Seymour S. Kety MD: the man and his accomplishments. Summary of a symposium in his honor at the VIIIth World Congress of Psychiatric Genetics, Versailles, France, 30 August 2000

Seymour S. Kety was a physician and neuroscientist of great distinction. His impact on both the dynamics and imaging of cerebral blood flow and metabolism, as well as the nature-nurture controversy about the etiology of schizophrenia, led to his receiving the Lasker Award in 1999. He died at the age of 84 in the year 2000, leaving medical research, and psychiatric genetics in particular, a bountiful legacy of rich science, thoughtful critiques and prophesies about hypotheses from the past and well into the future. Reviewed in this paper is a tribute to his work as presented during the VIIIth World Congress of Psychiatric Genetics in Versailles, France, August 2000.

Essence and origin of Mendel's discovery

In early 19th-century Moravia, breeders of animals and plants joined with other interested citizens in the Moravian and Silesian Agricultural Society to debate economic priorities. Several of the senior members had a profound influence upon breeding theory: J.K. Nestler, Professor of Natural History and Agriculture at the University of Olomouc, left a collection of influential writings. In the context of sheep breeding he defined 'inheritance capacity' (Vererbungsfähigkeit), 'hereditary history' (Vererbungsgeschichte) and 'developmental history' (Entwicklungsgeschichte). His linking of the last two terms, as two sides of the same coin, puts Mendel's use of the second one in context. Professor F. Diebl taught the same topics as Nestler at the Philosophical Institute in Brno, with a bias towards plants. Diebl's lectures were attended by Mendel who gained top marks in three examinations. Diebl stressed the importance of artificial pollination to produce new varieties and recognised peas and beans as suitable subjects for the procedure. Prelate Cyrill Napp, abbot before Mendel, had a deep interest in heredity and how it was transmitted through both sexes. He generously supported Mendel's research. A happy blend of economic and academic influences, together with original talent and inner drive, led to Mendel's great discovery.

Hugo De Vries: from the theory of intracellular pangenesis to the rediscovery of Mendel

On the basis of the article by the Dutch botanist Hugo De Vries 'On the law of separation of hybrids' published in the Reports of the Académie des Sciences in 1900, and the beginning of the controversy about priority with Carl Correns and Erich von Tschermak, I consider the question of the posthumous influence of the Mendel paper. I examine the construction of the new theoretical framework which enabled its reading in 1900 as a clear and acceptable presentation of the rules of the transmission of hereditary characters. In particular, I analyse the introduction of the idea of determinants of organic characters, understood as separable material elements which can be distributed randomly in descendants. Starting from the question of heredity, such as it was defined by Darwin in 1868, and after its critical developments by August Weismann, Hugo De Vries was able to suggest such an idea in his Intracellular Pangenesis. He then laid out a programme of research which helps us to understand the 'rediscovery' published in 1900.

France in the era of Mendelism (1900-1930)

This paper describes and explains the reception of Mendelism among French biologists at the beginning of the 20th Century. Three dimensions of description must be taken into account: scholarly diffusion; transmission of the new science through teaching and textbooks; and effective research. These three axes of description do not provide the same picture: Mendelian research was widely reported among specialists; no significant teaching of Mendelism took place in the years 1900-1930; by 1930 only one biologist, Lucien Cuénot, had carried out significant genetic research, but he abandoned his Mendelian research in 1914. The resistance to Mendelism can be attributed to four categories of factors, none of which is sufficient. The first category includes a series of intellectual factors: a massively positivist conception of science, an approach to heredity that privileged a 'physiological' theory, and a poor development of cytology. The second set of factors stems from the failure of French academic biologists to establish a strong interaction with plant and animal breeding. The third factor is the relatively weak influence of the eugenic ideology in France. Finally, the particular organization of French universities, together with the deaths of numerous young scientists during World War I, amplified the effects of the previous factors.

The reception of Mendelism in the United States, 1900-1930

Scholars have differed on the question of why Mendel's work was neglected between 1865 and 1900, and the (by contrast) relatively rapid acceptance of Mendelism in many countries after 1900. This paper focuses on two factors that have not been well explored in the debate. The first is that Mendelism fit perfectly into the atomistic philosophy associated with mechanistic materialism in western science, and thus was strongly promoted by a younger group of biologists around 1900 to raise the prestige of biology to the rigorous level of the physical sciences. The second factor was that Mendelian theory, with its experimental and predictive qualities, fit well into the new demands for industrialization of agriculture both to feed a growing urban population and to provide an arena for capital expansion. This paper proposes that the early promotion of Mendelian research, by both private and public funds, owed as much to economic and social as to biological causes.

Genetics and the evolutionary process

Population genetics was put forward as a mathematical theory between 1918 and 1932 and played a leading part in the rediscovery of the concept of natural selection. As an autonomous science developing Mendel's laws at the population scale and a key element of the Darwinian theory of evolution, its dual status led its practioners to initially overlook some consequences of Mendelism not accounted for by the Darwinian theory, including random drift and the cost of selection. The latter were put forward on purely theoretical grounds in the 1950s, but their importance was acknowledged only when empirical data on protein evolution and enzyme polymorphism (since 1965) and on DNA variation (since 1983) were obtained. The neutralist/selectionist debate that ensued involved disagreement over the scientific method as well as over the mechanisms of molecular evolution. Population genetics has long assumed the existence of natural selection a priori. It has since recentred around the null hypothesis that molecular evolution is neutral. This new approach, applied to sequence comparison and to the study of linkage disequilibrium, is logically more justified, yet empirical observations derived from it paradoxically show the overwhelming importance of selective effects within genomes.

Mendelian inheritance in Germany between 1900 and 1910. The case of Carl Correns (1864-1933)

Carl Correns (1864-1933) came to recognize Mendel's rules between 1894 and 1900 while trying to find out the mechanism of xenia, that is, the direct influence of the fertilizing pollen on the mother plant in maize and peas among other species. In this paper, I am concerned with the ten years of Correns' work after the annus mirabilis of 1900 until 1910, when the main outlines of the new science of genetics had been established. It is generally assumed that after 1900 Correns quickly began probing the limits of Mendelian inheritance, both as far as the explanatory force of formal transmission genetics and the generality of Mendel's laws are concerned. A careful examination of his papers however shows that he was much more interested in the scope of Mendelian inheritance than in its limits. Even his work with variegated Mirabilis plants, which historiographical folklore still presents as a result of Correns' growing interest in cytoplasmic inheritance, can be shown to have been conducted to corroborate just the opposite, namely, the validity of the nuclear paradigm. The paper will show that Correns' research results in those years (among them the Mendelian inheritance of sex in higher plants) were the outcome of a complex experimental program which involved breeding experiments with dozens of different species.

The rediscovery of Mendelism in agricultural context: Erich von Tschermak as plant-breeder

Why was Mendelism rediscovered? One way in which historians have addressed this issue is to look at wider trends in research during the 1890s of which the rediscoverers were part. Quite a lot is known about one such research tradition, namely the attempts to resolve the question of evolutionary mechanism through the use of varietal crosses. But another relevant research tradition is still largely unknown: the work of commercial breeders, several of whom were using hybridisation by the 1890s. In this paper I begin by looking at Tschermak's initial career, the sequence of events by which he came upon Mendel's work, and why he was excited by what he read. Then I place Tschermak's early work in the context of commercial plant-breeding in German-speaking Europe toward the end of the 19th century. Finally I look again at the question of Tschermak's somewhat ambivalent relationship to Mendelism after 1900. I argue that his initial misunderstanding of the concept of segregation was due to the fact that he approached Mendel's work with the perspective of a breeder rather than that of a geneticist.

Coming of age: 'dysgenetics'--a theory connecting induction of persistent delayed genomic instability with disturbed cellular ageing

INTRODUCTION

In recent years a new phenomenon has manifested itself: delayed, persistent genomic instability. When cells are treated with carcinogens not only direct induction of chromosome aberrations and mutations takes place, but there is also an indirect induction: in the distant progeny of treated cells persistently enhanced levels of new chromosome aberrations and enhanced mutation rates are found. This persistent enhanced genomic instability is not due to the presence of lesions in the DNA induced by the treatment because the response can be transmitted to untreated cells. Apparently it is caused by a persistent dysfunctioning of the cell as a whole. Due to these findings a new model for multistep carcinogenesis emerges. According to this model the initiation of carcinogenesis is the induction of a state of persistent genomic instability that not only is responsible for enhanced mutation rates of oncogenes and tumor suppressor genes, but also predisposes to immortalization. This view could lead to a radical change in our views on carcinogenesis. Therefore understanding the mechanism is of utmost importance.

PURPOSE

Up to now, the mechanism responsible for this persistent delayed genomic instability remains completely elusive and has only been described as 'unknown'. In this review the phenomenon is connected with a recent theory on cellular ageing and immortalization.

CONCLUSION

Although highly speculative this review provides a framework for further experimental approaches that will contribute to our understanding of delayed genomic instability and possibly even to a better understanding of cellular ageing also.

Horticulture: the font for the baptism of genetics

This year marks the centenary of the rediscovery of the laws of heredity, and their introduction to the English-speaking world. Here I introduce the main events and the characters who figure in this story before turning to the task of this essay--to ask why it was that support in England for the emerging science of genetics, or Mendelism as it was then called, came chiefly from horticulture, and was only belatedly accepted into the mainstream of British academic biology.

Fission yeast on the brink of meiosis

The fission yeast Schizosaccharomyces pombe (S. pombe) is now well established as a versatile genetic model organism. It is widely used to analyse the basic eukaryotic cell cycle during vegetative growth and it is also well suited to studies on the elementary processes of sexual reproduction, including intercellular communication and signal transduction in zygote formation, as well as meiosis before sporulation. Systematic mutant screening has contributed much to our current understanding of unicellular differentiation in S. pombe, and structural analysis has revealed a simplified meiotic prophase with abundant crossing-over but no homologue synapsis. This article is a personal account of how this branch of fission yeast genetics has developed.