A critical role for myoglobin in zebrafish development.

The globin family, including hemoglobin, myoglobin, neuroglobin and cytoglobin, plays an important role in oxygen storage and delivery. Myoglobin has been shown to be necessary for cardiac function during development, but no information is currently available on the developmental regulation of myoglobin gene expression during embryogenesis. In this study, we used whole mount in situ hybridization to visualize myoglobin mRNA expression during zebrafish development. Our results show for the first time the spatial and temporal gene expression pattern of myoglobin during embryogenesis. Myoglobin was expressed as a maternal RNA and ubiquitous expression was observed until the end of gastrulation. At later stages of development, we discovered novel expression domains for myoglobin, including several non-muscular ones. Environmental stresses, like low oxygen tension (hypoxia) can lead to a developmental delay in zebrafish embryos. We show here that hypoxic stress induces myoglobin expression in skeletal muscle cells of anterior somites and in the dorsal aorta of zebrafish larvae. Finally, we analyzed the role of myoglobins in development by targeted gene knock-down. Silencing myoglobin in zebrafish embryos with gene-specific morpholinos led to a dose dependent curvature, vascular defects, enlarged pericardia and reduction of the gut. In conclusion, our results indicate that myoglobin plays a crucial role in zebrafish development and is important for angiogenesis and gut development.