Biology subjects

Inaki, M.

Publications and source records attributed to Inaki, M..

7 recordsLinked to original sources

bioRxiv2025

Pak, a downstream gene of ecdysone signaling, determines left-right polarity in the Drosophila brain through neuronal cell chirality

Left-right (LR) asymmetry is a conserved characteristic of the brain in various animals and is related to its higher-order functions. The Drosophila brain has an LR asymmetric structure known as an asymmetrical body (AB). LR asymmetric neurite remodeling lateralizes the AB, and ecdysone signaling determines LR specificity. However, the mechanisms underlying LR specificity remain unclear. We found that the Slit/Dreadlocks/Roundabout/p21-activated kinase (Pak) signaling axis determines the LR polarity of the AB downstream of ecdysone signaling in the type II neuroblast lineage before LR asymmetric neurite remodeling. In Drosophila, the intrinsic chirality of cells (cell chirality) defines the LR asymmetry of various non-neuronal organs. We suggested that neurons derived from type II neuroblasts exhibit cell chirality, which is established through Pak and ecdysone signaling and determines the LR polarity of the AB. As cell chirality is broadly observed in eukaryotes, our study reveals a novel mechanism underlying LR asymmetry of the brain.

neuroscience↗

bioRxiv2025

Class I myosins direct circumferential F-actin flows to define cell chirality

Eukaryotic cells possess intrinsic chirality in their structure, motility, and intracellular dynamics, which are designated cell chirality. Cell chirality participates in the left-right asymmetric morphogenesis and tissue integrity. However, the mechanisms of cell chirality formation remain elusive. In Drosophila, two evolutionarily conserved myosin I genes, Myosin 1D (Myo1D) and Myosin 1C (Myo1C), respectively, dictate the dextral and sinistral chirality of the cells and body. Here, we reported that Myo1D and Myo1C respectively directed the clockwise and counterclockwise circumferential flow of F-actin in Drosophila macrophages. Both induced the corresponding circular cytoplasm flows and depended on Myosin2 (Myo2). In a modified in vitro motility assay using near-physiological actin concentrations, Myo1D triggered the self-organization of the F-actin ring (chiral F-actin ring) that rotated clockwise; conversely, Myo1C induced the random flow of F-actin. The chiral F-actin ring implied that the F-actin bundle was parallelly and annularly polarized concerning its barbed pointed end. Considering that Myo1D and Myo1C are localized to the dorsal plasma membrane of macrophages, Myo1D and Myo1C might organize the parallelly polarized F-actin in macrophages. Our results suggest that Myo2 might drive the clockwise circumferential flow of F-actin along its parallel and annular polarity induced by Myo1D, which may be a molecular basis of cell and organ chirality.

cell biology↗

bioRxiv2023

Distinctive cellular and junctional dynamics independently regulate the rotation and elongation of the internal organ

Complex structures of organs are formed at high reproducibility, and deformations of epithelia play major roles in these processes. To acquire the intricate morphology, an epithelium simultaneously suffers multiple structural changes. For example, to form the left-right asymmetric structure of Drosophila embryonic hindgut, its epithelial tube concurrently rotates and elongates, which are driven by cell sliding and convergent extension, respectively. However, how an epithelium simultaneously accomplishes multiple structural changes remains unclear. To address this issue, we here studied the relevancy between these two mechanisms in the hindgut morphogenesis. Our live imaging analysis revealed that Myosin1D and E-cadherin, or Par-3 are required only for cell sliding or convergent extension, respectively, while Myosin II is essential for both. Mathematical models showed that these cellular dynamics share a single mechanical system in the same time window. Such specificity and universality of the machineries controlling epithelial dynamics might be a general strategy adopted in complex tissue morphogenesis.

developmental biology↗

bioRxiv2022

The Drosophila AWP1 ortholog Doctor No regulates JAK/STAT signaling for left-right asymmetry in the gut by promoting receptor endocytosis

Many internal Drosophila organs show stereotypical left-right (LR) asymmetry, for which the underlying mechanisms remain elusive. Here, we identified an evolutionarily conserved ubiquitin-binding protein, AWP1/Doctor no (Drn), as a novel factor required for the LR asymmetry of the embryonic anterior gut in Drosophila. We showed that drn is essential in the circular visceral muscle cells of the midgut for JAK/STAT signaling, which contributes to the first known cue for anterior gut lateralization via LR-asymmetric nuclear rearrangement. Embryos homozygous for drn and lacking its maternal contribution showed phenotypes similar to that of depleted JAK/STAT signaling, suggesting that Drn is a general component of JAK/STAT signaling. The absence of Drn resulted in the specific accumulation of Domeless (Dome), the receptor of JAK/STAT signaling, in intracellular compartments. Thus, Drn is required for the endocytic trafficking of Dome, which is subsequently degraded in lysosomes. Our results suggest that the endocytosis of Dome is a critical step in activating JAK/STAT signaling. The roles of AWP1/Drn in activating JAK/STAT signaling and in LR-asymmetric development may be conserved in various organisms. Summary StatementDr. No, a Drosophila ortholog of AWP1, activates JAK/STAT signaling via Dome receptor endocytosis in a crucial step for left-right asymmetry in the developing gut.

developmental biology↗

bioRxiv2021

Live imaging of delamination in Drosophila shows that epithelial cell motility and invasiveness are independently regulated

Delaminating cells undergo complex, precisely regulated changes in cell-cell adhesion, motility, polarity, invasiveness, and other cellular properties. Delamination occurs during development and in pathogenic conditions such as cancer metastasis. We analyzed the requirements for epithelial delamination in Drosophila ovary border cells, which detach from the structured epithelial layer and begin to migrate collectively. We used live imaging to examine cellular dynamics, particularly epithelial cells acquisition of motility and invasiveness, in delamination-defective mutants during the time period in which delamination occurs in the wild-type ovary. We found that border cells in slow border cells (slbo), a delamination-defective mutant, lacked invasive cellular protrusions but acquired motility, while JAK/STAT-inhibited border cells lost both invasiveness and motility. Our results indicate that invasiveness and motility, which are cooperatively required for delamination, are regulated independently. Our reconstruction experiments also showed that motility is not a prerequisite for acquiring invasiveness. Summary statementLive imaging of epithelial delamination reveals that cell motility and invasiveness, both of which are required for delamination, are regulated independently and that motility is not a prerequisite for invasiveness.

developmental biology↗

bioRxiv2020

Collective nuclear behavior shapes bilateral nuclear symmetry for subsequent left-right asymmetric morphogenesis in Drosophila

Proper organ development often requires nuclei to move to a specific position within the cell. To determine how nuclear positioning affects left-right (LR) development in the Drosophila anterior midgut (AMG), we developed a surface-modeling method to measure and describe nuclear behavior at stages 13-14, captured in three-dimensional time-lapse movies. We describe the distinctive positioning and a novel collective nuclear behavior by which nuclei align LR-symmetrically along the anterior-posterior axis in the visceral muscles that overlie the midgut and are responsible for this organs LR-asymmetric development. Wnt4 signaling is crucial for the collective behavior and proper positioning of the nuclei, as are myosin II and LINC complex, without which the nuclei failed to align LR-symmetrically. The LR-symmetric positioning of the nuclei is important for the subsequent LR-asymmetric development of the AMG. We propose that the bilaterally symmetrical positioning of these nuclei may be mechanically coupled with subsequent LR-asymmetric morphogenesis.

cell biology↗

bioRxiv2020

Statistical validation verifies that enantiomorphic states of cell chirality are determinant dictating the left- or right-handed direction of the hindgut rotation in Drosophila

In the left-right (LR) asymmetric development of invertebrates, chirality of cells (cell chirality) plays crucial roles. Left- or right-handed structure of cells consequently directs the morphogenesis with corresponding LR asymmetry. In Drosophila, it has been suggested that cell chirality drives the LR-asymmetric development of various organs including the embryonic hindgut. However, this hypothesis is supported only by apparent concordance between these two events and by computer simulations connecting them [1-5]. Therefore, here, we mathematically evaluated the causal relationship between the cell chirality of the hindgut epithelial cells and the LR-directional rotation of the hindgut, which was previously postulated. Our logistic model obtained from various genetic backgrounds significantly explained the correlation between the enantiomorphic states of cell chirality and the LR directionality of hindgut rotation. This model also significantly explained the correlation between cell chirality stochastically formed in advance in each living embryo and the LR-directionality of the following rotation, suggesting the irrelevance of modes how cell chirality is formed. This analysis also showed that the cell chirality is not only sufficient but also required for the rotation. Considering the chronological order of these events, our study validated that cell chirality causally defines the LR asymmetry of the hindgut rotation.

developmental biology↗