The Genetic Basis Of Inbreeding Avoidance

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The Genetic Basis Of Inbreeding Avoidance

http://www.medicalnewstoday.com/articles/88288.php

A new study appearing online on November 8th in Current Biology, a

publication of Cell Press, offers new insight into how wild house

mice avoid mating with their relatives. The mice rely on a diverse

set of specially evolved proteins in their urine, called major

urinary proteins (MUPs), to identify relatives and avoid mating with

them.

Mating between close relatives is avoided in many animals because it

can lead faulty, otherwise hidden (or recessive) traits that are

shared between them to surface in their offspring, a phenomenon

known as inbreeding depression, the researchers explained.

" Mice use these variable proteins as a kind of genetic barcode that

normally differs between individuals, " said Jane Hurst of the

University of Liverpool. " Animals with the same sets of proteins can

recognize each other as relatives, and so avoid mating with each

other. It is not a perfect system -- some close relatives will not

share the same urine proteins. However, by simply checking the match

between their own urine proteins and those of any animal they meet,

they will be able to identify many of their closest relatives, even

if they have never met them before. "

The researchers found no evidence in the current study that a gene

family known as the major histocompatibility complex (MHC) -- which

has earlier been shown to influence individual scent in a broad

range of vertebrates -- plays a role in the mate choices of wild

mice. The MHC is an extremely variable set of genes that allows the

immune system to identify and defend the body against foreign

invaders.

Previous studies in humans and in laboratory mice had implicated the

MHC in scent recognition. For instance, " T-shirt-sniffing studies " --

experiments in which people are asked to sniff smelly shirts and

say which body odor they " prefer " -- showed that even humans, with

their relatively poor sense of smell, tend to like the odor of

individuals that have different MHC genes from their own, Hurst

said. Studies in mice also found that animals prefer mates with MHC

genes different from their own.

In the new study, the researchers let wild mice breed in outdoor

enclosures, and they used parentage testing on the offspring to

determine which animals had mated with each other.

" Surprisingly, we found that the MHC played no role in inbreeding

avoidance at all, " said study collaborator Amy Sherborne, also of

the University of Liverpool. " Instead, another specialized set of

proteins, which are produced at high concentration in mouse urine,

signal relatedness through their scent. It is these proteins that

allow animals to avoid mating with their close kin. "

The results of the new study might differ from previous findings in

mice because most of those studies were conducted in artificially

inbred, laboratory mice that were genetically identical except for

their MHC genes, Hurst said. " In dramatic contrast to wild mice,

[laboratory mice] do not have individually variable MUP patterns in

their urine, " Hurst said. " So no one working on lab animals would

have known that they were important. "

" This study, the first to examine wild animals with normal variation

in MHC, MUP, and genetic background, demonstrates that mice use self-

referent matching of a species-specific signal to avoid inbreeding, "

the researchers concluded. The finding suggests that " recognition of

close kin as unsuitable mates may be more variable across species

than a generic vertebrate-wide ability to avoid inbreeding based on

MHC. "