Tag Archives: frog

Reprogrammed frog and mouse cells win the 2012 Nobel Prize

This morning the Nobel Assembly announced that the 2012 Nobel Prize in Physiology or Medicine will be shared by John B. Gurdon and Shinya Yamanaka for their “discovery that mature cells can be reprogrammed to become pluripotent”.  Animal research played a key role in the research honoured by the prize, specifically the studies of frogs undertaken by Professor Gurdon and studies of mice performed by Professor Yamanaka.

Sir John Gurdon. Image: Nobel foundation.

Professor Gurdon’s key work showed in a series of studies undertaken at the University of Oxford in the late 1950’s and 1960’s that if the nucleus of a specialised cell from a frog of the species Xenopus laevis – initially from late embryonic cells and subsequently adult intestinal and skin cells – was transferred into an egg whose nucleus had been removed, it could give rise to normal frog that could themselves produce offspring. This demonstrated for the first time that the nucleus of an adult cell is totipotent, and that in under certain conditions it could give rise to all cell types, including eggs and sperm, that are required in a healthy adult.

The very first Xenopus frog produced by somatic nuclear transfer to reach sexual maturity. Image: J.B. Gurdon

In 2009 Sir John wrote an account of his research on nuclear transfer in Xenopus for Nature Medicine, which can be read online without subscription, after he and Professor Yamanaka were presented with the  Albert Lasker Basic Medical Research Award in 2009.

Professor Shinya Yamanaka. Image: Nobel foundation

Almost 4 decades later Professor Yamanaka, then at the Kyoto University Institute for Frontier Medical Sciences, made another great step forward by proving that it was possible to transform adult mouse cells into a pluripotent stem cells without nuclear transfer. By inserting 4 genes whose expression is associated with the embryonic state into the adult cell, his team were able to create the first induced pluripotent stem (iPS) cells, cells that could give rise to any tissue in the body.

Earlier this year in a post congratulating Professor Yamanaka’s on winning the 2012 Millenium Technology Prize I noted that:

The work briefly described above was a technological tour-de-force where Prof. Yamanaka and his colleagues selected 24 genes which had previously been identified as having key roles in mouse embryonic stem cells, and developed a screening method using skin fibroblast cells derived from mice that had be genetically modified with an antibiotic resistance gene that was only expressed in embryonic cells, so that only cells that were in an embryonic state would survive in a culture containing the antibiotic. Different combinations of these 24 genes were screened for their ability to induce to the production of colonies of embryonic -like cells from adult fibroblasts.  They eventually identified just 4 genes – Oct3/, Sox2, Klf4 and c-Myc – that together could reprogram adult mouse fibroblast cells to a pluripotent embryonic-like state (1), and subsequently demonstrated that these iPS cells could give rise to a wide variety of  tissue types when incorporated into mice, either by subcutaneous injection into adult mice or incorporation into early mouse embryos. By modifying their method slightly to also include expression of an important developmental gene named Nanog  they were then able to generate chimeric mice (mice whose tissues are made up of a mixture of cells derived from their own embryonic stem cells, and cells derived from iPS cells) which were capable of transmitting the iPS cells to the next generation of mice (2).

Soon after this Prof. Yamanaka succeeded in generating iPS cells from human fibroblasts, using the same techniques used for the mouse cells, and a whole new and exciting field of biomedical research was born.

1)      Takahashi K, Yamanaka S. “Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.” Cell 2006 Vol. 126(4):663-76. PubMed: 16904174

2)      Okita K., Ichisaka T., Yamanaka S. “Generation of germline-competent induced pluripotent stem cells.” Nature Vol. 448:313-317 (2007). PubMed:17554338””

It’s worth remembering that this breakthrough did not come out of thin air, and built on years of research that followed the pioneering work of Martin Evans and Gail Martin who demonstrated that cells derived from mouse embryos could be cultured and give rise to all tissue types…the first embryonic stem cells.

The field of iPS cell research has progressed swiftly since the first mouse iPS cells were produced just 6 years ago, and the techniques used to produce the cells have been refined to address early concerns that the inserted genes might give rise to tumors, but as Prof Yamanaka outlined in a recent review of progress in the field there is still a lot of scope for improvement.  Nevertheless iPS cells are already showing promise in a variety of medical research applications – for example to create nerve cell lines from Parkinson’s disease patients in order to study the processes that trigger the degeneration, or  to evaluate the toxicity of new drugs – and are expected to join  human embryonic stem cells as key components of regenerative medicine.

This year’s Nobel Prize in Physiology or Medicine highlights once again the key role played by animal research in making groundbreaking discoveries that give rise to new fields of medicine, and we offer our heart-felt congratulations to John Gurdon and Shinya Yamanaka.

 

Addendum: In a statement to Reuters on the problem of the unproven stem cell therapies being offered for a myriad of disorders by private health clinics around the world – and widely touted on the internet -Professor Yamanaka highlighted the key role played by animal research in ensuring that real stem cell therapies are safe and effective:

Yamanaka, who shared the Nobel Prize for Medicine on Monday with John Gurdon of the Gurdon Institute in Cambridge, Britain, called for caution [on stem cell therapies – PB].

“This type of practice is an enormous problem, it is a threat. Many so-called stem cell therapies are being conducted without any data using animals, preclinical safety checks,” said Yamanaka of Kyoto University in Japan.

“Patients should understand that if there are no preclinical data in the efficiency and safety of the procedure that he or she is undergoing … it could be very dangerous,” he told Reuters in a telephone interview.

Yamanaka and Gurdon shared the Nobel Prize for the discovery that adult cells can be transformed back into embryo-like stem cells that may one day regrow tissue in damaged brains, hearts or other organs.

“I hope patients and lay people can understand there are two kinds of stem cell therapies. One is what we are trying to establish. It is solely based on scientific data. We have been conducting preclinical work, experiments with animals, like rats and monkeys,” Yamanaka said.”

 

Paul Browne

 

 

 

Laying the foundations of medical research

For the past couple of weeks a debate has been raging on the Opposing Views website between Speaking of Research’s Dario Ringach and the anti-vivisectionist Ray Greek. It has been a debate shaped by Dr. Greek’s attempts to persuade readers to agree with his very narrow concept of what prediction means in biology and his frankly impoverished view on the role of basic research in advancing medical science, and to oblige those debating them to accept a playing field rigged to set them at a disadvantage.  Judging by Dario’s most recent opinion piece and an article written a couple of days ago on the role of basic research Dr. Greek failed in this attempt.

British biochemist Sir Tim Hunt, who won the Nobel Prize for medicine in 2001.

Among all the discussion was one comment that directed readers to an excellent example of the value of basic research and the how study of animal models made many key discoveries possible. Earlier this week the BBC aired a program in their Beautiful Minds series featuring Sir Tim Hunt, who was awarded the Nobel Prize in 2001 for his research on how the cell cycle – through which cells grow and divide – is controlled.  Sir Tim’s work focused on the role of a family of proteins known as cyclins and as the Beautiful Minds program explains the initial breakthrough came from studies of the fluctuations in the pattern of protein expression during the cell cycle in sea urchin eggs.  This discovery was followed swiftly by the demonstration that cyclins were also present in yeast, clams and frogs, allowing Sir Tim and his colleagues to predict that they would have a role in regulating the cell cycle in many species,  including humans, a prediction that was soon confirmed to be true (1).

This program is a reminder that while discussion of animal research tends to focus on animals such as mice, rats and monkeys a lot is being learned about the fundamentals of our physiology through research on more humble model organisms, a diverse collection that includes not just sea urchins and clams but also nematode worms and flies .  These animals, along with other model organisms such as yeast and bacteria, enable us to study how living things work at a very fundamental level, laying the theoretical foundations for future applied and translational research that yields innovative treatments for disease and injury. At the same time, researchers studying other aspects of physiology often require higher mammals. The study of complex brain functions, including vision, hearing, memory, attention and motor planning, as well as how these functions fail in diseases of the central nervous system, is a prime example of this.

If you haven’t watched the Beautiful Minds series yet I strongly urge you to do so, the programs provide a fascinating (if not always flattering) insight into how science works.  And don’t delay: they are only available to view on the BBC iPlayer for another 7 days!

Paul Browne

1)      Pines J.  and Hunter T. “Isolation of a human cyclin cDNA: evidence for cyclin mRNA and protein regulation in the cell cycle and for interaction with p34cdc2.” Cell Volume 58(5), Pages 833-846 (1989)  PubMed: 2570636