Jagged 1 is Necessary for Palatal Arterial Development

Abstract

ProblemPalatal development is a complex process of growth, elongation, and fusion of paired palatal shelves. We hypothesize that arterial formation is necessary for normal palatal growth and development. Alagille's syndrome, a recently categorized genetic syndrome, is linked to genetic mutations in Jagged 1, a Notch signaling ligand necessary for vascular development. The cranial neural crest (CNC) cells are a well known cell population crucial in palate formation. To test our hypothesis, we have selectively removed Jagged 1 in the CNC population.MethodsWe identified the normal pattern of Jagged 1 expression in the palate using in situ hybridization and immunohistochemistry. We selectively removed Jagged 1 from the craniofacial mesenchyme using Cre‐Lox technology, mutant Wnt1‐cre Jagged 1 f/f selective knockouts. Mutant embryos were harvested at e13, e14, and e15 (critical time points in palatal development). To visualize the vascular development, we used platelet endothelial cell adhesion molecule (PECAM) antibody staining and utilized immunoflouresence with confocal microscopy.ResultsJagged 1 gene and protein expression was found throughout the midface and palate. The expression of Jagged 1 was concentrated in the perivascular tissue in the palatal mesenchyme. As palatal development occurs, there is a concomitant increase in Jagged 1 expression. Wnt1‐cre Jagged1 f/f mice were found viable. However, the mutant mice died in the neonatal period secondary to severe midface hypoplasia. Mutant mice had a significantly hypoplastic osseous palate and irregularly spaced palatal rugae. Examination of e15 mutant palatal shelves, using PECAM immunoflouresence and confocal microscopy, demonstrated a complete absence of mature vasculature.ConclusionJagged1 is required for palatal vascular development. The absence of Jagged1 in the CNC leads to severe palatal hypoplasia and neonatal death.SignificanceCleft lip and palate is the most common craniofacial congenital deformity occurring in 1:1000 live births. Clefting in conjunction with vascular syndromes, such as Alagille's, is a common observation.