New Genetic Basis Discovered for Sex Determination: miRNAs

There may be a new genetic basis for sex determination. Scientists have found that a subset of very small genes encoding short RNA molecules, called microRNAs (miRNAs) play a key role in differentiating males and females.

Men and women differ in plenty of obvious ways, but the genetic differences buried within our DNA underlie these distinctions. Yet it seems like that it's not only DNA that plays a role; miRNA also shows differentiation.

A miRNA is a short segment of RNA that fine-tunes the activation of one or several protein-coding genes. In fact, miRNAs are able to silence the genes they target and orchestrate complex genetic programs that are the basis of development.

In this case, the researchers examined fruit flies. They found distinct miRNA populations in male and female flies. Not only that, but the scientists discovered that the differences in the miRNAs were important in shaping the structures that distinguished the two sexes and regulated the very proteins that acted as sex determinants during development.

"They send signals that allow germ cells, i.e., eggs and sperm, to develop, ensuring fertility," said Delphine Fagegaltier, lead author of the new study, in a news release. "Removing one miRNA from mature, adult flies causes infertility." In fact, the removal actually causes the flies to begin to produce both male and female sex-determinants. This means that the flies become both male and female at the same time.

"This is likely the tip of the iceberg," said Fagegaltier. "There are likely many more miRNAs regulating sexual identity at the cellular and tissue level, but we still have a lot to learn about these differenes in humans, and how they could contribute to development defects and disease."

The findings are published in the journal Genetics.