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Experiments conducted by Hilde Mangold and Hans Spemann taught us how an animal develops from a small ball of cells into an organism with distinct, functioning parts. The work was a foundational contribution to the field of developmental biology.

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Sources:
http://www.ijdb.ehu.es/web/paper.php?doi=11291841
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2464568/
https://www.jstor.org/stable/4330877?seq=1#page_scan_tab_contents

https://www.ncbi.nlm.nih.gov/books/NBK10101/
https://opentextbc.ca/biology/chapter/24-6-fertilization-and-early-embryonic-development/
https://www.nobelprize.org/prizes/medicine/1935/spemann/lecture/
https://www.dictionary.com/browse/developmental-biology

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Go to unbounce.com/SciShow and use the promo code “SciShow” to get 20% off your first 3 months. [♪ INTRO]. Hans Spemann won the Nobel Prize in Physiology or Medicine in 1935 for foundational contributions to what is now the field of developmental biology.

Without those experiments, we wouldn’t know how an animal develops from a small ball of cells into an organism with distinct, functioning parts. That work is taught in every introductory development course. However, if you look closely, you will notice that the work that claimed.

Spemann the Nobel prize had another name on it: Hilde Mangold. Hilde Mangold was a graduate student in Hans Spemann’s lab in. Freiburg, Germany, and it was her thesis work and experiments that helped propel Spemann to scientific fame and glory, though she herself would net little of the credit.

In the early 1920s, the field of developmental biology was just getting started. Researchers were just beginning to probe the many complex steps required for a single fertilized plant or animal egg cell, or zygote, to form into an embryo, and from there into an adult organism. This research wasn’t easy, because embryos are pretty small and fragile things.

To make matters worse, they’re also vulnerable to infection. And researchers didn’t have antibiotics yet to add to their cultures. Some things were already known, thanks to observing embryos under a microscope.

Researchers understood that the zygote starts by undergoing several cell divisions to become a blastula, a small, hollow cluster of cells. At that stage, individual cells are known as blastomeres. The blastula stage is where cells begin to specify, which is to say, they’re set down the path to becoming a specific cell type.

Eventually, that will mean the difference between becoming part of the nervous system versus, say, a skin cell. However, researchers didn’t yet know what set cells down that path. It could have been some kind of signal from their environment, like some sort of chemical.

Or maybe becoming a specific cell type was an intrinsic part of the cell, and different cells had different genetic information in their nucleus that controlled their eventual fate. We just didn’t know! At the time, Hans Spemann’s laboratory was well known for its ingenious experiments in amphibian embryos.

One of his first experiments in 1903 tested whether early newt blastomeres all carried identical information in their nucleus, and therefore had the same capacity to produce an organism. In the early 1920s, Hilde Mangold, at the time Hilde Proescholdt, joined Spemann’s lab at the University of Freiburg as a doctoral student. And after a time, Spemann gave her the experiment that would later change developmental biology.

Spemann had been interested for a while in the concept of a developmental organizer, a tissue or cluster of cells that would organize surrounding tissues into the parts of a mature organism. He suspected that in amphibian embryos, this organizer was located in a small region of the early embryo called the dorsal lip. That part of the organism would develop into the notochord, the embryonic precursor to the spinal cord.

Now, in order to test this, he had Mangold transplant the dorsal lip of one amphibian embryo to the region of another embryo that would become the belly region. That’s an important detail, because the notochord forms the spine on the opposite side of the organism. If a belly is developing into a spine, you can pretty much tell it’s because of your experiment.

They also used newt embryos of two different species, and different colors, so they could identify the host and donor tissue. If the dorsal lip had not been an organizer region, those cells would have gotten sucked into the host embryo’s belly and blended in. You’d get one newt with some cells the color of the host embryo and some cells the color of the donor.

Or it could’ve died, but you know. What happened was way weirder. The embryo with two dorsal lips developed two notochords, and given enough time, resulted in twin larvae attached at the belly.

One of those was the host color, while the other was a mixture of both host and donor colors. That tells us that the donor tissue was an organizer, and it went and organized some of the host tissue just like it was supposed to. Probably by sending them some signal -- which we now know to be the case.

These transplants were extremely difficult and labor-intensive, and often resulted in failure. At the end of two years of work, only six of Mangold’s embryos survived the microsurgeries to make it into the publication. The results were published in 1924, with Spemann’s name coming before Mangold’s on what was technically her dissertation.

Some of Spemann’s male colleagues noted after the fact that most other students were sole author of their dissertations. Unfortunately, around the time that the paper went into publication,. Hilde Mangold died of an accident at the age of 26.

She did not live to see the impact of her work, which is now a foundation of developmental biology. Spemann won the Nobel as a result of this experiment as well as his decades of work in early embryology. And Hilde Mangold’s project remains one of the only doctoral dissertations that directly helped result in a Nobel.

Despite sticking his name in front of hers on her work,. Spemann did credit Mangold numerous times in his Nobel lectures. But her name would never have joined him on his award, because.

Nobels are not granted posthumously. And their joint discovery would go down in history known as the “Spemann organizer.” Fortunately, more and more developmental biologists are now calling it the Spemann-Mangold organizer instead, to commemorate both the amazing scientists who discovered it. Thanks for watching this episode of SciShow, which was brought to you by Unbounce.

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