Did insect wings originate from a "genetic circuit"? Why only insects conquered the skies: The "brinker circuit" that supported wing evolution

"Flying in the Sky": One of the Greatest Updates in the History of Life

If we were to list Earth's history like an app update log, the "birth of insect wings" would undoubtedly be a major version update.
Around 400 million years ago, when trees were just beginning to cover the ground, the first animals to take to the skies were not birds or bats, but small insects that we usually don't pay much attention to.Phys.org

Why were they the only ones to quickly conquer the skies? The key lies in a surprisingly tech-like mechanism called "genetic circuits," as revealed in this study.

A team from the Francis Crick Institute in the UK, through analysis using fruit flies, discovered a feedback circuit created by a morphogen called Dpp (a signal molecule for shaping) and a molecule called **Brinker**. This circuit plays a crucial role in accurately developing large structures like wings.Phys.org

Morphogen Dpp: The "Gradient of Concentration" that Carries the Blueprint

In the world of developmental biology, the term morphogen frequently appears. It refers to signal molecules that convey "which cell becomes which part" through concentration. In areas of high concentration, gene A is activated, while in areas of medium concentration, gene B is activated, and so on, with the gradient itself forming a map.

In the wing buds of fruit flies (small tissues that become wings during the larval stage), the morphogen Dpp plays this role. Dpp is a member of the BMP family, which is widely present in animals, including humans, and is an important signal involved in the formation of bones and organs.

However, there is a problem.

Wings develop as "isolated patches" of tissue somewhat detached from the larva's body, making it difficult to receive "support signals" from other areas. Nevertheless, they must accurately convey positional information across the entire wing.

Dpp works strongly near its source, but as it moves further away, the signal weakens, and noise increases. Yet, the actual wings have a neatly arranged pattern all the way to the edges. How is this achieved?

Brinker Creates an Opposite Gradient

Here comes the main character, Brinker. The research group, led by Anqi Huang, found that as the concentration of Dpp decreases, the concentration of the inhibitor Brinker increases in the opposite direction.Phys.org

• Where Dpp is strong → Brinker is barely expressed

• Where Dpp is weak → Brinker is strongly expressed

In other words, not only the gradient of Dpp but also the "reverse" gradient of Brinker is laid across the entire tissue.

Furthermore, through collaborative analysis with physicists, it was found that Brinker is not merely a passive response but is at the center of the feedback circuit. The expression of Brinker is suppressed by the Dpp signal, and Brinker controls the on-off of Dpp's target genes. As a result of these interactions, in distant areas, the smooth gradient of Brinker, rather than Dpp itself, serves as the main clue for cells to determine "where they are."Phys.org

In other words,

"Since the original signal (Dpp) is too vague, it is once broken down and re-distributed as a clearer secondary signal (Brinker gradient)"

is embedded within the tissue.

The "Firebrat" Without Wings Tells the Story of Pre-Evolution

To explore when and how this circuit evolved, the research team traced the genealogy of genes. By comparing publicly available genome data, they found that the Brinker gene is unique to insects and does not exist in closely related crustaceans.Phys.org

Furthermore, they focused on the primitive insect **firebrat**, which does not have wings. Firebrats are an ancient lineage of insects and still do not have wings. If the Brinker circuit "evolved with wings," it is possible that the relationship with Dpp has not yet been established in firebrats.

In fact, although the Brinker gene was present in the firebrat genome, experiments showed that the reverse gradient was not formed, and it was not connected to the Dpp signal as seen in fruit flies.Phys.org

This result strongly supports the scenario that "Brinker originally emerged in the insect lineage and later became linked with Dpp in winged insect lineages, becoming refined as a feedback circuit."

The "Innovation to the Sky" That Happened Not 400 Years, but 400 Million Years Ago

Jean-Paul Vincent, who led the research, points out that

insects acquired the ability to fly about 400 million years ago, just when trees began to appear

.Phys.org

The Dpp signal network incorporating Brinker likely played a favorable role in allowing the stable and large growth of new structures like wings. As a result, insects ventured into the entirely new niche of the air, becoming one of the most prosperous animal groups on Earth—a grand evolutionary story that emerges from this single paper.

How Did Social Media React? (Virtual Timeline)

Here is a "virtual social media timeline" reconstructed to make the theme of this article more understandable. Although these are not real posts, such voices would likely appear on the timeline when this news breaks.

@evo_bio_lab
"The fact that Brinker is unique to insects and coincides with the timing of wing evolution is textbook-level stuff... #EvoDevo #InsectWings"

@dev_fly
"The idea of not reading the Dpp gradient directly but 're-encoding' it with Brinker is just too beautiful as signal processing."

@sci_illustrator
"The concept of the 'circuit not yet connected' in the firebrat's wings is so emotive. It's like looking at an evolutionary wiring diagram."

@bio_engineer
"Such feedback circuits could be applied in synthetic biology for creating artificial tissues. Like extending patterns to the edges of cell sheets."

@casual_reader
"The tagline 'wingless insects held the key to the evolution of winged insects' alone makes me want to read it."

In this way, the research community may view it as a "good example of evolutionary developmental biology (evo-devo)," while the general public may be drawn to the narrative of "a seemingly insignificant insect playing a superhero-level role."

How the Perspective of "Genetic Circuits" Changes the Image of Evolution

What makes this achievement interesting is that it portrays evolution not as "adding parts" but as "updating circuit designs.".

• The new component, Brinker, emerges in the insect lineage

• It is incorporated into the Dpp signal, forming a feedback circuit

• As a result, it becomes possible to precisely control large structures like wings

This flow is reminiscent of electronic circuits or software refactoring. Adding new modules to old systems and improving signal transmission and noise resistance—such an engineering perspective could provide a new way to view the evolution of life.
.

Future Applications: From Wings to Organs and Artificial Tissues

Dpp is a fundamental signal involved in the formation of various organs, not just insect wings. If feedback factors like Brinker and their network structures are found in other tissues, the following applications might emerge.

• Regenerative Medicine
  The possibility of artificially extending the "reach" of morphogens to provide design guidelines for uniformly growing three-dimensional organs.

• Synthetic Biology and Biomaterials
  The potential to apply genetic circuit designs to autonomously extend "biological patterns" composed of cells to a larger scale.

• Recreation of Evolutionary Experiments
  Introducing factors like Brinker into other lineages and rearranging signal networks to experimentally verify "what if different evolution had occurred at that time" in the laboratory—a dreamlike research possibility.
  
  
  

Conclusion: What Small Wings Teach Us

To our eyes, the transparent wings of fruit flies or the firebrats scuttling in the kitchen corners may not seem very appealing. However, behind these small structures, advanced information processing such as morphogens, genetic circuits, and feedback control is in full operation.

This study vividly captures a part of that.
Peering into the humble wings of insects might actually be one of the shortest routes to understanding "how life acquired complexity and diversity."