miRNA z-bio 2021-08-03 337

　　There are many obvious differences between men and women, and scientists have long known that these differences are caused by genetic differences buried deep in our DNA. In the past, most research focused on understanding how genes encoding proteins act as sex determinants. However, scientists at the Cold Spring Harbor Laboratory (CSHL) found that micrornA (miRNA) also plays an important role in distinguishing male and female tissues in fruit flies.

　　miRNA is a small segment of RNA that fine-tunes the activation of one or several protein-coding genes. miRNAs can also silence their target genes, and in the process, coordinate complex genetic processes (the basis of development).

　　Researchers at the Cold Spring Harbor Laboratory describe how miRNAs play a role in the sex differences in fruit flies. You may never notice, but males and females in fruit flies are significantly different, just like other animals. For example, females are more than 25% larger than males, and have lighter pigmentation and more abdominal segments.

　　The lead author of this study, Dr. Delphine Fagegaltier, a professor at the Cold Spring Harbor Laboratory, and Greg Hannon, a researcher at the Howard Hughes Medical Institute. It is determined that the miRNAs in male and female fruit flies are different. "We found that differences in miRNAs are important in shaping the structure that distinguishes the two sexes," Fagegaltier said. "In fact, miRNAs regulate proteins that are sex determinants during development."

　　The research team found that miRNA is essential in sex determination, even if the animal is an adult. "They send a signal to allow germ cells (that is, sperm and egg cells) to develop to ensure fertility," Fagegaltier explained. "Deleting a miRNA from mature cells can cause infertility in adult flies." More importantly, these flies begin to produce male and female sex determining factors. "In a sense, once they lose this miRNA, the fruit flies become hermaphrodite," Fagegaltier said. "It is surprising that such a small gene can have such a big impact on gender identity."

　　Some miRNA studies, such as let-7, have been preserved in evolution due to their utility. Humans and many other animals carry their versions. "This may be just the tip of the iceberg," Fagegaltier said. "There may be more miRNAs at the cell and tissue level that regulate gender identity, but regarding these differences in humans and how they promote developmental defects and diseases, we still have a lot to learn about."