Genetic Codes Illustration

Scientists find the genetic origin of our senses

Genetic Codes Illustration

A research group from the University of Innsbruck has found out how Cranial Sensory Ganglia was formed.

Researchers at the University of Innsbruck have identified the genetic origin of our senses

Researchers from the University of Innsbruck have determined the genetic origin of our senses. The findings reveal that the vertebrate animal’s cranial Sensory Ganglia arises from a genetic program shared with their closest living relatives, mantle animals.

It is definitely beneficial to have a head. This may seem obvious, but evolution went on a long journey to test it: invertebrates dominated the water at first when wildlife began to appear. Although they already had head features, vertebrates eventually succeeded as they developed a new, superior head. This “new head” enabled a widespread spatial spread and multiplication of sensory cells, leading to a much improved perception of the environment. This was also crucial for the development of a predatory lifestyle.

Cranial Sensory Ganglia are crucial for transmitting external sensations to the vertebrate brain. You can think of them as nerve nodes that are scattered throughout the brain and collect information from the sense organs. The exact process by which these ganglia were created was unknown to researchers up to this point. These issues have finally been resolved by a study published in Nature on May 18, 2022.

Bipolar tail neurons

An embryo of the mantle animal Ciona intestinalis. The microscope image shows bipolar tail neurons in the tail region (green) and epidermal cells (magenta). Credit: Alessandro Pennati

Prototype of vertebrates

Research group by Ute Rothbächer from the Institute of Zoology at University of Innsbruck was crucially involved in the final phase of the project, an international collaboration between several institutions, prepared by Oxford University. Their results show that the cranial sensory ganglia of vertebrates come from a genetic program that is also found in their closest living relatives, the mantle animals. In mantle larvae, certain sensory neurons, called bipolar tail neurons, are located in the tail region. These process external stimuli, but are also responsible for the animal’s movement. In both animal subfloors, the respective structures of the gene Hmx are formed.

“Tunics are like an evolutionary prototype for vertebrates,” explains Rothbächer. “There is a large anatomical gap between the adults in these subfiles, as they are adapted to ecological niches. This complicates research on their development. Common structures and mechanisms can only be identified at the embryonic stage – our common ancestor was probably very similar to a mantle larva.”

The model organisms of the study were the lamprey, a primitive fish that resembles an eel and is often called a “living fossil”, and the mantle animal Ciona intestinalis, which is surrounded by a yellowish, tubular mantle that protects the animal and filters the food.

The conserved gene

Alessandro Pennati, a doctoral student in Rothbacher’s research group, provided crucial data on the function of the Hmx gene in Ciona. He applied the CRISPR-Cas9 gene technology to selectively knock out genetic sequences, while the transient transgenesis method was used to overexpress genes.

The researchers found that Hmx controls the development of bipolar tail neurons in mantle animals, while in vertebrates it does for Cranial Sensory Ganglia. Surprisingly, Hmx gene segments from lamprey were inserted into Ciona

DNA
DNA, or deoxyribonucleic acid, is a molecule that consists of two long strands of nucleotides that wind around each other to form a double helix. It is the genetic material in humans and almost all other organisms that carries genetic instructions for development, function, growth and reproduction. Almost every cell in a person’s body has the same DNA. Most DNA is found in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).

“data-gt-translate-attributes =”[{” attribute=””>DNA were similarly active as Ciona’s own Hmx.

“Hmx has been shown to be a central gene that has been conserved across evolution. It has retained its original function and structure and was probably found in this form in the common ancestor of vertebrates and tunicates,” Pennati explains. Cranial Sensory Ganglia and Bipolar Tail Neurons thus have the same evolutionary origin, Hmx was probably crucially involved in the formation of highly specialized head sensory organs in vertebrates.

Reference: “Hmx gene conservation identifies the origin of vertebrate cranial ganglia” by Vasileios Papadogiannis, Alessandro Pennati, Hugo J. Parker, Ute Rothbächer, Cedric Patthey, Marianne E. Bronner, and Sebastian M. Shimeld, 18 May 2022, Nature.
DOI: 10.1038/s41586-022-04742-w


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