Comptes Rendus Biologies最新文献

Organoids and embryoids are self-organizing 3D cellular models derived from human pluripotent stem cells or dissociated stem cells from primary tissue, able of partially mimicking the development and function of tissues, organs, or embryos in vitro. Research using these models is advancing rapidly, starting to overcome challenges in studying human development, evolution, and disease. The conference from the French Académie des Sciences "Mini-organs and early embryos in vitro: what is at stake?" illustrated the promise of organoids and embryoids in basic and translational research. The lectures emphasized recent biomedical applications, particularly in disease modeling, drug discovery, and regenerative medicine. Current challenges and future directions have also been discussed alongside with the ethical implications of generating functional structures from human cells in vitro.

Protein synthesis involves a critical step where messenger RNA (mRNA) and transfer RNAs (tRNAs) must move in tandem to advance the mRNA reading frame by one codon. This process, known as translocation, is catalyzed by elongation factor G (EF-G) in prokaryotes and elongation factor 2 (eEF2) in archaea and eukaryotes. While eEF2 not only accelerates translocation but also maintains reading frame fidelity, high-resolution structural insights into eukaryotic translocation have remained limited compared to the extensively studied prokaryotic system. In our recently published study, we employed cryogenic-electron microscopy (cryo-EM) to determine ten high-resolution reconstructions of the elongating eukaryotic ribosome in complex with the full translocation module, including mRNA, peptidyl-tRNA, and deacylated tRNA (Milicevic et al.,2024). Seven of these structures included ribosome-bound, naturally modified eEF2. These snapshots captured the stepwise progression of the mRNA-tRNA2-peptide module through the eukaryotic 80S ribosome, from the initial accommodation of eEF2 until the final stages of translocation (Milicevic et al.,2024). We further showed a complex network of interactions that safeguards against reading frame slippage during translation. Additionally, we illustrated how the accuracy of translocation in eukaryotes is reinforced by specific features of the 80S ribosome and eEF2. Finally, we suggested that diphthamide, a conserved post-translational modification in eEF2, not only stabilizes correct Watson-Crick codon-anticodon pairing, but also restricts Wobble geometry of the second base pair.

How do closely related species interact in sympatry? And how do these interactions influence the evolution of their traits and the dynamics of species diversification? In this review, we show how recent research on the evolution of Morpho butterflies contributes to address these questions. We first show how sympatric species have colonized different vertical strata in the neotropical forest and how this divergence has produced cascading adaptive effects on behavioural (flight) but also morphological traits, including wing size, shape and coloration. We then focus on the evolution of peculiar dorsal blue coloration within the genus Morpho. During flight, the blue iridescence produces bright flashes that confuse predators and likely enhance the escape abilities of these butterflies. In turn, predators learn the association between such conspicuous coloration and escaping capacities. Such learning favours the locally abundant colour pattern and promotes the local convergence in sympatric species. However, this tight resemblance also induces sexual interference between mimetic species. Capture-Mark-Recapture data uncovered that mimetic species do not fly at the same hours: competition seems to have driven the divergence in the timing of flight activity between species. Overall, sympatry therefore promotes the intricated evolution of convergent and divergent traits among tightly related species, that jointly facilitate their coexistence. Whether ecological speciation was involved in this evolution is an intriguing open question. At the genomic level, analyses revealed a faster evolution of the sexual chromosome Z as compared to the autosomes, with extensive rearrangements and molecular signals of positive selection: these data thus suggest an important role for the Z chromosome in adaptive evolution in Morpho and possibly in speciation. Paving the way for future research, these various, multilevel studies show that Morpho are not just those showy butterflies in the box: they can also teach us much about evolutionary processes.

How do closely related species interact in sympatry? And how do these interactions influence the evolution of their traits and the dynamics of species diversification? In this review, we show how recent research on the evolution of Morpho butterflies contributes to address these questions. We first show how sympatric species have colonized different vertical strata in the neotropical forest and how this divergence has produced cascading adaptive effects on behavioural (flight) but also morphological traits, including wing size, shape and coloration. We then focus on the evolution of peculiar dorsal blue coloration within the genus Morpho. During flight, the blue iridescence produces bright flashes that confuse predators and likely enhance the escape abilities of these butterflies. In turn, predators learn the association between such conspicuous coloration and escaping capacities. Such learning favours the locally abundant colour pattern and promotes the local convergence in sympatric species. However, this tight resemblance also induces sexual interference between mimetic species. Capture-Mark-Recapture data uncovered that mimetic species do not fly at the same hours: competition seems to have driven the divergence in the timing of flight activity between species. Overall, sympatry therefore promotes the intricated evolution of convergent and divergent traits among tightly related species, that jointly facilitate their coexistence. Whether ecological speciation was involved in this evolution is an intriguing open question. At the genomic level, analyses revealed a faster evolution of the sexual chromosome Z as compared to the autosomes, with extensive rearrangements and molecular signals of positive selection: these data thus suggest an important role for the Z chromosome in adaptive evolution in Morpho and possibly in speciation. Paving the way for future research, these various, multilevel studies show that Morpho are not just those showy butterflies in the box: they can also teach us much about evolutionary processes.

Endosymbionts are very common in nature, offering multiple occasions to recapitulate events that have led to the generation of mitochondria and plastids. However, both these organelles are unique because they are thought to derive from two individual events that gave rise to all eukaryotes and the plastids in algae and plants (excluding Paulinella chromatophora), respectively. This review focuses on the differences and similarities existing between extant endosymbionts and the two major endosymbiont derived organelles: the mitochondria and plastids. Emphasis is put on recent developments that point to the major role of intracellular pathogens in the establishment of these organelles. We argue that metabolic integration of bacterial endosymbionts into mitochondria and plastids required an unusually high degree of preadaptation not shared by most extant endosymbionts. We propose that this was achieved by either recruiting intracellular bacterial pathogens as "helper genomes" providing needed gene products, or by selecting endosymbionts destined to become organelles directly from such obligate intracellular bacteria.

The differences between males and females represent the largest phenotypic dimorphism observed in most species. In humans, this variation contributes to disparities in the risk, incidence, and treatment responses for numerous diseases, with many of these significant differences remaining unexplained. While hormones derived from sex organs play critical roles in shaping and maintaining certain sex differences, recent research using the Drosophila model underscores the significance of cell-intrinsic mechanisms linked to the sex chromosomes.

A brief history of the field shows that the impression of novelty we have today when we talk about synthetic biology is merely the sign of a rapid loss of memory of the events surrounding its creation. The dangers of misuse were identified even before the first experiments, but this has not led to a shared awareness. Building a cell ab initio involves combining a machine (called a chassis by specialists in the field) and a program in the form of synthetic DNA. Only the latter—the program—is the subject of the vast majority of work in the field, and it is there that the risks of misuse appear. Combined with knowledge of the genomic sequence of pathogens, DNA synthesis makes it possible to reconstitute dangerous organisms or even to develop new ways of propagating malicious software. Finally, the lack of thought given to the risk of accidents when laboratories develop gain-of-function experiments that increase the virulence of a pathogen makes a world where this type of experiments is developed particularly dangerous.

“Nature-based solutions” (NBS) are now widely referred to as a way of making anthropized ecosystems more sustainable. NBS stems from the principles of ecological engineering as conceptualized by H. T. Odum. Odum (1962), based on an approach centered on energy flows and ecosystem self-regulation. Despite their growing popularity, the implementation of these NBS remains complex and often focused solely on societal benefits, with little benefit to biodiversity.The current climate and ecological crisis calls for a reconsideration of our relationship with nature, integrating both social and ecological objectives in a new mobilization of societies and ecosystems in crisis. This is what is advocated by socio-ecological restoration, a recent concept developed during the reconstruction of coastal cities after the 2011 tsunami in Japan. This concept proposes the joint repair of ecosystems and human social cohesion, using elements of the ecosystem taken as historical landmarks before disturbance, enabling a local anchoring to regain a viable social and ecological trajectory. Socio-ecological restoration is not a classic program activity, but a social process in which several actors get involved by relying on each other, without using the expression itself.We propose to generalize this socio-ecological restoration, beyond post-disaster or post-conflict situations, to modify development practices and create real synergies between living humans and non-humans. In this respect, we use the reopening of the Bièvre River in the Paris region as an example of relevant socio-ecological restoration, because it involves the local community and responds to ecological issues. In conclusion, we make five recommendations for adapting the principles of socio-ecological restoration to the implementation of NBS, with a view to making not only our environments more resilient in the face of global change, but also those environments that concern the entire non-human living world and are often overlooked in field practices. By opting for a more eco-centric approach, NBSs could be in line with the IUCN’s initial definition, ultimately becoming Solutions Based For and By Nature, in line with the challenges of an effective ecological transition in the field.

Cancer is one of the leading causes of mortality worldwide. Known since antiquity, its understanding has evolved over time and has significantly advanced with new technologies over the past four decades. Cancer initiation is currently admitted to be explainable by the somatic mutation theory, which postulates that DNA mutations altering the function of oncogenes and tumor suppressor genes initiate cancer. In addition to these mutations, epigenetic alterations, which heritably change gene expression without altering the DNA sequence, also play a key role. Recent data suggests that epigenetic components regulate all aspects of tumor progression, including cancer initiation. These discoveries prompt a reevaluation of the somatic mutation theory, of cancer prevention and treatment strategies.

Several bat species asymptomatically harbor certain viruses that are highly pathogenic in other mammals. The underlying mechanisms involve an evolutionary balance between tolerance and immune resistance to viral infections. However, how bats innate immunity has evolved in response to viruses remains to be elucidated. Here, we review the evolution of the protein kinase R (PKR) in bats, a major antiviral protein of vertebrate innate antiviral defense. Our recent results indicate that PKR has evolved under selective pressure and has undergone genomic duplications in bats, in contrast to all mammals studied, which possess only a single copy of the gene. The genetic changes in bat PKR are probably partly the result of genetic conflicts with ancient pathogenic poxviruses, shaping a bat-specific host–virus interface. Furthermore, the duplicated PKRs in Myotis species enable them to collectively escape viruses and enhance their viral control. These results suggest that viral adaptations of PKR contribute to the specificity of modern interactions between viruses and bats, and may explain unique antiviral mechanisms in bats.