lab miceIn a surprising twist of discovery, scientists at a research lab devoted to the study of taste and smell may have stumbled upon an environmental link to male infertility. Lead scientist Bedrich Mosinger is a geneticist specializing in the science of taste at the Monell Chemical Senses Center in Philadelphia. Monell is the world’s only independent, non-profit institute devoted to the scientific study of the senses of taste and smell.

Mosinger considers the sense of taste instrumental to human evolution. A bitter taste often signals poison, for example, while sweetness signals a calorie-dense food that provides sustenance. These distinctions may not seem so remarkable today but would have meant the difference between life and death to our evolutionary ancestors.

When food touches the tongue, genetic activity activates taste receptors that signal the brain. The tastes of sweet and of umami, the sense of deliciousness, activate genes on the tongue that are also active in the male testes and sperm.

Mosinger likens the process of taste to a microphone and its cord: the taste receptor in the mouth is the microphone and the protein signaling the brain is the cord. The microphone / taste receptor is controlled by a gene identified as TAS1R; the protein, gustducin, is activated by gene GNAT3.

Mosinger wanted to know what the long-term genetic effect would be to the sense of taste of lab mice when these two genes were rendered inactive, effectively eliminating both microphone and cable. The genes were deactivated and the mice allowed to mate.

Nothing happened. The male mice proved to be sterile after deactivation of both genes.

One class of drugs - fibrates - prescribed to treat high cholesterol levels also blocks expression of TAS1R, as do phenoxy-based herbicides. Mosinger wonders what would be the outcome in human men if exposure to these drugs or herbicides coincides with something that inhibits production of the GNAT3 gene. Would the men then be sterile?

Dennis Drayna is unaware of any environmental substances that affect function of GNAT3. Drayna, a human geneticist for the National Institutes of Health, says the surprising outcome of the Monell study reinforces the real power of science even if the findings may never lead to a clear link between the study and male infertility.

Even if that happens, all is not lost. While others strive to find a better mousetrap, Monell’s curious findings might prove to be better still. It could lead to effective rodent birth control.

Meanwhile, full details of the Mosinger / Monell study can be found in the latest online issue of the Proceedings of the National Academy of Sciences.

Source: Mosinger, Bedrich, et al. "Genetic Loss or Pharmacological Blockade of Testes-Expressed Taste Genes Causes Male Sterility." Proceedings of the National Academy of Sciences. 3 Jun 2013. Web. 5 Oct 2013.