Cas9-mediated excision ofNematostella brachyurydisrupts endoderm development, pharynx formation, and oral-aboral patterning

The mesoderm was a key novelty in animal evolution, though we understand little of how mesoderm arose. brachyury, the founding member of the T-box gene family, is a key gene in chordate mesoderm development. However, the brachyury gene was present in the common ancestor of fungi and animals, long before mesoderm appeared. To explore ancestral roles of brachyury prior to the evolution of definitive mesoderm, we excised the gene using CRISPR/Cas9...