Scientific research at the Laboratoire Arago (Banyuls, France) in the twentieth Century: Edouard Chatton, the "master", and André Lwoff, the "pupil"

Edouard Chatton (1883–1947) began his scientific career in the Pasteur Institute, where he made several important discoveries regarding pathogenic protists (trypanosomids, Plasmodium, toxoplasms, Leishmania). In 1908 he married a “Banyulencque”, Marie Herre; from 1920, he focused his research on marine protists. He finished his career as Professor at the Sorbonne (Paris) and director of the Laboratoire Arago in Banyuls-sur-mer, where he died in 1947. André Lwoff (1902–1994) lived several scientific lives in addition to his artistic and family life. But it is the study of protists that filled his first life after he encountered the exceptional Master who was Chatton. Lwoff’s father was a psychiatrist and his mother an artist sculptor. He became a Doctor of Medicine in 1927 and then a Doctor of Sciences in 1932, his thesis dealing with biochemical aspects of protozoa nutrition. He met Chatton in 1921 and —until Chatton’s death— their meetings, first in Roscoff and then in Banyuls-sur-mer, were numerous and their collaboration very close. Their monograph on apostome ciliates was one of the peaks of this collaboration. In 1938, Lwoff was made director of the Microbial Physiology Department at the Pasteur Institute in Paris, where he began a new life devoted to bacteria, and then to viruses, before pursuing his career as director of the Cancer Research Institute in Villejuif (France). Lwoff was awarded the Nobel Prize in Physiology or Medicine in 1965. He died in Banyuls in 1994. “Master” and “pupil”had in common perseverance in their scientific work, conception and observation, a critical sense and rigor but also a great artistic sensibility that painting and drawing in the exceptional surroundings of Banyuls-sur-mer had fulfilled

The Arago Laboratory of Banyuls and some of its Academicians

Since its founding in 1881 by Henri de Lacaze-Duthiers (1821–1901), the Arago Laboratory of Banyuls has been one of the three marine stations of the University Pierre and Marie Curie-Paris 6. It is located in Banyuls (Banyuls-sur-Mer) in Northern Catalonia. The center hosts researchers and students from all over the world. Some became famous, including four Nobel Prize winners: André Lwoff (1965), Pierre-Gilles de Gennes (1991), Albert Fert (2007) and Jules Hoffmann (2011). This article focuses on five scientists closely related to the center. The first three are Henri de Lacaze-Duthiers (1821–1901), the founder; Édouard Chatton (1883–1947), eminent director of the center; and André Lwoff (1902–1994), who before being known for his work in bacterial genetics and virology was an outstanding protozoologist under the direction of Chatton. Lynn Margulis (1938–2011), a great friend of the Arago Laboratory and personal friend of the author, is also remembered. Finally, there is a mention of Walter J. Gehring (1939–2014), professor at the University of Basel, Switzerland. [Int Microbiol 19(4): 183-190 (2016)]Keywords: Arago Laboratory of Banyuls · Lacaze-Duthiers, Henri de (1821–1901) · Chatton, Édouard (1883–1947) · Lwoff, André (1902–1994) · Margulis, Lynn (1938–2011) · Gehring, Walter J. (1939–2014

Edouard Chatton (1883–1947) and the dinoflagellate protists: concepts and models

Edouard Chatton contributed to our knowledge of single-celled protoctists, especially ciliates and dinoflagellates, free-living and/or symbiotic, in relation to the marine invertebrate animals in which they reside. More than the description of many new families, genera and species, and of their life cycles, he anticipated several major concepts of cell biology, including the fundamental difference between prokaryote and eukaryote protists, long time before the advent of electron microscopy. These concepts included: the reproductive ability of the kinetosomecentriole system; the homology of the kinetosome with the mitotic centriole of animal cells; and the different kinds of mitotic systems. Chatton trained more than thirty student collaborators, among them André Lwoff, who won the 1965 Nobel Prize in Physiology or Medicine. Later, the great cell biologist Hans Ris and I completed Chatton’s light microscopy descriptions on syndinian mitosis dinoflagellate. We had at our disposal sophisticated electron microscopes as well as biochemical and molecular techniques and thus succeeded in corroborating the correct interpretation by Chatton of chromosome structure and mitotic cytology. [Int Microbiol 2006; 9(2):173-177

Chromosomes of Protists: The crucible of evolution

As early as 1925, the great protozoologist Edouard Chatton classified microorganisms into two categories, the prokaryotic and the eukaryotic microbes, based on light microscopical observation of their nuclear organization. Now, by means of transmission electron microscopy, we know that prokaryotic microbes are characterized by the absence of nuclear envelope surrounding the bacterial chromosome, which is more or less condensed and whose chromatin is deprived of histone proteins but presents specific basic proteins. Eukaryotic microbes, the protists, have nuclei surrounded by a nuclear envelope and have chromosomes more or less condensed, with chromatin-containing histone proteins organized into nucleosomes. The extraordinary diversity of mitotic systems presented by the 36 phyla of protists (according to Margulis et al., Handbook of Protoctista, 1990) is in contrast to the relative homogeneity of their chromosome structure and chromatin components. Dinoflagellates are the exception to this pattern. The phylum is composed of around 2000 species, and characterized by unique features including their nucleus (dinokaryon), dinomitosis, chromosome organization and chromatin composition. Although their DNA synthesis is typically eukaryotic, dinoflagellates are the only eukaryotes in which the chromatin, organized into quasi-permanently condensed chromosomes, is in some species devoid of histones and nucleosomes. In these cases, their chromatin contains specific DNA-binding basic proteins. The permanent compaction of their chromosomes throughout the cell cycle raises the question of the modalities of their division and their transcription. Successful in vitro reconstitution of nucleosomes using dinoflagellate DNA and heterologous corn histones raises questions about dinoflagellate evolution and phylogeny. [Int Microbiol 18(4):209-216 (2015)]Keywords: dinoflagellates · protist chromosomes · dinokaryon · dinomitosis · eukaryotic nucleu

Esterases in marine dinoflagellates and resistance to the organophosphate insecticide parathion

Esterases are involved in the susceptibility or resistance of organisms to organophosphate pesticides. We have examined the action of parathion on the marine dinoflagellates Crypthecodinium cohnii and Prorocentrum micans by looking at their esterases. One-dimensional gel electrophoresis, immunoblotting and cytochemistry plus image analysis were used to characterize the nature and distribution of the enzymes. Esterases were found in both species, but there appeared to be no particular intracellular localization. The esterase activity of the heterotrophic species Crypthecodinium cohnii was 30-fold greater than that of the autotrophic Prorocentrum micans and had an antigenic site in common with mosquito esterase. The resistance of Crypthecodinium cohnii to parathion was specific and reversible. Less parathion entered the parathion-resistant Crypthecodinium cohnii cells than the untreated control cells. Parathion-resistant cell extracts of Crypthecodinium cohnii analyzed after immunoblotting also contained an additional band of esterase activity. These results confirm the importance of esterases in toxicological studies of organophosphate insecticides, especially those of marine dinoflagellates

Evidence for Link Between Mental Disorders and in Utero Exposure to Synthetic Hormones: A Long and Crucial History

Somatic effects of diethylstilbestrol on children exposed in utero have long been recognized. This is not the case for psychiatric disorders, although animal studies provide evidence of somatic and behavioral disorders. Recent studies have reported psychiatric effects of synthetic estrogens on the brain of children exposed in utero as schizophrenia, bipolar disorders, depression, eating disorders, suicides, suicide attempts. Recently, a team of St. Anne’s Hospital, Paris (Prof. Krebs, Dr. Kebir) demonstrated the epigenetic mechanism of DES effect on the brain, a specific methylation of two genes playing important roles in neurodevelopment: the ADAM TS9 (control of the formation of reproductive organs and of the fetus’s CNS) and the ZFP 57 gene suggested to be associated with psychosis. Progestins used in contraception and in hormone replacement therapy are known to affect the adult brain, but no data on children existed before our recent paper on their effects after in utero exposure. Clinical data were collected from 1934 children of the Association of Patients HHORAGES cohort. Our data show the presence of somatic disorders and a drastic increase of psychiatric disorders among children in utero exposed to progestins. These mental disorders are the same as pathologies provoked by exposure to synthetic estrogens

Cloning, characterization and chromosomal localization of a repeated sequence in Crypthecodinium cohnii, a marine dinoflagellate

Genomic DNA of Crypthecodinium cohnii has been extracted in the presence of cetylmethylammonium bromide and hydrolysed by 13 restriction enzymes. No typical ladder-like pattern or isolated band of satellite sequences were found with any of these enzymes. A “mini” genomic DNA library had been made and screened by reverse hybridization to isolate highly repeated sequences. Seven such DNA fragments were sequenced. The copy number of one of them (Cc18), 226 bp long, was estimated at around 25,000, representing 0.06% of the total genome. Cc18 was found to be included in a higher fragment of 3.0 kb by Southern blot analysis after cleavage by PstI. This higher molecular weight fragment could be composed either of tandemly repeated Cc18 sequences, or by only one or a very low copy number of Cc18. In this latter case, these fragments, also repeated 25,000 times would represent 1 to 2% of the total genome. Genomic localization of Cc18 by in situ hybridization on squashed C. cohnii cells showed that it was widely distributed on the different chromosomes. All the chromosomes observed displayed Cc18 labeling, which appeared homogeneously distributed. The ability of Cc18 to be a specific molecular marker to distinguish sibling C. cohnii species is discussed

Dinoflagellate chromosome behaviour during stages of replication

In most dinoflagellate species, chromosomes are characterized by an almost continuous condensation of the nucleofilaments throughout the cell cycle and the absence of longitudinal differentiation as Q, G, or C banding. Their supercoiled architecture is maintained by divalent cations and structural RNAs. Their chromatin is devoid of histones and nucleosomes and their DNA composition is distinctive: in several species, more than 60% of thymines are replaced by a rare base, hydroxymethyluracil. We report here an immunofluorescence (conventional and confocal laser scanning microscopy, CLSM) and immunogold transmission electron microscopy (TEM) analysis of some stages of the early replication process in Prorocentrum micans dinoflagellate cells, after long pulse incorporation (3, 6 or 9 days) with 50 μg/ml bromodeoxyuridine (BrdU) in the presence of 5-fluoro-2´- deoxyuridine (FUdR) and BrdU antibody technique (BAT) detection. The large DNA content (45 pg per nucleus) of P. micans cells is compacted on 100 chromosomes, 10 μm in length. In early S-phase, DNA replication sites are revealed as fluorescent domains organized in clusters, which appear in the periphery of the nucleus unlike other eukaryotes. In late S-phase, the number of labelled clusters increased; helically distributed, they did not appear synchronously in the whole chromosome. Under TEM, spherical domains of equivalent diameter appeared located all along the chromosomes after 6 days BrdU pulse. Replication occurs, but in our experimental conditions, segregation of daughter chromosomes was never observed. The blockade of the cell cycle after BrdU incorporation intervening just before the segregation of daughter chromosomes is discussed

Association between fetal DES-exposure and psychiatric disorders in adolescence/adulthood: evidence from a French cohort of 1002 prenatally exposed children

International audienceIn utero diethylstilbestrol (DES) exposure has been demonstrated to be associated with somatic abnormalities in adult men and women. Conversely, the data are contradictory regarding the association with psychological or psychiatric disorders during adolescence and adulthood. This work was designed to determine whether prenatal exposure to DES affects brain development and whether it is associated with psychiatric disorders in male and female adolescents and young adults. HHORAGES Association, a national patient support group, has assembled a cohort of 1280 women who took DES during pregnancy. We obtained questionnaire responses from 529 families, corresponding to 1182 children divided into three groups: Group 1 (n = 180): firstborn children without DES treatment, Group 2 (n = 740): exposed children, and Group 3 (n = 262): children born after a previous pregnancy treated by DES. No psychiatric disorders were reported in Group 1. In Group 2, the incidence of disorders was drastically elevated (83.8%), and in Group 3, the incidence was still elevated (6.1%) compared with the general population. This work demonstrates that prenatal exposure to DES is associated with a high risk of psychiatric disorders in adolescence and adulthood