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Revival of Frozen Rat Chromosomes in Mice: A Breakthrough in Genetic Research

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Chimeric mice with rat chromosomes from University of Yamanashi

Chimeric mice with rat chromosomes

University of Yamanashi

Colossal Biosciences, a now-defunct company, may be on the verge of revival. Scientists successfully transplanted rat chromosomes, preserved for over a year, into living mouse cells, paving the way for potential reconstruction of mammoth chromosomes within living cells. They crafted a complete mouse embedded with rat chromosomes in specific cells.

“Once we refine the technology, we will begin testing on elephant cells,” stated Teruhiko Wakayama from Yamanashi University in Japan. “If we can introduce elephant chromosomes into mouse embryonic stem cells, we would be eager to proceed with mammoth chromosomes as well.”

<p>The immediate objective of this research is to explore gene activity from extinct animals in contemporary species, potentially revealing insights beyond mere gene sequence analysis. This study also holds implications for conservation and de-extinction initiatives. For instance, in 2004, we preserved tissue from the Hawaiian pouri, an extinct bird. The unique characteristics of biological systems suggest that chromosome transfer is crucial for reviving this species.</p>
<p>An animal's genome is organized into structures known as chromosomes. During cell division, these extensive DNA strands tightly coil into the classic cylindrical shapes depicted in textbooks. These "condensed chromosomes" can be visually identified in living cells by employing dyes that bind to the surrounding proteins, enabling non-invasive observation.</p>
<p>Wakayama's method involves extracting a cell's nucleus and injecting it into an egg cell, initiating chromosome condensation—a process akin to nuclear transfer techniques utilized in cloning. This technique was first applied by Wakayama for cloning a mouse shortly after the birth of Dolly the sheep.</p>
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<p>Upon injection of the nucleus, the egg is treated with enzymes to assist in chromosome separation. A single chromosome is then retrieved using a minute hollow needle and introduced into another egg. As this egg develops into an embryo, the chromosomes subsequently integrate within all embryonic stem cells.</p>
<p>After honing this technique with mouse chromosomes, Wakayama extended the research to rats genetically modified for green fluorescence. Blood cells extracted from the tail of one such rat, preserved for over a year, successfully generated mouse embryonic stem cells containing additional chromosomes from the genetically altered rat.</p>
<p>These cells were then introduced into standard mouse embryos and implanted into female mice, resulting in chimeric animals with rat chromosomes in some of their cells. These mice appear normal but fluoresce green under UV light, indicative of the original rat cells.</p>
<p>The research team aims to create mice with an additional rat chromosome in every cell, but this objective remains unachieved. Currently, the technique appears effective only for chromosome 9 in rats, as attempts to add other chromosomes hinder embryo development. "We are actively exploring various methods to enhance the success rate," noted Wakayama.</p>
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                data-caption="Green cells in this mouse pup contain rat chromosomes" 
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                <p class="ArticleImageCaption__Title">This baby mouse has cells with rat chromosomes that glow green.</p>
                <p class="ArticleImageCaption__Credit">University of Yamanashi</p>
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<p>The observed interference in embryonic development may stem from activity elsewhere in the rat chromosomes. If this is the case, researchers might need to deactivate genes on supplementary chromosomes, similar to how one X chromosome is inactivated in female mammalian cells. However, Wakayama remains optimistic that this won't be necessary.</p>
<p>The team has acquired samples of frozen elephant tissue from the zoo for experimental purposes. They are collaborating with a team that <a href="https://doi.org/10.1038/s41598-019-40546-1">successfully extracted and studied cell nuclei</a> and are considering using mammoth chromosomes from a 28,000-year-old specimen named Yuka.</p>
<p>Cloning efforts to revive mammoths from these cells are unlikely to succeed due to extensive DNA damage. Nonetheless, Professor Wakayama believes recovery of individual chromosomes for study in living cells is within reach.</p>
<p>“Even a single successful transfer is a significant milestone,” remarked <a href="https://reviverestore.org/about-us/#Ben_Novak">Ben Novak</a>, of Revive & Restore, a conservation organization. "This research could have pivotal implications for passerine birds," a diverse group that encompasses over half of all bird species, where body tissue cells such as skin and muscle no longer carry complete chromosomal information. Reproductive cells, however, retain an extra chromosome essential for survival.</p>

<p>The Hawaiian puli is a passerine bird with only sterile male tissue frozen, necessitating the introduction of two chromosomes from a closely related species—one chromosome from reproductive cells and a W chromosome specific to female birds. "Though this would lead to partial hybrids, it could facilitate the revival of the species," Novak explained.</p>
<p>Wakayama's research is not unprecedented; in 2022, a Japanese team managed to <a href="https://doi.org/10.1016/j.ajhg.2021.12.015">create a rat with an additional human chromosome 21</a> to study Down syndrome. However, this method involves significant genetic modification, making it less applicable for conservation efforts.</p>
<p>The prevalence of extra reproductive chromosomes might be more common than currently recognized, according to Novak, suggesting much of the tissue being preserved by biobanks may be incomplete.</p>

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Source: www.newscientist.com

Research Suggests Invasive Polynesian Rat Contributed Significantly to Easter Island Deforestation

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The ecological shifts experienced on Easter Island (Rapanui) represent one of the most illustrative yet contentious examples in environmental archaeology. This discussion centers around the Polynesian rat (brown rat) amid the island’s deforestation, an event that wiped out an estimated 15 million to 19.7 million palm trees, specifically the palm tree (pashalococcos disperta) between approximately 1200 and 1650 AD.

Easter Island, known as Rapa Nui to its early inhabitants, is one of the least populated islands in the world. It is located approximately 3,512 km from the west coast of Chile and about 2,075 km west of the nearest inhabited island, Pitcairn Island. For reasons still unclear, the early Rapa Nui people began carving giant statues from volcanic rock. These monumental statues, known as moai, are among the most remarkable ancient artifacts discovered. Image credit: Bjørn Christian Tørrissen / CC BY-SA 3.0.

Prior to human settlement, Rapa Nui was dominated by large palm trees of now-extinct varieties, including the Chilean wine palm (Jubaea chillensis).

These majestic trees can survive for up to 500 years, but are slow-growing, taking around 70 years to mature and bear fruit.

By the time Europeans arrived in 1722, very few palm trees remained. When European interest in the island’s ecosystem peaked, these trees had largely disappeared.

“European accounts often describe islands devoid of trees, yet they also mention palm trees and their fronds,” notes Carl Lipo, a professor at Binghamton University.

“It’s uncertain whether they used this term to denote other types of trees.”

When exploring new islands, Polynesians transported various subsistence items such as taro, sweet potatoes, bananas, yams, dogs, chickens, and pigs, along with the omnipresent Polynesian rat.

In contrast to the Norway rat (brown rat), which was introduced post-European contact and favors the tree canopy, this smaller arboreal species provides a wealth of information for researchers.

“Their genetics showcase unique haplotypes due to the ‘founder effect’,” explains Professor Lipo.

“The genetic diversity of rats as they traverse the Pacific allows us to trace human migrations and the frequency of these settlements.”

The methods by which these rats entered Polynesian outrigger canoes is debated. Were they stowaways or intentionally included as a backup food source? Ethnographic evidence leans toward the latter.

“After European arrival, a naturalist collecting specimens for the British Museum witnessed a man walking with a mouse, who informed him it was for lunch.”

Additionally, rat bones have been uncovered in midden deposits, or ancient refuse piles, on various Pacific islands.

Upon their arrival at Rapa Nui around 1200 AD, the rats discovered a predator-free paradise filled with their preferred foods.

Their population surged into the millions within a few years, as they can breed multiple times annually.

“The palm fruit was like candy to the rats. They turned into a significant food source,” Professor Lipo commented.

Rapa Nui’s palm trees had coevolved with birds and did not develop the boom-and-bust production cycle that would have enabled some nuts to withstand rodent exploitation.

As a result, rats consumed the palm fruit, preventing the next generation of trees from establishing.

Simultaneously, humans cleared land for sweet potato fields. This dual pressure led to the deforestation now characteristic of the island.

Alongside plants and animals, Polynesians also incorporated practices such as slash-and-burn agriculture to enhance soil fertility.

Old volcanic islands like Rapa Nui possess poor soil, and rainfall depletes nutrients.

Clearing or burning parts of the forest temporarily rejuvenates soil quality.

Once nutrients are exhausted, farmers relocate, the land recuperates, and trees regrow.

“This pattern is also observable in New Guinea and other regions across the Pacific,” Professor Lipo mentions.

“However, in Rapa Nui, the slow growth of trees and the rats consuming coconuts inhibited regrowth.”

Eventually, the islanders shifted to a farming technique that utilized stone mulch to enrich their crops.

While the reduction of palm forests marked a significant ecological transformation, it was not a disaster solely orchestrated by humans.

The islanders’ survival did not hinge on the palm trees; rather, it depended on the availability of cleared land for agriculture.

Moreover, palms are not hardwoods; they belong to the grass family and do not provide material for canoes, homes, or fuel.

“The loss of palm forests is unfortunate, yet it wasn’t catastrophic for the people,” states Professor Lipo.

“They didn’t rely on them for survival.”

Though some palms may have persisted into European colonization, the introduction of sheep farming in the 19th century likely sealed their extinction, as any remaining seedlings would be consumed by sheep.

Ironically, the Polynesian mouse suffered a similar fate to the palm trees, being outcompeted by Norway rats or predated by non-native species like hawks on most islands.

Despite changes in species, islanders still discuss the rodents’ cyclical population booms and severe declines.

The narrative of Rapa Nui exemplifies unintended consequences as well as resilience and adaptability in one of the most remote inhabited islands, with its closest neighbor situated 1,931 km (1,200 miles) away.

“A more nuanced perspective on environmental change is essential,” says Professor Lipo.

“We are integral to the natural world and often modify it for our benefit; however, this does not necessarily imply we are creating an unsustainable environment.”

Findings from this study will be published in the archeology journal.

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Terry L. Hunt and Carl P. Lipo. 2025. Re-evaluating the role of Polynesian rats (brown rat) in the deforestation of Rapa Nui (Easter Island): Faunal evidence and ecological modeling. archeology journal 184: 106388; doi: 10.1016/j.jas.2025.106388

Source: www.sci.news

Australia reveals the discovery of two new native rat species

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genus mouse pseudosyndrome It is one of the few terrestrial placental mammals to have established itself in Australia without human intervention.

The delicate rat of the Pilbara (Pseudomys pyruvalensis). Image credit: Ian Boole.

of Native little mouse (Pseudomys delicaturus)The mouse, also known as the delicate mouse, was previously thought to be a single species that spread across a vast country, from the Pilbara in Western Australia, across parts of the Northern Territory, through Queensland to the New South Wales border. It was getting worse.

“We now know that there are actually three different species.” Dr. Emily Roycroftresearcher. Australian National University.

“Thanks to new genetic technology, we now identify not one but three species of these delicate mice.”

“Identifying undescribed species and giving them official names will go a long way in ensuring they are properly managed.”

“Although it may be difficult for amateurs to tell the species apart, this discovery is important for the future of this small mouse.”

“The two new species did not receive conservation or research attention because we did not know they were there.”

“For example, we don't know whether population declines were not detected as a result of all three species being assessed as a single unit.”

“This delicate rat was not a priority for conservation, but that's because the distribution of the rat was thought to be three times larger than it actually is. That would allow for a reassessment.”

“Sensitive mice differ from the mice you encounter in your home or backyard in several important ways.”

“Mus musculus, black rats and brown rats are non-native species that have been introduced to Australia since European colonization.”

“Evolutionarily and ecologically, they are very different from native rodents. They compete with our native species for resources.”

“Delicate mice are part of a group of native rodents that have evolved in Australia over the past five million years. They are an important part of Australia's natural environment and ecosystem.”

“The delicate mouse is Australia's smallest rodent. Weighing only 6 grams, it's really small.”

Researchers also discovered that the delicate mice were able to adapt well to their environment, whether it was an arid desert or a forest.

“These three species will now be referred to by common names that reflect their habitat: Western or Pilbara delicate mouse, Eastern delicate mouse and Northern delicate mouse,” they said. Stated.

The team's paper is journal molecular ecology.

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emily roycroft other. 2024. Rapid speciation of the Australian delicate mouse. molecular ecologyin press

Source: www.sci.news

Scientists Baffled by Mummified Rat Found on 20,000-Foot Volcano: How Could Anything Be Living There?

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A view from the top of Sarin Volcano, one of three volcanoes in the Andes where researchers discovered the mummified corpse of a rat. The combined analysis of mummies and the capture of live specimens suggests that the rodents are able to climb Mars-like peaks on their own and somehow survive there.

This study rules out any connection to Inca rituals and suggests that the rats ascended independently.

At the top of a 6,000-foot volcano in the middle of the driest desert on earth, the environment was harsh and unforgiving. Temperatures were consistently below freezing, oxygen levels were less than half that at sea level, and strong winds whipped over the mountaintops across the sparse, rocky terrain.

In the 1970s and 1980s, carcasses of several rats were first discovered during expeditions to several Andean peaks, and researchers believed that the rodents must have hitchhiked with the Incas. It was initially thought that these pinnacles served as altars for the ceremonial sacrifice of children to the Inca gods. This led to the assumption that the rats probably rushed into the firewood and other supplies that the Incas had hauled up the slopes, or they were sometimes among the animals sacrificed along with humans.

In early 2020, a live specimen of a hedgehog was captured at the 22,000-foot peak of Lullillaco, a volcano that straddles the Chilean-Argentine border, casting doubt on the initial hypothesis. The analysis of mummified corpses, combined with the capture of live specimens discovered across the Andes, confirmed that the rats ascended the volcanoes independently. The capture of additional live specimens and the study of the mummies further solidified the evidence that the rats are able to survive at such high altitudes.

Further research and analysis are underway to understand the genetic insights and mysterious survival of the rats and to determine what drives rats to such high altitudes. The researchers are working to answer the ongoing question of why the rats rise to such extreme altitudes in the first place. This research was funded by grants.

Source: scitechdaily.com