Title: Molecular and Cellular Mechanisms Underlying Cleft Palate in Trps1-/- Mice
Kah Yan Cho, University of Pittsburgh
Daisy Monier, University of Pittsburgh
Dobrawa Napierala (Presenter)
University of Pittsburgh
Objectives: TRPS1 gene codes for the transcriptional repressor TRPS1, which works by binding GATA sequences. Heterozygous TRPS1 mutations lead to an autosomal dominant disorder named trichorhinophalangeal syndrome (TRPS). Key features of TRPS involve hair, skeletal, dental and craniofacial abnormalities, including some cases of cleft palate. Mice with heterozygous Trps1 mutation (Trps1+/- mice) demonstrate hair, skeletal and high-arched palate phenotype similar to TRPS patients. Interestingly, homozygous mutant mice (Trps1-/- mice) exhibit cleft palate. Our objectives were to delineate the role of Trps1 during palatogenesis and identify the mechanism of cleft palate in Trps1-/- mice.
Methods: To determine the ability of Trps1-/- palatal shelves to fuse, 24h ex vivo culture of palatal shelves from wildtype (WT) and Trps1-/- E13.5 mice embryos was performed. Immunohistochemistry was used to delineate expression of Trps1 in WT mice at E12.5, E13.5 and E14.5. Chondroitin sulfate proteoglycan (CSPG), Tgfβ3, Twist1, and β-catenin, all of which play significant roles in palatal fusion, were analyzed by immunohistochemistry in E14.5 WT and Trps1-/- mice.
Results: The initiation of the palatal shelf fusion was observed in all cultured WT palates (n=11) but in none of the Trps1-/- palates (n=11). At earlier embryonic stages (E12.5 and E13.5), Trps1 was expressed in palatal shelf epithelium and maxillary mesenchyme. Trps1 expression was greater in posterior palatal epithelium than in anterior palate. At E14.5, Trps1 was expressed within the palatal shelves epithelium, specifically the medial edge epithelium (MEE), and maxillary mesenchyme. CSPG, Tgfβ3, β-catenin and Twist1 were detected at E14.5 WT MEE as well, but the expression of each protein was lost in Trps1-/- palatal shelves.
Conclusions: Our findings indicate that Trps1 is necessary for palatal fusion and expression of other proteins important for this process. The presence of Trps1 in maxillary mesenchyme also suggests that Trps1 plays additional roles in palatal development in addition to fusion.