New Zealand initiated this collaboration which has lasted for four years. It was at a conference in 1998 that researchers, from Joël Gellin's group at the Laboratoire de Génétique in Toulouse, France, presented the EU project Bio4-CT98-0237. There is great enthusiasm for the project, which foresees the setting up of a database that contains as much information as possible on pigs' genes. Breeding biologists have been waiting for this for a long time. It is hoped that this knowledge will provide important information on pig breeding, such as meat quality or resistance to diseases. "As Switzerland is not a member of the EU we didn't find out about the conference until later," says Stefan Neuenschwander. Neuschwander was at the time head assistant of the group Breeding Biology at the ETH Institut of Agriculture and Food Science. He now works in the Tissue Engineering Department Surgery at the University Hospital in Zurich. "I got in touch with the people involved with the project as soon as I heard of it and told them that we would be interested in taking part," Neuenschwander remembers. At first, without success because the EU Commission ruled that participation was not possible for "formal reasons" – apparently the pertinent application had not arrived in Brussels in time. Collaboration happened despite this; scientists from Denmark, Germany, France and Italy mapped genes that are active in the small intestine, liver, ovaries and in muscle tissue, while the researchers in Zurich turned their attention to active genes in fatty tissue. In all, a total of more than 700 genes were mapped and fed into the database "Genetpig" (1).

Important steps towards a gene map

"The aim of Genetpig is a genetic map for pigs, the results of which can be compared with the results of the human genome project. It was found that there is a great similarity in the disposition, or arrangement of genes on certain sections of chromosomes of humans and pigs," explains Neuenschwander. It is estimated that around 90 per cent of all expressed sequences are common to humans and pigs. "The Genetpig project is an important step on the way to a systematic mapping of economically important traits. Apart from the classic growth and reproductive characteristics, it is increasingly important to identify those genes that influence the quality of animal products and the health of the animal itself."

Comparative genetic mapping: same colours means homologeous chromosome parts. Example: homologous genes on chromosome 3 of pigs (above) have their counterpart on the human chromosomes HSA 2 and HSA 3, genes on SSC 6 on HSA 1, 16, 18 and 19. large

"In the initial phase researchers tried to allot as many genes as possible to single chromosomes," as Peter Vögeli, Professor of Breeding Biology at the ETH Institute of Animal Sciences (2), explains. This method is extremely time and resource intensive. Genes can be attributed by using family analysis, markers or somatic cell hybrids. "Most research groups use cell hybrids," explains Vögeli. These combine pig and rodent cells, that after dividing, exhibit various chromosome parts. By the means of polymerase chain reaction (PCR) the DNA of single hybrid cell lines can be used to show the existence of pig specific sequences. If an amplified sequence of an unknown gene shows the same pattern as that of a gene or marker that has already been mapped it can be linked to the same chromosomal region. Using this method ETH researchers were not only able to map genes specific to fatty tissue but also to determine the

The pig is genetically examined. The obtained data contains important information for breeding biologists.

chromosomal region of the spastine gene (SPG4). This gene is thought to be responsible for congenital ataxia and spastic paresis on chromosome 3 of pigs, debilitating muscular diseases that can lead to paralysis. The same gene is also known to exist in humans: "There is a phenotype on chromosome 2 that is responsible for paralysis," says Vögeli. "Because similar diseases often have the same cause, we can use an animal model to study how they are inherited and which genes are involved at which point in time in which forms," he adds.

Research focuses on five diseases

Apart from congenital ataxia and spastic paresis researchers from the ETH Institute of Animal Sciences are focusing on three further diseases that occur in pigs: ascorbic acid deficiency, arthrogryposis and the adhesion of the bacterium Escherichia (E.) coli to the mucous membrane in the intestines. Let us take a look at these in that order.

- "Like most animals, pigs can produce vitamin C themselves," explains Neuenschwander (guinea pigs and primates are exceptions). But some of them have a damaged gulonolacton oxidase-gene (GULO) which prevents the conversion of L-Gulonolacton to ascorbic acid to be catalysed. These pigs have to take in vitamin C with their food, just as humans do, and this is why an appropriate animal model can be used to study the influence of vitamin C in both species. Thanks to the great physiological parallels between pigs and humans (weight, digestive tract, heart and circulation) pigs are preferred to rodents.

- Arthrogryposis manifests itself as a constant continuous contraction of the extremities at birth. It cropped up in Switzerland for the first time about three years ago. "14 of Switzerland's 60 noble-stock breeding boars carry genetic variations of this disease," says Vögeli," this is a catastrophic state of affairs." Researchers at the ETH Institute of Animal Sciences are now planning to develop a test that can track the recessively inherited gene variant. Vögeli hopes that this test will prove instrumental in the elimination of the disease.

- Another hereditary disease is caused by the adhesion of the E. coli bacterium to the mucous membrane of the intestines. The coli bacterium can thus reproduce very rapidly and produce poison which leads to diarrhoea. ETH researchers were the first to identify pigs' susceptibility to this disease with a test. "We are able to ascertain whether intestinal cells have receptors for this bacterium," explains Vögeli. The molecular genetic test for the detection of the E. coli F18 receptor has been patented since September 1997 – in the meantime – in 120 countries.

Research is only just beginning

"These are examples of the application in classic genetics," says Neuenschwander. The Genetpig database is very helpful here. "The investigation into expressed sequences provides information on the way in which genes function." However, with the creation of a genetic database for pigs research has only just begun; the genome is not yet entirely decoded. "Efforts are being made to complete this work," says Neuenschwander, above all in China and Denmark. "But these projects are being run on a private basis. We probably won't have access to data resulting from these projects as quickly as in the case of the human genome."

For the time being the database Genetpig is being taken care of by the company Infobiogen, in Evry, just outside Paris. The EU project Bio4-CT98-0237 was concluded at the end of 2001 and results published in January 2003 in the specialist magazine "Nucleic Acids Research" (3).