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The domesticated dog (canis familiaris) is famously "man's best friend."
In contrast, at the opposite end of the animal scale, is the wild-type rat (rattus rattus). Unlike canines, rats - the bestial or the human kind - are reputed to be sneaky, dirty and despicable. Rats - the four-footed kind - are the most abundant order of mammals.
Black rats and Norway rats (Rattus norvegicus) may or may not desert sinking ships, but they do export blood-sucking fleas as ocean-going stowaways. These insect parasites hide out in rat fur, then sally forth to afflict their human prey with rat-borne pneumonic plague. Attacking its victim's lungs, the bacterial Yersinia pestis can kill its victim in 72 hours.
However, rats are not all bad - especially the white albino ones, raised as lab animals.
"Because," testifies French developmental biologist Jean Cozzi, "the rat is a very important model for developing new drugs against some major diseases, such as diabetes, obesity and hypertension. In all of these fields, especially neurological diseases like Alzheimer's, the rat biology is closer to humans than mice are."
Cozzi is project leader of a company in Lyon, France, called GenOway. He is senior author of a one-page "Brevia" Science Express report dated Sept. 25, 2003, and titled "Generation of fertile cloned rats using controlled timing of oocyte activation."
"We have acquired four cloned animals born alive at term," Cozzi told BioWorld Today. "At the moment, two males and two females are still alive and reproduce normally. We mated their clones, then their clones - and their progeny are fine. We have now reached more than 40 pups. They're growing well, with no physical pathology.
"Our plan for this growing rat colony," Cozzi said, "is to produce genes from rats genetically that will reproduce commercially against human neurological diseases. We'll try to target some genes in these rats that are homologous to the human diseases, in order to develop drugs for new medical strategies against these infections.
"Jointly with our collaborator, INRA, The National Institute of Agronomic Research," Cozzi related, "we have applied for European and U.S. worldwide patents to protect our exclusive cloning process. Beginning two years ago, we have come very quickly with INRA into joining our respective expertise, and developed quite original strategies for cloning the rat species.
"This process relies on SCNT - somatic cell nuclear transfer," Cozzi explained. "It means we took some new somatic cells from the rat's cells, which normally do not lead to embryonic development. We constructed embryos from these cells. Normally, one uses oocytes from the female donor and sperm from the male. But here we used an oocyte and another cell, which is not sperm. So we could start from cells like fibroblasts, skin stem cells, or other sources.
"It was a major hurdle for all the researchers who tried before us to clone the rat," Cozzi remarked. "We used special inhibitors, which add on the major complex of protein degradation of the cells - the proteosome. Once you lose the oocyte from the animal," he concluded, "these eggs activate by themselves into in vitro conditions. After that they stop their embryonic development and it's too late; you can't possess them for cloning."