How Heat Changes Fish Gender

Nile tilapia, a type of fish, can change sex based on water temperature. This might sound strange, but it's a real phenomenon called temperature-dependent sex reversal (TSR). Scientists have been trying to figure out how this happens at the molecular level. It's not just about the fish changing sex; it's about understanding the tiny changes inside the fish's cells that make this possible. The process starts with temperature changes affecting genes. When the water gets warmer, certain genes that promote male traits in fish become more active. These genes are amh, dmrt1, and gsdf. At the same time, genes that promote female traits, like wt1a and foxl3, become less active. This shift is linked to changes in how DNA is packaged in the cell, specifically changes in something called histone methylation. One key player in this process is an enzyme called Kdm6bb. This enzyme helps remove certain chemical tags from histones, which are proteins that help package DNA. When the temperature rises, Kdm6bb becomes more active. This activity changes how genes are expressed, influencing whether the fish develops male or female traits. Researchers found that Kdm6bb works by including a specific part of its genetic instructions that wasn't known before. This part allows Kdm6bb to move into the nucleus of the cell, where it can do its job of removing those chemical tags. This discovery challenges an older idea about how Kdm6bb works and shows that the way the enzyme's instructions are read and where it goes in the cell are crucial for sex reversal. The study used advanced techniques to look at the fish's genes and how they change with temperature. By deleting the Kdm6bb gene and studying its effects, scientists confirmed its role in sex determination. This research provides a deeper understanding of how temperature can influence sex in fish, offering insights into the complex world of genetic regulation and sex determination.