The lamprey and human hindbrains are built using very similar molecular and genetic toolkits, according to a new study led by the Stowers Institute for Medical Research.
These images show an adult lamprey (top and left) and a developing lamprey embryo. Image credit: Stowers Medical Research Institute.
“Our research on the hindbrain (the part of the brain that controls important functions such as blood pressure and heart rate) is essentially a window into the distant past and can serve as a model for understanding the evolution of complexity. “, said Dr. Hugo Parker. Researcher at Stowers Medical Research Institute.
Like other vertebrates, sea lampreys have a backbone and skeleton, but they noticeably lack a jaw, a characteristic feature of the head.
Most vertebrates, including humans, have jaws, so this striking difference in sea lampreys makes it a valuable model for understanding the evolution of vertebrate traits.
“About 500 million years ago, at the origin of vertebrates, there was a split between jawless and jawed animals,” said Dr. Alice Bedois, also of the Stowers Institute for Medical Research.
“We wanted to know how vertebrate brains evolved and whether there is something unique to jawed vertebrates that jawless vertebrates don't.”
Previous research had identified genes that structure and subdivide the sea lamprey's hindbrain as identical to genes in jawed vertebrates, including humans.
However, these genes are part of an interconnected network or circuit that needs to be initiated and directed to properly build the hindbrain.
In a new study, the authors identify common molecular cues known to direct head-to-tail patterning in a variety of animals as part of a genetic circuit that guides hindbrain patterning in the lamprey. .
“We found that the same genes, as well as the same cues, are involved in hindbrain development in sea lampreys. This suggests that this process is ancestral to all vertebrates. ,” Dr. Bedwa said.
“This signal is called retinoic acid, commonly known as vitamin A.”
Researchers have known that retinoic acid signals the genetic circuits that build the hindbrains of complex species, but they believe it is involved in more primitive animals like sea lampreys. was not considered.
Surprisingly, they discovered that the lamprey's core hindbrain circuit is also initiated by retinoic acid, providing evidence that these sea monsters and humans are much more closely related than expected.
“People thought that because lampreys don't have jaws, their hindbrains don't form like other vertebrates,” says Dr. Rob Krumlauf, a researcher at the Stowers Institute for Medical Research.
“We showed that this fundamental part of the brain is built exactly the same way as in mice, and even in humans.”
Signaling molecules that signal cell fate during development are well known.
Now, researchers have discovered that retinoic acid plays another key role in signaling important steps in development, such as the formation of the brainstem.
Furthermore, if hindbrain formation is a conserved feature in all vertebrates, other mechanisms must be involved to explain its incredible diversity.
“We all come from a common ancestor,” Dr. Bedwa said.
“The lamprey provided further clues.”
“We now need to go further back in evolutionary time to discover when the genetic circuits controlling hindbrain formation first evolved.”
of study It was published in the magazine nature communications.
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AMH Bedwa other. 2024. Lamprey reveals the origins of retinoic acid signaling and its coupling to vertebrate hindbrain segments. Nat Commune 15, 1538. doi: 10.1038/s41467-024-45911-x
Source: www.sci.news
