MICE leave a genetic calling card in their urine that can be 鈥渞ead鈥� when sniffed by other mice.
The calling cards are tiny protein fragments unique to each individual mouse, which probably reveal details about gender, identity and genetic kinship. 鈥淭hey provide information about the individual as a whole and their genetic make-up,鈥� says Thomas Boehm of the Max Planck Institute of Immunobiology in Freiburg, Germany, and member of the team that reported the discovery (Science, vol 306, p 1033).
The fragments are part of a cell surface protein called the major histocompatibility complex class I, which allows the immune system to recognise the cells as 鈥渟elf鈥� and so not attack them. The protein fragments end up in urine when cells die.
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Now Boehm and his colleagues have shown that the fragments can influence mouse behaviour. Pregnant female mice are known to spontaneously abort their pups if exposed to urine from a male who is not the father 鈥� probably because a foreign male will kill the pups anyway. The team showed that females could be tricked into aborting by contaminating urine from the biological father with artificially manufactured copies of protein fragments from a different male.