An opossum has become the world’s first genetically engineered marsupial, scientists in Japan have revealed.
In lab experiments, the experts successfully disrupted a gene responsible for pigments to create albino opossum offspring.
The gene-editing project on the creature was conducted by scientists at the RIKEN Center for Biosystems Dynamics Research (BDR) in Kobe, Japan.
They say their research will help decipher the genetic background of unique traits seen only in marsupials.
It could also help develop new treatments for diseases that affect people, such as cancer and Alzheimer’s disease, the team said.
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Genome editing targeting a gene responsible for making body pigments resulted in albino offspring (pictured) in the experiments at the RIKEN Center for Biosystems Dynamics Research (BDR) in Kobe, Japan
WHAT IS GEN EDITING?
Genome editing allows scientists to make changes to DNA, leading to changes in physical properties.
Scientists use different technologies for this.
These technologies work like scissors and cut the DNA in a specific place.
Then scientists can remove, add or replace the DNA where it was cut.
The first genome editing technologies were developed at the end of the twentieth century.
More recently, a new genome editing tool called CRISPR, invented in 2009, has made it easier than ever to edit DNA.
Source: US National Human Genome Research Institute (NHGRI)
Marsupials, which are mainly found in Australia and New Guinea, as well as in the Americas, are a class of mammals.
Their young are born incompletely developed, but continue to develop in the safety of a pouch – the most famous example being the kangaroo.
Opossums, which are found in America, are known for carrying their cute young on their backs after they leave the pouch.
They are also known for involuntarily “faking death” when confronted by predators, such as foxes, cats, and birds of prey.
They automatically fall into a state of unconsciousness and expel a foul-smelling substance from their anal glands.
“Marsupials represent one of three extant subclasses of mammals with some unique features not shared by other mammals,” said study leader Hiroshi Kiyonari.
“Once the technology is established in this proof-of-concept experiment, future studies could create genetically modified marsupials that will impact the areas of mammalian embryology, genomic imprinting, reproduction, neurobiology, immunogenetics, cancer biology and even comparative evolution.”
Like other marsupials, the opossum has a variety of characteristics not found in other mammals.
Pictured is a Virginia possum (Didelphis virginiana) female with her cute boy on her back
It develops without a functional placenta and puppies are born prematurely before developing in the mother’s pouch.
Amazingly, unlike other mammals, newborn opossum puppies with spinal cord injuries have the ability to heal themselves naturally.
Like humans, but not other non-marsupials, the opossum also develops skin cancer from exposure to ultraviolet light.
Now the researchers are using new gene-editing technology to learn more about the underlying genetics and reveal the biological processes at work.
DIFFERENCES BETWEEN POSSUM AND OPOSSUM
Opossums and opossums are two different orders (Phalangeriformes and Didelphimorphia, respectively).
Opossums are native to Australia and New Guinea while opossums are found in the Americas. In the US and Canada, the only opossum species is the Virginia opossum.
Opossums have a scaly, almost hairless rat-like tail. Opossums have a bushy tail that resembles that of a squirrel.
Opossums are mostly herbivores and inhabit most vegetated habitats while opossums are omnivores or scavengers.
Opossums also have unique defensive behaviors, including hissing and playing dead.
Source: AZ Dieren
The opossum became the first marsupial to have its entire genome sequenced nearly 15 years ago, followed by the Tasmanian devil and the kangaroo.
The genome is the complete set of genetic information in an organism, stored in long DNA molecules called chromosomes.
The experts argue that the opossum is a perfect representative for marsupials in general in such studies, as it is believed to be the ancestor of all marsupials.
Genome editing requires the systematic collection of fertilized eggs. The genome editing solution is injected into these eggs.
Because opossums have a long estrus cycle and a strong sense of territoriality, it takes about a week for a pair to mate, even if they live together.
So the team administered a hormone to stimulate estrus in females, to shorten the time it takes to mate.
They used gray short-tailed opossums (Monodelphis domestica), native to South America.
Transplantation of an embryo into a surrogate mother is necessary to generate a genome-edited fertilized egg.
Researchers transferred the fertilized egg into the uterus of a fertile female opossum and successfully gave birth to pups.
This is the first case that embryo transfer technology has been identified in marsupials, they report.
Usually, the solution needed for genome editing is injected into the fertilized egg with a fine needle.
However, because the opossum’s fertilized egg is surrounded by a thick layer of proteins and a hard shell-like structure, the hypodermic needle would not be able to penetrate it.
So the team applied piezoelectricity, compressing certain crystals to allow electricity to flow through them.
Pictured, a Virginia opossum baby ‘playing’ dead. Despite common misconceptions, this act is an involuntary biological response, not a voluntary one
“One of the tricks to our success was the use of a piezoelectronic element along with the needle, which allowed the needle to penetrate the hard shell layer and the thick layer around the egg,” said study leader Hiroshi Kiyonari of RIKEN BDR.
‘So the piezo made it possible to inject zygotes’ [fertilised eggs] without significant damage.’
To confirm the general methodology, researchers focused on a gene responsible for making body pigments.
When this gene is disrupted, no pigment can be produced and the skin therefore has no color.
Some of the experiment’s offspring were albinos, and their genes were inherited through the next generation, marking the first successful gene editing in marsupials.
Now that the process has been established, researchers can focus on answering all their questions about marsupial biology.
The study is published in the scientific journal Current Biology.