IT鈥橲 a recipe so simple, one day farmers could use it to genetically engineer their own animals. Milk some fresh sperm from your pig, cow or sheep. Dry and then wash thoroughly. Swish the washed sperm around in a centrifuge with the gene of your choice. Then use the altered sperm to artificially inseminate a female, wait a few months and hey presto, transgenic offspring.
Italian researchers have already used the technique to create pigs that could one day provide organ transplants for people. What鈥檚 more, it could revolutionise the genetic engineering of livestock because it鈥檚 25 times more efficient than the standard technique.
Marialuisa Lavitrano鈥檚 team at the University of Milano-Bicocc0a in Milan successfully transferred a hDAF gene into pigs. In theory, incorporating this gene will stop the human body from initially rejecting the pig organs.
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The standard way to insert genes into animals is to physically inject them through a fine needle into the pronucleus of a newly fertilised egg. But Lavitrano鈥檚 team has now shown that sperm naturally internalise DNA. The key is to get rid of the seminal fluid by drying and washing, she says, because it contains interferon-1, a factor that usually prevents the sperm from accepting new DNA. Once free of this constraint, sperm bind to the DNA and internalise it.
What鈥檚 more, the extra genetic material always seems to end up in parts of the DNA sequence where it will function and be passed to the next generation, compared to the injection technique, which inserts the DNA randomly, if at all.
Lavitrano says that this could explain why 57 per cent of the 93 piglets produced from the sperm carried the hDAF gene, a 25-fold improvement on injection success rates (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.222550299). 鈥淚t鈥檚 very easy and you could do it on the farm,鈥� she says.