Evolution: Remodelling Animal Body Plans, Gene by Gene

International audienceChanges in Homeotic (Hox) gene regulation have long been thought to drive the evolution of animal body plans. Direct genetic evidence of their evolutionary role has, however, remained limited. A new study reveals how several mutations distributed across a gene network mask the phenotypic effects of a Hox gene’s evolution

Evolution of multiple additive loci caused divergence between Drosophila yakuba and D. santomea in wing rowing during male courtship

International audienceIn Drosophila, male flies perform innate, stereotyped courtship behavior. This innate behavior evolves rapidly between fly species, and is likely to have contributed to reproductive isolation and species divergence. We currently understand little about the neurobiological and genetic mechanisms that contributed to the evolution of courtship behavior. Here we describe a novel behavioral difference between the two closely related species D. yakuba and D. santomea: the frequency of wing rowing during courtship. During courtship, D. santomea males repeatedly rotate their wing blades to face forward and then back (rowing), while D. yakuba males rarely row their wings. We found little intraspecific variation in the frequency of wing rowing for both species. We exploited multiplexed shotgun genotyping (MSG) to genotype two backcross populations with a single lane of Illumina sequencing. We performed quantitative trait locus (QTL) mapping using the ancestry information estimated by MSG and found that the species difference in wing rowing mapped to four or five genetically separable regions. We found no evidence that these loci display epistasis. The identified loci all act in the same direction and can account for most of the species difference

Evolution: return of the ant supersoldiers.

International audienceAn ancient developmental potential to form 'supersoldiers' facilitates the recurrent evolution of this subcaste in various species of Pheidole ants

Segmentation and Quantitative Analysis of Epithelial Tissues

International audienceEpithelial tissues regulate exchanges with the environment. They are very dynamic and can acquire virtually any shape. At the cellular level, they are composed of cells tightly connected by junctions. Most often epithelia are amenable to live imaging; however the vast number of cells composing an epithelium makes large scale studies tedious. Here we present Tissue Analyzer (TA), an open source tool that can be used to segment epithelia and monitor cell and tissue dynamics

Former l’apprenti juriste à une approche du droit réflexive, critique et sereinement positiviste : l’heureuse expérience d’une revisite du cours « Fondements du droit » à l’Université de Montréal

Au terme d’une série de pérégrinations en terre disciplinaire étrangère, l’auteure principale du présent article, professeure de droit, raconte les expériences et les anecdotes qui l’ont amenée à prendre conscience des irritations et des agacements, voire des guerres fratricides, que provoque, entre universitaires dont l’analyse est insuffisamment réflexive, l’inconscience de la possibilité d’une pluralité d’approches scientifiques différentes mais également dignes sur le plan savant. L’auteure explique ensuite comment ce passé universitaire l’a conduite à revisiter la forme du cours « Fondements du droit », au premier cycle, de façon à initier les apprentis juristes à l’interdisciplinarité et à une réflexivité accrue, source de sérénité nouvelle dans l’étude régulière du droit substantiel. Dans un premier temps, l’article raconte l’impact heuristique, en matière de prises de conscience épistémologiques, du fait d’être juriste en sciences humaines et sociales et, à l’inverse, du fait d’être théoricien interdisciplinaire en faculté de droit. Dans un second temps, l’article expose les principes pédagogiques à la base de cette revisite du cours « Fondements du droit », essentiellement centrée sur l’apprentissage d’une coexistence paisible entre juristes aux méthodes différentes et, par extension, d’une tolérance plus grande à l’égard de la différence. Enfin, l’article décrit les résultats d’une courte étude empirique menée auprès des étudiants quant à la « survie », un an plus tard, des habiletés intellectuelles acquises.Continuously crossing the disciplinary boundaries separating social sciences from law faculties, the principal author, law professor, describes the experiences that made her realize how strong were the difficulties, irritants and even fratricidal wars provoked by the unconsciousness, caused by a lack of reflexivity, of the possibility of having different, but as scientifically valuable, approaches to law. The author then explains how such experiences led her to revisit the course Fondements du droit, given to first degree students, in order to initiate them to interdisciplinary reasoning and to bring them to more reflexivity, therefore leading to a more serene and peaceful environment in which to study law. First, this paper explains the heuristic impact, in terms of epistemological reasoning, of being a jurist in social sciences faculties and, on the opposite, of being a legal and interdisciplinary theorist in law faculties. Second, the article exposes the pedagogical principles that are the foundations of this revisit of the course “Fondements du droit”, such revisit having for goal the peaceful coexistence and the growing tolerance of the different methods and approaches to law. Finally, the authors present the results of an empirical research measuring the survival, a year later, of the subjects taught during said course

EPySeg: a coding-free solution for automated segmentation of epithelia using deep learning

Epithelia are dynamic tissues that self-remodel during their development. At morphogenesis, the tissue-scale organization of epithelia is obtained through a sum of individual contributions of the cells constituting the tissue. Therefore, understanding any morphogenetic event first requires a thorough segmentation of its constituent cells. This task, however, usually implies extensive manual correction, even with semi-automated tools. Here we present EPySeg, an open source, coding-free software that uses deep learning to segment epithelial tissues automatically and very efficiently. EPySeg, which comes with a straightforward graphical user interface, can be used as a python package on a local computer, or on the cloud via Google Colab for users not equipped with deep-learning compatible hardware. By alleviating human input in image segmentation, EPySeg accelerates and improves the characterization of epithelial tissues for all developmental biologists

Transvection regulates the sex-biased expression of a fly X-linked gene

International audienceSexual dimorphism in animals results from sex-biased gene expression patterns. These patterns are controlled by genetic sex determination hierarchies that establish the sex of an individual. Here we show that the male-biased wing expression pattern of the Drosophila biarmipes gene yellow, located on the X chromosome, is independent of the fly sex determination hierarchy. Instead, we find that a regulatory interaction between yellow alleles on homologous chromosomes (or transvection), silences the activity of a yellow enhancer functioning in the wing. This enhancer can be, therefore, active in males (XY) but not in females (XX). This transvection-dependent enhancer silencing requires the yellow intron and th

The causes of repeated genetic evolution

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Relevance and mechanisms of transvection

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