Meeting Abstract
Members of the T-box (Tbx) gene family, founded by Brachyury class genes and well known for critical roles in gastrulation and notochord development, also play important roles in tissue and neural development including the development of heart and limbs in many vertebrate and invertebrate species. We employed genome and transcriptome information to better understand the role these genes play in the complex “multistage” development of medusozoan Cnidaria which involves dramatic metamorphosis from planula to polyp and and polyp to medusa. We identified 8 Tbx genes in Aurelia sp.1, including Brachyury-a, Brachyury-b, Tbx2/3a, Tbx2/3b, Tbx4/5a, Tbx4/5b, Tbx20 and Tbx1/10. Our results suggested evolution of a separate medusozoan specific Brachyury homologue, and additional cnidarian specific Tbx duplication. RNA-seq data revealed the differential expression pattern of 7 Tbx genes across planula, polyp, strobila, ephyra and juvenile life history stages of Aurelia. Two Brachyury and two Tbx2/3 are highly expressed in planula stage, potentially relating to planula neural development and apical organ formation. Tbx1/10 and two Tbx4/5 are highly expressed during strobilation, the initial phase of medusa formation, when rhopalial neurons and muscle cells differentiate from their progenitor cells and the rhythmic bell-contraction system develops. In chordates, Tbx1/10 is crucial for muscle differentiation and Tbx4/5 controls cardiac conduction system patterning including the development of the beat generating node. We hypothesize that these genes in Aurelia may similarly regulate the node driven contraction and neuromuscular differentiation in the development of the swimming ephyra/medusa stage initiated during strobilation.
