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Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Understand how a strange worm resumes its head (or its tail)

Understand how a strange worm resumes its head (or its tail)



  An image of orange stains on white coral.
Click to enlarge / Some of the worms (orange) cover corals. , who regained the lower half of his body through some serious awkward transient scenes. In fact, regeneration is accomplished by the mill, with lizards and amphibians, which grow limbs and tails, while different worms can recover half of their whole body. The way they manage this has been the subject of extensive research, and we have a good idea of ​​some of the involved genes and processes. But it is fair to say that we do not have a strong idea of ​​how the whole process is coordinated and directed to the formation of all necessary tissues.

One step in this direction comes from a recent study that takes a strange angle in regeneration. To understand the process, the authors arrange the genome of a worm that can be regenerated into two full bodies after it is cut in half. But the worm is also part of a group that contains the closest living relatives of two-sided animals ̵

1; those with the left and right sides. As such, it can provide a fascinating view of our own evolution, but this is something the researchers choose to ignore in this article.

Zena Coeo, what? have left and right sides. This includes some creatures (such as sea urchins), where both sides are not so obvious. These two-sided animals begin at the onset of their development as three layers of cells: an outer layer that forms the skin and nerve tissue; central, which forms internal structures such as muscles and bones; and an inner layer that forms the lining of the intestine.

But this is not the only plan of the body around him. Arrows like jellyfish seem to have complex structures that do not fit well with the organization we see in bi-lateral animals. But some ocean worms form a group called Xenacoelomorpha which appears to be closer to the two-sided animals. Xenocoelomer obviously has cells that form an outer layer, and there are also loosely packed cells in the interior that resemble those that form muscles and bones in animals like us. But it seems that there is no clear intestine; his mouth simply allows access to the cavity in which the free packed cells are located. They surround each part of the incoming food and assimilate it.

Researchers have suggested this structure to show that xenacolomorphs are probably the closest surviving relatives of bi-lateral animals. And the genome of one of these worms, as described in the latest report, seems to confirm this. The genom of Hofstedia indicates that it is more closely related to us than the jellyfish, and is most closely related to the least complex bilateral groups. Which means that a careful analysis of the genome tells us the origin of the bipartite life.

But this analysis is not in the new document. Mansy Srivästava, who heads the laboratory where most of the team is working, told Ars that scientists had previously identified almost all of the genes that Hapstenia transcribed into the RNA. They show that the content of the Hofstenia gene is quite typical for other animals and is approximately similar to that of the two groups of animals and other groups. So, says Srivastava, interest has shifted to how these genes are used, which requires analyzing how genes are activated or muted.

And what better way to focus on this than to be careful about the genetic activity associated with Hofstenia's remarkable regenerative capabilities that include the restoration of two complete animals when the adult worm is cut in half. To investigate this, the researchers cut the animals in half, waited a few hours (had time points between three hours and two days) and then marked the active sites in their genome.

To make a markup, the researchers used a mobile genetic element that is technically called a transposon and sometimes called a "jump gene". Under appropriate conditions, these jumping genes will move to new places in the genome, but only if these sites are accessible. Areas where the genes are not active tend to be tightly packaged and will not target the jumping gene. Areas where the genes are active, by contrast, have a freer and more open structure, making it a great target for the jumping gene.

By tracking which areas of the genome are targeted, the researchers have been able to track where the DNA has been opened so the new genes become active. They came out with 18,000 different sites, many of which are likely to become active to allow for regeneration. Some of them are head-specific, while others are mostly active in the queue. Others were active in both halves of the body

EGR

By computer, the team then searched for proteins that could cling to DNA in these places. It is already known that one of the proteins called EGR is involved in the healing of wounds in other organisms and seems to stick to the earliest places that become active. This suggests that the EGR acts as a "pioneer" that helps to open the DNA structure in places close to critical genes and allows them to participate in regeneration.

And it seems that EGR is part of an ancient road with deep roots in animals. Planetary worms, which are also known for their regenerative capability, also have a version of EGR. It also appears to be one of the earliest operating genes during the regeneration process. Of course, people have four EGR-related proteins, and we are pretty famous for having limited regeneration capacity. So understanding how the activity of these proteins differs from the activity observed in remote animals can help explain why.

Meanwhile, these new data provide a framework for further research on the regeneration process. The pioneering function of EGR initiates a cascade of regulation of gene activity – at least two of the genes that stick to encode the DNA-binding regulatory proteins themselves. So, over time, this can help provide a fuller picture of the regeneration process.

Science 2019. DOI: 10.1126 / science.aau6173 (For DOIs)
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