Joyce Chen ’23
As time progresses, all living organisms will age, decay, and perish. However, there are certain animal species that can halt their biological clocks and no longer develop. This state is known as diapause. The African Killifish are known organisms that can undergo diapause in order to survive unfavorable conditions, such as dry periods in the environment. Many of these fish remain in diapause for numerous months — some even surpassing their average lifespan of 5 months — without trade-offs for their future growth. Stony Brook University Professor Dr. Chi-Kuo Hu and a team of researchers at Stanford University aimed to investigate how diapause maintains the wellbeing of the African Killifish.
To determine which genes are upregulated and downregulated in diapause, the team analyzed the RNA transcripts in embryos during various stages of diapause. The patterns showcased the drastic changes in the RNA sequences. Genes linked to development, such as cell division, were mainly downregulated throughout or during the late stages of diapause. However, genes for muscle preservation and development were upregulated and then downregulated in the early and late stages, respectively. In addition, genes related to autophagy and metabolism were upregulated throughout the entirety of diapause, thereby proving that diapause is a highly active condition. The team conducted several additional experiments to further their understanding of gene regulation, one of which was on CBX7, a functioning member of a polycomb complex, or a family of proteins that participate in gene silencing. The team studied a wild-type embryo and a mutant embryo that lacked CBX7. They discovered that genes related to muscle preservation were downregulated and the UBE2H gene for muscle atrophy — a decrease in muscle size — was upregulated. Consequently, the CBX7 mutant embryos had deteriorating muscles and exited diapause early.
Dr. Hu and his team’s research showed that diapause is an active state and has upregulated genes that are needed for long-term muscle conservation. Hence, the organs are well-preserved and the fish can exit diapause without any biological trade-offs. Further studies are needed to see how a lack of CBX7 affects adult life by causing muscle defects.
 C.K. Hu, et al., Vertebrate diapause preserves organisms long term through Polycomb complex members. Science 21, 870-874 (2020). doi: 10.1126/science.aaw2601.
 Image retrieved from: https://cdn.pixabay.com/photo/2021/03/15/16/06/killi-6097346_1280.jpg