Stefan Janusz reports :: April 2007

The spread of agricultural pesticides and fungicides into the natural environment has worried the green-minded for decades; recently both have been implicated as hormone disruptors, affecting reproduction in humans and animals. Used to excess, agricultural chemicals can drain off fields into rivers, corrupting a greater span of environments and food sources. Now, a team at the University of Texas at Austin have investigated the male hormone-disrupting effects of the fungicide vinclozolin in populations of mice. Vinclozolin causes DNA methylation in the region of mammal genome called the Major Histocompatability Complex (MHC), which affects, among other things, the normal functioning of the sexual reproductive and immune systems. The alteration can then be passed on to subsequent generations.

Males whose MHC has been altered by methylation exhibit low sperm count and mobility, and in later life, immune abnormalities, kidney and prostrate disease, and cancer. Males are also the usual dispersing sex in mammals, which means that this epigenetic imprint could also cross from one population into another. It was shown that female mice whose great-grandparents was exposed to vinclozolin preferred males with no personal history of exposure, but that males with an altered MHC displayed no preference between exposed or untainted females. This is the first time that environmentally-induced epigenetic factors have been shown to be a determining force in evolution. The work was published in the Proceedings of the National Academy of Science