group and control group. MEE were treated with medium containing TCDD, 5 nmol/L, 10 nmol/L, 20 nmol/L and normal medium respectively. The expression of cytokeratin 19(CK-19) protein and vimentin protein in MEE were detected by immunofluorescence laser confocal microscopy and Western blotting after 72 hours. Statistical comparisons were made using one-way ANOVA.Results:A total of 36 fetuses were obtained in the experimental group, including 3 dead fetuses and absorbed fetuses. The incidence of cleft palate was 100% (33/33); the incidence of complete cleft palate was 84.8% (28/33), and the incidence of partial cleft palate was 15.2% (5/33); 40 fetuses were obtained in the control group, including 2 dead fetuses and resorbed fetuses, and the incidence of cleft palate was 0 (0/38). After 72 hours, the shape of MEE changed from uniform pebble-like to star-like or irregular shape with pseudopodia. The expressions of CK-19 protein were(0.739 ± 0.120, 0.483 ± 0.023, 1.007 ± 0.109, 1.086 ± 0.145) and fluorescence intensities were (53.384±5.785, 36.818 ± 8.250, 64.575±8.323, 76.898 ± 3.711) in control group and TCDD (5 nmol/L), TCDD (10 nmol/L) and TCDD (20 nmol/L) groups, respectively. The expressions of vimentin protein were (0.527 ± 0.112, 0.781 ± 0.095, 0.284 ± 0.046, 0.216 ± 0.040) and fluorescence intensities were (63.672±6.135, 82.632 ± 4.474, 52.608±7.525, 42.664 ± 7.659). Compared with the control group, the low-dose experimental group (5 nmol/L) had a decrease in CK-19 and an increase in vimentin; the high-dose experimental group (10 nmol/L, 20 nmol/L) had an increase in CK-19 and a decrease in vimentin, and the expression difference was statistically significant ( P<0.05), while there was no statistical significance among high-dose groups ( P>0.05). Conclusions:EMT process of MEE was identified in vitro and was a spontaneous procedure. TCDD-induced cleft palate may be related to the inhibition of the EMT process in MEE and with the increased dose of TCDD, the effects of EMT inhibiton were sustainable.

Objective:To explore the role of epithelial-mesenchymal transition(EMT) in fusion of the secondary palatal shelves to form the intact secondary palate induced by 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD).Methods:Twelve C57BL/6 J pregnant mice on gestation day (GD) 10.5 were divided into two groups: one group was conducted through gastric tubes with one dose of 28 μg/kg TCDD (experimental group) and the other group was operated through gastric tubes with equal volume corn oil (control group). Embryos were removed by cesarean section from pregnant mice during the palatal formation stage (GD 15.5) and the morphology of palatal tissue was observed. Primary media edge epithelial(MEE) were divided into experimental group and control group. MEE were treated with medium containing TCDD, 5 nmol/L, 10 nmol/L, 20 nmol/L and normal medium respectively. The expression of cytokeratin 19(CK-19) protein and vimentin protein in MEE were detected by immunofluorescence laser confocal microscopy and Western blotting after 72 hours. Statistical comparisons were made using one-way ANOVA.Results:A total of 36 fetuses were obtained in the experimental group, including 3 dead fetuses and absorbed fetuses. The incidence of cleft palate was 100% (33/33); the incidence of complete cleft palate was 84.8% (28/33), and the incidence of partial cleft palate was 15.2% (5/33); 40 fetuses were obtained in the control group, including 2 dead fetuses and resorbed fetuses, and the incidence of cleft palate was 0 (0/38). After 72 hours, the shape of MEE changed from uniform pebble-like to star-like or irregular shape with pseudopodia. The expressions of CK-19 protein were(0.739 ± 0.120, 0.483 ± 0.023, 1.007 ± 0.109, 1.086 ± 0.145) and fluorescence intensities were (53.384±5.785, 36.818 ± 8.250, 64.575±8.323, 76.898 ± 3.711) in control group and TCDD (5 nmol/L), TCDD (10 nmol/L) and TCDD (20 nmol/L) groups, respectively. The expressions of vimentin protein were (0.527 ± 0.112, 0.781 ± 0.095, 0.284 ± 0.046, 0.216 ± 0.040) and fluorescence intensities were (63.672±6.135, 82.632 ± 4.474, 52.608±7.525, 42.664 ± 7.659). Compared with the control group, the low-dose experimental group (5 nmol/L) had a decrease in CK-19 and an increase in vimentin; the high-dose experimental group (10 nmol/L, 20 nmol/L) had an increase in CK-19 and a decrease in vimentin, and the expression difference was statistically significant ( P<0.05), while there was no statistical significance among high-dose groups ( P>0.05). Conclusions:EMT process of MEE was identified in vitro and was a spontaneous procedure. TCDD-induced cleft palate may be related to the inhibition of the EMT process in MEE and with the increased dose of TCDD, the effects of EMT inhibiton were sustainable.