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Cattle cloning: Part science, part art. No sex please

The simplicity of the traditional somatic cell nuclear transfer technique for cloning belies the practical difficulty of producing an animal this way
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First Published: Mon, Feb 04 2013. 12 52 AM IST
The National Dairy Research Institute.
The National Dairy Research Institute.
Updated: Mon, Feb 04 2013. 07 51 AM IST
Karnal, Haryana: Sex is an expensive waste of time at the National Dairy Research Institute. None in the herds of virile buffalo and well-hoofed cows, several of whom have close genetic links with prime Dutch and Swiss cattle, have been born of so-called natural service, as the sexual act is quaintly described by stoic scientists.
“Natural service is too costly and quite unsuitable for our purposes,” said senior scientist Prabhat Palta, “which is ultimately to improve the quality of our cattle”.
Since 1990, when researchers at the institute produced Pratham, the first buffalo to be born anywhere in the world through in-vitro fertilization, researchers have slowly progressed to producing, in 2009, Samrupa, the first cloned Indian animal, followed by Shresth, a cloned bull, and cloned cows such as Garima in 2010.
The second version of Garima successfully gave birth to a calf called Mahima in late January. Of them, only Shresth and Garima are alive today, when the average age of buffaloes is between 15 and 20 years.
While Pratham proved Indian scientists didn’t need cattle to copulate to birth healthy progeny, Mahima was living proof that an animal created without the intervention of sperm could give birth to a normal calf.
To be sure, since Dolly, a ewe, was cloned in London in 1996, several cattle, including pigs and goat, have been cloned as a matter of routine in several countries, but India’s ambitions, as the scientists here affirm, is unique that it is a government-backed programme to create an assembly line of thoroughbred cattle that by virtue of their genetic constitution can live longer, be free of disease and improve India’s per capita availability of milk.
Despite being the world’s largest milk producer, India has a below-average per capita availability of milk, according to the Annual Economic Survey 2012. Thus, even as the country where farming and animal husbandry are key sources of livelihood has boosted milk production by 125% between 1990 and 2010, the corresponding rise in per capita milk availability has only been 60%.
In fact, A.K. Srivastava, director at the Karnal institute, is emphatic that even India’s broader economic transition, where more Indians are including meat in their diet propelled by rising income, isn’t immediately going to change his institute’s priorities of improving the milk yields of cattle over producing buffed animals that are bred for their meat.
“Even getting cows to be in estrous simultaneously is an important area of focus and we absolutely need to aim at higher levels of milk production,” said Srivastava. The idea is that more estrous cows improves the chances of having several cloned embryos implanted and, therefore, in any given year, a greater number of highly productive milch cattle.
The conventional approach to cloning animals is the somatic cell nuclear transfer technique, where an egg cell, sourced from a cow, is cleared of the nucleus that in normal circumstances would’ve been fertilized by a sperm cell. However, in this approach, the nucleus is discarded and another nucleus—which could come from a source as diverse as mammary glands or an ear (as was the case with Garima I) is fused into the egg cell.
A precise, electric jolt reprogrammes the egg cell and triggers cell division that, if successful, gives rise to a viable embryo that is then implanted and gestated in a cow.
The simplicity of the process, which according to a Suresh Singla, another scientist at NDRI, belies the practical difficulty of producing an animal this way. “It’s 50% science and 50% art, and our endeavour is to standardize processes to reduce this art component as much as possible.”
Every stage, whether it is removing the nucleus or fusion with a somatic cell or culture of the embryo in an incubator for nearly a week, is prone to error and even for producing a single calf, “many hundreds of eggs are used up”, according to Singla.
The older technique of artificial insemination, according to Palta, has a success rate of around 40%, and cloning by the present techniques is around 5%. “One in two is also a 50% success as is a million in two million,” Palta said. “The point is, unless we have a sufficiently large number of successful cloned births, we can’t call animal cloning a success or failure.”
In fact, it’s precisely this small rate of success as well as the emergence of a radical new way to look at cloning that has seen scientists the world over eschewing the cell transfer technique.
Ian Wilmut, who is credited with cloning Dolly in 1996, publicly stated that he wouldn’t be pursuing cell transfers because they used up too many eggs, didn’t give rise to perfect embryos and was too labour-intensive.
Such embryos weren’t perfect because even though DNA that’s responsible for giving rise to a new organism is concentrated entirely in a cell’s nucleus, some amount of DNA, called mitochondrial DNA that’s found outside the nucleus but within the egg cell, could get passed on. That means a resulting organism is still only about 99% clone of a particular animal.
What’s caught the fancy of researchers such as Wilmut is the induced pluripotency technique. The technique that earned John Gurdon and Shinya Yamanaka last year’s Nobel Prize in medicine for proving that it was possible by tweaking certain genes to regress even developed cells, such as a stomach cells, to a more primitive state—called pluripotency—that could then be directed to create almost any kind of stem cells.
Apart from being relatively non-destructive, such a cell could be 100% pure as it doesn’t require an egg to form an embryo.
“Right now, matters are in great flux. Induced pluripotency is certainly a promising way forward especially if you are looking at human cells and creating organs,” said Lalji Singh, former director, Centre for Cellular and Molecular Biology.
As the head of the centre, Singh tried for many years to clone and resurrect the extinct Indian cheetah and said that while SCNT was solid science, it was extremely laborious. “You need a level of superhuman dedication, and theory apart, it’s only brute trial and error that can get you results.”
Singla, who was among the team of scientists that began animal cloning at the institute as a doctoral student in 1993, is clear that SCNT is going to be the way forward at NDRI and emphasized that his organization had taken a step forward in reducing the effort required to clone animals.
According to him, the so-called hand-guided cloning technique—developed at the institute and employed to create Garima, as well as, more recently, a Pashmina goat called Noorie—makes the creation of viable cells “20 times easier”.
The difference, says Singla, lies in being able to use cheaper instruments that make it easier to isolate the nucleus and be manually sliced off from the rest of the cell. “Because it’s less complicated it can be taught to other people, and the easier it is to create embryos the greater the success of cloning buffalo.” he added.
Currently, there are no laws that restrict research or experiments around the use of embryos or animal cloning in India and most biologists feel that as long as there is no wanton destruction of embryos, the current laws suffice.
“We do need stronger laws on ongoing (human) stem cell research programmes because several private labs claim miracle cures,” said M.K. Bhan, former secretary at the department of biotechnology. “However, there are strict guidelines that control the use of animals. They suffice for now.”
To Singla, who is still wary of declaring cloning as the future of Indian dairy animal breeding, the infancy of the technique doesn’t affect his belief in its economic viability. He reckoned that the process of identifying an elite progeny-tested bulls required mating a large number of bulls with cows, waiting for the calves to grow and checking which of these were of high genetic merit costs crores.
“If somatic cells from a progeny-tested bull, which might even have died years ago, could be used for creating a clone of that bull, it could save many crores for every such bull produced,” Singla said.
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First Published: Mon, Feb 04 2013. 12 52 AM IST
More Topics: cloning | NDRI | insemination | sex |
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