Genetics can get really weird sometimes, particularly when two seemingly unrelated traits are connected by a common thread. In a recent and completely unexpected finding, scientists linked male sterility to a genetic inability to taste sweet and savory foods.

It's actually quite rare for cells to use just one signalling pathway. Evolution doesn't like to waste resources, so the body often combines these pathways to perform dual, but separate, tasks.


For example, scientists have observed that the signalling pathway that's involved in giving our tongues a sense of taste, namely the taste receptors responsible for sugar and amino acid sensing (i.e. umami — like the savory sensation we get from eating parmesan cheese), is strongly linked to testicles and sperm. But they were left scratching their heads as to why there should be any association at all.

While studying the sense of taste in mice, research scientist Bedrich Mosinger inadvertently stumbled upon the answer. His team was looking at three related receptors called TAS1Rs which signal through a protein called GNAT3. To do their work, the team was trying to create mice that were mutant in both GNAT3 and TAS1R3 — but they couldn't do it.

To their surprise, the genetic absence of both TAS1R3 — a component of sweet and amino acid taste receptors — and GNAT3 led to sterility in male mice.


Image: The strange dark blotches are sperm — but with no tails.

"Sperm formation in animals without functional TAS1R3 and GNAT3 is compromised, with malformed and immotile sperm," write the authors in their study.


It's not entirely clear why the sperm are so malformed, but it's clear that they're unable to mature in the absence of these crucial chemical triggers.

Mosinger and his team now speculate that TAS1R3 and GNAT3 activators may help infertile men. And though not discussed in the study, the insight could theoretically lead to novel male birth control techniques — but at the potential price of not being able to sense sweet and savory foods!

Read the entire study at PNAS: "Genetic loss or pharmacological blockade of testes-expressed taste genes causes male sterility."


Image credit: Associated Press.