Biology subjects

Aoki, D.

Publications and source records attributed to Aoki, D..

4 recordsLinked to original sources

bioRxiv2023

Mechanical Netrin-1-DCC Coupling Mediates Netrin-1-induced Axonal Haptotaxis

The growth cone, a motile structure located at the tip of growing axon, senses extracellular guidance cues and translates them into directional forces that drive axon outgrowth and guidance. Axon guidance directed by chemical cues on the extracellular adhesive substrate is termed haptotaxis. Recent studies reported that netrin-1 on the substrate functions as a haptotactic axon guidance cue. However, the mechanism mediating netrin-1-induced axonal haptotaxis remains unclear. Here, we demonstrate that substrate-bound netrin-1 induces axonal haptotaxis by facilitating physical interactions between the netrin-1 receptor, DCC, and the adhesive substrates. DCC serves as an adhesion receptor for netrin-1. The clutch molecule shootin1a interacted with DCC, linking it to actin filament retrograde flow at the growth cone. Speckle imaging analyses showed that DCC underwent either grip (stop) and retrograde slip on the adhesive substrate. The grip state was more prevalent on netrin-1-coated substrate compared to the control substrate polylysine, thereby transmitting larger traction force on the netrin-1-coated substrate. Furthermore, disruption of the linkage between actin flow and DCC by shootin1 knockout impaired netrin-1-induced axonal haptotaxis. These findings indicate that the directional force for netrin-1-induced haptotaxis is exerted on the substrates through the mechanical coupling between netrin-1 and DCC which occurs asymmetrically under the growth cone.

cell biology↗

bioRxiv2023

Phylogenomics reveals the demography of reverse colonization in a rail species

AimIslands have recently been recognized as potential sources of biodiversity, challenging the traditional view that their small population sizes and low genetic diversity limit such roles. This raises the question of how insular genetic variation becomes incorporated into continental populations, contrary to expectations of unidirectional colonization. Here, we investigate whether and how island-derived genetic variation has influenced a continental population through population establishment and gene flow in a bird species where frequent trans-ocean dispersal is expected. LocationContinental East Asia (Russian Far East), Japanese Archipelago TaxonSwinhoes Rail (Coturnicops exquisitus) Materials and MethodsWe apply integrative phylogenomics to reconstruct the spatiotemporal history of the species. Colonization sequences and gene flow are inferred by comparing four different phylogenetic reconstruction methods, using mitochondrial sequences obtained by Sanger sequencing and genome-wide data obtained by genotyping by sequencing (MIG-seq). We assess a history of colonization and gene flow based on summary statistics, demographic trajectory inference by Stairway Plot2, demographic modeling by fastsimcoal2, and species distribution modeling. ResultsAnalyses collectively supported asymmetric gene flow from the island to the continental population, following divergence around the Middle Pleistocene. Post-divergence, the island maintained a large and stable population, while the continental population underwent a severe bottleneck, suggesting a significant evolutionary role of the island for the continental population. Additionally, evidence of recent re-establishment of the island by continental individuals indicates dynamic exchange and persistence within a continent-island metapopulation. Main conclusionsThe maintenance of insular genetic variation within a dynamic continent-island metapopulation may have enabled the island to act as a genetic and demographic reservoir for the continental population. Thus, continent-island metapopulation dynamics may be a key evolutionary pathway through which island populations contribute to continental genetic diversity.

evolutionary biology↗

bioRxiv2021

The recent range expansion of Great Cormorants (Phalacrocorax carbo hanedae) in Hokkaido, Japan.

Though the Japanese subspecies of Great Cormorant (Phalacrocorax carbo hanedae) has increased its population in recent decades, information on its spread to the northern island of Hokkaido has not been reported outside of Japan. The purpose of this paper is to update the scientific community about the breeding and range ecology of P. carbo, and to provide comparative information on the abundant and similar looking resident Japanese Cormorant (P. capillatus). Several ornithological groups and researchers were contacted in order to gather information about the current distribution and breeding activities of P. carbo in the region. Here the findings of Japanese research groups, translated publications, and direct observations are made available.

zoology↗

bioRxiv2020

Examining the genetic influences of migratory status on island colonisation by naturally and recently established populations of a bird species

AimFounder effects and recurrent immigration are two major factors that potentially contribute to genetic differentiation and population persistence in the early-stage of remote island colonization. However, their relative importance remains controversial. By conducting population genetics analyses of multiple remote island populations of the bull-headed shrike established naturally within several decades, we examined the relative contributions of founder effects and recurrent immigration on these island populations. LocationJapan TaxonLanius bucephalus MethodsWe used 15 microsatellite loci to analyze the population genetics of four newly established island populations and five Japanese mainland populations. Allelic richness, heterozygosity, genetic differentiation, and the strength of the genetic bottleneck were compared among the islands. Two analyses, STRUCTURE and the DAPC, were conducted to assess the relative influence of founder effects and recurrent immigration on genetic differentiation. Temporal samples collected over eight years on Minami-Daito Island were used to detect any change in genetic structure due to recurrent immigration. ResultsThe founder effect strongly influenced genetic differentiation on the most remote oceanic island, Chichi-jima Island. However, this population became extinct 20 years after colonization, possibly owing to a lack of recurrent immigration. The founder effect moderately influenced a land-bridge island, Kikai-jima Island, indicating the presence of a relatively large founder population without recurrent immigration. Surprisingly, another distant oceanic island, Minami-Daito Island, was likely subject to multiple recurrent immigration events from the mainland, which obscured any genetic differentiation previously established by the founder effect. Main conclusionUnderlying the island-specific population dynamics of colonization, founder effects contributed to the genetic differentiation among the three studied island populations. Importantly, however, recurrent immigration strongly affected the population persistence and subsequent evolutionary processes of remote island populations, potentially overwhelming the founder effect. We argue the importance of recurrent immigration in highly remote island colonization, which has been previously overlooked.

ecology↗