Los dragones de Komodo adquirieron una armadura en sus cabezas para protegerse de sus familiares

The Komodo monitor lizard is covered with “chainmail” of osteoderms: bone plates in the dermis. Also, only adults have it, according to The Anatomical Record. Apparently, the researchers believe that this armor serves to protect against other Komodo dragons while facing each other over territory.

Komodo monitor lizards or Komodo dragons (Varanus komodoensis) live on the Indonesian islands of Komodo, Flores, Rincha and Gili Motang. These are the largest lizards on the planet, on average they weigh 70 kilograms and reach a length of three meters. Researchers believe that its size is due to the gigantism of the islands, since in the four islands where they live, lizards are the only predators.

Reptiles lead a solitary lifestyle, they meet with other individuals only during hunting, eating prey and mating. In the mating season, males face each other for females and territory. The females do not support the winner much and at first they resist their courtship with the help of teeth and claws.

Inner helmet
Previously, biologists found oranoderma: ossifications, which often take the form of platelets and grow in one of the layers of the skin, the dermis, in the monitor lizard (genus Varanus). The researchers also reported the presence of osteoderma on the head of the Komodo monitor lizards, but it was not clear if all the lizards had it or only adults, and what areas they covered.

Now, researchers from the University of Texas at Austin, led by Jessica A. Maisano, performed a high-resolution computed tomography on two Komodo dragons. One individual was an adult male who died at the Fort Worth Zoo in Texas at the age of 19.5, and the second was only two days from the San Antonio Zoo. Since the 2.5-meter monitor lizard did not fit in the device, the authors performed a tomography of only his head.

Scientists have discovered that the “chainmail” of bone excrescences covers almost the entire head of an adult, with the exception of the eye sockets and nostrils. But the baby had no osteoderm at all.

The scientists explained this difference by the fact that Komodo adult monitor lizards have to defend themselves against their rivals and aggressive females. While young people spend a lot of time in trees, where they do not run the risk of encountering an aggressive relative, adult monitor lizards are too heavy to climb trees.

The authors point out that conducting experiments with only one adult is not very correct, but they did not find other dead Komodo lizards, although they reviewed 171 vertebrate collections from 12 countries. It is even more important for researchers to create collections in zoos and exchange information with colleagues from other countries.

Earlier this year, scientists collected the genome of Komodo dragons and discovered how lizards acquired a good sense of smell, allowing them to smell prey at a distance of several kilometers and protect them from anticoagulants from their own saliva.

“Space mice” that returned to Earth could have healthy and trouble-free puppies

Japanese scientists found no significant changes in the reproductive function of mice after one month of life in the ISS. Researchers have discovered that the same genes work in sperm as “land” mice are also mobile and fertile. The work was published in Scientific Reports.

Flying into space involves many risks: stress during takeoff and landing, weightlessness and cosmic radiation. All of these factors can affect mobility, fertility and the condition of sperm DNA.

In previous research, scientists discovered space rats produced less sperm. In another experiment, frozen and dried mouse sperm were sent to space. Upon their return, they were able to fertilize the ovules, but the researchers found traces of radiation damage in them.

Space mice
Now Takafumi Matsumura and scientists from the University of Osaka have developed a new way to investigate the effects of space on the reproductive capacity of mice. They sent two groups of animals to the ISS: one spent 35 days in microgravity, and the other was in a centrifuge, which artificially creates gravity conditions similar to terrestrial ones. The third group lived on Earth and served as control.

After the animals returned from space, the authors verified the status of their gonads. They found that the auxiliary glands, the prostate and seminal vesicles, decreased in size in both “space” groups compared to the control. However, histologically, they were not different, and the gene expression profile also coincided in the three groups, showing no signs of pathology.

Then, the researchers examined the state of sperm in experimental mice. In all three groups, they did not differ morphologically. The sperm of both groups of “space” animals swam a little more slowly in a straight line, but otherwise remained mobile. Their DNA was the same length as that of “terrestrial” mice, that is, it had no additional interruptions. Finally, the sperm of the three groups fertilized eggs with the same success: about 87%.

The embryos obtained from these eggs were planted in mice, and they gave birth to healthy mice. Neither in appearance nor in growth rate differed from each other. In addition, they crossed each other and received the third generation of mice, in which the researchers also found no trace of their grandparents’ cosmic past.

The authors of the article conclude that they failed to detect any effect of microgravity on the reproductive capacity of mice, either externally or at the molecular level. It is true that they do not exclude that the effect can manifest itself on a different level: epigenetic, as was the case in a recent experiment with twin astronauts, one of whom went to the ISS and the second lived on Earth as a control.

Successful experiment with mice brings us closer to same-sex couples having children

A team of scientists in China has succeeded in creating offspring of apparently healthy mice from two mice of the same sex (females). The researchers also generated offspring of two male mice, but all those young died shortly after birth.

The results have been published in the journal Cell Stem Cell and show that although we are getting closer and closer to two men or two women having their own biological children, the new technique still faces serious obstacles should it be attempted in humans.

“It is never too much to emphasize the risks and the importance of security, before any human experiment is involved,” says Wei Li at the Chinese Academy of Sciences in Beijing. “But we believe that our work takes it closer,” he adds.

Genetic fight
The biggest obstacle to creating babies from parents of the same sex is a phenomenon called genetic imprinting. In mammals, certain genes are deactivated in the sperm genome, by adding epigenetic markers to the DNA. These markers do not change the underlying DNA sequence, but ensure that the gene is not expressed. Different genes are deactivated in the ovules.

Unfortunately, the imprint means that if in some way the genomes of two females, or two males, are combined in an ovule and it begins to develop, the resulting embryo will die. But in 2004, a team in Japan managed to create the first mammal with two mothers. They achieved this by removing a DNA fragment in one of the genomes to mimic the effect of the imprint, but from 500 attempts only two mice survived to adulthood.

On this occasion, Li’s team has greatly improved the success rate by removing three bits of DNA to better mimic the imprint. Of 200 attempts to create a mouse with two mothers, scientists succeeded 27 times. These mice grew normally, while those with less deletions were abnormally small.

In parallel, Li and his colleagues also created 12 mice of male parents (from a total of 500 attempts). However, they had to remove 7 DNA fragments and none of the offspring survived until adulthood.

Although surprising, this is not the first time that they have had mice of male parents. In 2010, a team used a genetic trick to make male mouse cells grow inside female mice. Females with ovaries derived from male cells mated with normal males. For obvious ethical reasons this technique could not be applied in humans.

The risks of applying them in humans
On the other hand, Li mice reveal more about which genes are crucial for normal development. However, it is not clear if the results apply to other mammals such as humans; The team will try trying to create monkeys with two mothers. And before we can think about trying to create human babies with same-sex parents, we would need a way to mimic the imprints without resorting to genetic modifications. Because eliminations would have detrimental effects on later generations.

This could be achieved with the editing of CRISPR genes; and several groups, including Li’s, are trying to add or remove epigenetic markers without changing the underlying DNA sequence. “We tried but we still don’t know the answer,” says the researcher.

However, even if it worked, there are still questions about how safe the method is. “Defective imprints do lead to human diseases,” says New Scientist Azim Surani of the University of Cambridge, who discovered the phenomenon of the imprint in 1984. Any manipulation could have serious consequences, he warns.

The same case of Li mice can serve as an example. Although mice seem healthy, having removed only three DNA fragments means they may have more subtle problems that can only be noticed over time.

About the Project

A Quantitative and Comprehensive Atlas of Gene Expression in Mouse Development.

The complex process of development, from the one cell zygote to the adult, requires extensive cell-cell communication networks to direct the differentiation and patterning of the body. These signalling networks regulate the function and expression of genes. Significantly, many disorders, such as cancer, result from disruption of the same communication networks, and the genes they regulate, that operate within tissues during development. Because disease is the result of the normal state going awry, a detailed characterization of the normal state is essential. The mouse has emerged as the premier model in biomedical research for studying normal mammalian development and human disease. The high degree of genetic homology between mouse and humans and the powerful ability to modify the genome of the mouse have established the importance of this model organism in biomedical studies.

A deep understanding of mammalian development and the engineering of murine models for human disease requires an intimate knowledge of the molecules involved. Thus, we propose to construct an Atlas of gene expression. This Atlas will define the normal state for many tissues by determining, in a comprehensive and quantitative fashion, the number and identity of genes expressed throughout development. The scope of the project will encompass multiple stages of development, from the single cell zygote to the adult, and will include an extensive initial collection of 200 tissues. We will focus whenever possible on individual cell types and tissues rather than on cruder preparations of material containing heterogenous mixtures of cells or tissues.

Serial Analysis of Gene Expression (SAGE) is the gene expression methodology of choice for this work. Unlike expressed sequence tags (ESTs) and gene chip data, SAGE data are independent of prior gene discovery and are quantitative. Furthermore, SAGE data are digital, easily exchanged between laboratories for comparison and can be added to by scientists for years to come. Thus, this Atlas will include a data structure and data curation strategy that will facilitate the ongoing collection of gene expression data, even after the completion of this project.

In addition, we will assemble gene expression profiles for a few focused experiments that will test hypotheses related to the techniques employed, tumour models and models of abnormal development. This will test the resource and provide quality control, validation and demonstrate applicabilty.

The Atlas will provide an enabling resource to both clinical and basic researchers. The resource will be comprehensive, quantitative, and publicly accessible, containing data on essentialy all genes expressed throughout select stages of mouse development. We anticipate that this Atlas will become a primary resource for researchers spanning multiple disicplines to facilitate the understanding of complex genetic pathways controlling normal development and disease progression in the mouse. Thus, this is a timely, important, large-scale high-throughput project, with a broad scope and an anticipated significant impact on both basic science and cancer research.

Preparation of a SAGE Library

Curious about how the Serial Analysis of Gene Expression (SAGE) method works? Read our brief introduction to this process.

Sponsoring the Mouse Atlas of Gene Expression

We are open to collaboration on the Mouse Atlas project. If you are interested in having us construct and/or sequence SAGE libraries for you, please contact Canada’s Michael Smith Genome Sciences Centre through our Custom Services contact for further information on services and pricing.

Acknowledgements

Funding provided by Genome Canada, BC Cancer Agency, BC Cancer Foundation and the National Cancer Institue (USA).