BRIGGS, ROBERT W.

(b. Watertown, Massachusetts, 10 December 1911; d. Indianapolis, Indiana, 4 March 1983)

developmental genetics, amphibian cloning, maternal gene products controlling embryogenesis.

The research contributions of Robert W. (Bob) Briggs to developmental genetics extended over four decades. They included in chronological order four mains periods of studies in amphibian development, involving neoplasia, ploidy (even sets of chromosome number), nuclear transplantation (cloning), and maternal genes.

Early Life. Bob Briggs was the son of Robin J. Briggs and Bridget (née McGonagle) Briggs. When Bob was two years old, his mother and a younger brother (his only sibling) died of tuberculosis, and Bob was sent to his father’s parents in Epping, New Hampshire. He learned how to play the piano from his aunt, and eventually he mastered the banjo, leading to a job as a banjo player in a small dance band that play two or three nights per week in southeastern New Hampshire towns. He developed an interest in classical music and later in life learned to play the recorder. Bob’s interest in biology is also traceable to his early years, when he collected minnows, frogs, insects, and worms and studied them under magnifying glasses and a borrowed microscope.

Briggs went to Boston University from where he graduated in 1934 with a BS degree. He then moved to Harvard University and, under the sponsorship of Leigh Hoadley, studied the metabolic rate and density of the frog embryo during embryogenesis. In 1938 he received his PhD. His introduction to the amphibian embryo would guide his research interests for the rest of his life. Bob married Janet Bloch, who also held a PhD; they had two sons, Evan and Alexander, and one daughter, Meredith Briggs Skeath.

Neoplasia. After receiving his doctoral degree, Briggs became a Fellow in the Zoology Department at McGill University (1938–1942) in Montreal and characterized tumor growths in tadpoles of the frog, Rana pipiens, in order to study the behavior of tumors in the organization fields operative during development. He was the first to induce tumors in a developing system and did so with

carcinogenic agent. He transplanted fragments of the frog kidney adenocarcinoma to various sites of tadpoles and found that they grew well but regressed prior to metamorphosis, even in tadpoles prevented from entering metamorphosis. Briggs suggested that regression of this malignant tumor might be caused by the development of tissue specificity. Extension of this research can be found in many later studies by others who were concerned with the development of immunocompetence, tumor immunosurveillance, and attempts to normalize cancer cells in embryonic systems.

Ploidy (Chromosome Number). In 1942 Briggs joined the Lankenau Hospital Research Institute, later the Institute for Cancer Research, and now the basic science component of the Fox Chase Cancer Center in Philadelphia. There he became head of the Embryology Department. First, he compared the effect of changes in ploidy (even sets of chromosome number) on development with normal diploids. For those outside this field, that era of research predated knowledge of the DNA molecule. It was

known that the nucleus was the bearer of heredity traits, but how it influenced development was unknown, so he focused on the nucleus and its organelles, the chromosomes. He developed a method for producing frog triploids by heat shocking fertilized eggs. This treatment prevented the egg from releasing the polar body (containing one set of chromosomes), and the embryo developed with an extra set of chromosomes. He found that triploid amphibians, unlike mammals, developed normally, except female gonads usually reversed to testes.

Next, Briggs characterized the development of haploid embryos containing only one set of chromosomes. Haploids were known previously to develop abnormally, and one interpretation for the cause of their abnormalities was that the nucleocytoplasmic ratio was abnormal. A serendipitous event permitted him to test this interpretation when he found a frog that produced very small eggs. Haploids from small eggs developed better than those from normal size eggs, but still they were not normal. He concluded that the nucleocytoplasmic ratio played a role but suggested that deleterious genes were mainly responsible for the haploid abnormalities, a suggestion verified later by others.

In his last ploidy studies, Briggs produced embryos lacking a functional nucleus (zero ploidy) but containing a normal organelle for cell division. Such embryos developed for one day into partial blastulae. This study, predating the molecular biology of embryos, indicated that gene products (RNAs and proteins) produced during oocyte growth in amphibians are sufficient to support cell division after fertilization but that postblastula development required new gene products. As no chromosomes bearing genes were present in zero ploidy embryos, no gene products could be made and, therefore, the embryos ceased growing and eventually died. This information provided important directions for molecular biologists that later would analyze the RNAs and proteins in oocytes and embryos in order to explain how their gene products control normal embryonic development.

Nuclear Transplantation (Cloning). Beginning in 1952, Briggs and Thomas J. King pioneered a technique to determine whether or not nuclei of specialized cells remain equivalent to the nucleus of the fertilized egg in developmental potential, a question that had been posed by embryologists since the turn of the nineteenth century. Initially, they focused on cell nuclei from undetermined regions of the blastula and showed that after transplantation of nuclei singly into enucleated frog eggs (R. pipiens), many of the nuclei directed eggs to develop into normal tadpoles and, in a later study, into normal metamorphosed frogs. This result demonstrated that transplanted blastula nuclei were equivalent in developmental potential to nuclei at fertilization. This was the first time nuclear transplantation had been accomplished in multicellular organisms. Next, they tested nuclei from progressively older embryonic stages and found a decrease in the number of eggs that developed normally, indicating that most nuclei acquire restrictions concomitant with cell specialization. Their results were confirmed and extended by various laboratories around the world, especially by Marie A. Di Berardino and Robert G. McKinnell in the United States, John Gurdon in England, and Louis Gallien in France, and their respective colleagues.

In the early twenty-first century these classic studies are still consistent with the changing patterns of gene expression occurring during embryogenesis that are controlled by relatively stable alterations in chromosome proteins and DNA methylation. Although nuclear transplantation was developed principally to study nuclear differentiation, it had many applications, including but not limited to the biological analysis of haploidy, hybrid incompatibility, cancer, immunobiology, and cellular aging. It provided insight into the cytoplasmic control of nuclear and gene function, including nuclear reprogramming of nuclear and gene function.

Nuclear reprogramming is jargon among scientists to describe the significant changes that occur in the nucleus of the donor cell after it is transplanted into an egg. For example, even when the donor nucleus is taken from a nonembryonic cell, the chemicals in the egg change its function and those of its genes to behave like those from an embryonic cell. This reversal of nuclear and gene function is most significant, because when the chemicals are identified, it may be possible to reverse differentiated cells in the dish and then convert them with appropriate chemicals into differentiated cell types needed for the repair of human diseases. Most notably, nuclear transfer became the prototype for cloning multicellular organisms and was extended to insects, fish, and mammals.

A dramatic consequence of the research came in 1996, when the clone Dolly was born. Dolly was derived from a nucleus of an adult sheep cell, the first clone ever derived from an adult cell. Subsequently, clones have been made from adult cells of other species, such as cats, cattle, horses, mice, pigs, rabbits, and sheep. Fifty years after the first tadpole clones were produced, the question of the totipotency of specialized cell nuclei was finally answered affirmatively in mice: sixteen fertile adults cloned from B-cell lymphocyte nuclei were produced, each carrying the rearranged DNA of immunoglobulin genes in all tissues. The presence of the rearranged DNA in the clones was proof that the injected nuclei were derived from a fully differentiated cell and not a progenitor or stem cell.

Some other applications stemming from cloning include the rescue of several endangered species and the production of transgenic animal clones producing human proteins. A transgenic animal clone derives from an egg receiving a transplanting nucleus into which an external gene was inserted into its DNA. For example, a human gene, producing a clotting factor to prevent hemophilia, was inserted into the DNA of fetal lamb cells, used as donor cells for cloning. The lamb Polly, the first transgenic clone, resulted and later produced milk containing the human clotting factor. This technique has been used to produce other transgenic farm animals secreting diverse human proteins in their milk. Testing of the human proteins for quality and safety from transgenic farm animals is in progress so that eventually human patients can be treated with these proteins.

Farm animal clones (cattle, sheep, goats, pigs) with uniform genetic backgrounds will be valuable for testing pharmaceutical drugs and vaccines, results that can be applied to humans, especially those from nonhuman primates (monkeys) when the latter can be routinely produced. Also, clones exhibiting exceptional growth rates, milk production, or beef quality could be produced faster than those emanating from selective breeding.

Maternal Genes. In 1956 Briggs became professor of zoology at Indiana University in Bloomington and initiated his fourth and last main research program, the effect of maternal genes on development in the salamander. In layperson’s language the question was how the mother’s genes affect the quality of her oocytes, from which the embryos develop after fertilization. Throughout his career, Briggs had focused on nucleocytoplasmic interactions during embryonic development, that is, how the nucleus interacts with the cytoplasm in directing embryogenesis

To pursue this goal more specifically, he wanted to combine embryology with genetics. Available at that time were genetic lines of the salamander, the Mexican axoltol (Ambystoma mexicanum), developed by Professor Rufus Humphrey. Briggs recruited Humphrey and together they developed a research program in the developmental genetics of the axolotl. Among the various mutations available at that time in axolotl, he focused on mutations showing maternal effects that were expressed in the embryo. Such gene mutations synthesize abnormal RNAs and proteins during the growth of the oocyte that are stored in its nucleus or cytoplasm. After fertilization of the oocyte, those products modify the normal pattern of embryonic development.

For example, four mutations caused early arrest of development. One,the 0⁺ gene,produced a substance

during oogenesis that is required for development beyond gastrulation, but embryos with the mutant gene failed to gastrulate. However, injections of cytoplasm or nuceloplasm from the nuclei from normal oocytes corrected the abnormality, resulting in normal development. Eight other genes produced specific effects on embryonic organs, four others caused alterations in pigment cells, and four did so in nucleoli. Cytological, biochemical, embryological, molecular, and physiological studies performed by Briggs, Humphrey, students, and others explained how many of the mutant genes modified the embryos.

This last period of Briggs’s research provided direction for the elegant molecular genetic experiments of others that followed in Drosophila(fruit fly), Xenopus (frog), zebrafish, chordates, and invertebrates, in which many genes contributing to pattern formation were identified and, in the best cases, their action was identified in a specific biochemical pathway. In 1995 Christiane Nüsslein-Volhard and Eric Wieschaus were awarded the Nobel Prize in Physiology or Medicine for explaining how the products of the maternal genes in the oocyte of the fruit fly Drosophila direct normal development of the embryo and why certain mutated maternal genes cause congenital abnormalities.

Briggs’s Legacy. Although all his research was of pioneering quality, no doubt those outside his field will remember Briggs for his cloning studies, first performed more than fifty years ago with Thomas J. King. Much progress has been made with cloning based on their initial work on nuclear transplantation. For example, the U.S. Food and Drug Administration will soon release (as of 2007) a Draft Assessment on Animal Cloning reporting that meat and milk from cattle, swine, and goat clones and their progeny do not pose food safety risks for human consumption. Also, in the future, the production of human embryonic stem cells for the treatment of human diseases is envisioned, and one approach would be to use embryos cloned through nuclear transfer from the patient’s own cells. This application is controversial because the technology currently involves the production of human embryos that have to be destroyed to produce embryonic stem cells. Although this has not yet been accomplished, some theorize that chemicals can be added to the culture medium to stimulate stem cells to differentiate into specialized cells that could be used to cure Parkinson’s and heart diseases or alleviate stroke problems and other ailments. As the cells were derived from the same patient, they would not be rejected as foreign. This technology has not been accomplished, and may never be, but the possibility began with the nuclear transfer techniques developed first by Briggs and his collaborator, King, more than half a century ago.

Honors and Awards. Briggs was the recipient of various honors and awards, including election to the American Academy of Arts and Sciences (1960) and the National Academy of Sciences (1962) for his pioneering research on amphibian cloning. He was named research professor of zoology (1963) at Indiana University in Bloomington and Fellow of the International Institute of Embryology. Briggs also received honorary degrees from the Medical College of Pennsylvania (1971; now the Drexel University College of Medicine) and Indiana University (1983). For pathbreaking studies in amphibian nuclear transplantation, the French Académie des Sciences awarded him and his collaborator, Thomas J. King, the Charles-Leopold Mayer Prize (1973). They were the first Americans to receive this prize, the highest biology award of the French Académie. During his career he participated in many major symposia, served on editorial boards of leading journals, and provided intellectual leadership as chair of the Zoology Department (1969–1972) at Indiana University, Bloomington.

Personal Life. Briggs was not only an outstanding scientist and mentor of students, but also a generous and cordial person, one who laid the foundation for numerous research problems for others to pursue. In his personal life Briggs enjoyed numerous interests, including golfing, bowling, and listening to classical music and performing it with the piano and recorder. He owned an Austin-Healy beginning in the 1950s, later a Corvette, and then a BMW motorcycle and delighted in his motor excursions. In 1983, following more than four decades as a leading international scientist, Briggs succumbed to kidney cancer in the Krannert Pavilion of the Indiana University School of Medicine in Indianapolis. He was survived by his second wife, Francoise Briggs, his children, and Janet Bloch Briggs, the mother of his children.

BIBLIOGRAPHY

The complete peer-reviewed bibliography of Briggs is published in the National Academy of Sciences Bibliographical Memoirs, vol. 76, 1998: “Robert W. Briggs: December 10, 1911–March 4, 1983,” by Marie A. Di Berardino. It is available from http://books.nap.edu/readingroom/books/biomems/rbriggs.html.

WORKS BY BRIGGS

“Tumour Induction in Rana pipiens Tadpoles.” Nature 146 (1940): 29.

“Transplantation of Kidney Carcinoma from Adult Frogs to Tadpoles.” Cancer Research 2 (1942): 309–323.

With R. Grant. “Growth and Regression of Frog Kidney Carcinoma Transplanted into the Tails of Permanent and Normal Tadpoles.” Cancer Research 3 (1943): 613–620.

“The Experimental Production and Development of Triploid Frog Embryos.” Journal of Experimental Zoology 106 (1947): 237–266.

“The Influence of Egg Volume on the Development of Haploid and Diploid Embryos of the Frog, Rana pipiens.”Journal of Experimental Zoology 111 (1949): 255–294.

With Rufus R. Humphrey and G. Fankhauser. “Sex Differentiation in Triploid Rana pipiens Larvae and the Subsequent Reversal of Females to Males.” Journal of Experimental Zoology 115 (1950): 399–428.

With E. U. Green and Thomas J. King. “An Investigation of the Capacity for Cleavage and Differentiation in Rana pipiens Eggs Lacking ‘Functional’ Chromosomes.” Journal of Experimental Zoology 116 (1951): 455–499.

With Thomas J. King. “Transplantation of Living Nuclei from Blastula Cells into Enucleated Frogs’ Eggs.” Proceedings of the National Academy Sciences of the United States of America 38 (1952): 455–463. Reports the first successful cloning in multicellular animals.

With Thomas J. King. “Nuclear Transplantation Studies on the Early Gastrula (Rana Pipiens). I. Nuclei of Presumptive Endoderm.” Developmental Biology 2 (1960): 252–270.

With Gloria Cassens. “Accumulation in the Oocyte Nucleus of a Gene Product Essential for Embryonic Development beyond Gastrulation.” Proceedings of the National Academy of Sciences of the United States of America55 (1966): 1103–1109.

“Developmental Genetics of the Axolotl.” In Genetic Mechanisms of Development, edited by Frank H. Ruddle. New York: Academic Press, 1973. An excellent review of the effects of maternal gene products in the oocyte on embryonic development.

“Genetics of Cell Type Determination.” In Cell Interactions inDifferentiation, edited by Marketta Karkinen-Jaaskelainen, Lauri Saxen, and Leonard Weiss. New York: Academic Press, 1977. A good review of nuclear transplantation studies up to 1977.

OTHER SOURCES

Cibelli, Jose, Robert P. Lanza, Keith H. S. Campbell, et al. Principles of Cloning. Amsterdam and Boston: Academic Press, 2002. An extensive coverage of cloning diverse mammalian species.

Di Berardino, Marie A. Genomic Potential of Differentiated Cells. New York: Columbia University Press, 1997. Covers the origin and development of cloning in unicellular and multicellular animals from the late nineteenth century up to the birth of Dolly.

———. “Animal Cloning—The Route to New Genomics in Agriculture and Medicine.” Differentiation 68 (2001): 67–83. Reviews the various applications of cloning.

Hoechedlinger, Konrad, and Rudolf Jaenisch. “Monoclonal Mice Generatedby Nuclear Transfer from Mature B and T Donor Cells.”Nature 415 (2002): 1035–1038. This is the first report yielding normal clones from documented differentiated donor cell nuclei.

Rudenko, Larisa, John C. Matheson, and Stephen F. Sundlof. “Animal Cloning and the FDA—The Risk Assessment

Paradigm under Public Scrutiny.” Nature Biotechnology 25 (2007): 39–43.

Verma, Paul J., and Alan O. Trounson, eds. Nuclear TransferProtocols, Cell Reprogramming, and Transgenesis. Totowa, NJ: Humana Press, 2006. Consists of recent protocols and reviews on cloning, nuclear reprogramming, transgenesis, embryonic stem cells, the rescue of endangered species by cloning, and other applications of animal cloning.

Wilmut, Ian, Angelika E. Schnieke, Jim McWhir, et al. “Viable Offspring Derived from Fetal and Adult Mammalian Cells.” Nature 385 (1997): 810–813. Reports on Dolly the sheep, the first clone derived from an adult cell, born in 1996.

———. “Cloning for Medicine.” Scientific American 279 (December 1998): 58–63. A good review for the general reader.

Marie A. Di Berardino