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The concept of the ecological niche, defined as the basic habitat requirements for a species, is central to understanding species geographic distributions and predicting their responses to environmental change. However, identifying the essential niche for large regional communities remains a challenge because niche axes can be “hidden” by the complexity of the underlying ecological processes. Here, applying advanced species distribution modelling to nationwide environmental DNA survey data, we identified hidden niche axes of the Japanese coastal fish community and investigated the response diversity to these axes. Our survey detected 1,220 coastal fish species. The hidden niche axes collectively explained most of the variation in fish biodiversity and revealed five biogeographic boundaries for the regional community. These niches of the Japanese fish community may primarily relate to several processes due to ocean currents, such as environmental filters, transport from source areas and dispersal barriers. We also found that the response diversity to niche axes was positively correlated with species richness, although local communities with particularly high response diversity were geographically biased. A better understanding of the niche axes of the regional ecological community should help to mitigate the loss of biodiversity and ecosystem services caused by ongoing environmental change.

It is well known that Rho family small GTPases (Rho GTPase) has a role of molecular switch in intracellular signal transduction. The switch cycle between GTP-bound and GDP-bound state of Rho GTPase regulates various cell responses such as gene transcription, cytoskeletal rearrangements, and vesicular trafficking. Rho GTPase-specific guanine nucleotide exchange factors (RhoGEFs) are regulated by various extracellular stimuli and activates Rho GTPase such as RhoA, Rac1, and Cdc42. The molecular mechanisms that regulate RhoGEFs are poorly understood. Our studies reveal that Dbl’s big sister (DBS), a RhoGEF for Cdc42 and RhoA, is phosphorylated at least on tyrosine residues at 479, 660, 727, and 926 upon stimulation by SRC signaling and that the phosphorylation at Tyr-660 is particularly critical for the serum response factor (SRF)-dependent transcriptional activation of DBS by Ephrin type-B receptor 2 (EPHB2)/SRC signaling. In addition, our studies also reveal that the phosphorylation of Tyr-479 and Tyr-660 on DBS leads to the actin cytoskeletal reorganization by EPHB2/SRC signaling. These findings are thought to be useful for understanding pathological conditions related to DBS such as cancer and non-syndromic autism in future.

Environmental DNA (eDNA) enables sensitive detection of species from environmental samples, particularly water. Large‐scale, standardized monitoring of coastal fish communities remains challenging across diverse regions. The ANEMONE Global network was established to address this gap, expanding the workflow developed in Japan to a coordinated worldwide survey using standardized eDNA metabarcoding. Between June and November 2024, 12 countries, including several in Southeast Asia, collected surface water samples from beaches, rocky shores, estuaries, and near coastal protective structures using harmonized protocols for filtration, RNAlater preservation, and metadata recording. Daytime and nighttime sampling captured temporal variation in community composition. All samples were processed with the MiFish metabarcoding protocol, quantitative internal standards, and rigorous contamination controls. Analysis of 90 samples generated over 16.6 million high‐quality reads, revealing more than 500 putative fish OTUs across diverse families, genera, and species. Species richness varied geographically, reflecting differences in fish fauna, and assemblages differed across the Atlantic, Indian, North Pacific, and South Pacific Oceans. Diel variation was most pronounced in the North Pacific, and diversity patterns reflected both habitat complexity and ocean basin, with waters adjacent to coastal protective structures and rocky shores supporting the highest diversity. These findings highlight how both habitat complexity and ocean basin geography shape coastal fish assemblages, offering insights for global marine biodiversity monitoring using eDNA. This survey demonstrates that a globally standardized eDNA workflow can generate comparable quality data across ecological and logistical contexts. By combining international collaboration, open data, and locally informed implementation, ANEMONE Global provides a framework for long‐term, high‐resolution monitoring of coastal biodiversity and sets the stage for expanding coverage to additional aquatic ecosystems worldwide.

Protein 4.1 family proteins are supposed to interact with intramembranous proteins and membrane skeletons. Protein 4.1B, one of the family proteins, was recently reported to be localized in basolateral regions of mouse renal proximal tubules. In this study, we extended the idea that protein 4.1B may be related to ion balance in the region by immunohistochemical studies by light and electron microscopy with our antibody against protein 4.1B. Protein 4.1B distribution in rodent kidneys was determined by comparing with lectin Lotus tetragonobulus agglutinin (LTA), a proximal tubule cell marker, and also with Na(+)/HCO(3)(-)-cotransporter-1 (NBC-1), being expressed in basolateral domains of segment S1 to S2 proximal tubule epithelial cells. Specific protein 4.1B immunolabeling was observed in cuboidal epithelial cells basolaterally, starting their localization from a urinary pole at the glomerulus, whereas the squamous epithelial cells of Bowman's capsules were immunonegative. Rat Bowman's capsules had no simple cuboidal cells, where no protein 4.1B immunostaining appeared. All the protein 4.1B-positive epithelial cells were LTA positive. By immunoelectron microscopy, protein 4.1B immunolabeling of the proximal epithelial cells was restricted to the basolateral membranes, including basal infoldings, whereas tight junctions were not immunolabeled. It is concluded that protein 4.1B might play a role related to membrane skeletal proteins in the basolateral membranes of S1 and S2 proximal tubule cells. Moreover, the immunolocalization of protein 4.1B was almost the same as that of NBC-1, indicating a possible function as a regulator of ion balance, such as Na(+) and HCO(3)(-) reabsorption.

The polarized architecture of epithelial cells is a fundamental determinant of cell structures and functions. Both formation and orientation of proper epithelial polarity are needed for cell-cell or cell-matrix adhesion, signal transduction and cytoskeletal interactions of multimolecular complexes at apical, lateral and basal cell membranes. These cell membrane domains are usually segregated by some junctional complexes. Recent molecular genetic studies on the anchor structure between myelin sheaths and axons have indicated the specific molecular organization for polarization of axolemma and the myelin sheaths at paranodes, termed ‘septate-like junctions’. It was also speculated that other mammalian organs may use a similar junctional system. The protein 4.1B was originally found to be localized in paranodes and juxtaparanodes of myelinated nerve fibers. Our recent immunohistochemical studies on protein 4.1B have indicated its significance for the cell-cell and/or cell-matrix adhesion in various rodent organs. The protein 4.1 family of proteins have been supposed to possess variable molecular domains relating to cell adhesion, ion balance, receptor responses and signal transduction. Therefore, more precise studies on the molecular structure and the functional domains of protein 4.1B, as well as on its changes under physiological and pathological conditions, may provide a clue for organogenesis in various mammalian organs.

Recently, we have reported that the protein 4.1B immunolocalization occurred only in matured columnar epithelial cells of normal rat intestines. This finding suggested that protein 4.1B expression could be examined for a possible change during neoplastic transformation of the intestinal mucosa. In the present study, we first present the distribution of mouse protein 4.1B in normal intestinal epithelial cells and tumor cells using the adenomatous polyposis coli (Apc) mutant mouse model. A low level of protein 4.1B expression coincided with the phenotypic transition to carcinoma. To examine the protein 4.1B expression in human intestinal mucosa, we used another antibody against an isoform of the human protein 4.1B, DAL-1 (differentially expressed adenocarcinoma of the lung). Human DAL-1 was also expressed in matured epithelial cells in human colons, with a definite expression gradient along the crypt axis. In human colorectal cancer cells, however, DAL-1 expression was not detected. These results suggest that mouse protein 4.1B and human DAL-1 might have a striking analogy of functions, which may be integrally involved in epithelial proliferation. We propose that loss of protein 4.1B/DAL-1 expression might be a marker of intestinal tumors, indicative of a tumor suppressor function in the intestinal mucosa.

Protein 4.1 families have recently been established as potential organizers of an adherens system. In the adult mouse testis, protein 4.1G (4.1G) localized as a line pattern in both basal and adluminal compartments of the seminiferous tubules, attaching regions of germ cells and Sertoli cells. By double staining for 4.1G and F-actin, their localizations were shown to be different, indicating that 4.1G was localized in a region other than the basal and apical ectoplasmic specializations, which formed the Sertoli-Sertoli cell junction and Sertoli-spermatid junction, respectively. By electron microscopy, immunoreactive products were seen exclusively on the cell membranes of Sertoli cells, attaching to the various differentiating germ cells. The immunolocalization of cadherin was identical to that of 4.1G, supporting the idea that 4.1G may be functionally interconnected with adhesion molecules. In an experimental mouse model of cadmium treatment, in which tight and adherens junctions of seminiferous tubules were disrupted, the 4.1G immunostaining in the seminiferous tubules was dramatically decreased. These results indicate that 4.1G may have a basic adhesive function between Sertoli cells and germ cells from the side of Sertoli cells.

Although it was reported that protein 4.1 G, a cytoskeletal protein characterized by its general expression in the body, interacts with some signal transduction molecules in the central nervous system (CNS), its distribution and significance in vivo remained to be elucidated. In the present study, we have identified 4.1 G-positive cells in the rodent CNS, and demonstrated its immunolocalization in the developing mouse CNS. In the rodent CNS, 4.1 G was colocalized with markers for microglia, such as CD45, OX-42 and ionized calcium-binding adapter molecule 1 (Iba1), but not with markers for neuronal or other glial cells. Additionally, colocalization of 4.1 G and A1 adenosine receptor was observed in the mouse cerebrum. In a mixed glial culture, most OX-42-positive microglia were positive for 4.1 G, and 4.1 G isoforms of the same molecular weight as in the rat brain were expressed in cultured microglia, where 4.1 G mRNA was detected by RT-PCR. In the developing mouse cerebral cortex, 4.1 G was detected in immature microglia, which were positive for Iba1. These results indicate that 4.1 G in the CNS is mainly distributed in microglia in vivo. Considering the interactions between 4.1 G and the signal transduction molecules, putative roles have been proposed for 4.1 G in microglial functions in the CNS.

Protein 4.1 family proteins are thought to interact with membrane proteins and also membrane skeletons. In this study, immunohistochemical studies by light and electron microscopy were performed with a specific antibody against protein 4.1B. Specific protein 4.1B immunolabeling was observed in simple columnar epithelium in the adult rat large intestine, small intestine and stomach. Protein 4.1B immunolabeling was localized along the membranes facing the adjacent cells (lateral portion) and also facing the extracellular matrix (basal portion). Moreover, a spatial protein 4.1B expression gradient was observed along the crypt-villus axis of the rat small and large intestinal epithelium: strong protein 4.1B expression was present within the villus, with the crypt showing barely any detectable protein 4.1B. The expression of protein 4.1B was not detected in the stratified squamous epithelium in the forestomach or the esophagus. By immunoelectron microscopy, the immunolabeling of the cells was observed to be restricted to the cytoplasmic side just beneath the plasma membrane, including the membranes adjacent to the next cells, except for the tight junctions. We conclude that the protein 4.1B expression pattern is related to the maturation of simple columnar epithelium in the rat digestive system, probably by the effect of adhesion.

Protein 4.1 family proteins are thought to interact with membrane proteins and membrane skeletons. Immunohistochemical studies by light and electron microscopy were performed on mouse pancreas with a specific antibody against protein 4.1B. Specific protein 4.1B immunolabeling was observed on endocrine cells in the islets of Langerhans. Protein 4.1B localized along the plasma membranes facing adjacent cells. By immunoelectron microscopy, the immunolabeling of the cells was restricted to the cytoplasmic side just beneath their plasma membrane, including the membranes adjacent to neighboring cells, while the plasma membranes facing endothelial cells were not immunolabeled for protein 4.1B. The immunolocalization of E-cadherin was similar, if not identical, to that of protein 4.1B supporting the idea that protein 4.1B may be functionally interconnected with adhesion molecules. In a transgenic mouse model of pancreatic [beta]-cell carcinogenesis (Rip1Tag2), the loss of protein 4.1B expression coincided with the phenotypic transition from adenoma to carcinoma. Therefore, we propose a role of protein 4.1B as a connecting and/or signaling molecule between membrane architecture, cell adhesion, and tumor cell invasion in mouse pancreatic endocrine cells.