An international team of researchers, including several life sciences researchers from the University of Arkansas (USA) publish in the journal eLife the discovery of a developmental gene related to touch in the tentacles of sea anemones, as well as with hearing in humans. This rare genetic link between humans and anemones is called pou-iv and is important for the development of hearing cells in the human inner ear.
This particular gene can be traced to the tentacles of the star sea anemone ( Nematostella vectensis ) native to the East Coast of the United States, where it plays a crucial role in the animal’s sense of touch.
The phylum to which sea anemones, jellyfish, and corals belong, Cnidaria , is the closest relative of Bilateria, animals with bilateral symmetry like humans, diverging from their last common ancestor that lived around 748 to 604 million years ago. years. That is why it is so useful to study them, due to their shared characteristics, probably, in our last common ancestor. This is the case in the nervous system, where both bilaterians and cnidarians use similar sets of genes in neuronal development.
The researchers suggest that this finding suggests that it was present in their common ancestor and probably also played a key role in sensory development at that time.
Although it is unknown if the hair cells of the tentacles can hear, they do use them to sense the movements of their prey. In mammals, this gene is also required for proper hair cell development, and indeed mice lacking the pou-iv gene are deaf.
Delving into mechanosensory hair cells
What exactly does the gene do? Using genetic engineering methods, that is, using the CRISPR-Cas9 gene editing tool, the authors of the work blocked the pou-iv gene in sea anemones by injecting a Cas9 protein cocktail into fertilized sea anemone eggs to eliminate this gene. gene and looked at what happened in developing embryos: ‘turning off’ this gene led to abnormal development of the hair cells of the sea anemones’ tentacles and made the animals unable to respond to touch. Without pou-iv, the anemones could not sense mechanical stimuli through their hair cells.
“This study is exciting because it not only opens up a new field of investigation into how mechanosensation develops and works in a sea anemone… but it also tells us that the building blocks of our sense of hearing have ancient evolutionary roots going back to date back hundreds of millions of years to the Precambrian,” said Nagayasu Nakanishi, a biologist at the University of Arkansas and co-author of the paper.
The findings suggest that the pou-iv gene played a vital role in the development of mechanosensory cells in the common ancestor of Cnidaria and Bilateria , according to the researchers. To trace the gene even further back, data from other phyla with earlier points of divergence will be needed. The puzzle still has many pieces to solve.
Referencia: Ethan Ozment et al, Cnidarian hair cell development illuminates an ancient role for the class IV POU transcription factor in defining mechanoreceptor identity, eLife (2021). DOI: 10.7554/eLife.74336