The sea cucumber genome points to genes for tissue regeneration

October 12, 2017
Though it may not look the part, this holothuroid -- or sea cucumber -- is a relatively close cousin of vertebrates, and a prized delicacy in Asian seafood markets. It also has the unique ability to discard its viscera and grow them back in a few weeks. Credit: Qiang Xu

A new high-definition genome sequence of the sea cucumber provides molecular insights into its ability to regenerate, according to a new study publishing 12 October in the open access journal PLOS Biology by Xiaojun Zhang, Lina Sun, Hongsheng Yang and Jianhai Xiang, of the Institute of Oceanology, Chinese Academy of Sciences, and colleagues. The genome sequence also helps explain why the sea cucumber has such a radically different skeletal structure from other members of the echinoderm phylum, and may be useful for understanding evolution of the animal kingdom.

Sea cucumbers form one class of the echinoderms, a phylum that also includes and sea stars ("star fish"). Echinoderms and chordates (a closely related phylum that includes humans) share a feature that distinguishes them from most other animals: they are so-called deuterostomes, in which the anus, rather than the mouth, forms first in development. Sea cucumbers are unique among echinoderms in not having a hardened calcium exoskeleton, and in their capacity to regenerate damaged or lost body parts and viscera to a much greater extent than sea urchins or .

To explore the genetic underpinnings of these features, and to better understand the evolution of the deuterostomes, the authors performed high-definition genomic sequencing of the sea cucumber Apostichopus japonicus (also known as the Japanese sea cucumber), covering about 92% of its estimated 880 megabases of DNA, including more than 30,000 genes.

By comparing the genome of A. japonicus with that of other organisms, the authors found evidence that the echinoderms diverged from hemichordates (a small group of marine deuterostomes that includes the acorn worms) about 533 million years ago and the split off from other the echinoderm classes about 479 million years ago. The authors showed that while the sea urchin genome includes 31 genes for biomineralization, critical for forming a calcified skeleton, the sea cucumber has only seven such genes. They also found that the sea cucumber expressed these biomineralization genes at much lower levels throughout development, likely accounting for their softer bodies compared to sea urchins.

As a strategy to scare off predators, sea cucumbers can expel their viscera, which they can then regenerate within several weeks. The authors found a group of duplicated genes, called PSP94-like genes, that were specifically expressed in the regenerating intestines of the sea cucumber, which had no corresponding genes in other echinoderms, suggesting that these genes may be crucial to the animals' ability to quickly regrow their viscera. A second group of , called fibrinogen-related proteins, were also duplicated and highly expressed during regeneration, indicating they likely contribute to this ability as well.

"The sea cucumber is a particularly promising model animal for regenerative medicine," said Xiang, and the availability of its genome should aid efforts to study the biology of regeneration and determine if echinoderm regrowth can offer insights that can be applied to human medicine. "Our findings should also facilitate the understanding of the requirements for sustainable utilization and effective breeding of echinoderms, in support of the high-value sea cucumber industry," which includes its use as a source of food and traditional Chinese medicine.

Explore further: Sea cucumbers and sea urchins could hold the key to looking young

More information: Zhang X, Sun L, Yuan J, Sun Y, Gao Y, Zhang L, et al. (2017) The sea cucumber genome provides insights into morphological evolution and visceral regeneration. PLoS Biol 15(10): e2003790. doi.org/10.1371/journal.pbio.2003790

Related Stories

430-million-year-old extinct echinoderm found in England

September 13, 2017

(Phys.org)—A team of researchers from the U.K. and the U.S. has identified the remains of a 430-million-year-old extinct echinoderm found in a fossil bed in Herefordshire, England. In their paper published in Proceedings ...

Xenacoelomorpha -- a new phylum in the animal kingdom

February 16, 2011

An international team of scientists including Albert Poustka from the Max Planck Institute for Molecular Genetics in Berlin has discovered that Xenoturbellida and the acoelomorph worms, both simple marine worms, are more ...

Extra DNA creates cucumber with all female flowers

June 4, 2015

Ask a plant researcher how the sex of a cucumber plant is determined and the person will tell you, "It's complicated." Depending on a complex mix of genetic and environmental factors, cucumbers can be seven different sexes. ...

Bitter food but good medicine from cucumber genetics

November 27, 2014

High-tech genomics and traditional Chinese medicine come together as researchers identify the genes responsible for the intense bitter taste of wild cucumbers. Taming this bitterness made cucumber, pumpkin and their relatives ...

Recommended for you

Live fast die young: Updating signal detection theory

October 18, 2017

Signal Detection Theory is a popular and well-established idea that has influenced behavioral science for around 50 years. Essentially, the theory holds that in a predator-prey relationship, prey animals will show more wariness ...

Tiny protein coiled coils that self-assemble into cages

October 17, 2017

(Phys.org)—A large team of researchers with members from Slovenia, the U.K, Serbia, France and Spain has developed a technique that causes proteins to self-assemble into geometric shapes on demand. In their paper published ...

The importance of asymmetry in bacteria

October 17, 2017

New research published in Nature Microbiology has highlighted a protein that functions as a membrane vacuum cleaner and which could be a potential new target for antibiotics.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.