Scientists saw the process of embryo's finger formation for the first time: it is not how they thought it happens

Dmytro IvancheskulNews
Fingers of embryos grow in a completely different way than scientists thought. Source: Getty/Zhang, B. et al/collage OBOZ.UA

For the first time in history, scientists have managed to trace the process of limb development in human embryos, seeing everything down to a single cell. Previously, this was not possible for both scientific and ethical reasons.

This is stated in the study, the details of which were reported by Freethink. The stunning result may eventually help prevent common types of birth defects.

Previously, scientists were well aware that at the age of four weeks, the parts of the human embryo that will later become arms and legs are essentially the beginnings of undifferentiated cells. Meanwhile, by the eighth week, the limbs are clearly defined and fingers and toes can be seen. However, the transition from one stage to the other has remained a mystery until now.

The reason is, in particular, that for ethical reasons, human embryos were previously allowed to be grown only up to the 14th day. This restriction is currently being relaxed, but it is not certain that this will change anything as scientists do not even know for sure whether it is possible to grow an embryo outside the womb until the fourth week, let alone the eighth week.

As for the study of embryos inside the womb, it is an extremely difficult procedure, because at the age of 8 weeks, the embryo is only a little over 2 centimeters long. Previously, scientists have studied the development of limbs in animals, but it is not known to what extent this coincides with the way limbs develop in humans.

Not understanding this development is an obstacle to understanding why this process often goes wrong: 1 in 500 babies are born with significant limb abnormalities, such as shortened fingers or extra toes. Therefore, scientists are looking for ways to prevent this.

Now, an international team of researchers led by scientists from the Human Cell Atlas initiative has tracked gene expression (the process by which the hereditary information of genes is used to synthesize a functional product: protein or RNA) and the differentiation of individual cells in donated embryonic tissue to create the first map of human limb development.

"For the first time, we were able to record the amazing process of limb development with an accuracy of one cell in space and time," said senior author of the study Sarah Teichmann.

The scientists found that the fingers and toes of the embryo do not actually grow from clusters of limb cells, as previously thought, but are formed inside the embryos. After that, the extra cells around them die off, opening the fingers.

"What we see is a very complex and precisely regulated process. It's like watching a sculptor chisel a block of marble to create a masterpiece. In this case, nature is the sculptor, and the result is the incredible complexity of our fingers and toes," explained senior author Hongbo Zhang.

During the study, the researchers also found a link between common limb abnormalities and disorders in certain genes. Subsequently, this may be the key to preventing these anomalies in the future.

Earlier, OBOZ.UA reported that scientists have created fully synthetic human embryos for the first time in history.

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