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Gene editing: Cut and paste the genetic code?

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We're at the beginning of this era.

could transform medicine is by expanding the variety of modified organisms available for modelling human health and disease. We have already noted the fact that mice dominate traditional genetic engineering, largely because, for reasons that are not fully understood, scientists have found it impossible to isolate embryonic stem cells from other mammalian species. Alas, the mouse is not always a good model for human disease. Most obviously, their brains are very different to ours, which limits the usefulness of mice studies for understanding mental disorders such as autism or schizophrenia. For this reason, Guoping Feng of the Massachusetts Institute of Technology is now using gene editing to create monkeys with defects in genes associated with human brain disorders – for instance SHANK3, which regulates how nerve cells communicate, and which has been linked to autism when defective in humans.

While gene editing is providing exciting new ways to model disease, it also offers potential clinical treatments in the here-and-now. It was recently successfully used to target the HIV virus in human cells (grown in culture, but still). Scientists at the Salk Institute in San Diego showed that this approach ‘completely removed all HIV, including viral sequences already hiding in the cell’s genome’, according to Juan Carlos Izpisua Belmonte, who led the study. And clinical trials are underway to test the approach on AIDS sufferers.

As well as providing biomedical models, there’s also a good deal of interest in using genome editing to create new animals and plants for food. It’s possible, for example, to create domestic pig breeds that contain desirable wild boar genes. Domestic pigs are highly susceptible to a lethal disease called African swine fever. Outbreaks have recently been reported in Lithuania, Ukraine, Poland and Latvia, and the disorder represents a serious threat to domestic pigs across Europe. However, wild boars are resistant to the disease. Enter Bruce Whitelaw and colleagues at the Roslin Institute in Edinburgh, the place where Dolly the sheep was cloned.

Whitelaw used genome editing to create domestic pigs containing the genetic difference found in warthogs. And in trials that began this summer, the modified pigs are being exposed to the virus to see if they have acquired resistance. At a recent talk he gave about the project, Whitelaw said that the first question from a Lithuanian farmer was: ‘When can I get these animals?’ Good question. If the clinical trial is a success, the next step is to apply to regulatory bodies for commercial approval. ‘The limitations are no longer technical,’ Whitelaw explained, ‘they’re legal.’

This is just the beginning. Other judicious edits might adjust meat quality, or give a pig the ability to thrive on a more economical type of diet. We could design preternaturally robust food crops, like the potatoes recently modified to be resistant to blight. You probably know that blight was the fungal infection that caused the great Irish Famine of the mid-19th century. You might not have realised that the same disease is kept under control today only thanks to the extensive use of costly and toxic fungicides. Perhaps we could do away with that.

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