Oliver Smithies

A Toolmaker's Story


Abstract

Looking back over 60 years as a bench scientist, I see how often new tools have led to quantum increases in our understanding of biology - a connection that I will illustrate by sharing with you some experiments in which I have participated.
When I first began bench work, in 1948, many uncertainties about the nature of proteins remained. The invention of the ultra-centrifuge by Svedberg (Nobel Prize, 1926) had removed some by showing that proteins had defined molecular weights. But his tool raised new problems, one of which indirectly led to my thesis problem. When mixtures of two proteins of different sizes, such as serum globulin (MW ~ 140,000) and serum albumin (MW ~ 70,000), were centrifuged, the larger protein appeared to dissociate and form the smaller. My thesis problem was to measure the osmotic pressures of protein mixtures to see whether any dissociation was detectable non-centrifugally. I enjoyed my experiments, but did not resolve the puzzle.
Tiselius’ invention (Nobel Prize, 1948) of protein electrophoresis provided another tool, which as a post-doc I used to study the homogeneity of β2-lactoglobulin. In my hands, this tool also had anomalies, although in the hands of others it proved invaluable. For example, with it Pauling & Itano (1949) showed that sickle cell anemia is a molecular disease. In my first job, I tried a different form of electrophoresis, on filter paper, to study insulin, but insulin absorbed to paper and would not migrate. If I used a moist bed of starch grains instead of paper no absorption was likely (Kunkel & Slater, 1952), but determining the electrophoretic pattern would require measuring the protein content of 40 segments cut from the moist bed of starch grains. Avoiding that task led me somewhat serendipitously to invent a new tool – molecular sieving gel electrophoresis (Smithies, 1956), which in various forms molecular biologists continue to find indispensable. Using it, I discovered that several serum proteins had genetic variants.
The next tool that influenced my work and that of the whole biological community was the invention of recombinant DNA techniques (Berg, Nobel Prize, 1980). But scientists‘ concerns that some cloned DNAs might be hazardous (Berg et al., 1975) led my friend Fred Blattner at the University of Wisconsin, an expert in bacteriophage genetics and in working with DNA, to derive a cloning vector that would not grow outside the laboratory. I joined him in executing this task, and I learned how to work with DNA and bacteria. Fred’s Charon ‚phages provided the first really successful tool certified for use in cloning human DNA. Together our groups used it to clone the genes coding for fetal hemoglobin, and I began to think about using cloned DNA to correct human genetic diseases.
A new tool was needed – a means of using cloned DNA to correct a mutant human gene in suitable cells. That tool, invented by our group (Smithies et al., 1985) and by Thomas & Capecchi (1987), and its application to modify genes in the mouse genome via embryonic stem cells (Evans & Kaufmann, 1981) led to another Nobel Prize, and to a new era of biology. In North Carolina we had an exciting time using the tool to determine how genetic variations affect common complex diseases.
My own research has returned to studying gels. I am making gold nanoparticles that we use to see if the kidney separates proteins by gel permeation. Experiments continue to be a joy.


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