According to new Cornell research, cnidocytes or stinging cells that are characteristic of sea anemones, hydrae, corals, and jellyfish, and which make us careful of our feet while wading in the ocean are also excellent methods to understanding the emergence of new cell types.
In new research published in the Proceedings of the National Academy of Sciences on May 2,Leslie Babonis, an adjunct professor of ecology and evolutionary biology at the College of Arts and Sciences, demonstrated that these stinging cells evolved by repurposing a neuron from a pre-cnidarian animal.
These surprising findings demonstrate how new genes have acquired new functions to drive biodiversity''s evolution, according to Babonis. They suggest that the co-option of ancestral cell types was a valuable source for new cell functions during the early evolution of animals.
Understanding how special cell types, such as stinging cells, become necessary in evolutionary biology is one of the most significant challenges in this world of medicine. Despite this belief, researchers have found that cnidocytes evolved from a pool of stem cells that provide nutrients to neurons, but no one was aware until now of how those stem cells decided to make either a neuron or a cnidocyte. Babonis believes this understanding is useful in explaining how these cells evolved in the first place.
Cnidocytes (cnidos is Greek for stinging nettle), common to species in the diverse phylum Cnidaria, can launch a toxic barb or blob or enable cnidarians to stun prey or deter invaders. So she and her colleagues at the University of Florida''s Whitney Lab for Marine Bioscience developed a neural network to identify a neuron.
One of the unusual features of cnidocytes is that they all have an explosive organelle (a small pocket inside the cell) that makes you sad. These harpoons are made of a protein that is also found in cnidarians, so these cnidocytes seem to be one of the most obvious examples of how the origin of a new gene (that encodes a unique protein) might influence the development of a new cell type.
Using functional genomics in the starlet sea anemone and Nematostella vectensis, researchers demonstrated that cnidocytes develop by suppressing the expression of a neuropeptide, RFamide, in a subset of developing neurons, and repurposing those cells as cnidocytes. Moreover, researchers demonstrated that a single cnidarian-specific regulatory gene is both responsible for suppressing the neural function of those cells and turning on
Both neurons and cnidocytes are similar in size, according to Babonis; both are tiny cells capable of ejecting something out of the cell. Neurons secrete neuropeptides proteins that quickly communicate information to other individuals. harpoons are secreted in poison-laced cells.
When the cell is on, you get a cnidocyte, and when it''s off, you get a neuron, according to Babonis. It''s a pretty simple logic for controlling cell identity.
According to Babonis, this is the first experiment to prove that this logic is in place in a cnidarian, so this feature was likely to influence how cells became different from each other in the early multicellular animals.
Future research will be undertaken by Babonis and her lab to investigate how widespread this genetic off-on switch is in creating new cell types in animals. One project, for example, will investigate whether a similar mechanism is the origin of novel skeleton-secreting cells in corals.
The National Science Foundation and the NASA have all provided the funds necessary to do the research.