Announcing the first genome sequence of marsupials

Today, an international research group led by MIT Insider and Harvard Institute of Broad Insitute scientists and funded by the National Institutes of Health, published the first genome sequence of a mammal. bag, belonging to the South American opossum. When comparing the genome of the marsupial versus the genome of the non-pocketed animals, including humans, was published in the May 10 issue of the journal Nature. The team discovered the latest changes that led to the sequence of the human genome not located in the protein-decoding genes but in areas that are thought to be ' garbage ' DNA.

An attempt to solve the high-quality genome sequence of a gray-tailed South American opossum, Monodelphis domestica, began in 2003 at a cost of about $ 25 million. The sequencing work was funded by NHGRI National Institute of Genome Research, a unit of the National Institutes of Health and implemented at the Broad Institute Sequencing Platform, a member of the genome sequencing research system. Large tissue of NHGRI Institute.

'The opium genome occupies an unusual position on the tree of life. How this analysis fills an important gap in our understanding of the mammalian genome, including us, has evolved over millions of years. ' The director of the NHGRI Institute, Ph.D. and medical doctor Francis S. Collins said. 'These findings illustrate just how important it is to understand all of the human genome not only as a small part of the protein-decoding genes. We must identify all the functional elements in the genome if we plan to have the most complete toolbox capable of exploring biology, improving human health. "

The marsupials are unique mammals because their offspring are born at a very early stage of development, clinging to the mother's nipple and completing the next stage of development during the protective bag. This makes the animals can be used in the study of early development.

South American opossum (Photo: Physorg.com)

Monodelphis can be used as a model to serve many other biomedical research areas. For example, it is the only experimental animal that only ultraviolet radiation can make them melanoma, a type of skin cancer that attacks humans when exposed to too many rays. purple of the sun. The sequencing of the opioid genome will enable scientists to better understand the molecular basis of melanin and its development and develop methods for disease prevention and treatment. new.

The genome sequence of opossum marsupials also gives scientists a new perspective on the evolutionary origin of the human genome. It shows the genetic differences between placental mammals, such as humans, mice and dogs and marsupial mammals, such as opossum and kangaroo marsupials.

'Pocketed mammal is an existing animal with the closest relative to mammals having the placenta. Because of this relationship, the genome of the opossum marsupial will have a unique look and, through this perspective, can see the evolution of our own genome. ' Dr. Kirstin Lindblad-Toh, co-director of the sequencing and genome analysis program of Broad Institute and the lead author of the study, said.

The marsupial and ancestors of placental mammals branched 180 million years ago. By comparing the genome of opossum and human mammals, scientists identified the genetic elements that exist in mammals that have placenta, but lack in marsupials - that is, gene elements. This may be the basis of the differences between these two mammals.

Interestingly, about one-fifth of the key functional elements in the human genome arise during the relatively recent evolutionary period. By focusing on genetic innovations, scientists have made two major discoveries:

- First , the vast majority (about 95%) of the recent genetic innovation is not in the protein decoding genes, but in the regions of the genome where these regions do not contain genes and many of these regions. recently considered 'garbage' DNA in recent times. Now, scientists know that junk DNA may contain regulatory elements and these factors affect the activity of nearby genes, but the importance of areas that do not contain the gene remains. is being explored. The new results show that mammals evolve by creating new proteins not much by correcting molecular controls , when and where control orders to make protein .

- Secondly , many of the new DNA instructions seem to come from transposons or ' jumping genes ', genes that are located in places once thought to be junk DNA.

'The jumping gene has a restless way of life, often they are shuttled from one chromosome to another,' said Tarjei Mikkelsen, the first author of the study. 'Now it is clear that in these movements, these jumping genes have disseminated important gene innovations throughout the genome.'

Other important findings are from the genome analysis of opossum marsupials, including:

- Poisonous animals have many genes involved in immunity, and this has challenged the hypothesis that marsupials possess only primitive immune systems.

- The genome of opossous marsupials has an unusual structure with fewer chromosomes than the human genome (9 pairs of opiate chromosomes in comparison to 23 human chromosomes) but has a total longer-term (3.4 billion gene genes in opalescent mammals compared with 3 billion human genes).

Thanh Van

According to the National Human Genome Research Institute