Tentacle of a Transgenic Sea Anemone

Forever Young: Scientists Reveal the Secret to a Strange Animal’s Eternal Youth

Tentacle of a transgenic sea anemone

Cross-section through a tentacle of a transgenic sea anemone showing the differentiation products of the SoxC cell population (magenta) and retractor muscles (yellow). Credit: Andreas Denner

In sea anemones, highly conserved genes ensure the life-long differentiation of neurons and gland cells.

Sea anemones are seemingly immortal animals. They seem to be immune to aging and the negative impacts that humans experience over time. However, the exact reasons for their eternal youth are not fully understood.

The genetic fingerprint of the sea anemone Nematostella vectensis reveals that members of this incredibly ancient animal phylum use the same gene cascades for neural cell differentiation as more complex organisms. These genes are also responsible for maintaining the balance of all the cells of the organism during the life of the anemone. These results were recently published in the journal Cell reports by a group of developmental biologists led by Ulrich Technau of the University of Vienna.

Almost all animal organisms are made up of millions, if not billions, of cells that come together in complex ways to create specific tissues and organs, which are made up of a range of cell types, such as a variety of neurons and gland cells. However, it is unclear how this critical balance of diverse cell types emerges, how it is regulated, and whether different cell types from different animal organisms have a common origin.

Optical longitudinal section of a sea anemone

Optical longitudinal section of a sea anemone with nanos1 transgenic neuronal cells (red) in both cell layers. Muscles are stained green, cell nuclei blue. Credit: Andreas Denner

Single-celled fingerprint leads to common ancestry

The research group, led by evolutionary developmental biologist Ulrich Technau, who is also head of the Single Cell Regulation of Stem Cells (SinCeReSt) research platform at the University of Vienna, has deciphered the diversity and evolution of all nerve and gland cell types and their developmental origins in the sea anemone Nematostella vectensis.

To achieve this, they used single-cell transcriptomics, a method that has revolutionized biomedicine and evolutionary biology over the past decade.

“With this, entire organisms can be resolved into single cells – and the entirety of all genes currently expressed in each individual cell can be decoded. Different cell types differ fundamentally in the genes they express. Therefore, the Single-cell transcriptomics can be used to determine the molecular fingerprint of each individual cell,” says Julia Steger, first author of the current publication.

In the study, cells with an overlapping fingerprint were grouped together. This allowed scientists to distinguish between defined cell types or cells at transitional stages of development, each with unique expression combinations. It also allowed researchers to identify common populations of progenitor and stem cells from different tissues.

To their surprise, they found that contrary to previous assumptions, neurons, gland cells and other sensory cells come from a common progenitor population, which could be verified by genetic marking in living animals. Since some glandular cells with neuronal functions are also known in vertebrates, this could indicate a very ancient evolutionary relationship between glandular cells and neurons.

Old genes constantly used

A gene plays a particular role in the development of these common ancestor cells. SoxC is expressed in all precursor cells of neurons, gland cells and cnidocytes and is essential for the formation of all these cell types, as the authors were also able to show in knockout experiments.

“Interestingly, this gene is not foreign: it also plays an important role in the formation of the nervous system in humans and many other animals, which, together with other data, shows that these key regulatory mechanisms of nerve cell differentiation appear to be retained. across the animal kingdom,” says Technau.

By comparing different life stages, the authors also found that in sea anemones, the genetic processes of neuronal development are maintained from the embryo to the adult organism, thus contributing to the balance of neurons throughout. of anemone life. Nematostella Vectensis.

This is remarkable because, unlike humans, sea anemones can replace missing or damaged neurons throughout their lives. For future research, this raises the question of how the sea anemone manages to maintain these mechanisms, which in more complex organisms only occur at the embryonic stage, in the adult organism in a controlled manner.

Reference: “Single-Cell Transcriptomics Identifies Conserved Regulators of Neuroglandular Lineages” by Julia Steger, Alison G. Cole, Andreas Denner, Tatiana Lebedeva, Grigory Genikhovich, Alexander Ries, Robert Reischl, Elisabeth Taudes, Mark Lassnig and Ulrich Technau, September 20, 2022 , Cell reports.
DOI: 10.1016/j.celrep.2022.111370

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