HIRA is essential for the development of gibel carp

HIRA is one of the chaperones of histone H3.3. Mutation of Hira results in embryonic lethality in mice, suggesting a critical role in embryogenesis. However, Hira-mutated Drosophila may survive to adults, indicating that it is dispensable in Drosophila development. The role of Hira in fish development is unknown. In this study we first investigated the expression of Hira during embryogenesis of gibel carp (Carassius auratus gibelio) by whole-mount in situ hybridization. We found that Hira signal appeared ubiquitously in the early embryos. After gastrulation, it appeared mainly along the anterior-posterior axis, including the tail bud. In hatching period, the signal was detected in head, heart, and the endoderm region on the back of yolk. Then by microinjection with morpholino-HIRA at the beginning of development, we observed delayed gastrulation and abnormal somitogenesis in gibel carp embryos. The HIRA morphants exhibited short trunk, limited yolk extension, and twisted tail. Most of the mutants died during embryogenesis or shortly after hatching. The rest of the HIRA morphants could survive to larvae but with severe defects in organogenesis. These data suggest that HIRA may be essential for the development of gibel carp, and this function is conserved in vertebrates.