Biology subjects

Molinier, C.

Publications and source records attributed to Molinier, C..

6 recordsLinked to original sources

bioRxiv2026

Haplotype tagging sheds light on speciation between two divergent cryptic species of the brown algae Ectocarpus

Understanding how genome-wide divergence translates to barriers to gene flow is a central question in speciation research, particularly in marine environments where interconnected habitats frequently accommodate cryptic diversity. Using linked-read whole-genome data from the brown alga Ectocarpus, we investigated genome-wide reproductive isolation between two cryptic brown algal species E. siliculosus and E. crouaniorum across replicated hybrid zones in Europe and Chile. We first uncover deep genetic structure within E. crouaniorum, revealing a more intricate species complex than previously recognized. Despite this complexity, we found parallel patterns of asymmetric introgression that emerged independently in Europe and Chile, where we detected both, F1 and low-level introgressed individuals. However, the specific lineage pairs involved in hybridization depended on local demographic history. Demographic modeling further indicated that reproductive isolation strengthens gradually with divergence time and differs markedly between geographic regions, with ongoing asymmetric gene flow even between lineage pairs where hybrids were not detected in the field. In all cases, the genomic landscape of hybridization is consistent with a polygenic, genome-wide barrier to gene flow rather than a few large-effect regions. Our results show that cryptic speciation in brown algae is driven by repeatable, regionally parallel architectures of genome-wide reproductive isolation which is shaped by ecological and demographic context.

evolutionary biology↗

bioRxiv2021

No support for a meiosis suppressor in Daphnia pulex: Comparison of linkage maps reveals normal recombination in males of obligate parthenogenetic lineages.

It is often assumed that obligate parthenogenesis (OP) evolves by a disruption of meiosis and recombination. One emblematic example that appears to support this view is the crustacean Daphnia pulex. Here, by constructing high-density linkage maps, we estimate genome-wide recombination rates in males that are occasionally produced by OP lineages, as well as in males and females of cyclical parthenogenetic (CP) lineages. The results show no significant differences in recombination rates and patterns between CP and OP males nor between CP male and CP females. The observation that recombination is not suppressed in OP males invalidates the hypothesis of a general meiosis suppressor responsible for OP. Rather, our findings suggest that in D. pulex, as in other species where OP evolves from CP ancestors, the CP to OP transition evolves through a re-use of the parthenogenesis pathways already present in CP and through their extension to the entire life cycle, at least in females. In addition to the implications for the evolution of OP, the genetic maps produced by this study constitute an important genomic resource for the model species Daphnia.

evolutionary biology↗

bioRxiv2021

Ultrafast Light Targeting for High-Throughput Precise Control of Neuronal Networks

Understanding how specific sets of neurons fire and wire together during cognitive-relevant activity is one of the most pressing questions in neuroscience. Two-photon, single-cell resolution optogenetics based on holographic light-targeting approaches enables accurate spatio-temporal control of individual or multiple neurons. Yet, currently, the ability to drive asynchronous activity in distinct cells is critically limited to a few milliseconds and the achievable number of targets to several dozens. In order to expand the capability of single-cell optogenetics, we introduce an approach capable of ultra-fast sequential light targeting (FLiT), based on switching temporally focused beams between holograms at kHz rates. We demonstrate serial-parallel photostimulation strategies capable of multi-cell sub-millisecond temporal control and many-fold expansion of the number of activated cells. This approach will be important for experiments that require rapid and precise cell stimulation with defined spatio-temporal activity patterns and optical control of large neuronal ensembles.

neuroscience↗

bioRxiv2019

Multiplexed temporally focused light shaping through a GRIN lens for precise in-depth optogenetic photostimulation

In the past 10 years, the use of light has become irreplaceable for the optogenetic study and control of neurons and neural circuits. Optical techniques are however limited by scattering and can only see through a depth of few hundreds {micro}m in living tissues. GRIN lens based micro-endoscopes represent a powerful solution to reach deeper regions. In this work we demonstrate that cutting edge optical methods for the precise photostimulation of multiple neurons in three dimensions can be performed through a GRIN lens. By spatio-temporally shaping a laser beam in the two-photon regime we project several tens of targets, spatially confined to the size of a single cell, in a volume of 150x150x400 m3. We then apply such concept to the optogenetic stimulation of multiple neurons simultaneously in vivo in mice. Our work paves the way for an all-optical investigation of neural circuits at previously unattainable depths.

neuroscience↗

bioRxiv2018

Identification of general patterns of sex-biased expression in Daphnia, a genus with environmental sex determination

Daphnia reproduce by cyclic-parthenogenesis, where phases of asexual reproduction are intermitted by sexual production of diapause stages. This life cycle, together with environmental sex determination, allow the comparison of gene expression between genetically identical males and females. We investigated gene expression differences between males and females in four genotypes of Daphnia magna and compared the results with published data on sex-biased gene expression in two other Daphnia species, each representing one of the major phylogenetic clades within the genus. We found that 42% of all annotated genes showed sex-biased expression in D. magna. This proportion is similar both to estimates from other Daphnia species as well as from species with genetic sex determination, suggesting that sex-biased expression is not reduced under environmental sex determination. Among 7453 single copy, one-to-one orthologs in the three Daphnia species, 707 consistently showed sex-biased expression and 675 were biased in the same direction in all three species. Hence these genes represent a core-set of genes with consistent sex-differential expression in the genus. A functional analysis identified that several of them are involved in known sex determination pathways. Moreover, 75% were overexpressed in females rather than males, a pattern that appears to be a general feature of sex-biased gene expression in Daphnia.\n\nShort summaryIn some species with environmental sex determination, gene expression can be compared between genetically identical males and females. Here, we investigated sex-biased expression in one such species, D. magna, and compared it with data from two congeners. We found that all three species have a common set of 675 genes with consistent differential expression and with a strong bias towards overexpression in females rather than males. Moreover, the proportion of sex-biased genes in each of the three Daphnia species was similar to Drosophila species with genetic sex determination, suggesting that sex-biased expression is not necessarily reduced under environmental sex determination.

genomics↗

bioRxiv2017

Multiplexed temporally focused light shaping for high-resolutionmulti-cell targeting

Patterning light at the single-cell level over multiple neurons in the brain is crucial for optogenetic photostimulation that can recapitulate natural activity patterns and, thereby, determine the role of specific components of brain activity in behavior. To this end we have developed a method for projecting three-dimensional, 2-photon excitation patterns that are confined to many individual neurons. The new versatile optical scheme generates multiple extended excitation spots in a large volume with micrometric lateral and axial resolution. Two-dimensional temporally focused shapes are multiplexed several times over selected positions, thanks to the precise spatial phase modulation of the pulsed beam. This permits, under multiple configurations, the generation of tens of axially confined spots in an extended volume, spanning a range in depth of up to 500 m. We demonstrate the potential of the approach by performing multi-cell volumetric excitation of photoactivatable GCaMP in the central nervous system of Drosophila larvae, a challenging structure with densely arrayed and small diameter neurons, and by photoconverting the fluorescent protein Kaede in zebrafish larvae. Our technique paves the way for the optogenetic manipulation of a large number of neurons in intact circuits.

neuroscience↗