Biology subjects

Nagashima, M.

Publications and source records attributed to Nagashima, M..

25 records · Page 2Linked to original sources

bioRxiv2021

Heterogeneous pdgfrβ+ cells regulate coronary vessel development and revascularization during heart regeneration

Endothelial cells emerge from the atrioventricular canal (AVC) to form nascent coronary blood vessels in the juvenile zebrafish heart. We found that pdgfr{beta} is first expressed in the epicardium around the AVC and later becomes localized mainly in the mural cells. pdgfr{beta} mutant fish display severe defects in mural cell recruitment and coronary vessel development. pdgfr{beta}+ mural cells are heterogeneous and those associated with coronary arteries also express cxcl12b. Mural cells positive for both pdgfr{beta} and cxcl12b transgenic reporters had elevated expression of smooth muscle cell genes. Interestingly, these mural cells were associated with coronary arteries even in the absence of Pdgfr{beta}, although smooth muscle gene expression was downregulated in these cells. We found that pdgfr{beta} expression dynamically changes in the epicardium derived cells, which we found to be a heterogeneous population. mdka was identified as a gene upregulated in subpopulations of pdgfr{beta}+ cells during heart regeneration. However, pdgfr{beta} but not mdka mutants showed defects in heart regeneration. Our results demonstrated that pdgfr{beta}+ cells and Pdgfr{beta} signaling are essential for coronary development and heart regeneration. SUMMARY STATEMENTHeterogeneous pdgfr{beta} positive cells are present in developing and regenerating zebrafish hearts and are required for development of mural cells and their association with the nascent coronary vessels during zebrafish heart development and regeneration.

developmental biology↗

bioRxiv2020

Importin α2 associates with chromatin via a novel DNA binding domain

Nuclear transport of proteins is important for facilitating appropriate nuclear functions. The proteins of the importin family play key roles in nuclear transport as transport receptors for a huge number of nuclear proteins. Additionally, these proteins possess other functions, including chromatin association and gene regulation. However, these non-transport functions of importin are not yet fully understood, especially their molecular-level mechanisms for functioning with chromatin and their consequences. Here, we report the novel molecular characteristics of importin involving binding to diverse sequences in chromatin. We newly identified and characterized a DNA-binding domain--the Nucleic Acid Associating Trolley pole domain (NAAT domain)--in the N-terminal region of importin within the conventional importin {beta} binding (IBB) domain, which was shown to be necessary for nuclear transport of cargo proteins. We propose a stroll and locate model to explain the association of importin with chromatin. This is the first study to delineate the interaction between importin and chromatin DNA via the NAAT domain, indicating the bifunctionality of the importin N-terminal region for nuclear transport and chromatin association.

molecular biology↗

bioRxiv2020

Midkine-a functions as a universal regulator of proliferation during epimorphic regeneration in adult zebrafish

Zebrafish have the ability to regenerate damaged cells and tissues by activating quiescent stem and progenitor cells or reprogramming differentiated cells into regeneration-competent precursors. Proliferation among the cells that will functionally restore injured tissues is a fundamental biological process underlying regeneration. Midkine-a is a cytokine growth factor, whose expression is strongly induced by injury in a variety of tissues across a range of vertebrate classes. Using a zebrafish Midkine-a loss of function mutant, we evaluated regeneration of caudal fin, extraocular muscle and retinal neurons to investigate the function of Midkine-a during epimorphic regeneration. In wildtype zebrafish, injury among these tissues induces robust proliferation and rapid regeneration. In Midkine-a mutants, the initial proliferation in each of these tissues is significantly diminished or absent. Regeneration of the caudal fin and extraocular muscle is delayed; regeneration of the retina is nearly completely absent. These data demonstrate that Midkine-a is universally required in the signaling pathways that convert tissue injury into the initial burst of cell proliferation. Further, these data highlight differences in the molecular mechanisms that regulate epimorphic regeneration in zebrafish.

developmental biology↗

bioRxiv2019

Defect patterns on the curved surface of fish retinae suggest mechanism of cone mosaic formation

The outer epithelial layer of zebrafish retinae contains a crystalline array of cone photoreceptors, called the cone mosaic. As this mosaic grows by mitotic addition of new photoreceptors at the rim of the hemispheric retina, topological defects, called \"Y-Junctions\", form to maintain approximately constant cell spacing. The generation of topological defects due to growth on a curved surface is a distinct feature of the cone mosaic not seen in other well-studied biological patterns like the R8 photoreceptor array in the Drosophila compound eye. Since defects can provide insight into cell-cell interactions responsible for pattern formation, we characterize the arrangement of cones in individual Y-Junction cores as well as the spatial distribution of Y-junctions across entire retinae. We find that for individual Y-junctions, the distribution of cones near the core corresponds closely to structures observed in physical crystals. In addition, Y-Junctions are organized into lines, called grain boundaries, from the retinal center to the periphery. In physical crystals, regardless of the initial distribution of defects, grain boundaries can form via the mobility of individual particles. By imaging in live fish, we demonstrate that grain boundaries in the cone mosaic instead appear during initial mosaic formation, without requiring defect motion. Motivated by this observation, we show that a computational model of repulsive cell-cell interactions generates a mosaic with grain boundaries. In contrast to paradigmatic models of fate specification in mostly motionless cell packings, this study emphasizes the role of cell motion, guided by cell-cell interactions during differentiation, in forming biological crystals. Such a route to the formation of regular patterns may be especially valuable in situations, like growth on a curved surface, where long-ranged, elastic, effective interactions between defects can help to group them into grain boundaries.\n\nAUTHOR SUMMARYFrom hair cells in the mammalian inner ear to the bristles on a flys back, sensory cells often form precise arrays, ensuring that these cells are evenly spread out on the tissues surface. Here we consider the zebrafish cone mosaic, a crystal of cone photoreceptors in the outer retinal layer. Because the cone mosaic grows from the rim of the curved retinal surface, new rows of cones (i.e., defects) are inserted to maintain constant spacing between sensory cells. We study the spatial distribution of these defects to gain insight into how the cone pattern forms. By imaging retinae in live fish, we find that as differentiating cones are incorporated into the mosaic, defects form lines (grain boundaries) that separate mostly defect-free domains. Then, we show that a computational model based on repulsion between mobile cells during their incorporation into the mosaic generates similar grain boundaries. This study thus suggests that cell motion governed by repulsive cell-cell interactions can play an important role in establishing regular patterns in living systems.

biophysics↗

bioRxiv2019

Midkine-a is required for cell cycle progression of Müller glia during neuronal regeneration

In zebrafish, Muller glia function as intrinsic retinal stem cells that can regenerate ablated neurons. Understanding the mechanisms governing neuronal stem cells may provide clues to regenerate neurons in mammals. We report that in Muller glia the cytokine/growth factor, Midkine-a, functions as a core autocrine regulator of the cell cycle. Utilizing midkine-a mutants, we determined that Midkine-a regulates elements of an Id2a-retinoblastoma network in reprogrammed Muller glia that controls the expression of cell cycle genes and is required for transition from G1 to S phases of the cell cycle. In mutants, Muller glia that fail to divide undergo reactive gliosis, a pathological hallmark of Muller glia in mammals. Finally, we show that activation of the Midkine-a receptor, ALK, is required for Muller glia proliferation. These data provide mechanistic insights into Muller glia stem cells in the vertebrate retina and suggest avenues for eliciting neuronal regeneration in mammals.

developmental biology↗

bioRxiv2019

Higher seroprevalence of Entamoeba histolytica than that of HIV-1 at a voluntary counselling and testing centre in Tokyo

BackgroundAmebiasis, which is caused by Entamoeba histolytica, is a re-emerging public health issue owing to sexually transmitted infection (STI) in Japan. However, epidemiological data are quite limited. MethodologyTo reveal the relative prevalence of sexually transmitted E. histolytica infection to other STIs, we conducted a cross-sectional study at a voluntary counselling and testing (VCT) centre in Tokyo. Seroprevalence of E. histolytica was assessed according to positivity with an enzyme-linked immunosorbent assay for E. histolytica-specific IgG in serum samples collected from anonymous VCT clients. Principal FindingsAmong 2,083 samples, seropositivity for E. histolytica was 2.64%, which was higher than that for HIV-1 (0.34%, p < 0.001) and comparable to that for syphilis (rapid plasma reagin (RPR) 2.11%, p = 0.31). Positivity for Chlamydia trachomatis in urine by transcription-mediated amplification (TMA) was 4.59%. Seropositivity for E. histolytica was high among RPR-or Treponema pallidum hemagglutination (TPHA)-positive individuals and it was not different between clients with and without other STIs. Both seropositivity of E. histolytica and RPR were high among male clients. The seropositive rate for anti-E. histolytica antibody was positively correlated with age. TMA positivity for urine C. trachomatis was high among female clients and negatively correlated with age. Regression analysis identified that male sex, older age, and TPHA-positive results are independent risk factors of E. histolytica seropositivity. ConclusionsSeroprevalence of E. histolytica was 7.9 times higher than that of HIV-1 at a VCT centre in Tokyo, with a tendency to be higher among people at risk for syphilis infection. Author summaryAmebiasis caused by Entamoeba histolytica is an increasingly prevalent sexually transmitted infection (STI) in Japan; however, relative to other STIs, the prevalence of E. histolytica has not been fully assessed. We investigated the seropositivity of E. histolytica using serum samples from 2,083 clients of a voluntary counselling and testing centre in Tokyo. E. histolytica seroprevalence (2.64%) was 7.9 times higher than that of HIV-1 (0.31%) and the same as that of syphilis (rapid plasma reagin: 2.11%). Logistic regression analysis showed that E. histolytica seroprevalence tended to be higher among individuals who were male, older, and positive in Treponema pallidum hemagglutination. These results strongly suggest that public health interventions should be considered to control sexual transmission of E. histolytica infection, which is currently neglected in Japan.

microbiology↗

bioRxiv2019

Inflammation and matrix metalloproteinase 9 (Mmp-9) regulate photoreceptor regeneration in the adult zebrafish

Brain injury activates complex inflammatory signals in dying neurons, surviving neurons, and glia. Here, we establish that inflammation regulates the regeneration of photoreceptors in the zebrafish retina and determine the cellular expression and function of the inflammatory protease, matrix metalloproteinase 9 (Mmp-9), during this regenerative neurogenesis. Following sterile photoreceptor ablation anti-inflammatory treatment suppresses both the number of injury-induced progenitors and regenerated photoreceptors. Upon photoreceptor injury, mmp-9 is induced in Muller glia, the intrinsic retinal stem cell, and Muller glia-derived photoreceptor progenitors. Deleting mmp-9 results in over production of injury-induced progenitors and regenerated photoreceptors, but over time the absence of Mmp-9 compromises the maturation and survival of the regenerated cones. Anti-inflammatory treatment in mutants rescues the defects in cone maturation and survival. These data provide a link between injury-induced inflammation in the vertebrate CNS, Mmp-9 function during photoreceptor regeneration and the requirement of Mmp-9 for the survival of regenerated cones. Significance StatementThe innate immune system is activated by neuronal death, and recent studies demonstrate that in zebrafish neuroinflammation is required for neuronal regeneration. The roles of inflammatory cytokines are being investigated, however, the function of the inflammatory protease, matrix metalloprotease Mmp-9, in neuronal regeneration is unknown. We show herein that in adult zebrafish retinal inflammation governs the proliferative phase of the stem cell-based regeneration of rod and cone photoreceptors and determine the specific roles for Mmp-9 in photoreceptor regeneration. This study provides the first mechanistic insights into the potential role of Mmp-9 and serves to link neuroinflammation, stem cell-based regeneration of photoreceptors and human photoreceptor disease.

neuroscience↗