Ok, animals don’t get awarded the Nobel Prize, it is the scientists who use them in their work that do. Most people think of scientists as working with mice or rats (hence the term “lab rat”), which a hell of a lot of them do.
However, there are plenty of other “model organisms” that are used, and some have led to very important results, at least in the eyes of people who dish out Nobel Prizes.
(Picture of Xenopus frog taken by the author)
The Frog Xenopus laevis
The 2012 Nobel prize was awarded to John B. Gurdon and Shinya Yamanaka for the discovery that mature differentiated cells can revert to a stem cell undifferentiated state. John Gurdon is a British developmental biologist who uses frog embryos for his work on nuclear reprogramming.
The major breakthrough in his work happened in 1962 when he transplanted a nucleus from a cell from the intestine of a tadpole into an egg. The egg developed into a normal tadpole, a clone of the donor frog.
Dolly the cloned sheep is very famous. But very few people know that the first cloned vertebrate was in fact a Xenopus frog, decades before Dolly was born.
The work was fundamentally important because it showed that mature, differentiated cells contain all the genetic information required to make a frog (or by extrapolation a human). At that time it was thought that cells lose the genes they don’t use as they mature and specialise.
The frog Xenopus laevis is a favourite of developmental biologists. The female lays hundreds of large eggs which develop outside the body, so can be observed easily.
The eggs are robust and it is easy to inject them and alter their gene expression so the role of different genes in producing a tadpole from an egg can be studied.
What’s more female frogs can be made to lay eggs on demand by injecting them with chorionic gonadotrophin hormone.
The Roundworm C. elegans
The 2002 Nobel prize was awarded to Sydney Brenner, Robert Horvits and John Sulston for their work on apoptosis, programmed cell death, in this transparent 1 mm nematode worm.
This tiny, hermaphroditic worm was established as an important model organism for developmental biology by Sydney Brenner starting in 1963. Its advantages are that it is very easy to grow in bulk, and to store.
The worms can be stored in an antifreeze solution of 15% glycerol in liquid nitrogen for decades.
Adult hermaphroditic worms consist of exactly 959 somatic (not egg or sperm) cells. The fate of all the cells during development is now known.
131 extra cells, which would have become neurones, disappear by “committing suicide”. This programmed cell death, also called apoptosis occurs in multicellular organisms. It is the reason we have toes and fingers, during human embryonic development the cells in between our fingers die by apoptosis.
Of course you don’t want cells to be just committing suicide at the drop of a hat, so the pathway that controls this is very complex, controlled by many proteins and with many safeguards.
Some of the factors responsible for controlling the apoptotic pathway were discovered in the C. elegans worm, because programmed cell death is so predictable in it, in terms of which cells will die and when.
The Fruit Fly Drosophila Melanogaster
The simple fruit fly Drosophila melanogaster is another small, simple organism that has been very intensively studied since 1910 when Thomas Hunt Morgan devoted his time to using them to study heredity.
Not only are flies small, easy to keep, and produce many eggs at a time, but they also have a much simpler genome than more complicated organisms like us.
Despite the evolutionary distance that separates them from humans, many similarities in gene function have been conserved.
About 75% of known human disease genes have their fly equivalents, allowing the diseases to be modeled and studied in flies.
Morgan and his students identified many naturally occurring fly mutants, and by observing the way the mutant traits were passed on to the progeny, worked out many of the principles of genetic inheritance.
For this work Morgan was awarded the Nobel Prize in 1933.
Mutations are an incredibly useful tool in figuring out the function of a gene, since by observing what happens when the gene is “broken”, you can figure out what it does. However, finding naturally occurring mutations is a slow process and a matter of luck.
Christiane Nüsslein-Volhard, Eric Wieschaus and Edward B. Lewis decided to speed matters up by using a mutagen to create random mutations in flies.
The progeny of mutation carriers showed a variety of developmental defects, like the lack of heart in the tinman mutation, or flies developing with legs on their heads instead of antennae.
For their work in identifying “master genes” that initiated whole developmental pathways they were awarded the 1995 Nobel Prize. (Image of the fly is in the public domain).