Stowers scientists study evolution of animal development mechanisms, show how some of Earth’s first animals evolved

KANSAS CITY, MO — June 13, 2023 — Lacking bones, brains and even a full intestine, the body plans of simple animals like sea anemones appear to have little in common with humans and their vertebrate relatives. However, new research by investigator Matt Gibson, Ph.D., at the Stowers Institute for Medical Research shows that appearances can be deceiving and that a common genetic toolkit can be used in different ways to guide embryological development to produce a body very different adult plans.

It is well known that sea anemones, corals and their jellyfish relatives shared a common ancestor with humans who plied Earth’s ancient oceans over 600 million years ago. A new study from Gibson Lab, published in Current biology on June 13, 2023, illuminates the genetic basis for body plan development in the starlet sea anemone, Nematostella vectensis. This new knowledge paints a vivid picture of how some of the first animals on earth progressed from egg to embryo to adult.

“Studying the developmental genetics of Nematostar it’s a bit like taking a time machine into the very distant past,” said Gibson. “Our work allows us to ask ourselves what life was like long ago, hundreds of millions of years before the dinosaurs. Did ancient animals develop from egg to adult, and to what extent have the genetic mechanisms that drive embryonic development endured over the millennia?

Most contemporary animals, from insects to vertebrates, develop as a series of segments from head to tail that assume distinct identities depending on their location. Within a given segment, there is an additional axis of polarity which informs the cells whether they are at the front or back of the segment. Collectively, this is referred to as segment bias.

Shuonan He, Ph.D., a former Gibson Lab predoctoral researcher, discovered the genes involved during sea anemone development, Nematostella vectensiswho guide the formation of segments and others who direct the polarity programs of the segments strikingly similar to organisms higher up the evolutionary tree of life, including humans.

“The significance is that the genetic instructions underlying the construction of extremely different animal body plans, such as a sea anemone and a human being, are strikingly similar,” said Gibson. “The genetic rationale is largely the same.”

This new study builds on a 2018 study published in Science by the Gibson Lab who demonstrated that sea anemones have internal bilateral symmetry early in development with eight radial segments. The study proved it Hox genes, major developmental genes that are crucial to human development, act to delineate boundaries between segments and probably had an ancient role in the construction of segments.

The team’s latest finding explores how segments form and what explains the differences in their identities. Using spatial transcriptomics, or differences in gene expression between segments, the team discovered hundreds of new segment-specific genes. These include two crucial genes that encode transcription factors that regulate the polarization of the segment under the control of Hox genes and are required for proper positioning of sea anemone muscles.

The astonishing diversity of organisms on Earth can be compared to the assembly of Legos. “Whether you build a dinosaur, a sea anemone, or a human, many of the fundamental genetic building blocks are largely the same despite drastically different animal shapes,” Gibson said.

This is the first time scientists have evidence of a molecular basis for segment polarization in a pre-Bilaterian animal. Although extensively studied in bilateral species such as fruit flies and humans, the idea that cnidarian animals possessed cleavage was unexpected. Now, the team has evidence that these segments are also polarized.

“This provides further evidence that investigating a broad diversity of animals can have direct implications for understanding general principles, including those that apply to human biology,” said Gibson. “By taking it a step further, understanding the rationale for sea anemone development and comparing it to what we see in vertebrates, we can also extrapolate back in time to understand how animals likely developed hundreds of millions of years ago.”

Other authors include Wanqing Shao, Ph.D., Shiyuan Chen, Ph.D., and Ting Wang, Ph.D.

This work was funded by the National Institutes of Health (NIH) (award: RO1HG007175, award: U24ES026699, award: U01CA200060, award: U01HG009391, award: U41HG010972) and institutional support from Stowers Institute for Medical Research. The content is the sole responsibility of the authors and does not necessarily represent the official views of the NIH.

About Stowers Institute for Medical Research

Founded in 1994 through the generosity of Jim Stowers, founder of American Century Investments, and his wife Virginia, the Stowers Institute for Medical Research is a non-profit biomedical research organization with a focus on fundamental research. Its mission is to expand our understanding of the secrets of life and improve the quality of life through innovative approaches to the cause, treatment and prevention of disease.

The Institute is composed of 20 independent research programs. Of the approximately 500 members, more than 370 are scientific staff including principal investigators, technology center directors, postdoctoral scientists, graduate students, and technical support staff. Learn more about the Institute at www.stowers.org and its graduate program at www.stowers.org/gradschool.

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