Shar-pei wrinkles explained by dog geneticists

Just how did the Shar-pei get its famous wrinkled appearance?

Scientists who have analysed the genetics of 10 pedigree dog breeds believe they now have the answer.

Their research identifies 155 distinct locations in the animals' genetic code that could play a role in giving breeds their distinctive appearances.

In the Shar-pei, the team found differences in a gene known as HAS2 which makes an enzyme known to be important in the production of skin.

"There was probably a mutation that arose in that gene that led to a really wrinkly puppy and a breeder said, 'hey, that looks interesting, I'm going to try to selectively breed this trait and make more of these dogs'," explained Joshua Akey from the Department of Genome Sciences at the University of Washington, Seattle, US.

Small differences

The pedigree dog has become a fascination - and a remarkably useful research tool - for geneticists.

The domestication of the grey wolf more than 10,000 years ago, and the selective breeding that followed, has resulted in more than 400 breeds - each with a distinctive physique, coat colour and temperament.

The study compared the genetics of 10 pure-bred dog groups

These discrete populations give scientists the opportunity to compare and contrast the genetics of the different groups, making it easier to find the causes of specific traits.

"Man's best friend" is helping scientists locate the faulty genes that cause disease in both dogs and humans, as well giving a useful insight into how evolution works at a molecular level.

Dr Akey and colleagues studied 32 wrinkled and 18 smooth-coated Shar-peis and compared a specific stretch of their DNA with that of other breeds.

The team found four small, but significant, differences in the genetics of the two skin types of the Shar-pei versus the other breeds. These single nucleotide polymorphisms (SNPs), as they are called, were located in the HAS2 gene.

New targets

"HAS2 makes hyaluronic acid synthase 2, and it's an enzyme that makes hyaluronic acid, and that's one of the principal constituents of the skin," explained Dr Akey.

"There are rare human cases where there are mutations that lead to really severe wrinkling in humans, too.

"So, that suggested it was a good candidate to look at; and sure enough, when we sequenced it we saw that that gene explained wrinkling in Shar-peis," he told BBC News.

Science explained: What is a genome?

As well as giving insights into the Shar-pei, the research has also identified a raft of other locations in the dog genome that can now be investigated further to understand better why pedigree animals look the way they do.

"The thing that excites me most about our study is that in the last five years, five genes have been identified that contribute to this vast diversity in dog breeds," said Dr Akey.

"So our study found all five of those genes and then we found 150 new targets to explore. It's a powerful approach to look at the genetic legacy of selective breeding."

Dr Akey and colleagues report their findings in the Proceedings of the National Academy of Sciences (PNAS).

Sweden culls its resurgent wolves

Swedish hunters have begun culling wolves for the first time in 45 years after parliament ruled that numbers needed to be reduced again.

More than half the quota of 27 may have died on the first day alone with nine shot dead in Dalarna and up to nine killed in Varmland, Swedish radio says.

Hunters have until 15 February to complete the cull, which will leave Sweden with an estimated 210 wolves.

Some 10,000 hunters were reported to be planning to take part in the hunt.

Hunting in the county of Dalarna was halted as the county's individual quota was nine wolves.

Varmland's quota of nine "may also have been filled", the radio reported later on Saturday.

'Five injured'

In Dalarna, hunters reportedly injured another five wolves.

Every time a hunter shoots and hits a wolf he has to report it to the county authorities, so they can keep track of the local cull.

Earlier, hunters insisted there were measures in place to prevent them shooting too many.

"There's a lot of regulation, hunters have to check the quota every hour," Gunnar Gloersson, of the Swedish Hunters Association, told Swedish radio.

Nevertheless, the Swedish Society for Nature Conservation was critical of the decision to proceed with the cull, saying it was against EU legislation as the Swedish wolf population had not reached a healthy level.

A formal complaint was to be issued to the EU Commission, Swedish radio said.

The hunt is timed to end before the mating season, which begins in mid-February.

Snow vital

Wolves were hunted to near extinction in southern Scandinavia until a hunting ban was imposed in the 1970s.

Sweden and Norway have worked together to reintroduce the species to the forests along their border. When Norway culled some wolves in 2001, saying the population had spread too far, Sweden lodged a protest.

But the Swedish parliament recently decided there should be at most 210 wolves in Sweden.

Michael Schneider of the Swedish Environmental Protection Agency says that was the level last year, and since then more than 20 pairs of wolves have had pups.

"We have to remove this increase to keep the population at this level," he said.

Mr Gloersson, of the hunting association, said: "We have a lot of problems with wolves - in reindeer areas, with livestock, and for hunters they kill our valuable dogs."

"Since they came back we have to live with them, but we have to keep their numbers down."

He said the success of the cull would depend on the weather.

"The only easy way to hunt wolves is if we have snow, so the hunters can track them on the snow. If we don't have snow I don't think we'll even be able to reach the quota of 27 wolves," he said.