Potential Uses of Cloning

POTENTIAL USES OF CLONING

1. Rapid multiplication of desired livestock: Controlled release of selected lines of elite cloned animals would rapidly disseminate superior genotypes from breeding stocks directly to commercial farmers. It has been estimated that these sorts of strategies could result in improvements equivalent to 15 - 17 years of traditional animal breeding. Natural mating of cloned sheep & cattle sires would be cheaper & more convenient than artificial insemination. It would be best to ensure genetic variation is maintained in the breeding population by only using clones in some specialised areas. However, a herd of clones could be expected to produce commercial product (milk, wool, beef) of very similar characteristics.

2. To evaluate & select phenotypes: Cloning could be used to determine the phenotype of different clone lines in different environmental conditions & so improve the accuracy of selecting superior animals for breeding.

3. Animal Conservation: To be able to clone an endangered species:-

· Its reproductive biology must be understood adequately

· There must be an adequate source of suitable eggs for nuclear transfer

· Its nuclear reprogramming must be sufficiently understood

· Suitable surrogate females are needed to gestate the cloned pregnancies

For many species these requirements limit their prospects. However, at the very least, cryo-

preservation of somatic cells from rare & endangered animals may be possible, to allow future

advances to make it possible to reintroduce them. Cloning extinct animals where there are no viable

cells, nuclei or intact DNA is the realm of science fiction.

4. Transgenic Applications: Transgenic animals contain novel genes which are passed on to subsequent offspring via conventional breeding. They are created by modifying specific genes in cultured cells in vitro (gene targetting), selecting those cells & transferring their nuclei to produce cloned transgenic animals. This increases the efficiency of output from 10 % of offspring to 100 %. Current international developments include:-

· Pharmaceuticals: Specific human genes coding for particular proteins could be introduced into the cultured cells to be expressed only in the mammary gland of lactating sheep, cattle or goats. These pharmaceuticals may then be extracted from the milk & purified for use in treating human diseases eg:-

- a-1-anti-trypsin for emphysema & cystic fibrosis

- blood clotting factors for haemophiliacs

- serum albumin used to extend blood volume during operations

- anti-thrombin III used during surgery to regulate blood clotting

This method is cheaper & more effective than using microbes or fermentation &

safer than

extraction from human blood (with potential viral contaminants) - though plants have yet to be tried

· Nutraceuticals: Adjusting the components of cow’s milk to contain human milk proteins (eg for babies) or without b-lactoglobulin or lactose (for those allergic to cow’s milk or lactose-intolerant) or lactoferrin (to increase Fe absorption) with lysozyme (to improve passive immunity). Adding more casein ( to increase Ca levels) in combination with less milk fat could provide a high-protein, low-fat health food.

· Production traits: Currently AgResearch NZ is investigating producing milk for cheese manufacture that has less b-lactoglobulin (which makes processing difficult) & more casein (the protein) by deleting/adding cow genes before nuclear transfer.

· Xenotransplantation: Pigs have a similar anatomy, organ size & physiology to humans & a transplant of parts could be made immunologically compatible. It would involve changing specific genes in cultured pig cells & then cloning to generate pathogen-free herds of pigs.

· Research Models: Sheep (cystic fibrosis, Huntington’s chorea & lung diseases) & mice could be generated by cloning for use in research on human diseases.

5. Human Cell-based Therapy: Once the mechanisms that control cell differentiation & reprogramming are clearer it may be possible to generate a patient’s own bank of replacement tissue. This would be particularly useful for disorders in tissues which don’t repair or replace themselves easily eg diabetes, muscular dystrophy, some cancers, some neurological disorders. To do this a healthy cell from the patient would be cloned to form a blastocyst. From this, undifferentiated embryo stem cells could be isolated which could grow indefinitely in vitro & could be differentiated into the cell type needed.