Biology subjects

Duchesne, L.

Publications and source records attributed to Duchesne, L..

5 recordsLinked to original sources

bioRxiv2026

An internal scaffold supports microtubule architectural diversity in Xenopus spermatids

During spermiogenesis, early round spermatids differentiate into specialized spermatozoa through an extensive reshaping of the nucleus driven by coordinated cytoskeletal and chromatin-based mechanisms. In mammals, this process critically relies on the transient manchette, a microtubule-based structure that remodels the spermatid nucleus and serves a track to transport material required for flagellum assembly. However, the existence, organization, and molecular composition of such a structure in other vertebrates have remained poorly investigated. Here, we establish that an organized microtubule network is present in Xenopus spermatids and shares key architectural and molecular hallmarks of the mammalian manchette. We further uncover a large structural heterogeneity of spermatid microtubules, with variable protofilament numbers, skew angles, and lattice organizations. We reveal the presence of a Spaca9-Saxo2 internal scaffold in spermatid microtubules suggesting an internal reinforcement mechanism necessary for extensive nuclear reshaping and cytoplasm remodeling.

cell biology↗

bioRxiv2024

Optimized expansion microscopy reveals species-specific spindle microtubule organization in Xenopus egg extracts

The spindle is a key structure in cell division as it orchestrates the accurate segregation of genetic material. While its assembly and function are well-studied, the mechanisms regulating spindle architecture remain elusive. In this study, we investigate the differences in spindle organization between Xenopus laevis and Xenopus tropicalis, leveraging expansion microscopy (ExM) to overcome the limitations of conventional imaging techniques. We optimized an ExM protocol tailored for Xenopus egg extract spindles, improving upon fixation, denaturation and gelation methods to achieve higher resolution imaging of spindles. Our protocol preserves spindle integrity and allows effective pre-expansion immunofluorescence. This method enabled detailed analysis of the differences in microtubule organization between the two species. X. laevis spindles overall exhibited a broader range of bundle sizes, while X. tropicalis spindles contained mostly smaller bundles. Moreover, while both species exhibited larger bundle sizes near and at the spindle center, X. tropicalis spindles otherwise consisted of very small bundles, and X. laevis spindles medium-sized bundles. By enhancing resolution and minimizing distortions and fixation artifacts, our optimized ExM approach offers new insights into spindle morphology and provides a robust tool for studying the structural intricacies of these large cellular assemblies. This work advances our understanding of spindle architecture and opens up new avenues for exploring underlying mechanisms. SIGNIFICANCE STATEMENTO_LICorrect spindle morphology is key to its function; however, traditional microscopy methods limit our view of spindle architecture. This study addresses the gap in resolving detailed spindle microtubule organization by using advanced imaging. C_LIO_LIThe research utilizes Expansion Microscopy (ExM) to reveal previously unobservable details of spindle morphology in egg extracts of two Xenopus species (X. laevis and X. tropicalis). This approach provides unprecedented clarity on microtubule arrangement and variations in spindle architecture. C_LIO_LIThis work establishes a new protocol for high-resolution imaging of spindle structures, offering insights into how spindle architecture is adapted in differently-sized spindles to ensure proper function. C_LI

cell biology↗

bioRxiv2021

Interactions between xylem traits linked to hydraulics during xylem development optimize growth performance in conifer seedlings

O_LIClimate change has threatened forests globally, challenging tree species ability to track the rapidly changing environment (e.g., drought and temperature rise). Conifer species face strong environmental filters due to climatic seasonality. Investigating how conifers change their hydraulic architecture during xylem development across the growing season may shed light on possible mechanisms underlying hydraulic adaptation in conifers. C_LIO_LILaser microscopy was used to assess the three-dimensional hydraulic architecture of balsam fir (Abies balsamea (Linnaeus) Miller), jack pine (Pinus banksiana Lambert), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Miller) Britton, Sterns & Poggenburgh) seedlings. We measured hydraulic-related xylem traits in different regions (from early to latewood), during four years of plant growth. C_LIO_LIThe xylem development of jack pine seedlings contrasts with the other species by maintaining torus overlap (a hydraulic safety-associated xylem trait), relatively constant across the season (from early to latewood), and over the years studied. The expansion of tracheids and torus was positively associated with plant growth. C_LIO_LIPit aperture-torus covariance is central to the seasonal dynamics of jack pine xylem development, which jointly with a rapid tracheid and pit expansion is consistent with strong growth performance. Linking xylem structural changes during xylem development with hydraulics is a major issue for future research to assess conifers vulnerability to climate change. C_LI

ecology↗

bioRxiv2021

Structural heterogeneity of the microtubule lattice

Microtubules are tubes of about 25 nm in diameter that are critically involved in a variety of cellular functions including motility, compartmentalization, and division. They are considered as pseudo-helical polymers whose constituent {beta}-tubulin heterodimers share lateral homotypic interactions, except at one unique region called the seam. Here, we used a segmented sub-tomogram averaging strategy to reassess this paradigm and analyze the organization of the {beta}-tubulin heterodimers in microtubules assembled from purified porcine brain tubulin in the presence of GTP and GMPCPP, and in Xenopus egg cytoplasmic extracts. We find that in all conditions, microtubules incorporate variable protofilament and/or tubulin subunit helical-start numbers, as well as variable numbers of seams. Strikingly, the seam number and location vary along individual microtubules, generating holes of one to a few subunits in size within their lattices. Together, our results reveal that the formation of mixed and discontinuous microtubule lattices is an intrinsic property of tubulin that requires the formation of unique lateral interactions without longitudinal ones. They further suggest that microtubule assembly is tightly regulated in a cytoplasmic environment.

cell biology↗

bioRxiv2018

Enhanced cell-cell contact stability upon Fibroblast Growth factor Receptor/N-cadherin cross-talk

N-cadherin adhesion has been reported to enhance cancer and neuronal cell migration either by mediating actomyosin-based force transduction or initiating Fibroblast Growth Factor Receptor (FGFR)-dependent biochemical signalling. Here we show that FGFR1 reduces N-cadherin-mediated cell migration. Both proteins are co-stabilised at cell-cell contacts through direct interaction. As a consequence, cell adhesion is strengthened, limiting the migration of cells on N-cadherin. Both the inhibition of migration and the stabilisation of cell adhesions require the FGFR activity stimulated by N-cadherin engagement. FGFR1 stabilises N-cadherin at the cell membrane through a pathway involving Src and p120. Moreover, FGFR1 stimulates the anchoring of N-cadherin to actin. We found that the migratory behaviour of cells depends on an optimum balance between FGFR-regulated N-cadherin adhesion and actin dynamics. Based on these findings we propose a positive feedback loop between N-cadherin and FGFR at adhesion sites limiting N-cadherin-based single cell migration.

cell biology↗