Cross-section through probes of a transgenic sea anemone showing the differentiation outgrowths of SoxC cell clusters (purple) and macrophages (yellow). Credit: Andreas Diener
In sea anemones, highly conserved genes ensure lifelong differentiation between neurons and gland cells.
Sea anemones are apparently immortal animals. They appear to be immune to aging and the negative effects that humans experience over time. However, the exact reasons for their eternal youth are not fully understood.
The genetic imprint of the anemone Nematostella vectensis It reveals that members of this incredibly ancient animal phylum use the same gene cascades for neuronal differentiation as more complex organisms. These genes are also responsible for maintaining the homeostasis of all cells of the organism during the life of the anemone. These results were recently published in the journal cell reports by a group of evolutionary biologists led by Ulrich Technau of the University of Vienna.
Almost all living things are made up of millions, if not billions, of cells that come together in complex ways to form specific tissues and organs, which are made up of a range of cell types, such as a variety of neurons and glandular cells. However, it is unclear how this critical balance of diverse cell types appears, how it is regulated, and whether different cell types of different organisms have a common origin.
Optical longitudinal section of a sea anemones with genetically modified neurons (in red) in both cell layers. Muscles stained green, cell nuclei blue. Credit: Andreas Diener
Single-celled imprinting leads to a common ancestry
The research group, led by developmental evolutionary biologist Ulrich Technau, who also heads the Single Cell Regulation of Stem Cells (SinCeReSt) Research Platform at the University of Vienna, has deciphered the diversity and evolution of all types and types of neurons and glands. Developmental origins of sea anemones Nematostella vectensis.
To achieve this, they used single-celled transcription, a method that has revolutionized biomedicine and evolutionary biology over the past decade.
“With this, whole organisms can be resolved into single cells – and all the genes that are currently expressed in each individual cell can be decoded. Different cell types differ fundamentally in the genes they express. Therefore, single-cell transcripts can be used to determine the molecular fingerprint of each individual cell,” says Julia Steiger, first author of the current publication.
In the study, cells with overlapping fingerprints were grouped together. This allowed scientists to distinguish between specific cell types or cells in transitional stages of development, each with unique expressive groups. It also allowed researchers to identify groups of progenitors and stem cells from different tissues.
To their surprise, they found that, contrary to previous assumptions, neurons, glandular cells and other sensory cells come from a common ancestral group, which can be verified by genetic tagging in living animals. Since some glandular cells with neuronal functions are also known in vertebrates, this may indicate a very ancient evolutionary relationship between neurons and glandular cells.
Old genes are constantly used
The gene plays a special role in the development of these common progenitor cells. SoxC is expressed in all neuronal precursor cells, gland cells, and neurons and is essential for the formation of all these cell types, as the authors were also able to demonstrate in knockout experiments.
“Interestingly, this gene is not exotic: 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 neuronal differentiation appear to be retained. across the animal kingdom,” says Technow.
By comparing different life stages, the authors also found that in sea anemones, genetic processes of neuronal development from embryo to adult organism are maintained, contributing to neuronal homeostasis throughout the anemone’s life. Nematostella victensis.
This is remarkable because, unlike humans, sea anemones can replace lost or damaged neurons throughout their lives. For future research, this raises the question of how sea anemones manage to maintain these mechanisms, which occur in more complex organisms only at the embryonic stage, in the adult organism in a controlled manner.
Reference: “Single-cell transcription identifies conserved regulators of glandular neuronal lineages” by Julia Steiger, Alison J. Cole, Andreas Diener, Tatiana Lebedeva, Grigory Jenikovich, Alexander Reis, Robert Rischel, Elizabeth Taudes, Mark Lassnig, and Ulrich Teknau, Sept. 20, 2022, cell reports.
DOI: 10.1016 / j.celrep.2022.111370