LAUSR

Putting vertebrate development on hold Suspended animation is an often-used device in science fiction, but it also exists in several forms in nature: hibernation, torpor, and diapause. Hu et al. studied diapause in the African turquoise killifish, a vertebrate model system (see the Perspective by Van Gilst). They found that diapause protects a complex living organism without trade-offs for future growth, fertility, and even life span. Diapause is actively regulated, with a dynamic switch to specific Polycomb complex members. One Polycomb member, CBX7, is critical for the regulation of organ genes and is involved in muscle preservation and diapause maintenance. This work illuminates the mechanisms that underlie suspended life. Science, this issue p. 870; see also p. 851 In fish, a type of suspended animation that occurs under extreme environmental conditions involves a Polycomb regulatory mechanism. Diapause is a state of suspended development that helps organisms survive extreme environments. How diapause protects living organisms is largely unknown. Using the African turquoise killifish (Nothobranchius furzeri), we show that diapause preserves complex organisms for extremely long periods of time without trade-offs for subsequent adult growth, fertility, and life span. Transcriptome analyses indicate that diapause is an active state, with dynamic regulation of metabolism and organ development genes. The most up-regulated genes in diapause include Polycomb complex members. The chromatin mark regulated by Polycomb, H3K27me3, is maintained at key developmental genes in diapause, and the Polycomb member CBX7 mediates repression of metabolism and muscle genes in diapause. CBX7 is functionally required for muscle preservation and diapause maintenance. Thus, vertebrate diapause is a state of suspended life that is actively maintained by specific chromatin regulators, and this has implications for long-term organism preservation.