Biology subjects

Takai, Y.

Publications and source records attributed to Takai, Y..

4 recordsLinked to original sources

bioRxiv2026

Changes in dysbiosis and gene expression in the gut of wharf roach (Ligia Spp.) fed with expanded polystyrene

The East Asian region, known for its high levels of human and fishery activities, experiences serious plastic pollution in the marine environment, especially in seawater and along coastlines. Wharf roaches (Ligia spp.) collected from the coast of western Japan frequently ingest expanded polystyrene (EPS), which is then excreted as microplastic through their feces. However, the impact of EPS exposure and ingestion on the gut microbiome of wharf roaches remains unclear. Thus, this study aimed to investigate the effects of EPS ingestion on the gut microbiota of wharf roaches by examining their gut microbiota and gene expression. The expression levels of more than 400 genes, including those associated with xenobiotic metabolism, and the abundance of gut microbial community were altered. Microbial analysis revealed that at least five archaeal types, two to four bacterial types, three to seven eukaryotic types, and three viral types were involved in a correlation network composed of strong associations. Among them, Haloquadratum, Halalkalicoccus, and Methanospirillum (archaea); Volvox (eukaryote); and Varicellovirus and T4-like viruses showed significantly increased abundance. Furthermore, covariance structure analysis indicated that the viruses and methanogens played key causal roles as characteristic factors related to EPS administration. In conclusion, EPS disrupts the intestinal environment of wharf roaches and serves as a potential material for viral activation and methane production. Building on our previous field study that identified wharf roaches as potential indicators of coastal EPS pollution, this study provides novel insights into the ecological impacts of EPS ingestion and consequences of plastic pollution.

pharmacology and toxicology↗

bioRxiv2025

Astrocytic Cathepsin D truncates α-synuclein and promotes Lewy neurite-like aggregation in neurons

Parkinsons disease (PD) and related synucleinopathies are marked by the accumulation and propagation of -synuclein (-syn) aggregates, a process primarily studied in neurons. However, the contribution of astrocytes to this process remains unclear. Here, using a physiologically relevant neuron-astrocyte co-culture system that recapitulates tripartite synapse architecture, we show that astrocytes actively process and propagate -syn aggregates. Astrocytes internalize -syn pre-formed fibrils (PFFs) and cleave them into C-terminally truncated, seeding-competent species via the lysosomal protease Cathepsin D (CtsD). These truncated species are subsequently transferred to neurons, where they promote the growth of Lewy neurite (LN)-like aggregates. Notably, -syn PFF exposure disrupts lysosomal membrane integrity in astrocytes, leading to CtsD upregulation. These findings reveal a feed-forward mechanism in which astrocytic lysosomal dysfunction amplifies -syn pathogenicity. Our findings identify astrocytes as active contributors to -syn propagation and highlight the astrocytic lysosomal pathway as a potential therapeutic target in PD.

pathology↗

bioRxiv2024

Afadin-deficient retinas exhibit severe neuronal lamination defects but preserve visual functions

Neural lamination is a common feature of the central nervous system (CNS), with several subcellular structures, such as adherens junctions (AJs), playing a role in this process. The retina is also heavily laminated, but it remains unclear how laminar formation impacts retinal cell morphology, synapse integrity, and overall retinal function. In this study, we demonstrate that the loss of afadin, a key component of AJs, in mice leads to significant pathological changes. These include the disruption of outer retinal lamination and a notable decrease as well as mislocalization of photoreceptors, their outer segments, and photoreceptor synapses. Interestingly, despite these severe impairments, we recorded small local field potentials, including the a- and b-waves. We also classified retinal ganglion cells (RGCs) into ON, ON-OFF, and OFF types based on their firing patterns in response to light stimuli. Additionally, we successfully characterized the receptive fields of certain RGCs. Overall, these findings provide evidence that retinal circuit function can be partially preserved even when there are significant disruptions in both retinal lamination and photoreceptor synapses. Our results indicate that retinas with severely altered morphology still retain some capacity to process light stimuli.

neuroscience↗

bioRxiv2020

Production of a tributyltin-binding protein 2 knockout mutant strain of Japanese medaka, Oryzias latipes

Tributyltin-binding proteins (TBT-bps), members of the lipocalin family, bind TBT in fish blood and are presumed to contribute to detoxification of TBT. Recent studies have shown that many fish species have TBT-bp genes, and that these genes are induced by stresses such as exposure to chemicals or fish pathogenic bacteria. However, the function of TBT-bps, and the mechanisms of their induction and detoxification activity are still unclear. Here, towards elucidating the functions of TBT-bp2, we produced a TBT-bp2 knockout (TBT-bp2-/-) strain of Japanese medaka, Oryzias latipes, by using the CRISPR/Cas9 system. Gene expression of the mutated TBT-bp2 was reduced, and the cDNA sequencing and predicted protein structure suggested possible loss of function. However, the fish could be grown under normal conditions. Exposure of the TBT-bp2-/- strain of medaka to various stresses in future experiments is expected to contribute to our understanding of this novel detoxification system in aquatic organisms.

pharmacology and toxicology↗