Gene expression patterns during palatal shelf fusion

Abstract

Abstract Introduction: Cleft palate is a common disorder that occurs when there is failure of the palatal shelves to fuse during normal development. The genes mediating normal palatal fusion are largely unknown. Methods: We harvested mRNA and performed microarray (∼40,000 element) analysis of mice palatal shelves at timepoints before, during, and after palatal fusion (E13.5, E14.5, and E15.5). IHC was performed using standard techniques. Results: Replicates clustered together by time point indicating consistency between harvests. Hox-7A, a gene implicated in both mice and humans as important to cleft lip and palate formation was upregulated during palatal fusion. Several retinoic acid responsive genes such as Stra6 were also upregulated during fusion. Furthermore, we found the homeobox gene Lim-1 to be upregulated during palatal fusion. To confirm our microarray findings of differential expression of LIM-1 during palate formation, we performed immunohistochemistry. During early secondary palate formation (E12.5), as the shelves are pointing inferiorly, LIM-1 expression was maximal at the lateral wall and tip of the palate epithelia. Interestingly, minimal expression was noted in the medial palatal wall epithelia. LIM-1 expression regressed with epithelial to mesenchymal transition at the midline epithelial seam as the approaching palates fuse on E14.5. LIM-1 expression was completely abolished within the palate mesenchyme by E16.5 after completion of fusion. Conclusions: We have identified novel genes that may be involved in normal palatogenesis using large-scale microarray analysis. These data may be a valuable resource for other researchers attempting to elucidate the complex dysregulation of expression cascades involved in cleft palate formation.