Nav: Home

Undercover evolution

September 03, 2019

Providing a glimpse the hidden workings of evolution, a group of researchers at UC Santa Barbara have discovered that embryos that appear the same can start out with surprisingly different instructions.

"We found that a lot of undercover evolution occurs in early embryos," said Joel Rothman, a professor in the Department of Molecular, Cellular, and Developmental Biology, who led the team.

Indeed, although members of the same species are identical across the vast majority of their genomes, including all the genetic instructions used in development, Rothman and his colleagues found that key parts of the assembly instructions used when embryos first start developing can differ dramatically between individuals of the same species.

This finding may shed light on two important areas: how animals can evolve quickly, and why patients can show very different responses to particular drugs.

The scientists' research is published in the journal eLife.

"Many of the distinctive features that make us unique, including our color, height and susceptibility to diseases, are determined by our genomes," Rothman said. "But since everyone looks pretty similar as embryos, the genetic assembly instructions that get us started at conception were thought to be nearly identical between us."

Enter the C. elegans nematode worm, a celebrated laboratory animal model used for decades to investigate how animals develop. Rothman's team, which included researchers at the University of Auckland, targeted the gene switches that turn on the development of the animal's intestine with a tool called RNAi -- a technique that shuts down individual gene functions. What they learned was that the widely accepted "standard one-size-fits-all" concept of genetic assembly instructions did not apply.

"This remarkable difference is well-hidden in the genome, but was uncovered when one of the switches was removed," noted Yamila Torres Cleuren, formerly of University of Auckland and now a postdoctoral fellow at the University of Bergen and lead author of the study. "We were startled to find that while some members of the species absolutely require one of the critical switches to start making an intestine, others can almost dispose of it." While some animals generally failed to develop intestines, relatives from the same species made them regardless.

"It's stunning that such an important event at the earliest stages of embryo formation can occur by such different means within one species and yet produce essentially the same outcome," said Rothman. "Prior to these findings, we were unaware that the blueprints for an early embryo change so rapidly within a species."

This discovery would be equivalent to finding that the manufacturing of two iPhones, which look and function identically, started out with different assembly instructions, the researchers said.

While humans are a far cry from C. elegans, once the initial events in embryo development begin, the later genetic instructions that create the endoderm appear to be similar to those likely used in all animals with a digestive tract, including humans.

This result is particularly striking given that the endoderm is both the first layer formed in embryos and was probably the first to evolve over half a billion years ago. "It reveals an extreme version of the first part of the 'hourglass' view of embryo development, in which very similar instructions across widely different animals during the middle stages of development are preceded and followed by very different starting and ending points," Rothman said.

These findings also shine light on why patients can respond so differently to drug therapies. "We found that these animals with relatively subtle genetic differences respond wildly differently to a genetic 'drug' that we used to turn off a gene," Torres Cleuren said.

Thus, just as two people who might look very similar can respond very differently to a drug therapy, so these little worms of the same species respond dramatically differently to an administered substance as a result of their subtle but all-important genetic individuality, the researchers said.

The discovery of such hidden genetic mechanisms could help guide how pharmaceuticals are developed in this era of precision medicine, in which drugs are ideally tailored to an individual's genome.

This discovery also underscores the importance of natural variation in allowing evolution to occur. "Genetic variation fuels the machine of evolution," Rothman said. "Without it, life would be stuck in a dead end. There is much more of this variation than we had realized when evolution sculpts the remarkable entities known as embryos."
Research in this study was conducted also by Chee Kiang Ewe, Kyle C. Chipman, Cricket G. Wood, Melissa R. Alcorn, Thomas L. Turner and Pradeep M. Joshi at UCSB; and Emily R. Mears, Coco Emma Alma Al-Alami and Russell G. Snell at University of Auckland.

University of California - Santa Barbara

Related Evolution Articles:

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
Guppies teach us why evolution happens
New study on guppies shows that animals evolve in response the the environment they create in the absence of predators, rather than in response to the risk of being eaten.
Undercover evolution
Our individuality is encrypted in our DNA, but it is deeper than expected.
Evolution designed by parasites
In 'Invisible Designers: Brain Evolution Through the Lens of Parasite Manipulation,' published in the September 2019 issue of The Quarterly Review of Biology, Marco Del Giudice explores an overlooked aspect of the relationship between parasites and their hosts by systematically discussing the ways in which parasitic behavior manipulation may encourage the evolution of mechanisms in the host's nervous and endocrine systems.
Tracing the evolution of vision
The function of the visual photopigment rhodopsin and its action in the retina to facilitate vision is well understood.
Directed evolution comes to plants
Accelerating plant evolution with CRISPR paves the way for breeders to engineer new crop varieties.
More Evolution News and Evolution Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#540 Specialize? Or Generalize?
Ever been called a "jack of all trades, master of none"? The world loves to elevate specialists, people who drill deep into a single topic. Those people are great. But there's a place for generalists too, argues David Epstein. Jacks of all trades are often more successful than specialists. And he's got science to back it up. We talk with Epstein about his latest book, "Range: Why Generalists Triumph in a Specialized World".
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at