Biology subjects

Kitazawa, M.

Publications and source records attributed to Kitazawa, M..

4 recordsLinked to original sources

bioRxiv2026

The impacts of seventy years of changes in stopover habitats on the critically endangered Spoon-billed Sandpiper Calidris pygmaea

Natural habitat loss due to land use change is a major driver of global biodiversity loss. Human-created seminatural environments can function as artificial habitats for many species, partially offsetting these negative impacts. However, it remains unclear how species respond to the short- and long-term changes in both natural and artificial habitats, particularly for long-distance migratory species at stopover sites. We investigated how the globally endangered habitat specialist species, Spoon-billed Sandpipers Calidris pygmaea, responded to 70 years of changes in natural wetlands, sandy beaches, and artificial wetlands across stopover habitats in the Japanese Archipelago. We compiled historical observation records of the species from multiple sources and quantified the extent of these three habitat types from 1950 to 2020. Spoon-billed Sandpiper abundance consistently declined from the 1970s to the 2010s, with a particularly sharp decrease between the 1980s and the 1990s. While more than 50% of natural wetlands and sandy beaches have also been lost since 1950, we found that sandpiper abundance was lower at sites experiencing greater cumulative natural habitat loss. By contrast, changes in artificial wetland extent were not significantly associated with abundance, despite their temporal expansion peaking in the 1970s and subsequently declining. Our findings demonstrate that historical loss of natural stopover habitats have had lasting negative effects on local sandpiper populations, and the temporary expansion of artificial wetlands failed to compensate for these effects. This underscores the critical importance of preserving the networks of natural stopover habitats to sustain migration success, particularly for habitat specialists.

ecology↗

bioRxiv2025

Resf1 is required for proper placental development and configuration of trophoblast cell-specific heterochromatin

Resf1 (Retroelement silencing factor 1) is involved in retroelement silencing cooperated with H3K9 methyltransferase SETDB1 by regulating H3K9 methylation in mouse embryonic stem cells (mESCs). However, it remains unknown whether Resf1 functions in retroelement silencing in vivo, and has a role in development. Here, we established Resf1-deficient mice, which exhibited developmental delay, partial embryonic lethality, and placental defects. Notably, retroelements were also upregulated in the Resf1-deficient placenta, correlating with increased expression of nearby genes. To further assess whether Resf1 functions within the trophoblast lineage, we generated Resf1-deficient trophoblast stem cell (TSC) lines. Both undifferentiated TSCs and differentiated TSCs (D-TSCs) display increased retroelement expression along with elevated levels of genes associated with placental development. Moreover, Resf1-deficient TSCs exhibit compromised maintenance of H3K9me3 domains in a manner independent of SETDB1. Collectively, our findings reveal that Resf1 plays multifaceted roles beyond retroelement silencing, underscoring its importance in development and its critical function in trophoblast lineage regulation.

developmental 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↗

bioRxiv2020

Therapeutic Efficacy and Safety of Lenvatinib for Unresectable Hepatocellular Carcinoma Beyond Progression with Sorafenib

Background & AimsThe efficacy and safety of lenvatinib (LEN) as a second/third-line treatment for unresectable hepatocellular carcinoma (HCC) after sorafenib (SOR) therapy remains unknown. We evaluated the outcomes of second/third-line treatment of LEN, investigated the sensitivity of SOR-resistant HCC cell line (PLC/PRF5-R2) to LEN, and their signal transduction pathway by protein array analysis. MethodsWe retrospectively enrolled 57 unresectable HCC patients. Radiologic responses in 53 patients were evaluated by modified Response Evaluation Criteria in Solid Tumors. Active signal transduction pathways in cells were identified by protein array analysis, including 1205 proteins. ResultsPatients comprised 34 tyrosine kinase inhibitor (TKI)-naive (first-line), nine SOR-intolerant (second-line), and ten resistant to regorafenib (third-line). Objective response rates (ORRs) were 61.8% (21/34) in TKI-naive, 33.3% (3/9) in second-line, and 20.0% (2/10) in third-line groups. The overall survival (OS) and the progression free survival (PFS) in the first-line was significantly longer than those in third-line group (p<0.05). Patients with better liver functional reserve (Child score, ALBI grade) exhibited higher ORR and longer OS. LEN was well-tolerated as second/third-line treatment. The IC50 value of LEN against PLC/PRF5-R2 cells (30 M) was significantly higher than that against PLC/PRF5 cells (6.4 M). LEN inhibited significantly more signal transduction pathways related to FRS2, a crucial FGFR downstream molecule, in PLC/PRF5 than PLC/PRF5-R2 cells. ConclusionsLEN was active and safe as a second/third-line treatment for unresectable HCC. LEN seems to be more effective for HCC patients with better hepatic reserve function or before TKI-resistance is acquired because of partial cross-resistance to SOR.

molecular biology↗