Scientists from the University of North Carolina, US, have discovered a gene that is linked to whether female embryos survive or not. The gene, called eed, is thought to keep the X chromosome that is inherited from the father (females have two X chromosomes) inactive during early embryo development. The gene also keeps many of the other genes on this chromosome switched off during the first stages of development of the placenta.
The scientists, who carried out the research on mouse embryos, have found that female embryos that do not have a working eed gene do not survive because the placenta does not develop properly. They also believe that a functioning eed gene causes cells in the embryo to organise themselves correctly, and that if the gene does not function properly, many problems, such as the development of leukaemia, skeletal abnormalities or other birth defects, can occur.
Meanwhile, scientists led by Jonathan Tilly of the Massachusetts General Hospital in Boston, US, have found that a 'killer gene' in women can be triggered by smoking. The gene, when activated, undermines fertility, by inducing the menopause prematurely. Chemicals in tobacco, known as polycyclic aromatic hydrocarbons (PAH), 'turn on' the gene, known as Bax, in egg cells. Bax is thought to cause the degeneration and eventual death of those cells. Both studies were published in the journal Nature Genetics.