"Dolly the Sheep" cloning methods could hold key to breakthrough in conserving animal genetic diversity
The cloning techniques that made headlines with the creation of Dolly the sheep may also be used to save hundreds of animal breeds from extinction, according to experts who attended a workshop in Rome co-organized by FAO and an Italian biotechnology research institute, the Istituto Sperimentale per la Zootecnia. Twenty-three scientists, including leading experts in biotechnology, met for two days at the Italian Ministry of Agricultural Policy, from 26 to 28 November 1997.
The scientific breakthrough that sparked the interest of scientists concerned about conserving the diversity of livestock breeds was not so much the cloning itself, as the ability to use DNA obtained from body cells of adult animals. In the past, cloning has had to rely on nucleuses from embryonic (totipotent) cells, because, once cells become specialized, most of the genes that are not relevant to their functions (such as genes for eye colour in a fingernail cell) get "switched off" in a process known as DNA quiescence. Reversing this process and switching the genes back on - achieved by the Roslin Institute in Scotland for the first time as a forerunner to the research that produced Dolly - will allow scientists to clone animals from somatic cells, such as skin and hair follicles. This process of "reverse DNA quiescence" offers the possibility of simplifying techniques for conserving in laboratories animal genetic resources at risk of extinction.
FAO estimates that some 30 percent of livestock breeds - or 1 500 - are endangered or on the critical list. Most of them are in developing countries and less than 100 of these breeds at risk are currently being conserved.
Conservation of unique breeds will enable humankind to meet unforeseen future challenges, such as environmental change or spread of disease. A poultry breed that survives with little food or special care may be neglected today because it is low in production, but tomorrow it may be the only one of its species to have natural resistance to some devastating virus or pest.
At present, the conservation of endangered breeds is only possible either by cryogenic storage (freezing at very low temperatures) of semen and embryos - a costly and delicate operation that is not feasible in a number of developing countries because of lack of trained personnel and the necessary equipment - or by in situ or ex situ conservation of animals themselves, that is, keeping the animals alive in their natural or another habitat, respectively.
Domestic animal breeds are disappearing because, too often, particularly in developing countries, these conservation options are not feasible. The scientists concluded that reversible DNA quiescence could be a technique to save the genomes (the complete genetic information) of animals for a breed in danger of extinction and offer the possibility of utilizing the breed in the future, once the techniques have been refined and further developed. This would mean that a sample of skin from an animal could be enough to guarantee that its genetic potential is not lost. The number of animals required to conserve the breed can be sampled in just a day or two.
According to Dr Mandy Reynolds, a specialist in skin healing aspects and tissue culture at Durham Hospital, United Kingdom, skin samples, if treated properly, keep reasonably well for up to two weeks before it is necessary to freeze them. This means that samples can easily be collected even in remote rural areas and then transported to countries' conservation units.
"For some countries", said Keith Hammond, who heads FAO's programme on animal biodiversity, these new techniques "could make the difference between taking no action on breeds currently being eroded and conserving these without further delay." (Full text of interview with Keith Hammond)
18 December 1997