Endothelium is required for the promotion of interrenal morphogenetic movement during early zebrafish development

The adrenal cortex has a complex vasculature that is essential for growth, tissue maintenance, and access of secreted steroids to the bloodstream. However, the interaction between vasculature and adrenal cortex during early organogenesis remains largely unclear. In this study, we focused on the zebrafish counterpart of adrenal cortex, interrenal tissue, to explore the possible role of endothelium in the development of steroidogenic tissues. The ontogeny of interrenal tissue was found to be tightly associated with the endothelial cells (ECs) that constitute the axial vessels. The early interrenal primordia emerge as two clusters of cells that migrate centrally and converge at the midline, whereas the central convergence was abrogated in the avascular cloche (clo) mutant. Neither loss of blood circulation nor perturbations of vessel assembly could account for the interrenal convergence defect, implying a role of endothelial signaling prior to the formation of axial blood vessels. Moreover, as the absence of trunk endothelium in clo mutant was rescued by the forced expression of SCL, the interrenal fusion defect could be alleviated. We thus conclude that endothelial signaling is involved in the morphogenetic movement of early interrenal tissue.