Now, in the advanced online issue of Nature1, scientists show that, although originating from different cell types, human limbs and median fins share a common developmental mechanism. These results support the idea that it was from median fins that all fins and limbs evolved, a hypothesis that has been around since the 19 century, but, until now, has never been proved.
The earliest vertebrate fossils show only well-developed dorsal and ventral (median) fins what has led researchers to suspect that these were the basis for which all paired fins and limbs evolved. However, their different location (median versus side of the body) seemed to indicate that they appeared from different cells in the embryo, which challenged the common-origin idea.
In order to investigate the issue, Renata Freitas, a Portuguese scientist, together with Guang Jun Zhang and Martin J. Cohn, all working at the department of Zoology, University of Florida, studied the embryonic development of Catshark’s fins. Catsharks are sharks found in the Atlantic and owe their name to their flat heads and long, catlike eyes.
The researchers started by marking the different cells from the embryo and following their development, in order to understand which cells originated the different parts of the shark’s body. Next, they investigated the activity of different genes during fin development. From these two experiments, Freitas and colleagues discovered that the median fin of Catsharks, although originating from different embryonic cells, uses the same genes (Hox and Tbx18) during development as limbs and paired fins.
“Given that paired fins made their evolutionary debut at a particular location on the sides of the body, intuitively one would think the genetic tools for fin development would be brought together in that place,” said developmental biologist Martin Cohn, an associate professor with the University of Florida (UF) departments of zoology and anatomy and cell biology and a member of the UF Genetics Institute. “We’ve discovered that the genetic circuitry for building limbs first appeared in an entirely different place — the midline of the animal.”
To further confirm this hypothesis, Freitas, G Zhang and Cohn decided to study lampreys, which developed into an independent lineage before the appearance of the first modern fish (and so before the appearance of paired fins). Again, they found that lamprey’s median fin used the same developmental program as catshark’s median fins or human limbs.
Furthermore, the fact that lampreys – one of the most primitive of living vertebrates- already use this fin’s developmental mechanism raises the possibility that this genetic program might have developed even before vertebrates. To investigate that, the researchers now plan to see if cephalocordates, which have appeared before the vertebrates, share a similar genetic mechanism behind the development of their fins.
Catarina Amorim | alfa
Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University
How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy