Abstract 31: Irf6 Regulates The Wnt Signaling Pathway During Craniofacial Development Through The Regulation Of Dact Expression

Abstract

Purpose:IRF6 gene variants are associated with both syndromic and nonsyndromic cleft lip and palate (CLP). Irf6 is a transcription factor and its regulatory targets are beginning to be identified. We and others have shown that Irf6 is genetically required for palate development, conserved between human, mouse and zebrafish. It has been shown that a couple of Irf6 target genes are also required for palate development and gene variants are associated with CLP. We reasoned that additional genes important for CLP pathogenesis can be discovered by identifying Irf6 target genes in a robust global approach. Methods: We carried out ChIP-seq and RNA-seq in wildtype and irf6 mutants, integrated the resultant datasets, and identified dact1 as a transcriptional target of irf6. We utilized CRISPR-Cas9 technology to generate dact1, dact2 double mutant zebrafish. Detailed phenotypic analysis was performed. Results: Gene expression analysis of dact1 and dact2 detected co-expression with irf6 in the oral epithelium during early embryogenesis. Disruption of dact1/2 severely impaired craniofacial development where a dysmorphic palate structure formed, missing the median portion of the palate, a phenotype that is consistent with disrupted wnt signaling. Conclusions: We have identified dact1 as a transcriptional target of irf6. Dact1 is a known modulator of wnt signaling, but its requirement in craniofacial development was not previously described. We have uncovered a novel requirement of a Wnt regulator in craniofacial and palate development. This work is immediately clinically important in improving genetic diagnosis of CLP by recognizing DACT1 to be important, and opens up new pharmacologic approaches that modulate Dact1 and Wnt to mitigate cleft pathogenesis.