Advertisements
Feeds:
Posts
Comments

Posts Tagged ‘cloning’


Heroes in Medical Research: Green Fluorescent Protein and the Rough Road in Science

Curator: Stephen J. Williams, Ph.D.

In this series, “Heroes in Medical Research”, I like to discuss the people who made some important contributions to science and medicine which underlie the great transformative changes but don’t usually get the notoriety given to Nobel Laureates or who seem to fly under the radar of popular news. Their work may be the development of research tools which allowed a great discovery leading to a line of transformative research, a moment of serendipity leading to discovery of a cure, or just contributions to the development of a new field or the mentoring of a new generation of scientists and clinicians. One such discovery, which has probably been pivotal in many of our research, is the discovery of the green fluorescent protein (GFP), commonly used as an invaluable tool to monitor protein for cellular expression and localization studies. Although the development of research tools, whether imaging tools, vectors, animal models, cell lines, and such are not heralded, they always assist in the pivotal discoveries of our time. The following is a heartwarming story by Discover Magazine’s Yudhijit Bhattacharjee behind Dr. Douglas Prasher’s discovery of the green fluorescent protein, his successful efforts to sequence the gene and subsequent struggles in science and finally scientific recognition for his work. In addition the story describes Dr. Prather’s perseverance, a trait necessary for every scientist.

http://discovermagazine.com/2011/apr/30-how-bad-luck-networking-cost-prasher-nobel

 

The following is a wonderful entry into Wikipedia about Dr. Prasher at:

http://en.wikipedia.org/wiki/Douglas_Prasher

including a listing of his publications including the seminal Science and PNAS publications1,2.

 

prasher

 

 

(Photo: Dr. Prasher in the lab at UCSD. Photo credit UCSD and John Galstaldo)

 

 

 

In summary, Dr. Prather had been working at Wood’s Hole in Massachusetts trying to discover, isolate, then clone the protein which allowed a species of jellyfish living in the cold waters of the North Pacific, Aequorea victoria, to emit a green glow. Eventually he cloned the GFP gene, but gave up on work to express the gene in mammalian cells. Before leaving Wood’s Hole he gave the gene to Dr. Roger Tsien, who with Dr. Martin Chalfie and Osamu Shimomura showed the utility of GFP as an intracellular tracer to visualize, in real time, the expression and localization of GFP-tagged proteins (all three shared the 2008 Nobel Prize for this work). Dr. Tsien however realized the importance of Douglas’s cloning work as pivotal for their research, contacted Douglas (who now due to the bad economy was working at a Toyota dealership in Alabama) and invited him to the Nobel Prize Award Ceremony in Sweden as his guest. Although Dr. Prasher had “left academic science” he never really stopped his quest for a scientific career, using his spare time to review manuscripts.

Other researchers have invited their colleagues who made important contributions to the ultimate Nobel work. One such guest was one of my colleagues Dr. Leonard Cohen, who worked with Dr. Irwin Rose and Avram Hershko at the Institute for Cancer Research in Philadelphia a cell-free system from clams to discover the mechanism how cyclin B is degraded during the exit from the cell cycle (from A. Hershko’s Nobel speech). Dr. Hershko had acknowledged a slew of colleagues and highlighted their contributions to the ultimate work. It shows how even small discoveries can contribute to the sphere of scientific knowledge and breakthrough.

Luckily, in the end, perseverance has paid off as Dr. Prasher is now using his talents in Roger Tsien‘s group at the University of California in San Diego.

References:

1. Chalfie, M., Tu, Y., Euskirchen, G., Ward, W.W., Prasher, D.C., Green fluorescent protein as a marker for gene expression. Science, 263(5148), 802-805 (1994).

 

2. Heim, R., Prasher, D.C., Tsien, R.Y., Wavelength mutations and posttranslational autoxidation of green fluorescent protein. Proc. Natl. Acad. Sci. USA, 91(26), 12501-12504 (1994).

More posts on this site on Heroes in Medical Research series include:

Heroes in Medical Research: Developing Models for Cancer Research

Heroes in Medical Research: Dr. Carmine Paul Bianchi Pharmacologist, Leader, and Mentor

Heroes in Medical Research: Dr. Robert Ting, Ph.D. and Retrovirus in AIDS and Cancer

Heroes in Medical Research: Barnett Rosenberg and the Discovery of Cisplatin

 

Advertisements

Read Full Post »


Heroes in Medical Research: Developing Models for Cancer Research

Author, Curator: Stephen J. Williams, Ph.D.

 

The current rapid progress in cancer research would have never come about if not for the dedication of past researchers who had developed many of the scientific tools we use today. In this issue of Heroes in Medical Research I would like to give tribute to the researchers who had developed the some of the in-vivo and in-vitro models which are critical for cancer research.

 

The Animal Modelers in Cancer Research

Helen Dean King, Ph.D. (1869-1955)

Helen Dean King

Helen Dean King, Ph.D. from www.ExplorePAhistory.com; photo Courtesy of the Wistar Institute Archive Collection, Philadelphia, PA

 

 

The work of Dr. Helen Dean King on rat inbreeding led to development of strains of laboratory animals. Dr. King taught at Bryn Mawr College, then worked at University of Pennsylvania and the Wistar Institute under famed geneticist Thomas Hunt Morgan, researching if inbreeding would produce harmful genetic traits.   At University of Pennsylvania she examined environmental and genetic factors on gender determination.

 

 

 

 

Important papers include [1-6]as well as the following contributions:

“Studies in Inbreeding”, “Life Processes in Gray Norway Rats During Fourteen Years in Captivity”, doctoral thesis on embryologic development in toads (1899)

 

Milestones include:

 

1909    started albino rat breeding and bred 20 female and male from same litter (King colony) to 25

successive generations (inbreeding did not cause harmful traits)

 

1919     started to domesticate the wild Norwegian rats that ran thru Philadelphia (six pairs Norway rats

thru 28 generations)

A good reference for definitions of rat inbreeding versus line generation including a history of Dr. King’s work can be found at the site: Munificent Mischief Rattery and a brief history here.[7] In addition, Dr. King had investigated using rat strains as a possible recipient for tumor cells. The work was an important advent to the use of immunodeficient models for cancer research.

 

As shown below Philadelphia became a hotbed for research into embryology, development, genetics, and animal model development.

 

Beatrice Mintz, Ph.D.

(Beatrice Minz, Ph.D.; photo credit Fox Chase Cancer Center, www.pubweb.fccc.edu) Mintz

Dr. Mintz, an embryologist and cancer researcher from Fox Chase Cancer Center in Philadelphia, PA, contributed some of the most seminal discoveries leading to our current understanding of genetics, embryo development, cellular differentiation, and oncogenesis, especially melanoma, while pioneering techniques which allowed the development of genetically modified mice.

If you get the privilege of hearing her talk, take advantage of it. Dr. Mintz is one of those brilliant scientists who have the ability to look at a clinical problem from the viewpoint of a basic biological question and, at the same time, has the ability to approach the well-thought out questions with equally well thought out experimental design. For example, Dr. Mintz asked if a cell’s developmental fate was affected by location in the embryo. This led to her work by showing teratocarcinoma tumor cells in the developing embryo could revert to a more normal phenotype, essentially proving two important concepts in development and tumor biology:

  1. The existence of pluripotent stem cells
  2. That tumor cells are affected by their environment (which led to future concepts of the importance of tumor microenvironment on tumor growth

Other seminal discoveries included:

  • Development of the first mouse chimeras using novel cell fusion techniques
  • With Rudolf Jaenisch in 1974, showed integration of viral DNA from SV40, could be integrated into the DNA of developing mice and persist into adulthood somatic cells, the first transgenesis in mice which led ultimately to:
  • Development of the first genetically modified mouse model of human melanoma in 1993

Her current work, seen on the faculty webpage here, is developing mice with predisposition to melanoma to uncover risk factors associated with the early development of melanoma.

In keeping with the Philadelphia tradition another major mouse model which became seminal to cancer drug discovery was co-developed in the same city, same institute and described in the next section.

It is interesting to note that the first cloning of an animal, a frog, had taken place at the Institute for Cancer Research, later becoming Fox Chase Cancer Center, which was performed by Drs. Robert Briggs and Thomas J. King and reported in the 152 PNAS paper Transplantation of Living Nuclei From Blastula Cells into Enucleated Frogs’ Eggs.[8]

 

 The Immunodeficient Animal as a Model System for Cancer Research – Dr. Mel Bosma, Ph.D.

 

Bosma

Melvin J. Bosma, Ph.D.; photo credit Fox Chase Cancer Center

In the summer of 1980 at Fox Chase Cancer Center, Dr. Melvin J. Bosma and his co-researcher wife Gayle discovered mice with deficiencies in common circulating antibodies and since, these mice were littermates, realized they had found a genetic defect which rendered the mice immunodeficient (upon further investigation these mice were unable to produce mature B and T cells). These mice were the first scid (severe combined immunodeficiency) colony. The scid phenotype was later found to be a result of a spontaneous mutation in the enzyme Prkdc {protein kinase, DNA activated, catalytic polypeptide} involved in DNA repair, and ultimately led to a defect in V(D)J recombination of immunoglobulins.

The emergence of this scid mouse was not only crucial for AIDS research but was another turning point in cancer research , as researchers now had a robust in-vivo recipient for human tumor cells. The orthotopic xenograft of human tumor cells now allowed for studies on genetic and microenvironmental factors affecting tumorigenicity, as well as providing a model for chemotherapeutic drug development (see Suggitt for review and references)[9]. A discussion of the pros and cons of the xenograft system for cancer drug discovery would be too voluminous for this post and would warrant a full review by itself. But before the advent of such scid mouse systems researchers relied on spontaneous and syngeneic mouse tumor models such as the B16 mouse melanoma and Lewis lung tumor model.

Other scid systems have been developed such as in the dog, horse, and pig. Please see the following post on this site The SCID Pig: How Pigs are becoming a Great Alternate Model for Cancer Research. The athymic (nude) mouse (nu/nu) also is a popular immunodeficient mouse model used for cancer research

Two other in-vivo tumor models: Patient Derived Xenografts (PDX) and Genetically Engineered Mouse models (GEM) deserve their own separate discussion however the success of these new models can be attributed to the hard work of the aforementioned investigators. Therefore I will post separately and curate PDX and GEM models of cancer and highlight some new models which are having great impact on cancer drug development.

 

References

1.         Loeb L, King HD: Transplantation and Individuality Differential in Strains of Inbred Rats. The American journal of pathology 1927, 3(2):143-167.

2.         Lewis MR, Aptekman PM, King HD: Retarding action of adrenal gland on growth of sarcoma grafts in rats. J Immunol 1949, 61(4):315-319.

3.         Aptekman PM, Lewis MR, King HD: Tumor-immunity induced in rats by subcutaneous injection of tumor extract. J Immunol 1949, 63(4):435-440.

4.         Lewis MR, Aptekman PM, King HD: Inactivation of malignant tissue in tumor-immune rats. J Immunol 1949, 61(4):321-326.

5.         Lewis MR, King HD, et al.: Further studies on oncolysis and tumor immunity in rats. J Immunol 1948, 60(4):517-528.

6.         Aptekman PM, Lewis MR, King HD: A method of producing in inbred albino rats a high percentage of immunity from tumors native in their strain. J Immunol 1946, 52:77-86.

7.         Ogilvie MB: Inbreeding, eugenics, and Helen Dean King (1869-1955). Journal of the history of biology 2007, 40(3):467-507.

8.         Briggs R, King TJ: Transplantation of Living Nuclei From Blastula Cells into Enucleated Frogs’ Eggs. Proceedings of the National Academy of Sciences of the United States of America 1952, 38(5):455-463.

9.         Suggitt M, Bibby MC: 50 years of preclinical anticancer drug screening: empirical to target-driven approaches. Clinical cancer research : an official journal of the American Association for Cancer Research 2005, 11(3):971-981.

 

Other posts on this site about Cancer, Animal Models of Disease, and other articles in this series include:

The SCID Pig: How Pigs are becoming a Great Alternate Model for Cancer Research

A Synthesis of the Beauty and Complexity of How We View Cancer

Guidelines for the welfare and use of animals in cancer research

Importance of Funding Replication Studies: NIH on Credibility of Basic Biomedical Studies

FDA Guidelines For Developmental and Reproductive Toxicology (DART) Studies for Small Molecules

Report on the Fall Mid-Atlantic Society of Toxicology Meeting “Reproductive Toxicology of Biologics: Challenges and Considerations:

What`s new in pancreatic cancer research and treatment?

Heroes in Medical Research: Dr. Carmine Paul Bianchi Pharmacologist, Leader, and Mentor

Heroes in Medical Research: Dr. Robert Ting, Ph.D. and Retrovirus in AIDS and Cancer

Heroes in Medical Research: Barnett Rosenberg and the Discovery of Cisplatin

Richard Lifton, MD, PhD of Yale University and Howard Hughes Medical Institute: Recipient of 2014 Breakthrough Prizes Awarded in Life Sciences for the Discovery of Genes and Biochemical Mechanisms that cause Hypertension

Reuben Shaw, Ph.D., a geneticist and researcher at the Salk Institute: Metabolism Influences Cancer

 

Read Full Post »