Genome of humans` closest invertebrate relative sequenced

Scientists have sequenced the genome of Botryllus schlosseri - a small sea creature which is humans` closest living invertebrate relative.

Washington: Scientists have sequenced the genome of Botryllus schlosseri - a small sea creature which is humans` closest living invertebrate relative.

The advance will make it possible to find the genetic basis for some of the animal`s amazing regenerative abilities and immunity features, which potentially could be applied to human medicine.

Botryllus schlosseri fuses together with others to form colonies that look like psychedelic blobs, encrusting rocks and seaweeds. It can reproduce asexually, and an entire individual can be regenerated from its blood vessels alone.

In total, the group led by Stanford scientists sequenced the animal`s 580 million base pairs of DNA. (The human genome, by comparison, consists of more than 3 billion base pairs.)

Though the researchers haven`t studied the entire genome, they found evidence that Botryllus makes a useful invertebrate model for studying human genetics, in particular for highlighting the evolution of immunity and stem cell-mediated regeneration.

The researchers compared the Botryllus genome with several vertebrate and invertebrate genomes.

Focusing on genes involved in various human diseases ? affecting things such as heart and eye development, pregnancy and cancer ? they found homologous genes for each in Botryllus, far more matches than in any of a dozen other invertebrates commonly used in research.

An additional investigation of blood-related genes revealed that Botryllus was probably the first invertebrate to have vasculature in the same context of the human circulatory system, with blood cells travelling through blood vessels.

"The whole body can regenerate from the vasculature alone: the heart, digestive system, sophisticated tissues," said Ayelet Voskoboynik, the lead author on the study.

"And it can do this relatively fast, probably using stem cells. Now that we have the genome, we can try to understand the mechanism behind it," Voskoboynik said.

The study of Botryllus` genome could also lead to advances in transplant medicine. When two genetically distinct Botryllus colonies come into contact with each other, they either fuse their blood vessels to create a single organism, or reject one another and maintain individuality.

When the blood vessels between the two colonies fuse into one interconnected network, the stem cells from each partner colony begin to circulate throughout the other.

The stem cells compete and in many cases one partner`s stem cells "win" ? and any new or replacement tissue grown through the fused colony does so based on the "winner`s" genetic code.

A similar process occurs in humans who undergo an allogeneic transplant when a patient receives tissue or cells from a non-identical donor.

The study was published in the journal eLIFE.


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