Smelling a rat

Cloned mice suffering from obesity shed more doubts on the cloning technique

Last Updated: Saturday 04 July 2015

-- (Credit: Kumar)the debate regarding the viability of cloning technique was once again refuelled with a recent research revealing that cloned mice may develop obesity when they reach adulthood. The research was carried out by Randall R Sakai and colleagues from the University of Cincinnati, usa . They studied a batch of nine obese mice cloned by researchers from the University of Hawaii and found that the mice were normal in every way except for having a great deal of excess body fat. "These animals were very active, but they had extra body fat, high levels of insulin and excess leptin hormone that is produced by fat cells," said Sakai ( , March 2, 2002).

Surprisingly, when these mice were allowed to mate and reproduce normally , their offsprings did not suffer from the same problem. According to the researchers, this indicates that either the donor cells used or the method of cloning itself may be responsible for the obesity.

To confirm their theory, the researchers studied another group of mice termed ivem. This group was allowed to mate normally, but their embryo was removed and developed in the same laboratory setting as the clones. "Even the ivem offsprings developed increased body weight as adults. This suggests that some factor associated with the manipulation of cells in culture may be producing the adverse effects," Sakai said.

According to him, the study shows that manipulations used to produce clones result in some unexpected changes. Ian Wilmut, the pioneer researcher who cloned the sheep Dolly, agrees. "The study raises a crucial question: can any clone can be entirely normal?" said Wilmut. However, Duane C Kraemer, a veterinary professor at Texas a&m University, usa , is not ready to indict the cloning process. "We just have to have a lot more information than what we have now to evaluate the consequences of such abnormalities. The findings of the study are another reason to continue the research."

Worldwide, many attempts to clone animals have ended in failure, with deformed fetuses dying in the womb or having oversized organs. In January 2002, scientists in the uk reported that Dolly, the world's first cloned sheep, had developed arthritis at a relatively young age. In 1999, the cells in her body had started to show signs of wear more typical of an older animal.

Such failures have generated a heated debate in many countries, particularly in the wake of some scientists planning to clone humans. "We must be very cautious about prematurely applying the technology in humans," Sakai said. "As far as we can tell, the cloning procedure has not been proven to be medically and genetically safe."

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