Scientists have discovered genes they think are responsible for making embryos look alike at an early developmental stage. This knowledge could help us understand the earliest stages of human life
A team of biologists have identified the specific genes and their associated chemical ‘switches’ that make vertebrates – all animals with backbones – closely resemble each other during embryonic development.
The Australian-led research was done in international collaboration with scientists from Spain and the Netherlands, and published today in Nature Genetics.
“It’s imagined as this hourglass of development,” says chief investigator of the study Professor Ryan Lister, an expert in genetics from the University of Western Australia and a Future Fellow at the ARC Centre for Excellence in Plant Energy Biology (PEB).
“Vertebrates of different species very early in embryo development look less similar to one another, then they become much more similar at this phylotypic stage, and then they diverge again.”
This similarity was first observed in the early 1800s by the biologist Karl Ernst von Baer, who is regarded as the founding father of embryology. During his experiments, von Baer mixed up the embryos of different vertebrate species and was unable to tell them apart.
Like toad, like mouse
The phylotypic stage of embryonic development is critical for setting out the body plan of a vertebrate animal in terms of organ development and limb development.
To find out what happens to DNA during this stage, the biologists studied the embryos of zebrafish, toads, and mice.
The team were able to not just identify the genes that control the phylotypic stage, but also the chemical ‘signposts’ that control the activation of these genes.
“These chemical signposts, which can also be called the epigenome, act as another layer of information that’s superimposed on top of the DNA sequence,” says Lister. “[The epigenome] can control how the cell is able to utilise the underlying DNA sequence, the information encoded in the underlying DNA sequence.”
“What we were able to see is these regions that appear to be little control switches, which can act to turn ‘on’ or turn ‘off’ these genes that are important at that developmental stage.”
The fundamentals of early life
According to lead author Dr Ozren Bogdanovic from PEB, the findings could help us to understand the link between gene activation at this early stage of human life and various diseases and conditions.
"Our research provides answers to fundamental questions such as how do genes get turned ‘on’ or ‘off’ during development,” says Bogdanovic. “The understanding of such processes is crucial for the proper understanding of developmental disorders, but also diseases such as cancer that occur in adults but often display improper activation of developmental genes/pathways.”
“[The study] is important because it tells us that we all share the same genes for the basic body pattern,” says Professor Marciej Hennebergan expert in comparative biology from the University of Adelaide.
“We can see how further development differentiates bodies depending on what genes are there in various animals… [and the] genetic regulation of embryonic development.”