Sex-chromosome evolution of Palearctic tree frogs in space and time

Sexual reproduction is nearly universal in eukaryotes and genetic determination of sex prevails among animals. The astonishing diversity of sex-determining systems and sex chromosomes is yet bewildering. Some taxonomic groups possess conserved and dimorphic sex chromosomes, involving a functional copy (e.g. mammals' X, birds' Z) and a degenerated copy (mammals' Y, birds' W), implying that sex- chromosomes are expected to decay. In contrast, others like amphibians, reptiles and fishes yet maintained undifferentiated sex chromosomes. Why such different evolutionary trajectories? In this thesis, we empirically test and characterize the main hypotheses proposed to prevent the genetic decay of sex chromosomes, namely occasional X-Y recombination and frequent sex-chromosome transitions, using the Palearctic radiation of Hyla tree frogs as a model system. We take a phylogeographic and phylogenetic approach to relate sex-chromosome recombination, differentiation, and transitions in a spatial and temporal framework. By reconstructing the recent evolutionary history of the widespread European tree frog H. arborea, we showed that sex chromosomes can recombine in males, preventing their differentiation, a situation that potentially evolves rapidly. At the scale of the entire radiation, X-Y recombination combines with frequent transitions to prevent sex-chromosome degeneration in Hyla: we traced several turnovers of sex-determining system within the last 10My. These rapid changes seem less random than usually assumed: we gathered evidences that one chromosome pair is a sex expert, carrying genes with key role in animal sex determination, and which probably specialized through frequent reuse as a sex chromosome in Hyla and other amphibians. Finally, we took advantage of secondary contact zones between closely-related Hyla lineages to evaluate the consequences of sex chromosome homomorphy on the genetics of speciation. In comparison with other systems, the evolution of sex chromosomes in Hyla emphasized the existence of consistent evolutionary patterns within the chaotic diversity of flexibility of cold-blooded vertebrates' sex-determining systems, and provides insights into the evolution of recombination. Beyond sex-chromosome evolution, this work also significantly contributed to speciation, phylogeography and applied conservation research. -- La reproduction sexuée est quasi-universelle chez les eucaryotes et le sexe est le plus souvent déterminé génétiquement au sein du règne animal. L'incroyable diversité des systèmes de reproduction et des chromosomes sexuels est particulièrement étonnante. Certains groupes taxonomiques possèdent des chromosomes sexuels dimorphiques et très conservés, avec une copie entièrement fonctionnelle (ex : le X des mammifères, le Z des oiseaux) et une copie dégénérée (ex : le Y des mammifères, le W des oiseaux), suggérant que les chromosomes sexuels sont voués à se détériorer. Cependant les chromosomes sexuels d'autres groupes tels que les amphibiens, les reptiles et les poissons sont pour la plupart indifférenciés. Comment expliquer des trajectoires évolutives si différentes? Au cours de cette thèse, nous avons étudié empiriquement les processus évolutifs pouvant maintenir les chromosomes sexuels intacts, à savoir la recombinaison X-Y occasionnel ainsi que les substitutions fréquentes de chromosomes sexuels, en utilisant les rainettes Paléarctiques du genre Hyla comme modèle d'étude. Nous avons adopté une approche phylogéographique et phylogénétique pour appréhender les événements de recombinaison, de différenciation et de transitions de chromosomes sexuels dans un contexte spatio-temporel. En retraçant l'histoire évolutive récente de la rainette verte H. arborea, nous avons mis en évidence que les chromosomes sexuels pouvaient recombiner chez les mâles, empêchant ainsi leur différenciation, et que ce processus avait le potentiel d'évoluer très rapidement. A l'échelle plus globale de la radiation, il apparait que les phénomènes de recombinaison X-Y soient également accompagnés de substitutions de chromosomes sexuels, et participent de concert au maintien de chromosomes sexuels intacts dans les populations: le système de détermination du sexe des rainettes a changé plusieurs fois au cours des 10 derniers millions d'années. Ces transitions fréquentes ne semblent pas aléatoires: nous avons identifié une paire de chromosomes qui présente des caractéristiques présageant d'une spécialisation dans le déterminisme du sexe (notamment car elle possède des gènes importants pour cette fonction), et qui a été réutilisée plusieurs fois comme tel chez les rainettes ainsi que d'autres amphibiens. Enfin, nous avons étudié l'hybridation entre différentes espèces dans leurs zones de contact, afin d'évaluer si l'absence de différenciation entre X et Y jouaient un rôle dans les processus génétiques de spéciation. Outre son intérêt pour la compréhension de l'évolution des chromosomes sexuels, ce travail contribue de manière significative à d'autres domaines de recherche tels que la spéciation, la phylogéographie, ainsi que la biologie de la conservation.

Simultaneous use of alcohol, tobacco and cannabis in relation to severity of substance dependence: a study among young Swiss men

Objective: This study investigated patterns of the simultaneous use of alcohol, tobacco and cannabis among young polydrug users, and whether use of one substance might be a cue for use of another and associations with the severity of substance dependence. Methods: The study focused on 3 subsamples from the ongoing Swiss Cohort Study on Substance Use Risk Factors (C-SURF, N=5,990). It used 12 months of data on alcohol/tobacco co-users, alcohol/cannabis co-users and tobacco/cannabis co-users (N=2,660, 1,755 and 1,460 respectively. Simultaneous use, numbers of symptoms of substance dependence, and hazardous use of alcohol, tobacco and cannabis were assessed. The effect of simultaneous polydrug use (SPU) on the numbers of symptoms of substance dependence was tested using analysis of variance. Results: Polydrug use was most common as SPU, and less common as non/occasional SPU. Moreover, when participants started to use one substance while using another, the severity of substance dependence was more strongly associated with the triggered substance than with cue. Conclusions: This study highlights the necessity to take SPU into account. First, SPU rather than separate drug use was the most common pattern for polydrug users. Second, frequent SPU was associated with increased numbers of symptoms of substance dependence compared to non/occasional SPU. Furthermore, SPU may reveal the severity of substance use dependence, when substance use is triggered by a cue substance. For these reasons, SPU should be a serious cause for concern for prevention and intervention purposes.

Uses of cancer registries for public health and clinical research in Europe : results of the European Network of Cancer Registries survey among 161 population-based cancer registries during 2010-2012

AIM: To provide insight into cancer registration coverage, data access and use in Europe. This contributes to data and infrastructure harmonisation and will foster a more prominent role of cancer registries (CRs) within public health, clinical policy and cancer research, whether within or outside the European Research Area. METHODS: During 2010-12 an extensive survey of cancer registration practices and data use was conducted among 161 population-based CRs across Europe. Responding registries (66%) operated in 33 countries, including 23 with national coverage. RESULTS: Population-based oncological surveillance started during the 1940-50s in the northwest of Europe and from the 1970s to 1990s in other regions. The European Union (EU) protection regulations affected data access, especially in Germany and France, but less in the Netherlands or Belgium. Regular reports were produced by CRs on incidence rates (95%), survival (60%) and stage for selected tumours (80%). Evaluation of cancer control and quality of care remained modest except in a few dedicated CRs. Variables evaluated were support of clinical audits, monitoring adherence to clinical guidelines, improvement of cancer care and evaluation of mass cancer screening. Evaluation of diagnostic imaging tools was only occasional. CONCLUSION: Most population-based CRs are well equipped for strengthening cancer surveillance across Europe. Data quality and intensity of use depend on the role the cancer registry plays in the politico, oncomedical and public health setting within the country. Standard registration methodology could therefore not be translated to equivalent advances in cancer prevention and mass screening, quality of care, translational research of prognosis and survivorship across Europe. Further European collaboration remains essential to ensure access to data and comparability of the results.

Increases in condomless sex in the Swiss HIV Cohort Study.

Condomless sex is a key driver of sexually transmitted diseases. In this study, we assess the long-term changes (2000-2013) of the occurrence of condomless sex among human immunodeficiency virus (HIV)-infected individuals enrolled in the Swiss HIV Cohort study. The frequencies with which HIV-infected individuals reported condomless sex were either stable or only weakly increasing for 2000-2008. For 2008-2013, these rates increased significantly for stable relationships among heterosexuals and men who have sex with men (MSM) and for occasional relationships among MSM. Our results highlight the increasing public health challenge posed by condomless sex and show that condomless sex has been increasing even in the most recent years.

Ultra-high-resolution 3D imaging of atherosclerosis in mice with synchrotron differential phase contrast: a proof of concept study.

The goal of this study was to investigate the performance of 3D synchrotron differential phase contrast (DPC) imaging for the visualization of both macroscopic and microscopic aspects of atherosclerosis in the mouse vasculature ex vivo. The hearts and aortas of 2 atherosclerotic and 2 wild-type control mice were scanned with DPC imaging with an isotropic resolution of 15 μm. The coronary artery vessel walls were segmented in the DPC datasets to assess their thickness, and histological staining was performed at the level of atherosclerotic plaques. The DPC imaging allowed for the visualization of complex structures such as the coronary arteries and their branches, the thin fibrous cap of atherosclerotic plaques as well as the chordae tendineae. The coronary vessel wall thickness ranged from 37.4 ± 5.6 μm in proximal coronary arteries to 13.6 ± 3.3 μm in distal branches. No consistent differences in coronary vessel wall thickness were detected between the wild-type and atherosclerotic hearts in this proof-of-concept study, although the standard deviation in the atherosclerotic mice was higher in most segments, consistent with the observation of occasional focal vessel wall thickening. Overall, DPC imaging of the cardiovascular system of the mice allowed for a simultaneous detailed 3D morphological assessment of both large structures and microscopic details.

Cannabis use and other predictors of the onset of daily cigarette use in young men: what matters most? Results from a longitudinal study.

BACKGROUND: According to the gateway hypothesis, tobacco use is a gateway of cannabis use. However, there is increasing evidence that cannabis use also predicts the progression of tobacco use (reverse gateway hypothesis). Unfortunately, the importance of cannabis use compared to other predictors of tobacco use is less clear. The aim of this study was to examine which variables, in addition to cannabis use, best predict the onset of daily cigarette smoking in young men. METHODS: A total of 5,590 young Swiss men (mean age = 19.4 years, SD = 1.2) provided data on their substance use, socio-demographic background, religion, health, social context, and personality at baseline and after 18 months. We modelled the predictors of progression to daily cigarette smoking using logistic regression analyses (n = 4,230). RESULTS: In the multivariate overall model, use of cannabis remained among the strongest predictors for the onset of daily cigarette use. Daily cigarette use was also predicted by a lifetime use of at least 50 cigarettes, occasional cigarette use, educational level, religious affiliation, parental situation, peers with psychiatric problems, and sociability. CONCLUSIONS: Our results highlight the relevance of cannabis use compared to other potential predictors of the progression of tobacco use and thereby support the reverse gateway hypothesis.

Sex-Chromosome Homomorphy in Palearctic Tree Frogs Results from Both Turnovers and X-Y Recombination.

Contrasting with birds and mammals, poikilothermic vertebrates often have homomorphic sex chromosomes, possibly resulting from high rates of sex-chromosome turnovers and/or occasional X-Y recombination. Strong support for the latter mechanism was provided by four species of European tree frogs, which inherited from a common ancestor (∼5 Ma) the same pair of homomorphic sex chromosomes (linkage group 1, LG1), harboring the candidate sex-determining gene Dmrt1. Here, we test sex linkage of LG1 across six additional species of the Eurasian Hyla radiation with divergence times ranging from 6 to 40 Ma. LG1 turns out to be sex linked in six of nine resolved cases. Mapping the patterns of sex linkage to the Hyla phylogeny reveals several transitions in sex-determination systems within the last 10 My, including one switch in heterogamety. Phylogenetic trees of DNA sequences along LG1 are consistent with occasional X-Y recombination in all species where LG1 is sex linked. These patterns argue against one of the main potential causes for turnovers, namely the accumulation of deleterious mutations on nonrecombining chromosomes. Sibship analyses show that LG1 recombination is strongly reduced in males from most species investigated, including some in which it is autosomal. Intrinsically low male recombination might facilitate the evolution of male heterogamety, and the presence of important genes from the sex-determination cascade might predispose LG1 to become a sex chromosome.

Plasma cell and terminal B-cell differentiation in mantle cell lymphoma mainly occur in the SOX11-negative subtype.

Mantle cell lymphoma is a mature lymphoid neoplasm characterized by the t(11;14)(q13;q32) and cyclin D1 overexpression. SOX11 is a transcription factor commonly overexpressed in these tumors but absent in most other mature B-cell lymphomas whose function is not well understood. Experimental studies have shown that silencing of SOX11 in mantle cell lymphoma cells promotes the shift from a mature B cell into an early plasmacytic differentiation phenotype, suggesting that SOX11 may contribute to tumor development by blocking the B-cell differentiation program. The relationship between SOX11 expression and terminal B-cell differentiation in primary mantle cell lymphoma and its relationship to the plasmacytic differentiation observed in occasional cases is not known. In this study we have investigated the terminal B-cell differentiation phenotype in 60 mantle cell lymphomas, 41 SOX11-positive and 19 SOX11-negative. Monotypic plasma cells and lymphoid cells with plasmacytic differentiation expressing cyclin D1 were observed in 7 (37%) SOX11-negative but in none of 41 SOX11-positive mantle cell lymphomas (P<0.001). Intense cytoplasmic expression of a restricted immunoglobulin light chain was significantly more frequent in SOX11-negative than -positive tumors (58 vs 13%) (P=0.001). Similarly, BLIMP1 and XBP1 expression was also significantly more frequent in SOX11-negative than in -positive cases (83 vs 34% and 75 vs 11%, respectively) (P=0.001). However, no differences in the expression of IRF4/MUM1 were observed among these subtypes of mantle cell lymphoma. In conclusion, these results indicate that SOX11-negative mantle cell lymphoma may be a particular subtype of this tumor characterized by more frequent morphological and immunophenotypic terminal B-cell differentiation features that may be facilitated by the absence of SOX11 transcription factor.

Phenotypic Association Analyses With Copy Number Variation in Recurrent Depressive Disorder.

BACKGROUND: Defining the molecular genomic basis of the likelihood of developing depressive disorder is a considerable challenge. We previously associated rare, exonic deletion copy number variants (CNV) with recurrent depressive disorder (RDD). Sex chromosome abnormalities also have been observed to co-occur with RDD. METHODS: In this reanalysis of our RDD dataset (N = 3106 cases; 459 screened control samples and 2699 population control samples), we further investigated the role of larger CNVs and chromosomal abnormalities in RDD and performed association analyses with clinical data derived from this dataset. RESULTS: We found an enrichment of Turner's syndrome among cases of depression compared with the frequency observed in a large population sample (N = 34,910) of live-born infants collected in Denmark (two-sided p = .023, odds ratio = 7.76 [95% confidence interval = 1.79-33.6]), a case of diploid/triploid mosaicism, and several cases of uniparental isodisomy. In contrast to our previous analysis, large deletion CNVs were no more frequent in cases than control samples, although deletion CNVs in cases contained more genes than control samples (two-sided p = .0002). CONCLUSIONS: After statistical correction for multiple comparisons, our data do not support a substantial role for CNVs in RDD, although (as has been observed in similar samples) occasional cases may harbor large variants with etiological significance. Genetic pleiotropy and sample heterogeneity suggest that very large sample sizes are required to study conclusively the role of genetic variation in mood disorders.

Interdependency management in universities: a case study

There remains uncertainty in scientific discussions regarding the governance of universities in new public management regimes in terms of who actually 'rules' in the university. Apparently, a strengthened management leadership is confronted with continuing elements of academic self-regulation and professional autonomy in knowledge production and diffusion. Organisational and academic rationales coexist in today's management of universities. This article endeavours to clarify some of the ambiguities pertaining to the coexistence of two authorities by demonstrating the working of 'interdependency management' that is taking place within universities. For this purpose, the authors have scrutinised research, teaching and recruitment policies in one Swiss university that is subject to such ambiguities. The study confirms existing research in that a command-and-control system is not applied. Policymaking in universities is instead based on a mix of negotiations in faculties that are taking place in the 'shadow of hierarchy', negotiated bargaining between faculties and leaders and occasional unilateral decisions of leaders. This mitigates latent conflicts between management and the academic community: strategic orientations of the university are generally accepted by the academic community while the academic community has influence on policy formulation and maintains defining powers over policy substance.

E-cigarette use in young Swiss men : is vaping an effective way of reducing or quitting smoking ?

QUESTION UNDER STUDY: To test longitudinally differences in conventional cigarette use (cigarettes smoked, cessation, quit attempts) between vapers and nonvapers. METHODS: Fifteen months follow-up of a sample of 5 128 20-year-old Swiss men. The onset of conventional cigarette (CC) use among nonsmokers, and smoking cessation, quit attempts, changes in the number of CCs smoked among smokers at baseline were compared between vapers and nonvapers at follow-up, adjusted for nicotine dependence. RESULTS: Among baseline nonsmokers, vapers were more likely to start smoking at follow-up than nonvapers (odds ratio [OR] 6.02, 95% confidence interval [CI] 2.81, 12.88 for becoming occasional smokers, and OR = 12.69, 95% CI 4.00, 40.28 for becoming daily smokers). Vapers reported lower smoking cessation rates among occasional smokers at baseline (OR = 0.43 (0.19, 0.96); daily smokers: OR = 0.42 [0.15, 1.18]). Vapers compared with nonvapers were heavier CC users (62.53 vs 18.10 cigarettes per week, p <0.001) and had higher nicotine dependence levels (2.16 vs 0.75, p <0.001) at baseline. The number of CCs smoked increased between baseline and follow-up among occasional smokers (b = 6.06, 95% CI 4.44, 7.68) and decreased among daily smokers (b = -5.03, 95% CI -8.69, -1.38), but there were no differential changes between vapers and nonvapers. Vapers showed more quit attempts at follow-up compared with nonvapers for baseline occasional smokers (incidence rate ratio [IRR] 1.81, 95% CI 1.24, 2.64; daily smokers IRR 1.28, 95% CI 0.95, 1.73). CONCLUSIONS: We found no beneficial effects of vaping at follow-up for either smoking cessation or smoking reduction.