Stone grouper re-structure the genome

Researchers have discovered that seabass grouper originating from non-jawed fish that appeared 500 million years ago suddenly re-structure their genome. As soon as the fertilized stone grouper divides into a few cells, the developing embryo removes millions of DNA units.

The research results were published in the Proceedings of the National Academy of Sciences issue this month. The lead author is Dr. Jeramiah Smith, a genetic expert at Washington University.

This result is considered to be the first observation to record the process of restructuring a vertebrate genome as a normal part of the development process. Scientists have previously discovered some invertebrate species, such as roundworms, that systematically reorganize the genome. However, the vertebrate genome is thought to need stability to ensure the correct functioning of animals in everyday life. It is believed that the genomes of these species only accept a few small changes that guarantee immune response, large-scale rearrangement has never been recorded before.

Smith and his team happened to discover changes in the sea lamprey genome while studying the genetic origins of the immune system in this species. Scientists have tried to understand how this species used a replication mechanism to create different receptors that detect pathogens.

The team was surprised to see the difference between the gene structure in germline - the cells will become eggs and sperm - and the genome structure in the embryos is then produced. DNA in embryonic cells has countless reefs like cells that are about to die (but don't actually die). Embryonic cells have fewer DNA sequences than sperm cells and their precursors.

'The reconstruction process begins when the embryo uses its genome instead of relying on the mRNA of the maternal individual,' Smith said. Restructuring is not completed at a time, but lasts for a long time during embryonic development. Scientists take a lot of effort to find out what has been lost and lost at a particular time. One of the findings is that the genome after the structure has fewer repetitive genes and more gene coding sequences.

Scientists do not know exactly how this happened and why. Smith said his hypothesis is that excess genetic material could play a role in the proliferation of precursor cells that produce eggs and sperm later on, as well as for embryonic development at the stage. head.Genetic matter can be eliminated because it is no longer needed or for the purpose of preventing abnormal growth.

A close-up shot of the oral structure of adult sea-rock grouper with concentric ring teeth. (Photo: copyrighted by the Great Lakes Fisheries Commission)

According to Smith, genome alterations in sea rock and some invertebrates seem to follow strict rules, although these changes are quite similar to DNA errors that cause cancer or genetic disorders in muscles. Higher levels of animals Understand how DNA rearrangement in rock grouper is regulated during the development process can indicate what holds or stabilizes the genome, as well as the role of restructure in shaping. into different cell groups in the body, such as squamous cells, muscle cells or liver cells.

If 20% of the genome disappears, how does the grouper have enough additional genes to share with its offspring?

'Crystalline cells - the precursor cells that develop into eggs and sperm later - are groups of cells that survive over time,' explains Smith. 'The precursor cells will be preserved throughout the development of the grouper. The genome in this cell group never changes. ' It is thought that only genetic material lost in later embryonic cells will develop into body parts, not lose in cells that maintain the race. Scientists have put a lot of effort into finding primordial stem cells that transform into eggs and sperm in stone grouper bodies, but this effort does not yield any results.

The team has not yet discovered how the sea lamprey's genome rearranges according to specific rules. This animal has spent a long time living in freshwater environment as larvae, where they do not need food but survive by snuggling in the mud.In their adulthood they live almost entirely in the sea as a parasite specializing in sucking blood from large fishes of the ocean. Mouth round, no jaw plugs into the prey like a straw. The rings of teeth arranged concentricly clung to the bad animal's skin. Rocky grouper is a voracious species.

Later, when they returned to the rivers and streams along the North Atlantic coast, the shrunken body was only for the purpose of reproduction and then died immediately after mating. The continental sea grouper herds in the Great Lakes lake and some nearby large lakes began when people built dams and canals in this area in the early 20th century. They grow very fast thanks to blood sucking. (and kill) artificially cultured fish for economic benefits and become a major threat to the fisheries of the Great Lakes region.

Biologists who are interested in sea-rock grouper are in part because of the lifestyle that moves between freshwater and saltwater areas, but mainly because of the intact fossils like the life of this species around the time that vertebrate animals catch head appears. Their close relatives are on Earth before dinosaurs. It is very likely that one day it will be discovered that the dynamics of this species in evolutionary history have been linked to the common ancestor of all vertebrates today.

'Sea lamprey has an evolutionary history of half a billion years,' said Smith. 'Evolutionary biologists and geneticists can compare their genomes with those of other vertebrate animals and genomes in humans to see which parts of this genome can already existed in our ancient ancestors. One would probably understand how changes in the grouper genome have led to their particular body structure and fish species have generally evolved from the mouth of the jaw to the mouth of the jaw. star."

Amemiya, the scientist who participated in the study, added: 'We cannot know any further discoveries about genetically modified animals in this animal. In science, there are times when a finding will leave results after several decades of publication. '

In addition to Smith and Amemiya, the list of scientists involved in the study also included Francesca Antonacci and Evan E. Eichler from the University of Washington School of Genetics. The research was funded by the National Institutes of Health, the National Science Foundation, and the Howard Hughes Medical Institute.