Biology subjects

Mirouse, V.

Publications and source records attributed to Mirouse, V..

7 recordsLinked to original sources

bioRxiv2024

The transcription factor Traffic jam orchestrates the somatic piRNA pathway in Drosophila ovaries

The PIWI-interacting RNA (piRNA) pathway is essential for transposable element (TE) silencing in animal gonads. While the transcriptional regulation of piRNA pathway components in germ cells has been documented in mice and flies, their control in somatic cells of Drosophila ovaries remains unresolved. Here, we demonstrate that Traffic jam (Tj), the Drosophila orthologue of large Maf transcription factors in mammals, is a master regulator of the somatic piRNA pathway. Tj binds to regulatory regions of somatic piRNA factors and the major piRNA cluster flamenco, which carries a Tj-bound enhancer downstream of its promoter. Depletion of Tj in somatic follicle cells causes downregulation of piRNA factors, loss of flam expression and de-repression of gypsy-family TEs. We propose that the arms race between the host and TEs led to the co-evolution of promoters in piRNA pathway genes as well as TE regulatory regions that both rely on a shared transcription factor. Highlights- Traffic jam (Tj) acts as a master regulator of the somatic piRNA pathway in Drosophila. - Tj regulates a network of piRNA pathway genes, mirroring the gene-regulatory mechanism of A-MYB in the mouse testis and Ovo in fly ovaries. - Cis-regulatory elements with Tj motifs are present at the promoters of somatic piRNA pathway genes. - The expression of the flamenco piRNA cluster is directly controlled by Tj.

molecular biology↗

bioRxiv2024

Tricellular junction recruitment of the Wave regulatory complex by Sidekick and Lar induces protrusive activity resolving cell intercalation

Cell intercalation, a fundamental morphogenetic process characterized by the exchange of neighboring cells, plays a pivotal role in epithelial tissue development. While the initiation of new junctions remains poorly understood, recent research indicates the involvement of tricellular junction actors. In this study, we explore the contribution of the WAVE regulatory complex (WRC), a critical regulator of branched F-Actin generation, in tissue elongation and cell intercalation within the Drosophila ovarian follicular epithelium. WRC localizes at tricellular junctions, where it orchestrates the generation of highly dynamic protrusions emanating from one cell and extending between the bicellular junctions of neighboring cells. This protrusive activity is essential for the initiation of new junctions in cells located at the extremities of these junctions. Furthermore, our findings indicate that WRC recruitment at tricellular junctions is a redundant process, involving the cooperative action of the two transmembrane proteins Sidekick and Lar. Disruption of this recruitment impairs protrusive activity, cell intercalation resolution, and tissue elongation, thereby mechanistically bridging molecular, cellular and tissular scales. Consequently, this elucidates a critical mechanism underlying epithelial morphogenesis through actin polymerization at tricellular junctions.

cell biology↗

bioRxiv2024

The Dystrophin-Dystroglycan complex ensures cytokinesis efficiency in Drosophila epithelia

Cytokinesis physically separates daughter cells at the end of cell division. This step is particularly challenging for epithelial cells, which are connected to their neighbors and to the extracellular matrix by transmembrane protein complexes. To systematically evaluate the impact of the cell adhesion machinery on epithelial cytokinesis efficiency, we performed an RNAi-based modifier screen in the Drosophila follicular epithelium. Strikingly, this unveiled adhesion molecules and transmembrane receptors that facilitate cytokinesis completion. Among these is Dystroglycan, which connects the extracellular matrix to the cytoskeleton via Dystrophin. Live imaging revealed that Dystrophin and Dystroglycan become enriched in the ingressing membrane, below the cytokinetic ring, during and after ring constriction. Using multiple alleles, including Dystrophin isoform-specific mutants, we show that Dystrophin/Dystroglycan localization is linked with unanticipated roles in regulating cytokinetic ring contraction and in preventing membrane regression during the abscission period. Altogether, we provide evidence that, rather than opposing cytokinesis completion, the machinery involved in cell-cell and cell-matrix interactions has also evolved functions to ensure cytokinesis efficiency in epithelial tissues.

cell biology↗

bioRxiv2023

Gap junction-dependent amino acid transfer promotes germ cell growth

Gap junctions allow the exchange of small molecules between cells. How this function could be used to promote cell growth is not yet fully understood. During Drosophila ovarian follicle development, germ cells, which are surrounded by epithelial somatic cells, undergo massive growth. We found that this growth depends on gap junctions between these cell populations, with a requirement for Innexin4 and Innexin2, in the germ cells and the somatic cells, respectively. Translatomic analyses revealed that somatic cells express enzymes and transporters involved in amino acid metabolism that are absent in germ cells. Among them, we identified an amino acid transporter required for germline growth. Its ectopic expression in the germline can compensate for its absence in somatic cells. Moreover, affecting either gap junctions or amino-acid import in somatic cells induces P-bodies in the germ cells, a feature associated with an arrest of translation. Finally, in somatic cells, innexin2 expression and gap junction assembly are regulated by the insulin receptor/PI3K kinase pathway. Overall, these results support the view that metabolic transfer through gap junction promotes cell growth and illustrate how such a mechanism can be integrated into a developmental programme, coupling growth control by extrinsic systemic signals with the intrinsic coordination between cell populations.

developmental biology↗

bioRxiv2023

Basement membrane diversification relies on two competitive secretory routes defined by Rab10 and Rab8 and modulated by dystrophin and the exocyst complex

The basement membrane (BM) is an essential structural element of tissues, and its diversification participates in organ morphogenesis. However, the traffic routes associated with BM formation and the mechanistic modulations explaining its diversification are still poorly understood. Drosophila melanogaster follicular epithelium relies on a BM composed of oriented BM fibrils and a more homogenous matrix. Here, we determined the specific molecular identity and cell exit sites of BM protein secretory routes. First, we found that Rab10 and Rab8 define two parallel routes for BM protein secretion. When both routes were abolished, BM production was fully blocked; however, genetic interactions revealed that these two routes competed. Rab10 promoted lateral and planar-polarized secretion, whereas Rab8 promoted basal secretion, leading to the formation of BM fibrils and homogenous BM, respectively. We also found that the dystrophin-associated protein complex (DAPC) and Rab10 were both present in a planar-polarized tubular compartment containing BM proteins. DAPC was essential for fibril formation and sufficient to reorient secretion towards the Rab10 route. Moreover, we identified a dual function for the exocyst complex in this context. First, the Exo70 subunit directly interacted with dystrophin to limit its planar polarization. Second, the exocyst complex was also required for the Rab8 route. Altogether, these results highlight important mechanistic aspects of BM protein secretion and illustrate how BM diversity can emerge from the spatial control of distinct traffic routes.

cell biology↗

bioRxiv2019

Oriented basement membrane fibrils provide a memory for F-actin planar polarization via the Dystrophin-Dystroglycan complex during tissue elongation

How extracellular matrix participates to tissue morphogenesis is still an open question. In the Drosophila ovarian follicle, it has been proposed that after Fat2-dependent planar polarization of the follicle cell basal domain, oriented basement membrane (BM) fibrils and F-actin stress fibers constrain follicle growth, promoting its axial elongation. However, the relationship between BM fibrils and stress fibers and their respective impact on elongation are unclear. We found that Dystroglycan (Dg) and Dystrophin (Dys) are involved in BM fibril deposition. Moreover, they orient stress fibers, by acting locally and in parallel to Fat2. Nonetheless, Dg-Dys complex-mediated cell autonomous control of F-actin fibers orientation relies on the previous BM fibril deposition, indicating two distinct but interdependent functions. Thus, the Dg-Dys complex works as a critical organizer of the epithelial basal domain, regulating both F-actin and BM. Furthermore, BM fibrils act as a persistent cue for the orientation of stress fibers that are the main effector of elongation.

developmental biology↗

bioRxiv2017

Jak-Stat pathway induces Drosophila follicle elongation by a gradient of apical contractility

Tissue elongation and its control by spatiotemporal signals is a major developmental question. Currently, it is thought that Drosophila ovarian follicular epithelium elongation requires the planar polarization of the basal domain cytoskeleton and of the extra-cellular matrix, associated with a dynamic process of rotation around the anteroposterior axis. Here we show, by careful kinetic analysis of fat2 mutants, that neither basal planar polarization nor rotation is required during a first phase of follicle elongation. Conversely, a JAK-STAT signaling gradient from each follicle pole orients early elongation. JAK-STAT controls apical pulsatile contractions, and Myosin II activity inhibition affects both pulses and early elongation. Early elongation is associated with apical constriction at the poles and oriented cell rearrangements, but without any visible planar cell polarization of the apical domain. Thus, a morphogen gradient can trigger tissue elongation via a control of cell pulsing and without planar cell polarity requirement.\n\nImpact StatementFollicle elongation does not rely solely on the basal side of the cells but also requires a mechanism integrating a developmental cue with a morphogenetic process involving their apical domain.

developmental biology↗