Task: Integrate biological knowledge to develop an informed response to a socio-scientific issue
Introduction
New Zealand stunned the world in 2016 announcing a goal to eradicate mammalian predators by 2050. The key targets are rats as they cause enormous damage to our flora and fauna and in some cases are an economic burden to our productive sectors.
New gene editing technologies, such as CRISPR, alter existing genes to be deactivated or deleted to prevent the expression of a trait, or to make it express at a higher level or in a different way, providing a way to fix a malfunctioning gene. The are a potential method to eradicate rats. However, this new technology comes with worrying biological implications, and if successful, it also comes with varied opinions and multiple cultural, environmental and economic implications.
I will be analysing the implications, opinions, and risks and advantages to forge my own opinions on whether New Zealand should change the regulations around GMOs and propose further actions.
Gene Drives
Kiwis and other native birds are in trouble. Many non-native animals, such as rats, prey on flightless native birds. A gene-editing tool known as a gene drive has been considered as an option to get rid of the danger of rats. Gene drives can copy and paste themselves onto the genomes of organisms, and once inside, have the ability to change the genes of rats in a way that would make them infertile at sites where they do not belong. The invasive population in that habitat would decrease over time, eventually ceasing to exist.
CRISPR (clustered regularly interspaced short palindromic repeats) is a gene editing tool which allows scientists to be able to completely remove or even adding pieces of DNA. Two key components are required for CRISPR to work: an RNA guide that locates and binds to the target piece of DNA and the Cas9 endonuclease that unwinds and cuts the DNA. Single guide RNA (sgRNA) is a short synthetic RNA sequence designed to guide Cas9 to the site of interest. It contains a nucleotide section which is complementary to the DNA of interest. The PAM sequence lies directly downstream of the target sequence on the non-target DNA strand. Recognition of PAM by Cas9 destabilises the DNA allowing sgRNA to be inserted. Cas9 will not function if PAM is absent. Cas9 is guided to the target site by sgRNA. Cas9 unwinds the DNA and cuts both strands at a specific point.
Gene drives refine this CRISPR method. They paste extra pieces of DNA which contain the code to make the CRISPR system into the cut. When infertile rats carrying the gene drives mate, their gametes create the protein and guide RNA. When this gamete fuses with a gamete from an unaltered organism, RNA leads Cas9 to the site of the target unaltered DNA which is cut then repaired by placing a copy of a gene drive. It is this additional step that makes a gene drive different to the regular CRISPR method. Parents normally have a fifty percent possibility of passing a gene to offspring. Gene drives counteract this by overwriting any unaltered version of the target gene, meaning they can be passed along almost one hundred percent of the time. With this, CRISPR gene drives have made it possible to make gene edits in nearly every member of a selected species by adding the new gene, of which all offspring are guaranteed to inherit.
Biological Implications of Gene Drives
One positive implication of gene drives lies in their ability to introduce new bits of DNA into genes in a short period to create a desired effect on a population. For example, if research shows all rats within the target population are susceptible to the gene drive linked gene, then it will be predicted that the gene drive will rapidly spread. This has the potential to make gene edits in nearly every member of a selected species. Scientists just add the new gene they want to alter to the targeted species, i.e. the “taming” gene. The CRISPR gene drive will make this change whenever it finds a wild version of the gene. When the transgenic rats breed with the wild ones, the CRISPR gene drive cuts the original version of the fertility gene and inserts of a gene drive code into the DNA of male rats would destroy the ‘x’ chromosomes in their sperm, meaning they can only pass on a ‘y’ chromosome, so they would be unable to bear female offspring. Releasing genetically engineered male mice with the edited code into a population of wild mice, where they could breed with wild females, is be effective in spreading the gene drive through a population and increasing the relative proportion of male mice in a population. With fewer females over time, the population would eventually decline. In a small population and for short-lived animals like rats, the change occurs within several years.
However, rats also have native populations where ecosystems depends on them. One negative implication of a gene drive is if modified go elsewhere, there is the possibility of spreading that gene drive into a new population. For instance, rats are really good stowaways on ships and can swim over two kilometres, allowing them to reach farther places and populations. Only a few altered organisms released into new populations would be able to quickly spread the gene drive through them all. This may cause adverse unintended effects to the unidentified and un-researched new population. Extreme effects could be death, throwing off the ecological balance.
Social Implications of Gene Drives on Rat Population
Cultural
When introducing new biotechnologies such as gene drives, New Zealand has a network of legal instruments and treaties that require consideration, including the Te Tiriti o Waitangi.
A close and sacred connection to the land and its inhabitants is a defining element of Māori culture. In 2014, Kevin Esvelt, a biologist at MIT, writes, “scientists should hold themselves morally responsible for all the consequences of their research,” and “[i]nviting people who might be affected by a technology to help guide its development is important because any other approach would deny them a voice in decisions that will affect them.” Māori scientists, tribal leaders and community members have a right to call for a seat at the table.
The traditional Māori view considers all parts of the natural world to be related through whakapapa, and the use of gene drives to ‘humanely’ eliminate rats, interferes with natural processes and relationships, violates the tapu of different species, and threatens the sanctity of mauri (life principle) and wairua (spirit) of living things. Additionally, scientists deciding to use gene drives to eradicate rats in an area without consulting Māori affects Māori’s ability to be kaitiaki (guardians) of their taonga.
Economic
In 2018, the government gave $81.3m to allow the Department of Conservation to carry out sustained predator control over more than 1.8 million hectares over four years.
Current pest control measures, as demonstrated by the removal of pests from large offshore islands, are effective; but they are relatively expensive and take a lot of planning. Given the alternatives of a broad-range poison (1080), dropped from the air, and expensive and intensive trapping campaigns, gene-drive solutions could provide another avenue for pest control.
The ability to cost-effectively keep rats at zero density will be transformational for New Zealand conservation. Rat eradication through gene drives will accelerate the provision of improved tools, methodologies and strategies for mammal pest control in general and for local elimination in particular. They will be socially acceptable, cost-effective and targeted next-generation technologies that have been proven at pilot scale to effectively eliminate small mammal pests.
However a study done by the royal commission, out of 10,861 New Zealanders, 92% out of 10,861 were against the use of GMOs in New Zealand. Although we can only speculate why this is, I theorise this could be because New Zealand is commonly referred and known for its clean and green image and we do not want to disassociate ourselves from that title and surroundings. Tourists are largely drawn to this image, and losing it would mean a decline in tourists. As tourism is one of the most important sectors in New Zealand’s economy, this could mean an economic downfall due to the release of genetically edited rats.
Environmental
Rats are a very serious pest problem. In New Zealand there are three rat species: the ship or common rat (Rattus rattus), the Norway or brown rat (Rattus norvegicus) and the Polynesian rat or kiore (Rattus exulans). Of the three, the ship rat is of greatest conservation concern, but all prey on native birds and invertebrates, eat native plants and are carriers for diseases. Many endemic species now persist only in offshore islands where rats have been successfully eradicated, such as Tiritiri Matangi Island, or in small mainland sites like Maungatautari where they are encircled by predator-proof fences.
In recent years, many of the country’s conservationists and residents have rallied behind Predator-Free 2050, an extraordinarily ambitious plan to save the country’s birds by eradicating its invasive predators. Native birds of prey will be unharmed, but Predator-Free 2050’s research strategy spells doom for rats. Gene drives have been identified as a potential answer for ‘humane’ and cost-effective eradication.
2019-5-20-1558349065