| Summary: | The correct formation of the aortic arch arteries depends on a coordinated and regulated gene expression profile within the tissues of the pharyngeal arches. Perturbation of the gene regulatory networks in these tissues results in congenital heart defects affecting the arch arteries and the outflow tract of the heart. Aberrant development of these structures leads to interruption of the aortic arch and double outlet right ventricle, abnormalities that are a leading cause of morbidity in 22q11 Deletion Syndrome (DS) patients. We have recently shown that <i>Pax9</i> functionally interacts with the 22q11DS gene <i>Tbx1</i> in the pharyngeal endoderm for 4th pharyngeal arch artery morphogenesis, with double heterozygous mice dying at birth with interrupted aortic arch. Mice lacking <i>Pax9</i> die perinatally with complex cardiovascular defects and in this study we sought to validate further potential genetic interacting partners of <i>Pax9</i>, focussing on <i>Gbx2</i> which is down-regulated in the pharyngeal endoderm of <i>Pax9</i>-null embryos. Here, we describe the <i>Gbx2-</i>null cardiovascular phenotype and demonstrate a genetic interaction between <i>Gbx2</i> and <i>Pax9</i> in the pharyngeal endoderm during cardiovascular development.
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