FOXD1 Duplication Causes Branchial Defects and Interacts with the TFAP2A Gene Implicated in the Branchio-Oculo-Facial Syndrome in Causing Eye Effects in Zebrafish

Branchio-oculo-facial syndrome (BOFS) is a rare disorder characterized by maldevelopment of the first and second branchial arches, skin defects, facial dysmorphism, auricular, ophthalmological and oral abnormalities. A high clinical variability has been reported. Recently, mutations in TFAP2A were found to underlie this condition. A small duplication on 5q13 was detected in 2 family members with mild BOFS features. Molecular cytogenetic delineation of the duplication demonstrated that only 7 genes are affected: LOC100289045, RGNEF, UTP15, ANKRA2, FUNDC2P1, BTF3 and FOXD1. The latter is expressed in the developing branchial arches and involved in cranio-facial development. Zebrafish embryos with combined inhibition of the expression of foxd1l and tfap2a show optic axis defects. We identified a novel locus associated with a mild BOFS-like phenotype. The functional in vivo experiments suggest an interaction between FOXD1 and TFAP2A.