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Common ancestor for cells involved in hearing and touch…

The sensory cells in the inner ear and the touch receptors in the skin have a lot in common.

“There are striking similarities in the development of two types of specialised sensory cells: the so-called ‘hair cells’ that receive sound vibrations in the inner ear, and the Merkel cells that sense light touch at the surface of the skin,” said Segil, who is a professor in Stem Cell Biology and Regenerative Medicine, California University.

“Ultimately, these developmental similarities are a legacy of shared evolutionary history.”

Each human cell can store around two metres of DNA in its nucleus, because this DNA is wound around tiny spools made up of proteins called histones. These spools of DNA and histone protein are further packed together to form what are known are nucleosomes, which are stacked to create chromatin, which is the material that makes up the chromosomes.

When DNA is wound tightly into this storage configuration, the chromatin is closed and inaccessible to the protein ATOH1. This protein is a “master regulator” that can activate a network of differentiation genes in the DNA within the chromatin — but not without first gaining access.

To this end, ATOH1 stimulates the production of a second protein known as POU4F3, an aptly named “pioneer factor” with the ability to venture into new frontiers by binding to closed and inaccessible chromatin. After POU4F3 blazes a trail by binding to the closed chromatin, ATOH1 can move forward with engaging and activating the network of genes that drives differentiation into hair cells and Merkel cells.

“It’s remarkable that these two cell types, which are both involved in sensing mechanical stimuli but derive from distinct parts of the embryo, both rely on the same ATOH1/POU4F3 mechanism in order to differentiate. Our study suggests that this mechanism is extremely ancient and emerged before hair cells and Merkel cells diverged from a common evolutionary ancestor.”

From Science Daily