Needing a change? Researchers find GABA is the key to metamorphosis

March 31, 2020

Tsukuba, Japan - Metamorphosis, or a dramatic change in physical appearance, is a normal part of the life cycle of many animals, carried out to take advantage of different ecological niches. Yet the process of metamorphosis--how a caterpillar becomes a butterfly, or a tadpole transforms into a frog--is not well understood and has only been studied in a small number of species.

In a study published this week in Current Biology, a team led by researchers from the University of Tsukuba investigated the role of various neurotransmitters in the regulation of metamorphosis, identifying GABA as a key regulator in the model sea squirt Ciona intestinalis.

Ciona are some of the closest living relatives of vertebrates. Starting life as tadpole-like larvae, Ciona undergo a metamorphosis into vase-shaped adults that is triggered by their attachment to a solid surface.

"Ciona have organs called adhesive papillae that sense when the animal attaches to a surface, triggering metamorphosis," explains Professor Yasunori Sasakura, senior author. "The adhesive papillae contain sensory neurons that transmit signals to the rest of the body, suggesting that the nervous system plays an essential role in initiating metamorphosis."

To investigate the role of the nervous system in metamorphosis, the researchers treated Ciona larvae with various neurotransmitters, among which only GABA induced the physical changes associated with maturation. Upon blocking the genes required for GABA synthesis, transport, and maturation, the researchers observed decreased induction of metamorphosis, confirming they had found the right regulatory molecule.

GABA, or gamma aminobutyric acid, is one of the main neurotransmitters in mammals. It is usually thought of as an inhibitory molecule because it blocks certain signals in the brain, decreasing nervous system activity. Interestingly, however, the researchers found that this was not the case in Ciona metamorphosis.

"Using expression analysis and gene knockout/knockdown assays, we showed that GABA activates the neurons expressing gonadotropin-releasing hormone (GnRH), which is essential for reproductive maturation in vertebrates," says Professor Sasakura. "Knocking out the genes encoding GnRH showed that it is essential for metamorphosis in Ciona larvae and confirmed its place as the downstream component of GABA-mediated regulation."

Further experimentation showed that while larvae lacking GnRH could not carry out the initial steps of metamorphosis, they did exhibit normal adult organ growth. In contrast, no adult organ growth was observed in GABA mutants, suggesting that GABA is essential for all metamorphic events.

The researchers now hope to understand how the GABA-GnRH pathway causes the dramatic physical changes that occur during Ciona metamorphosis and, given the wide conservation of these molecules among animals, to explore whether the GABA-GnRH mechanism plays a role in the metamorphosis of other animal species.
-end-


University of Tsukuba

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.