Skip to main content
Move the World.
brain organoids

Lead Image © S.Benito-Kwiecinski/MRC LMB/Cell

Humans have giant brains. 

Even though we spend just as much time in the womb as our closest relatives, gorillas and chimpanzees, our newborn brains have three times the number of neurons — something that has long been a mystery.

Now, researchers have looked at gene expression — which genes are switched on and off — in human brain organoids compared to other apes to discover the genetic mechanism behind these variations.

In the mini-brains, they found a molecular switch that could be crucial to triggering the human brain's rapid growth and published their results in the journal Cell.

Why Study Mini-Brains?

Led by a team at the Medical Research Council Laboratory of Molecular Biology in Cambridge, U.K., the study compared early tissue growth in mini-brains or brain organoids developed from human, gorilla, and chimpanzees stem cells.

Brain organoids are small bundles of brain cells that researchers grow from stem cells in a lab. They provide researchers with an opportunity to study stages of brain development they might not otherwise be able to see.

"This early stage of development is usually very inaccessible," says Lancaster. "It's a kind of black box in human biology. Apes are an endangered species, so ethically, we wouldn't want to do experiments at this stage. We usually don't even know the gorilla is pregnant this early on," Madeline Lancaster, lead researcher on the study, told New Scientist.

"It's important to understand how the brain develops normally, partly because it helps us understand what makes humans unique and partly because it can give us important insights into how neurodevelopmental disorders can arise."

John Mason

In this study, it was no surprise that the human brain organoids grew much larger and faster than the organoids from the other primates, at a rate that parallels the growth patterns of real brains.

After two days, the human brain organoids had already grown much larger than the gorilla or chimp organoids, New Scientists reports. The human mini-brains were twice the size of their ape counterparts after five weeks, measuring four millimeters across.

Switching Genes On and Off

When the team looked closer at the genes, they found that a gene named ZEB2 was triggered earlier in apes than in humans — the gene acted like a molecular switch that slowed the brain's growth.

The team decided to test the switch in gorillas and found that delaying the switch's effects caused the gorilla mini-brain to grow larger. By contrast, switching the gene on earlier in the human mini-brain development repressed the human organoids' growth.

In other words, when the switch is on, the brains don't grow as large. Turn it off, and mini-brain growth races ahead.

"This provides some of the first insight into what is different about the developing human brain that sets us apart from our closest living relatives, the other great apes. The most striking difference between us and other apes is just how incredibly big our brains are," Lancaster said. "I feel like we've really learnt something fundamental about the questions I've been interested in for as long as I can remember — what makes us human."

This research takes us one step further in understanding the mysteries of the human brain. Doing so could lead to future research or treatments for neurodegenerative disorders or other ailments of the brain.

John Mason, a professor of molecular neural development at the University of Edinburgh, who was not involved with the research, told The Guardian, "It's important to understand how the brain develops normally, partly because it helps us understand what makes humans unique and partly because it can give us important insights into how neurodevelopmental disorders can arise."

Mason noted that macrocephaly (an unusually large head) often co-occurs with autism, so this research could help us understand how early brain growth affects such cognitive disorders.

We'd love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected]

Up Next

Science
Scientists Grew a Mini Brain in a Lab. It Has Human-Like Brain Waves.
Scientists Grew a Mini Brain in a Lab. It Has Human-Like Brain Waves.
Science
Scientists Grew a Mini Brain in a Lab. It Has Human-Like Brain Waves.
For the first time, a lab-grown mini brain has brain waves. Researchers can now launch new ways to study brain disorders. But the question of consciousness in the brain-like organoid could raise concern.

For the first time, a lab-grown mini brain has brain waves. Researchers can now launch new ways to study brain disorders. But the question of consciousness in the brain-like organoid could raise concern.

Clean Energy
Artificial Photosynthesis Machine Improves Itself Over Time
artificial photosynthesis
Clean Energy
Artificial Photosynthesis Machine Improves Itself Over Time
An artificial photosynthesis device that gets more efficient with time could finally allow us to harness solar energy for uses beyond electricity.

An artificial photosynthesis device that gets more efficient with time could finally allow us to harness solar energy for uses beyond electricity.

Brain
Injectable “Glue” Helps Heal Traumatic Brain Injury in Rats
Traumatic Brain Injury
Brain
Injectable “Glue” Helps Heal Traumatic Brain Injury in Rats
By injecting a “brain glue” into rats, researchers were able to speed up their recovery after a traumatic brain injury.

By injecting a “brain glue” into rats, researchers were able to speed up their recovery after a traumatic brain injury.

Virology
One Mosquito Protein Weakens Several Deadly Flaviviruses
Flaviviruses
Virology
One Mosquito Protein Weakens Several Deadly Flaviviruses
A mosquito protein that targets the viral envelope of flaviviruses, inhibiting their activity, could help doctors treat several life-threatening diseases.

A mosquito protein that targets the viral envelope of flaviviruses, inhibiting their activity, could help doctors treat several life-threatening diseases.

Aerospace
A Sunblock to Save Martian Explorers from Radiation in Space
Radiation in Space
Aerospace
A Sunblock to Save Martian Explorers from Radiation in Space
Radiation in space is a major threat to astronauts’ health, but a new biomaterial could make space exploration a little less dangerous by blocking x-rays.

Radiation in space is a major threat to astronauts’ health, but a new biomaterial could make space exploration a little less dangerous by blocking x-rays.

Space Exploration
Closer to the Sun: NASA’s Parker Solar Probe
parker solar probe
Space Exploration
Closer to the Sun: NASA’s Parker Solar Probe
NASA is getting closer to the sun than ever before with the Parker Solar Probe, leaving researchers excited and bewildered by the data they saw.

NASA is getting closer to the sun than ever before with the Parker Solar Probe, leaving researchers excited and bewildered by the data they saw.

Global Health
Could Another Measles Outbreak Open up Pandora’s Box?
Could Another Measles Outbreak Open up Pandora’s Box?
Global Health
Could Another Measles Outbreak Open up Pandora’s Box?
The global resurgence of measles has sparked renewed scientific interest in this old foe. If the theory — which is contested — turns out to be true, a measles infection could be less an isolated bout of illness and more a Pandora’s box.

The global resurgence of measles has sparked renewed scientific interest in this old foe. If the theory — which is contested — turns out to be true, a measles infection could be less an isolated bout of illness and more a Pandora’s box.

On The Fringe
These Bacteria-Eating Sewer Viruses are Saving Lives
These Bacteria-Eating Sewer Viruses are Saving Lives
On The Fringe
These Bacteria-Eating Sewer Viruses are Saving Lives
The world discovered phages before antibiotics, but these lowly sewer viruses are getting renewed attention in the...
By Blake Snow

The world discovered phages before antibiotics, but these lowly sewer viruses are getting renewed attention in the age of antibiotic resistance.

Superhuman
Gaining Independence with the World's Most Advanced Prosthetic Arm
Gaining Independence with the World's Most Advanced Prosthetic Arm
Watch Now
Superhuman
Gaining Independence with the World's Most Advanced Prosthetic Arm
Jerral was hit by a roadside bomb in Iraq and left paralyzed. Now he's partnering with researchers to regain his independence. »
Watch Now

Jerral was serving in Iraq, his tank was hit by a roadside bomb. The attack left him paralyzed and without his left arm. But rather than letting his injuries define him, Jerral is fighting back with the help of the world’s most advanced prosthetic arm. He’s working with a team of researchers from Johns Hopkins to test the arm that could help Jerral and many other wounded vets like him take back their independence.