Thoughts of the family tree may not be uppermost in the mind of a person suffering from a slipped disc, but those spinal discs provide a window into our evolutionary past. They are remnants of the first vertebrate skeleton, whose origins now appear to be older than had been assumed.
Scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, have found that, unexpectedly, this skeleton most likely evolved from a muscle. The study, carried out in collaboration with researchers at the Howard Hughes Medical Institute in Janelia Farm, USA, is published today in Science.
Humans are part of a group of animals called chordates, whose defining feature is a rod of cartilage that runs lengthwise along the middle of their body, under their spinal chord. This structure, called the notochord, was the first vertebrate skeleton.
It is present in human embryos, and is replaced with the backbone as we develop, with the cartilage reduced to those tell-tale discs. Since starfish, sea urchins and related animals have no such structure, scientists assumed the notochord had emerged in a relatively recent ancestor, after our branch of the evolutionary tree split away from the ‘starfish branch’.
“People simply haven’t been looking beyond our direct relatives, but that means you could be fooled, if the structure appeared earlier and that single group lost it,” says Detlev Arendt from EMBL, who led the study. “And in fact, when we looked at a broader range of animals, this is what we found.”
Antonella Lauri and Thibaut Brunet, both in Arendt’s lab, identified the genetic signature of the notochord – the combination of genes that have to be turned on for a healthy notochord to form. When they found that the larva of the marine worm Platynereis dumerilii has a group of cells with that same genetic signature, the scientists teamed up with Philipp Keller’s group at Janelia Farm to use state-of-the-art microscopy to follow those cells as the larva developed.
They found that the cells form a muscle that runs along the animal’s midline, precisely where the notochord would be if the worm were a chordate. The researchers named this muscle the axochord, as it runs along the animal’s axis. A combination of experimental work and combing through the scientific literature revealed that most of the animal groups that sit between Platynereis and chordates on the evolutionary tree also have a similar, muscle-based structure in the same position.
The scientists reason that such a structure probably first emerged in an ancient ancestor, before all these different animal groups branched out on their separate evolutionary paths. Such a scenario would also explain why the lancelet amphioxus, a ‘primitive’ chordate, has a notochord with both cartilage and muscle. Rather than having acquired the muscle independently, amphioxus could be a living record of the transition from muscle-based midline to cartilaginous notochord.
The shift from muscle to cartilage could have come about because a stiffened central rod would make swimming more efficient, the scientists postulate.
Policy regarding use
EMBL press and picture releases including photographs, graphics and videos are copyrighted by EMBL. They may be freely reprinted and distributed for non-commercial use via print, broadcast and electronic media, provided that proper attribution to authors, photographers and designers is made.
Sonia Furtado Neves | EMBL Research News
More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn
How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy