![\"Hawaiian](\"\/\/media.nature.com\/w800\/magazine-assets\/d41586-019-01300-9\/d41586-019-01300-9_16662452.jpg\")
<\/div>\n<\/div>The Hawaiian bobtail squid (Euprymna scolopes) alters the camouflage patterns on its skin based on what it sees.<\/span>Credit: Eric Roettinger\/Kahi Kai Images<\/p>\n<\/figcaption><\/figure>\n <\/p>\n <\/p>\n Joseph Parker has wanted to know what makes rove beetles tick since he was seven years old. The entomologist has spent decades collecting and observing the insects, some of which live among ants and feed on their larvae. But without tools for studying the genetic and brain mechanisms behind the beetles\u2019 behaviour, Parker focused his PhD research on\u00a0Drosophila<\/i>\u00a0fruit flies \u2014 an established model organism.<\/p>\n Now, more than a decade later, the rise of the CRISPR gene-editing technique has put Parker\u2019s childhood dream within reach. He is using CRISPR to study symbiosis in rove beetles (Staphylinidae<\/i>) in his lab at the California Institute of Technology in Pasadena. By knocking out genes in beetles that live with ants and in those that do not, Parker hopes to identify how the insects\u2019 DNA changed as their lifestyles diverged. \u201cWe\u2019re designing a model system from scratch,\u201d he says.<\/p>\n Biologists have embraced CRISPR\u2019s ability to\u00a0quickly and cheaply modify the genomes<\/a>\u00a0of popular model organisms, such as mice, fruit flies and monkeys. Now they are trying the tool on more-exotic species, many of which have never been reared in a lab or had their genomes analysed. \u201cWe finally are ready to start expanding what we call a model organism,\u201d says Tessa Montague, a molecular biologist at Columbia University in New York City.<\/p>\n Montague works on the Hawaiian bobtail squid (Euprymna scolopes<\/i>) and the dwarf cuttlefish (Sepia bandensis<\/i>),\u00a0species whose unusual camouflage acts as an outward display of their brain activity<\/a>. The cephalopods project patterns onto their skin to match what they see around them. But probing how their brains process stimuli has been difficult. Researchers would normally do this by embedding electrodes or other sensors into the skull \u2014 but squid and cuttlefish are boneless.<\/p>\n Last year, Montague and her colleagues successfully injected CRISPR components into cuttlefish and bobtail-squid embryos for the first time. Now, they are trying to genetically modify the cephalopods\u2019 neurons to light up when they fire.<\/p>\n <\/p>\n Technical knock out<\/strong><\/p>\n Other researchers are using CRISPR to study species\u2019 distinctive social behaviours. Daniel Kronauer, a biologist at the Rockefeller University in New York City, has created raider ants (Ooceraea biroi<\/i>) that cannot smell pheromones. In experiments, the genetically modified ants were not able to sustain the complex hierarchy seen in a normal raider-ant colony1<\/a><\/sup>. The scientists are now using CRISPR to alter genes thought to influence raider ants\u2032 behaviour.<\/p>\n Then there are species that threaten human or environmental health \u2014 such as the pea aphid (Acyrthosphion pisum<\/i>), an insect that attacks legume crops worldwide. To edit the aphid\u2019s genome with CRISPR, a team led by Shuji Shigenobu, an evolutionary geneticist at the National Institute for Basic Biology in Okazaki, Japan, had to manipulate the insect\u2019s complex life cycle. Female aphids born in summer reproduce asexually, by cloning themselves, whereas those born in autumn lay eggs.<\/p>\n Shigenobu\u2019s team set up an incubator that simulated the cool temperatures and short days of autumn so their aphids would lay eggs that the scientists could inject with CRISPR components.<\/p>\n After four years, the team succeeded in editing a pigment gene as a proof of concept, Shigenobu announced last month during a conference at the Howard Hughes Medical Institute\u2019s Janelia Research Campus in Ashburn, Virginia. He hopes that by modifying other parts of the aphid\u2019s genome, researchers can learn more about how the insects interact with plants. That information could lead to the production of better pesticides.<\/p>\n <\/p>\n Inching forward<\/strong><\/p>\n Developing animal models requires immense amounts of time and money, and until recently there was little support for such work. In 2016, the US National Science Foundation launched a US$24-million programme to create model organisms \u2014 and in doing so, reveal the genetic and molecular mechanisms behind complex traits and behaviours.<\/p>\n The programme supports research to create tools for probing species\u2019 genomes, study organisms\u2019 life cycles and develop protocols to raise these species in the lab. This support has begun to pay off: in March, for instance, researchers at the University of Georgia in Athens said2<\/a><\/sup>\u00a0that they had used CRISPR to create the first genetically modified reptile, the brown anole (Anolis sagrei<\/i>).<\/p>\n Despite such promising early results, the push to create model organisms with CRISPR has revealed how little is known about many species\u2019 genomes, life cycles and habits. Researchers face practical challenges such as determining how to inject CRISPR components into embryos and coaxing finicky, fragile species to breed in the lab.<\/p>\n \u201cThe reason classic model systems were chosen was they\u2019re basically pests. Nothing can stop them growing,\u201d Montague says. \u201cBut if we take on this challenge of working on new organisms because they have an amazing feature, they\u2019re often not happy to grow under [just] any conditions.\u201d<\/p>\n This has forced scientists to weigh the effort required to study a particular trait against the potential rewards. Modifying a genome requires a deep understanding of a species\u2019 behaviour and lifecycle \u2014 a tall order when that organism is studied by only a handful of people worldwide. \u201cPeople are not choosing these model systems lightly,\u201d says David Stern, a biologist at Janelia.<\/p>\n Stern knows this first hand: he and his colleagues succeeded in breeding one fruit-fly species only after discovering that the insects need an olfactory cue to lay eggs \u2014 the smell of a particular chemical made by plants.<\/p>\n Still, researchers\u2019 interest in developing atypical animal models continues to grow. Montague and her colleagues have created a tool called CHOPCHOP, which allows them to design a CRISPR system for editing specific genes in any DNA snippet. So far, scientists have sent her genetic sequences from more than 200 different species, including plants, fungi, viruses and farm animals.<\/p>\n \u201cI had this weekly reminder that these molecular tools do work in pretty much every organism on the planet,\u201d Montague says. \u201cIt\u2019s such an exciting time to work on any model organism \u2014 especially these new and weird creatures.\u201d<\/p>\n <\/p>\n <\/p>\n<\/div>\n Nature<\/span>\u00a0568<\/strong>, 441-442 (2019)<\/p>\n <\/p>\n <\/p>\n (\uc6d0\ubb38: \uc5ec\uae30<\/a>\ub97c \ud074\ub9ad\ud558\uc138\uc694~)<\/p>\n <\/p>\n <\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":"