In memoriam: Roger Guillemin, neuroendocrinologist, Nobel Prize in physiology or medicine

Abstract

Roger Guillemin was born in Dijon, Burgundy (France) on January 11, 1924. In 1942, he began studying Medicine at the University of Burgundy. After a mandatory break during World War I, he obtained his medical degree from the Faculty of Medicine of Lyon in 1949.

He began to practice as a family doctor, during which he acquired many excellent memories. However, he also quickly realized the limitations of medicine at that time. He recalled that he “could only prescribe three types of medicine, one of which being aspirin.” His scientific curiosity made him read specialized journals, which made him aware of Hans Selye's research in Montreal on the “General Adaptation Syndrome,” now known as the endocrine reaction of the organism to stress. He heard that the Canadian professor was invited to give a series of lectures at the Pitié Hospital and decided to attend his talks. Fortunately, Hans Selye presented his lectures in French, as Roger Guillemin did not speak English at that time. At the end of the third lecture, he introduced himself to Pr. Selye and asked him if he could join his lab for a year to prepare for his medical doctorate. Roger Guillemin left his native Burgundy and flew to Montreal. During his stay in Pr. Selye's laboratory, he first prepared a medical thesis, followed by a PhD in Physiology, specializing in Experimental Endocrinology, which he obtained in 1953.

Pr. Selye was the head of the Institute of Experimental Medicine and Surgery, where he established a series of lectures called “The Claude Bernard Lectures” inviting internationally renowned researchers. This is how Roger Guillemin met Geoffrey Harris, who is nowadays considered the father of Neuroendocrinology. Through various approaches of electrical stimulation, ligation or section of the pituitary stalk, and pituitary transplantation, Pr. Harris demonstrated a key role of the portal system in the relationship between the hypothalamus and the adenohypophysis.¹ Harris's work made it possible to understand how the “first mediators” (according to Selye's terminology), which will later be called “releasing factors,” reached the pituitary cells. The objective of Roger Guillemin was now clear: to chemically identify hypothalamic factors that govern the anterior pituitary's function, starting with the neural mediator suspected by Hans Selye controlling the hypothalamic–pituitary–adrenal axis.

Hans Selye's laboratory did not have the equipment and expertise to identify chemical factors governing the anterior pituitary function. Roger Guillemin decided to move to the Department of Physiology of Baylor College in Houston, Texas, which was headed by Hebbel Hoff. However, Roger Guillemin did not have the expertise to purify the hypothalamic factors he was looking for. Therefore, he teamed up with talented (bio)chemists, including Walter Hearn, with whom he used paper chromatography on a few dozen sheep hypothalami with the hope of isolating the famous “first mediator” of Hans Selye. Unfortunately, this method proved not sensitive enough to detect pituitary hormones. It became evident to Roger Guillemin that he had to collect a much larger quantity of tissue samples with all the organization that goes with it. He also switched to liquid gel chromatography, a more sensitive method that Viktor Mutt used successfully at the Karolinska Institute to purify peptides from the porcine digestive tract.²

Concomitantly, he was offered a position as associate director of the Experimental Endocrinology laboratory directed by Robert Courrier at the Collège de France. He, therefore, moved to Paris with his wife Lucienne Billard, whom he met during his tenure in Hans Selye's lab. However, Hebbel Hoff insisted that Roger kept his laboratory at Baylor active, where he could rely on Andrew Schally to carry out the analytical steps and Harry Lipscomb for the biological tests. At the Collège de France, he teamed up with a Polish chemist, Marian Jutisz, who would later play an important role in the French Society of Neuroendocrinology (SNE), and Edouard Sakiz, the future CEO of the Roussel-Uclaf pharmaceutical company. Roger Guillemin outsourced the collection of several hundred thousands sheep hypothalamic to a private Parisian company. He also decided to stop the search for corticotropin-releasing factor (CRF) temporarily and to focus on thyrotropin-releasing factor (TRF), for which he developed a more straightforward biological test based on the incorporation of radioactive iodine into co-cultures of pituitary and thyroid.

After these 3 years in Paris, Guillemin returned with his family to Houston, TX, carrying the lyophilized extracts of about half a million hypothalami in his luggage. Wylie Vale joined the laboratory with the initial mission to collect thousands of additional hypothalami in the San Antonio slaughterhouses. He then developed a revolutionary method of primary cultures of pituitary cells which was combined with a very sensitive radioimmunoassay developed by Solomon Berson and Rosalyn Yalow. In 1965, Guillemin recruited the chemist Roger Burgus, a student of Walter Hearn, who had expertise with new mass spectrometry techniques. After 14 years of hard work, Guillemin and his team's efforts finally paid off with the purification and elucidation of the sequence of sheep TRF. As a side note, the article reporting this fundamental discovery was first rejected by the journal Science in February 1969, and the results were finally published in the Comptes Rendus de l'Académie des Sciences de Paris on April 21, 1969³ and then in the journal Nature on April 24, 1970.⁴

This discovery had a considerable impact on the academic community, and Guillemin was immediately offered several positions to set up his laboratory on various American campuses. It was ultimately Jonas Salk, a researcher who discovered the first safe and effective vaccine against polio, who convinced Guillemin to leave Houston, TX, and move his lab to La Jolla, CA, in the recently built oceanfront building by the architect Louis Kahn. Guillemin was seduced as much by the elegance of the building as by the announced launch of two new research programs within the Institute, one in Neuroscience and the other in the Biology of birth control. In June 1970, his entire team moved to the Neuroendocrinology laboratory, which was created especially for them at the Salk Institute. Several new collaborators joined them, including Catherine Rivier, who completed her PhD thesis in physiology, her husband Jean Rivier, an expert in high-field NMR, and Nicholas Ling. This newly established team decided to undertake the characterization of the gonadotropin-releasing factor, also known as the LH-releasing factor or LRF. All the tools were available to Guillemin's team, from the pituitary cell cultures to the radioimmunoassay of LH, to screen the fractions saved during the purification of the TRF. In July 1971, the first article was published in Biochemical and Biophysical Research Communications describing the overall amino acid composition of a nonapeptide, in which the tryptophan residue was missing.⁵ In January 1972, the full sequence of ovine LRF was finally reported in Proceedings of the National Academy of Sciences (PNAS),⁶ just a few months after the description of the porcine TRF by Schally's team.⁷ The first neuroanatomical description of peptidergic neurons distribution in the brain was subsequently published in 1973 by Julien Barry in Lille for LRF.⁸

It was known that a lesion of the ventromedial region of the rat hypothalamus caused growth arrest, indicating the existence of a nerve factor stimulating the release of growth hormone. The purification of this new neurohormone from hypothalamic extracts seemed possible based on the well-mastered technique of primary pituitary cell cultures of Wylie Vale, combined with the radioimmunoassay of GH developed by Paul Brazeau. Surprisingly, the obtained active fractions only had inhibitory effects on GH release, leading Guillemin and his team to conclude that the extracts contained an inhibitory factor of GH secretion. Roger Burgus identified the sequence of this inhibitory peptide, and Jean Rivier synthesized it. The primary structure of this cyclic tetradecapeptide, called somatostatin, was published in PNAS in January 1973.⁹ In addition to its inhibitory effect on GH release, it became clear that somatostatin also blocked insulin and glucagon secretion in primates. Roger Guillemin discussed this discovery with one of the best French morphologists of the time, Maurice Dubois, who later demonstrated by immunohistochemistry the presence of somatostatin-immunoreactivity in delta cells of Langerhans islets. This fundamental observation marked the starting point of a very fruitful new field of research on the expression and role of hypothalamic neuropeptides outside the brain.

But Guillemin was still searching for the GH-releasing factor. He knew that the injection of morphine caused an increase in circulating GH in humans and became intrigued with the discovery of John Hughes and Hans Kosterlitz, who identified two pentapeptides with morphine-mimetic activity. Was it possible that these enkephalins would be good candidates? In their 1975 publication in Nature,¹⁰ Hughes and Kosterlitz pointed out that the sequence of Met-enkephalin corresponds to that of the 61–65 region of β-LPH characterized 10 years earlier by Michel Chrétien and Choh Hao Li. Guillemin, therefore, decided to search for peptides with opioid properties in his lyophilized samples and managed to isolate several active fractions that he named α-, β-, and γ-endorphins, all bearing the sequence of Met-enkephalin at the N-terminal position. In September 1976, Ling and Guillemin published in PNAS the sequence of β-endorphin, a 31-amino acid peptide whose morphine-mimetic activity is five times greater than that of Met-enkephalin.¹¹ However, β-endorphin stimulated GH release in vivo but did not affect GH secretion on pituitary cells in culture. The nature of GHRH was, therefore, still enigmatic.

In 1977, Roger Guillemin received the Nobel Prize in Physiology or Medicine, which he shared with Andrew Schally, for “their discoveries concerning the production of peptide hormones by the brain,” and with Rosalyn Yalow for “the development of radioimmunoassays for peptide hormones.” Guillemin recalled: “A month before the official ceremony, I received instructions about the one-hour lecture I would have to present. Then, three weeks later, I was informed that the duration would be reduced to 45 minutes. Finally, the day before the ceremony, while I was already in Stockholm, I was told that since Rosalyn Yalow and Andrew Schally were intervening the same day, my speaking time was now only 30 minutes. It was a unique experience to apprehend the mechanisms of the neuroendocrine response to stress!”

The beloved “first mediator” of Hans Selye, CRF, was finally characterized in 1981 by Roger Guillemin's former student, Wylie Vale.¹² Vale's team then isolated several urocortins, paralogous peptides of CRF, and orthologs of urotensin I extracted by Karl Lederis from the urophysis of teleost fish.¹³

The isolation of GHRH took a very different path from that taken for the other four hypophysiotropic neuropeptides since Geneviève Sassolas carried out its identification from a pancreatic tumor of a patient with acromegaly. The sequences of the different molecular forms of GHRH were published a few days apart, in November 1982, by Guillemin's team in Science and Vale's team in Nature.^{14, 15} The identification of the main hypophysiotropic neurohormones finally ended after nearly 40 years of research!

Guillemin and his team then turned to two other families of polypeptide mediators, fibroblast growth factor (FGF) and inhibin. These new research programs resulted in the concurrent publication of two foundational articles describing the primary structure of basic FGF, a 146-amino acid polypeptide (PNAS, May 1986),¹⁶ and the characterization of inhibin and activin, two heterodimers of the TGF-β family.¹⁷

Roger Guillemin maintained solid ties with the French research community throughout his career. He and his trainees welcomed many talented researchers in their laboratories, such as Bertrand Bloch, David Chatenet, Pierre Mormède, Jean-Louis Nahon, Françoise Presse, Jean Rossier, and Edouard Sakiz, to name a few. He served as President of the French Society of Endocrinology from 1982 to 1983, and awarded the first annual SFE Prize at the Marseille congress. He was elected a foreign member of the French Academy of Sciences in 1984. He was the guest of honor at the International Congress of Neuroendocrinology held in Rouen in July 2010, where he gave the inaugural lecture. He received honorary doctorates from several French universities, including Burgundy and Franche-Comté. In 2015, he was promoted to the rank of Commandeur de la Légion d'Honneur.

Roger Guillemin was not only a visionary, but also a remarkable talent-spotter who surrounded himself with the brightest scientists, many of whom have, in turn, become leaders in Neuroendocrinology. He and his collaborators generously provided reagents such as peptides and antibodies to all researchers who requested them without compensation. Fred Gage, a former Director of the Salk Institute, said: “Roger has been very supportive and generous with his encouragement and advice to me and many scientists he has helped.”

In addition to being a humanist medical doctor, an eminent researcher, and a brilliant speaker, Roger Guillemin was also an enlightened art lover. He was a recognized artist for his flamboyant digital paintings. His wife Lucienne was a talented musician, and five of their children also embraced artistic careers. Throughout his professional life, Roger Guillemin managed to maintain a good balance between his two passions: science and family.

Roger Guillemin will be missed but his name and contribution to Science, Medicine, and Neuroendocrinology will stay forever.

Sebastien G. Bouret: Writing – original draft; writing – review and editing. Hubert Vaudry: Writing – original draft; writing – review and editing. Vincent Prevot: Writing – original draft; writing – review and editing.

The authors declare no conflicts of interest.