Integrative genome and transcriptome mining identifies a diverse repertoire of cyclooxygenase/prostaglandin- endoperoxide synthase-like candidates in Porifera
By integrating extensive genomic and transcriptomic data, this study identifies a diverse repertoire of cyclooxygenase/prostaglandin-endoperoxide synthase-like candidates in Porifera, challenging previous assumptions of their absence and suggesting the enzyme lineage originated in the last common ancestor of sponges, cnidarians, and bilaterians.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
For billions of years, animals have relied on a sophisticated chemical language to manage inflammation, blood flow, and reproduction. At the heart of this system are enzymes called cyclooxygenases. Think of these enzymes as specialized molecular machines that take a common fatty acid found in cell membranes and transform it into powerful signaling molecules known as prostaglandins. These signals tell the body when to heal a wound, when to fight an infection, or when to trigger a reproductive cycle. For a long time, scientists believed these machines were a relatively recent invention, appearing only in complex animals like vertebrates and perhaps some corals. The reasoning was simple: the earliest branches of the animal family tree, such as sponges, seemed to lack the genetic blueprints for these enzymes entirely. If sponges, which have existed for hundreds of millions of years, did not have them, then the machinery must have evolved later, after sponges had already split off from the rest of the animal kingdom.
This assumption has now been challenged by a comprehensive search through the genetic code of sponges. A researcher named Sebastiano Scibelli, working independently, decided to look deeper than ever before. Instead of relying on a few scattered genetic sequences, he gathered a massive collection of data, including the complete genetic blueprints of 213 different sponge species and thousands of RNA sequences that show which genes are active. He then used powerful computer tools to scan this data for the specific patterns that define cyclooxygenase enzymes. The goal was to see if the genetic signatures of these molecular machines were hiding in the sponge genome, perhaps disguised by millions of years of evolutionary change.
The search was rigorous. The researcher did not just look for a single match; he built a multi-layered verification system. He compared sponge genetic sequences against known enzymes from other animals, checked for the specific structural parts that make the enzyme work, and verified that the genes were actually being read by the cell. He also looked at the physical structure of the genes, ensuring they had the correct number of sections and that the RNA evidence matched the DNA predictions. This careful filtering process whittled down millions of potential matches to a set of highly credible candidates. The result was a discovery of 67 broad genetic models, which were further refined into 47 distinct locations in the sponge genomes. Among these, 15 candidates stood out as the strongest evidence, possessing all the necessary structural features and confirmed by RNA data to be real, intact genes, though a small subset of these models relied on eukaryotic context rather than direct same-species RNA support.
These findings suggest that sponges do indeed possess the genetic machinery for cyclooxygenase enzymes, but they look different from the versions found in humans or other complex animals. The researcher identified 18 key candidates that retained the critical core components required for the enzyme to function. However, these sponge versions showed variations in the parts of the enzyme that control how it grabs its target molecule. Some of these variations suggest the enzymes might produce different types of signals or work in slightly different ways compared to their counterparts in more complex animals. For instance, some sponge enzymes had changes in the "channel" where the fatty acid enters, which could alter the shape of the final product. This implies that while the basic tool exists, sponges may have customized it for their own unique biological needs.
The study also revealed that these genes are not just rare anomalies; they are widespread across different types of sponges. The researcher found evidence of these genes in 22 different species, including representatives from three major sponge groups. In some species, he even found multiple versions of the gene living side-by-side in the same genome, suggesting that sponges have been duplicating and diversifying these genes over time. This diversity indicates that the genes are not a fluke or a contamination from another organism, but a genuine part of the sponge biological toolkit.
Perhaps most significantly, this discovery changes our understanding of when these enzymes first appeared in the history of life. Because sponges are the oldest surviving branch of the animal family tree, finding these genes in them means the machinery must have existed in the last common ancestor of all animals, including sponges, corals, and humans. This pushes the origin of the cyclooxygenase lineage back hundreds of millions of years further than previously thought. It suggests that the ability to make these vital chemical signals was a fundamental trait inherited by all animals, rather than a later invention.
However, the researcher is careful to note what this study does not prove. While the genetic evidence is strong, the actual chemical activity of these sponge enzymes has not yet been tested in a lab. The study confirms that the genes are there and that they look like cyclooxygenases, but it does not show that they successfully produce prostaglandins or that they function exactly like the human versions. The next step for science is to take these genetic candidates and test them in the laboratory to see what chemical signals they actually make. Until then, the discovery stands as a powerful revision of the animal family tree, revealing that the genetic roots of our own inflammatory and reproductive systems are far deeper and more ancient than we ever imagined.
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