Scientific News
Gender-bending mice
Cellular reprogramming
March 2010 - EMBL researchers have uncovered the gene responsible for keeping females female.
In humans and most other mammals, an individual’s sex is determined by its sex chromosomes: females have two X chromosomes, and males have an X and a Y. Scientists had long assumed that the female pathway – the development of ovaries and all the other female traits – was the default: if an embryo had a gene called Sry, which is located on the Y chromosome, it would develop into a male; if not, then the result would be a female.
A gene called Foxl2, which is located on a non-sex chromosome and therefore present in both sexes, was known to play an important role in the female pathway, but its precise function remained elusive. When Mathias Treier’s group turned off this gene in the ovaries of adult female mice, they found that cells in the ovaries turned into cells typically found in testes.
“We were surprised,” saysMathias, who collaborated with colleagues from the MRC’s National Institute forMedical Research (NIMR), inMill Hill, UK, for the study. “We expected the mice to stop producing oocytes, but what happened was much more dramatic: somatic cells which support the developing egg took on the characteristics of cells which usually support developing sperm, and female hormone- producing cells switched to the male type.” This challenges the long-held assumption that the development of female traits is a default pathway, showing that the male pathway needs to be actively suppressed, and also grants a valuable insight into how sex determination evolved.
These findings will have wide-ranging implications for reproductive medicine and may help to treat sex differentiation disorders in children or understand the masculinising effects of menopause on some women. The study is discussed by Mathias in a Cell ‘PaperFlicks’ video on YouTube