Biology subjects

Moussian, B.

Publications and source records attributed to Moussian, B..

6 recordsLinked to original sources

bioRxiv2025

Diversity of Resilin incidence in the insect leg

Insect movements rely on membranous elastic types of cuticle that bridge hard and tanned types, which serve as an exoskeleton. A prominent, polymerous protein of membranous cuticles is Resilin, known for its flexibility and elasticity. In the articulated legs, including the coxa, the trochanter, the femur, the tibia and the tarsi, Resilin incidences in or at the joints of these podomers have been identified in various species such as the fruit fly Drosophila melanogaster and the desert locust Schistocerca grigaria. A systematic, comparative work on Resilin identification in insect legs is missing. Here, using a microscopic intensity subtraction method, we identified Resilin incidences in the legs of 29 species belonging to the major insect orders. This method relies on the classical identification of Resilin based on Dityrosine (DT) bonds between Resilin monomers, Pro-Resilin, that emit blue light when illuminated with UV light. By subtracting the background intensity counts per pixel (counts) of a common blue filter from the counts obtained by a specific filter for the DT spectrum in insects (microscopic intensity subtraction method, MISM), we both confirm the presence of known Resilin locations and identify new incidences in the podomers such as a coxa-trochanter signal. Together, we find that Resilin distribution in insect legs is highly diverse with no incidence common to all species tested. This underlines that the use of Resilin follows a rapid and optimizing evolutionary adaptation. Our data pave the path for studies of the comparative function of Resilin in insect legs.

zoology↗

bioRxiv2021

Autophagy suppression by TORC1 maintains epithelial plasma membrane integrity and inhibits syncytium formation

Epithelial wound healing in Drosophila involves the formation of multinucleate cells surrounding the wound. We show that autophagy, a cellular degradation process often deployed in stress responses, is required for the formation of a multinucleated syncytium during wound healing. In addition, uncontrolled autophagy in the unwounded epidermis leads to the degradation of endo-membranes and the lateral plasma membrane, while the apical and basal membranes and the epithelial barrier function remain intact. Proper functioning of TORC1 is needed to prevent autophagy from destroying the larval epidermis, which depends on membrane isolation and phagophore expansion, but does not require the fusion of autophagosomes to lysosomes. Our findings reveal a function for TORC1-mediated regulation of autophagy in maintaining membrane integrity and homeostasis in the epidermis and during wound healing. Finally, autophagy can counteract experimentally induced nuclear defects resembling laminopathies. Key findingsO_LIA novel role for TORC1/autophagy pathway to control plasma membrane integrity and homeostasis. C_LIO_LIAutophagy as the only known necessary and sufficient inducer of syncytium formation in the epithelium and during wound healing. C_LI

cell biology↗

bioRxiv2019

Epidermal cell surface structure and chitin-protein co-assembly determine fiber architecture in the Locust cuticle

The geometrical similarity of helicoidal fiber arrangement in many biological fibrous extracellular matrices, such as bone, plant cell wall or arthropod cuticle, to that of cholesteric liquid mesophases has led to the hypothesis that they may form passively through a mesophase precursor rather than by direct cellular control. In search of direct evidence to support or refute this hypothesis, here, we studied the process of cuticle formation in the tibia of the migratory locust, Locusta migratoria, where daily growth layers arise by the deposition of fiber arrangements alternating between unidirectional and helicoidal structures. Using FIB/SEM volume imaging and scanning X-ray scattering, we show that the epidermal cells determine an initial fiber orientation from which the final architecture emerges by the self-organized co-assembly of chitin and proteins. Fiber orientation in the locust cuticle is therefore determined by both active and passive processes.

biophysics↗

bioRxiv2019

Dysfunction of Torr causes a Harlequin-type ichthyosis-like phenotype in Drosophila melanogaster

Prevention of desiccation is a constant challenge for terrestrial organisms. Land insects have an extracellular coat, the cuticle, that plays a major role in protection against exaggerated water loss. Here, we report that the ABC transporter Torr - a human ABCA12 paralog - contributes to the waterproof barrier function of the cuticle in the fruit fly Drosophila melanogaster. We show that the reduction or elimination of Torr function provokes rapid desiccation. Torr is also involved in defining the inward barrier against xenobiotics penetration. Consistently, the amounts of cuticular hydrocarbons that are involved in cuticle impermeability decrease markedly when Torr activity is reduced. GFP-tagged Torr localises to membrane nano-protrusions within the cuticle, likely pore canals. This suggests that Torr is mediating the transport of cuticular hydrocarbons (CHC) through the pore canals to the cuticle surface. The envelope, which is the outermost cuticle layer constituting the main barrier, is unaffected in torr mutant larvae. This contrasts with the function of Snu, another ABC transporter needed for the construction of the cuticular inward and outward barriers, that nevertheless is implicated in CHC deposition. Hence, Torr and Snu have overlapping and independent roles to establish cuticular resistance against transpiration and xenobiotic penetration. The torr deficient phenotype parallels the phenotype of Harlequin ichthyosis caused by mutations in the human abca12 gene. Thus, it seems that the cellular and molecular mechanisms of lipid barrier assembly in the skin are conserved in vertebrates in invertebrates.\n\nAuthor SummaryAs in humans, lipids on the surface of the skin of insects protect the organism against excessive water loss and penetration of potentially harmful substances. During evolution, a greasy surface was indeed an essential trait for adaptation to life outside a watery environment. Here, we show that the membrane-gate transporter Torr is needed for the deposition of barrier lipids on the skin surface in the fruit fly Drosophila melanogaster through extracellular nano-tubes, called pore canals. In principle, the involvement of Torr parallels the scenario in humans, where the membrane-gate transporter ABCA12 is implicated in the construction of the lipid-based stratum corneum of the skin. In both cases, mutations in the genes coding for the respective transporter cause rapid water-loss and are lethal soon after birth. We conclude that the interaction between the organism and the environment obviously implies an analogous mechanism of barrier formation and function in vertebrates and invertebrates.

cell biology↗

bioRxiv2018

The C-type lectin Schlaff ensures epidermal barrier compactness in Drosophila

The stability of extracellular matrices is in general ensured by cross-linking of its components. Previously, we had shown that the integrity of the layered Drosophila cuticle relies on the presence of a covalent cuticular dityrosine network. Production and composition of this structure remained unstudied. In this work, we present our analyses of the schlaff (slf) gene coding for a C-type lectin that is needed for the adhesion between the horizontal cuticle layers. The Slf protein mainly localizes between the two layers called epicuticle and procuticle that separate from each other when the function of Slf is reduced or eliminated paralleling the phenotype of a cuticle with reduced extracellular dityrosine. Localisation of the dityrosinylated protein Resilin to the epicuticle-procuticle interface suggests that the dityrosine network mediates the adhesion of the epicuticle to the procuticle. Ultimately, compromised Slf function is associated with massive water loss. In summary, we propose that Slf is implied in the stabilisation of a dityrosine layer especially between the epicuticle and the procuticle that in turn constitutes an outward barrier against uncontrolled water flow.\n\nSummary statementExtracellular matrices adopt a stereotypic organisation for function during development. The lectin Schlaff assists adhesion reactions to ensure compactness of the epidermal cuticle in Drosophila.

cell biology↗

bioRxiv2017

The ABC transporter Snu drives formation of the lipid-based inward and outward barrier in the skin of Drosophila

Lipids in extracellular matrices (ECM) contribute to barrier function and stability of epithelial tissues such as the pulmonary alveoli and the skin. In insects, skin waterproofness depends on the outermost layer of the extracellular cuticle termed envelope that contains cuticulin, an unidentified water-repellent complex molecule composed of proteins, lipids and catecholamines. Based on live-imaging analyses of fruit fly larvae, we find that initially envelope units are assembled within vesicles harbouring the ABC transporter Snu and the extracellular protein Snsl. In a second step, the content of these vesicles is distributed to cuticular lipid-transporting nanotubes named pore canals and to the cuticle surface in dependence of Snu function. Consistently, the surface of snu and snsl mutant larvae is depleted from lipids and cuticulin. By consequence, these animals suffer uncontrolled water loss and penetration of xenobiotics. Our data allude to a two-step model of envelope i.e. barrier formation. The proposed mechanism in principle parallels the events occurring during differentiation of the lipid-based ECM by keratinocytes in the vertebrate skin suggesting establishment of analogous mechanisms of skin barrier formation in vertebrates and invertebrates.

cell biology↗