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Friday, July 12, 2013

Taste receptors in the testes

A few years ago, researchers were surprised to find taste buds in lungs. Apparently, that’s not the only unusual place to find taste receptors. They’re also present in testes and sperm. Bedrich Mosinger and his colleagues from the Monell Chemical Senses Center bred some special mice to investigate why that’s so.

TAS1R receptors are responsible for detecting sugar (sweet) and umami (amino acids, or protein). That’s a useful function when the receptors are in the mouth or even in the gastrointestinal tract. After all, nutrition and taste are closely connected. An operating sense of taste dictates not only what animals choose to eat but also how much they eat. But what would taste receptors be doing in testes or sperm?

Well, we still don’t know. We do know that they play some critical role in reproduction because male mice that lack these testes taste receptors are sterile. Admittedly, there weren't a lot of data points for this because the scientists were only able to breed two male mice that were completely lacking the taste receptors, despite many tries. Both of those mice seemed to be perfectly healthy and ordinary, apart from being sterile. 

However, when the researchers bred mice to have a human version of TAS1R, they could reversibly sterilize the mice by feeding the mice compounds that block those receptors. Thus, not only did the taste receptors have to be present, but they also had to be functional in order for the male mice to reproduce.

This is significant because compounds that are chemically similar to the ones the researchers used to block the taste receptors are currently used in anti-lipid medications for humans and in herbicides. The authors speculate that these compounds may be affecting human male fertility.

Mosinger B, Redding KM, Parker MR, Yevshayeva V, Yee KK, Dyomina K, Li Y, & Margolskee RF (2013). Genetic loss or pharmacological blockade of testes-expressed taste genes causes male sterility. Proceedings of the National Academy of Sciences of the United States of America PMID: 23818598.

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