Title: Rescue Craniofacial Defects in Pax9 Deficient Mice Targeting Wnt Signaling Pathway
Shihai Jia (Presenter)
University of Utah
Jing zhou, University of Utah
John Bonds, Texas A&M University
Christopher Fanelli, University of Utah
Yinshen Wee, University of Utah
Pascal Schneider, University of Lausanne
gabriele mues, Texas A&M University
Rena D'Souza, University of Utah
Objectives: PAX9 is known to be associated with human craniofacial abnormalities such as cleft palate and tooth agenesis. Homozygous mice lacking Pax9 gene die at birth with cleft palate and tooth developmental arrest at bud stage. The objective of this study is to use this mouse model to explore the molecular relationship of Pax9 and Wnt signaling pathway in palate development. This study will provide new molecular mechanism of Pax9-Wnt signaling in regulating palate formation and candidates for the therapeutic treatment of the patients with craniofacial defects.
Methods: To increase Wnt signaling activities, the Dkk inhibitors WAY-262611 and IIIc3a were injected into pregnant Pax9+/- mice which had been mated with Pax9+/- males for Pax9-/- embryos. The inhibitors were injected through the tail vein of Pax9+/- pregnant mice daily with two dosages of 12.5 mg/kg and 25 mg/kg. Time course of the treatments are from embryonic day E10.5 to E14.5, which covered the early developmental stages of palate and tooth formation. Further Dkk1 expression was reduced through genetic intercross, one allele of Dkk1 was conditional deleted in Pax9 deficient palatal mesenchyme in the compound mutant of Pax9-/-Dkk1f/+;Wnt1Cre embryos. The phenotypes were analyzed at E18.5 via whole mount view and HE stained sections.
Results: WAY-262611 and IIIc3a treatments rescued cleft palate defects in Pax9-/- embryos with a range of ratio from 37.5% to 100%. The secondary palate was fused in Pax9-/-Dkk1f/+;Wnt1Cre embryos. However, correction of the palatal defects did not prevent postnatal death of Pax9-/- pups. Neither WAY-262611 nor IIIc3a had negative effects on the mother or control littermates.
Conclusions: Restoring Wnt signaling activity by reducing the inhibition of Dkks, through small molecule treatment or genetic interaction, the secondary palates of Pax9-/- embryos were fused. The small molecule WAY-262611 and IIIc3a could rescue the craniofacial defects in Pax9-/- embryos without any overt associated toxicities, suggesting that they have the potential to be used as safe therapeutic drugs for treating developmental abnormalities related to Pax9 and Wnt signaling deficiency. The up regulation of Wnt pathway activity seems to have an important function of Pax9 during palate development.