What are gene drives?

We've been hearing a lot about this technology over recent years - yet the concept has been about for half a century.

The concept of a synthetic gene drive was devised almost 50 years ago by Christopher Curtis who proposed rearranging genetic material to "drive" anti-pathogenic genes into wild species.

The idea was taken further by UK evolutionary geneticist Professor Austin Burtin, who discussed how a synthetic gene drive could be used to prevent insects spreading diseases such as malaria.

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Natural gene drive mechanisms vary and can be characterised by attributes such as species specificity, fitness cost, susceptibility to resistance, removability, reversibility and, perhaps most importantly, the rate of spread.

So called "high threshold" gene drives would only spread if the number of individuals with the drive genotype reaches a high level.

These types of drive systems could be confined to local areas and breeding populations by controlling the number of individuals with and without the drive.

By contrast, "low threshold" gene drives, which are considered invasive, would spread with a low initial release, requiring only a small number of gene drive-carrying organisms to be released to spread.

Gene drive research is hoped to provide the technical means to fully eradicate predators.
Gene drive research is hoped to provide the technical means to fully eradicate predators.

To date, no synthetic gene drives have yet been released into wild populations, so the concepts essentially remain untested.

How has the technology evolved?

Scientists can now harness gene drive mechanisms which were previously merely theoretical to control or alter natural populations.

While not a gene drive tool in its own right, clustered regularly interspaced short palindromic repeats of base sequences (CRISPR), can be used as part of a system to produce a synthetic gene drive.

When CRISPR is paired with a guide RNA and with specific proteins, such as Cas9 that cuts DNA, it can be used to efficiently edit genetic material.

For gene editing purposes, the Cas9 protein and guide RNA are injected into the cell to cut the DNA at a sequence complementary to the RNA guide.

For synthetic gene drives, the target organism is transformed with a construct that includes the gene for the Cas9 protein, a guide RNA that is complementary to the sequence at the insertion site, and the "cargo" gene controlling the desired trait.

What does it mean for New Zealand?

New Zealand's leading body for science, Royal Society Te Aparangi, has acknowledged the gene-editing revolution is happening quickly and has significant implications for this country.

New Zealand-specific examples could be cows that produce low levels of methane or using the technology to meet our predator free ambitions.

Rats are a focus for making New Zealand predator free by 2050. Photo / D.Mudge
Rats are a focus for making New Zealand predator free by 2050. Photo / D.Mudge

However, there were also important legal and ethical decisions to consider - and the society has convened a multidisciplinary panel of leading experts to look at the research, ethical, social, legal, regulatory, environmental, cultural and economic considerations.

In a recent perspective article, researchers from New Zealand and the US looked at repercussions if gene-edited pests were inadvertently spread outside our borders.

They argued that while there was merit in the possible use of genetic technologies for conservation work, there would need to be protections to ensure only local target populations were affected.

Other New Zealand scientists responded by pointing out no one was currently advocating for the use of the experimental and untested technology of gene drives as conceived in their most basic way.

"Contrary to the hype, gene drive technology for mammals is still highly theoretical, and I must emphasise that no such research is currently being conducted in New Zealand," Landcare Research scientist Dr Andrea Byrom said last month.

"We have literally years of technological development ahead of us before we could proceed with deployment in the field, and future use of gene editing technologies, including gene drive, will be in the hands of the public of New Zealand to decide."