Biology subjects

Legros, J.

Publications and source records attributed to Legros, J..

3 recordsLinked to original sources

bioRxiv2025

Geometric morphometric analysis of facial sexual dimorphism in a contemporary sample : An application to sex prediction of ancient human remains

Focusing on craniofacial bones, this study investigates morphological variation related to sexual dimorphism in order to deepen our understanding of human biological diversity and to provide new data from a contemporary reference sample. Accordingly, the research was guided by three objectives (i) identify the facial regions exhibiting the greatest sexual dimorphism using landmark-based geometric morphometric method; (ii) evaluate the reliability of discriminant models based on these dimorphic regions; and (iii) conduct exploratory analyses to assign sex classification probabilities to ancient subjects using the discriminant models derived from a contemporary reference sample. The reference sample comprised 44 skulls from subjects of known sex who died in 2024. The ancient sample included 4 skulls recovered from the Grotte de La Medecine (France), attributed to the chalcolithic period. Fourteen facial landmarks were digitized using 3DSlicer. Generalized Procrustes Analysis was performed to extract shape variables and standardized coordinates for statistical analysis. Thin -Plate Spline transformations quantified and visualized deformation amplitudes between the female and male shapes. Landmarks in the orbital showed the highest deformation amplitudes. Goodall F-test comparing male and female shapes across three facial regions revealed significant sexual dimorphism only in the orbital region and the global facial shape. Discriminant analysis demonstrated that the orbital region provided the highest classification accuracy (88.6%) compared to the global facial region (72.7%). The discriminant models yielded high probabilities of male and female sex classification for the ancient subjects. Using a reproducible method, comparable levels of accuracy to those reported in the scientific literature were achieved despite a relatively modest sample size. These findings further confirm the significant role of the orbital region in human craniofacial sexual dimorphism.

evolutionary biology↗

bioRxiv2024

A type I 3' UTR-derived sRNA is involved in heme metabolism and virulence in Staphylococcus aureus

Staphylococcus aureus is a pathogen responsible for a wide array of superficial to life-threatening infections. To efficiently adapt to environmental cues, a complex regulatory network is needed, involving among others regulatory RNAs (sRNAs). Here, we studied Srn_9342, an sRNA transcribed into two isoforms of different lengths and known to interact with RNAIII, leading to a modulation of {delta}-hemolysin production. We showed that the two isoforms are oppositely expressed in a growth phase-dependent manner. Then, we demonstrated using transcriptional fusions and various chromosomally recombinant strains that Srn_9342 is a type I 3UTR-derived sRNA whose the expression of the long form (Srn_9342L) is SigB-dependent. Using a{Delta} srn_9342 mutant, we monitored the transcript level of various RNA partners previously identified by MAPS and showed that the hemQ mRNA level, encoding a protein involved in heme biosynthesis and reported to participate in small colony variant (SCV) phenotype, increased in the mutant. In silico and in vitro biochemical investigations showed that a 5 region of Srn_9342 binds hemQ leading to a repression of the HemQ protein level whereas the overexpression of Srn_9342 induced an SCV phenotype which was partially relieved by the addition of hemin. Finally, we report that the deletion of srn_9342 significantly increased the virulence of the pathogen in a Galleria mellonella model. Taking together, these data uncovered a novel type I 3 UTR-derived sRNA regulating the heme biosynthesis pathway and implicated in virulence and SCV formation in S. aureus.

molecular biology↗

bioRxiv2024

Guided by touch: Tactile Cues in Hand Movement Control

Traditionally, touch is associated with exteroception and is rarely considered a relevant sensory cue for controlling movements in space, unlike vision. We developed a technique to isolate and evaluate tactile involvement in controlling sliding finger movements over a surface. Young adults traced a 2D shape with their index finger under direct or mirror-reversed visual feedback to create a conflict between visual and somatosensory inputs. In this context, increased reliance on somatosensory input compromises movement accuracy. Based on the hypothesis that tactile cues contribute to guiding hand movements, we predicted poorer performance when the participants traced with their bare finger compared to when their tactile sensation was dampened using a smooth finger splint. The results supported this prediction. EEG source analyses revealed smaller current in the presumed somatosensory cortex during sensory conflict, but only when the finger directly touched the surface. This finding suggests the gating of task-irrelevant somatosensory inputs. Together, our results emphasize touchs involvement in movement control, challenging the notion that vision predominantly governs goal-directed hand or finger movements.

neuroscience↗