Biology subjects

Goto, M.

Publications and source records attributed to Goto, M..

25 records · Page 2Linked to original sources

bioRxiv2020

Movements of ancient human endogenous retroviruses detected in SOX2-expressing cells

Human endogenous retroviruses (HERVs) occupy approximately 8% of human genome. HERVs, which are transcribed in early embryos, are epigenetically silenced in somatic cells, except in pathological contexts. HERV-K is thought to protect the embryo from exogenous viral infection. However, uncontrollable HERV-K expression in somatic cells has been implicated in several diseases. Here, we show that SOX2, which plays a key role in maintaining pluripotency of stem cells, is critical for the transcription of HERV-K LTR5Hs. HERV-K can undergo retrotransposition within producer cells in the absence of Env expression. Furthermore, new HERV-K integration sites were identified in a long-term culture of induced pluripotent stem cells, which express SOX2. Together, these results suggest the possibility that the strict dependence of HERV-K on SOX2 have allowed contribution of HERV-K to the protection of early embryos during evolution while limiting potentially harmful effects of HERV-K retrotransposition on host genome integrity to these early embryos.

microbiology↗

bioRxiv2020

Downregulation of a Type III Secretion System under Reducing Conditions in Bordetella pertussis

Bordetella pertussis uses a type III secretion system (T3SS) to inject virulence proteins into host cells. Although the B. pertussis T3SS was presumed to be involved in host colonization, the efficient secretion of type III secreted proteins from B. pertussis has not been observed. To investigate the roles of type III secreted proteins during infection, we attempted to optimize culture conditions for the production and secretion of a type III secreted protein, BteA, in B. pertussis. We observed that B. pertussis efficiently secretes BteA in ascorbic acid-depleted (AsA-) medium. When L2 cells, a rat lung epithelial cell line, were infected with B. pertussis cultured in the AsA- medium, BteA-dependent cytotoxicity was observed. We also performed an immunofluorescence assay of L2 cells infected with B. pertussis. The clear fluorescence signals of Bsp22, a needle structure of T3SS, were detected on the bacterial surface of B. pertussis cultured in the AsA- medium. Since ascorbic acid is known as a reducing agent, we cultured B. pertussis in liquid medium containing other reducing agents such as 2-mercaptoethanol and dithioerythritol. Under these reducing conditions, the production of type III secreted proteins was repressed. These results suggest that in B. pertussis, the production and secretion of type III secreted proteins are downregulated under reducing conditions. IMPORTANCEThe type III secretion system (T3SS) of Bordetella pertussis forms a needle-like structure that protrudes from the bacterial cell surface. B. pertussis uses T3SS to translocate virulence proteins called effectors into host cells. The culture conditions for effector production in B. pertussis have not been investigated. We attempted to optimize culture medium compositions for producing and secreting type III secreted proteins. We found that B. pertussis secretes type III secreted proteins in reducing agent-deprived liquid medium, and that BteA-secreting B. pertussis provokes cytotoxicity against cultured mammalian cells. These results suggest that redox signaling is involved in the regulation of B. pertussis T3SS.

microbiology↗

bioRxiv2019

LaeA controls citric acid production through regulation of a citrate exporter encoding cexA in Aspergillus luchuensis mut. kawachii

The putative methyltransferase LaeA is a global regulator of metabolic and development processes in filamentous fungi. We characterized the homologous laeA genes of the white koji fungus Aspergillus luchuensis mut. kawachii (A. kawachii) to determine their role in the hyperproduction of citric acid. The {Delta}laeA strain exhibited a significant reduction in citric acid productivity. Cap-analysis gene expression (CAGE) revealed that laeA is required for the gene expression of a putative citrate exporter encoding cexA, which is critical for citric acid production. The deficit in the productivity of citric acid by the {Delta}laeA strain was rescued by the overexpression of cexA to a level comparable with that of the cexA-overexpressing {Delta}cexA strain. In addition, chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) analysis indicated that LaeA regulates the expression of cexA via methylation levels of the histones H3K4 and H3K9. These results indicate that LaeA is involved in citric acid production through epigenetic regulation of cexA in A. kawachii.\n\nIMPORTANCEA. kawachii has been traditionally used for production of the distilled spirit shochu in Japan. Citric acid produced by A. kawachii plays an important role in preventing microbial contamination during the shochu fermentation process. This study characterized homologous laeA genes; using CAGE, complementation test, and ChIP-qPCR, it was found that laeA is required for citric acid production though regulation of cexA in A. kawachii. The epigenetic regulation of citrate production elucidated in this study will be useful for controlling the fermentation processes of shochu.

microbiology↗

bioRxiv2019

Evaluation of biodiversity metrics through environmental DNA metabarcoding outperforms visual and capturing surveys

O_LIInformation on alpha (local), beta (between habitats), and gamma (regional) diversity is fundamental to understanding biodiversity as well as the function and stability of community dynamics. Methods like environmental DNA (eDNA) metabarcoding are currently considered useful to investigate biodiversity. C_LIO_LIWe compared the performance of eDNA metabarcoding with visual and capture surveys for estimating alpha and gamma diversity of river fish communities, and nestedness and turnover in particular. C_LIO_LIIn five rivers across west Japan, by comparison to visual/capture surveys, eDNA metabarcoding detected more species in the study sites (i.e., alpha diversity). Consequently the overall number of species in the region (i.e., gamma diversity) was higher. In particular, the species found by visual/capture surveys were encompassed by those detected by eDNA metabarcoding. C_LIO_LIEstimates of community diversity within rivers differed between survey methods. Although we found that the methods show similar levels of community nestedness and turnover within the rivers, visual/capture surveys showed more distinct community differences from upstream to downstream. Our results suggest that eDNA metabarcoding may be a suitable method for community assemblage analysis, especially for understanding regional community patterns, for fish monitoring in rivers. C_LI

ecology↗

bioRxiv2018

Ectopic expression induces abnormal somatodendritic distribution of tau in the mouse brain

Tau is a microtubule-associated protein that is localized to the axon. In Alzheimers disease, the distribution of tau undergoes a remarkable alteration, leading to the formation of tau inclusions in the somatodendritic compartment. To investigate how this mis-localization occurs, we recently developed immunohistochemical techniques that can separately detect endogenous mouse and exogenous human tau with high sensitivity, which allows us to visualize not only the pathological but pre-aggregated tau in mouse brain tissues of both sex. In tau transgenic mouse brains, exogenous human tau was abundant in dendrites and somata even in the presymptomatic period, whereas the axonal localization of endogenous mouse tau was unaffected. In stark contrast, exogenous tau was properly localized to the axon in human tau knock-in mice. We tracked this difference to the temporal expression patterns of tau. Tau mRNA was continuously expressed in the transgenic mice, whereas endogenous tau and exogenous tau in the knock-in mice exhibited high expression levels during the neonatal period and strong suppression into the adulthood. These results indicated the uncontrolled expression of exogenous tau beyond the developmental period as a cause of mis-localization in the transgenic mice. Super-resolution microscopic and biochemical analyses also indicated that the interaction between microtubules and exogenous tau was indeed impaired in the tau transgenic mice. Thus, the ectopic expression of tau may be critical for its somatodendritic mis-localization, a key step of the tauopathy.\n\nSignificance StatementSomatodendritic localization of tau may be an early step leading to the neuronal degeneration in tauopathies. However, the mechanisms of the normal axonal distribution of tau and the mis-localization of pathological tau remain obscure. Our immunohistochemical and biochemical analyses demonstrated that the endogenous mouse tau is transiently expressed in neonatal brains, that exogenous human tau expressed corresponding to such tau expression profile can distribute into the axon, and that the constitutive expression of tau into adulthood (ex. human tau in Tg mice) results in abnormal somatodendritic localization. Thus, the expression profile of tau is tightly associated with the localization of tau, and the ectopic expression of tau in matured neurons may be involved in the pathogenesis of tauopathy.

neuroscience↗

bioRxiv2018

Mitochondrial citrate transporters CtpA and YhmA are involved in lysine biosynthesis in the white koji fungus, Aspergillus luchuensis mut. kawachii

Aspergillus luchuensis mut. kawachii produces a large amount of citric acid during the process of fermenting shochu, a traditional Japanese distilled spirit. In this study, we characterized A. kawachii CtpA and YhmA, which are homologous to the yeast Saccharomyces cerevisiae mitochondrial citrate transporters Ctp1 and Yhm2, respectively. CtpA and YhmA were purified from A. kawachii and reconstituted into liposomes. The proteoliposomes exhibited only counter-exchange transport activity; CtpA transported citrate using counter substrates especially for cis-aconitate and malate, whereas YhmA transported citrate using a wider variety of counter substrates, including citrate, 2-oxoglutarate, malate, cis-aconitate, and succinate. Disruption of ctpA and yhmA caused deficient hyphal growth and conidia formation with reduced mycelial weight-normalized citrate production. Because we could not obtain a {Delta}ctpA {Delta}yhmA strain, we constructed a ctpA-S conditional expression strain in the {Delta}yhmA background using the Tet-On promoter system. Knockdown of ctpA-S in {Delta}yhmA resulted in a severe growth defect on minimal medium, indicating that double disruption of ctpA and yhmA leads to synthetic lethality; however, we subsequently found that the severe growth defect was relieved by addition of lysine. Our results indicate that CtpA and YhmA are mitochondrial citrate transporters involved in citric acid production and that transport of citrate from mitochondria to the cytosol plays an important role in lysine biogenesis in A. kawachii.\n\nIMPORTANCECitrate transport is believed to play a significant role in citrate production by filamentous fungi; however, details of the process remain unclear. This study characterized two citrate transporters from Aspergillus luchuensis mut. kawachii. Biochemical and gene disruption analyses showed that CtpA and YhmA are mitochondrial citrate transporters required for normal hyphal growth, conidia formation, and citric acid production. In addition, this study provided insights into the links between citrate transport and lysine biosynthesis. The characteristics of fungal citrate transporters elucidated in this study will help expand our understanding of the citrate production mechanism and facilitate the development and optimization of industrial organic acid fermentation processes.

microbiology↗

bioRxiv2017

HNF1A is a Novel Oncogene and Central Regulator of Pancreatic Cancer Stem Cells

The biological properties of pancreatic cancer stem cells (PCSCs) remain incompletely defined and the central regulators are unknown. By bioinformatic analysis of a PCSC-enriched gene signature, we identified the transcription factor HNF1A as a putative central regulator of PCSC function. Levels of HNF1A and its target genes were found to be elevated in PCSCs and tumorspheres, and depletion of HNF1A resulted in growth inhibition, apoptosis, impaired tumorsphere formation, PCSC depletion, and downregulation of OCT4 expression. Conversely, HNF1A overexpression increased PCSC numbers and tumorsphere formation in pancreatic cancer cells and drove PDA cell growth. Importantly, depletion of HNF1A in primary tumor xenografts impaired tumor growth and depleted PCSCs in vivo. Finally, we established an HNF1A-dependent gene signature in PDA cells that significantly correlated with reduced survivability in patients. These findings identify HNF1A as a central transcriptional regulator of the PCSC state and novel oncogene in pancreatic ductal adenocarcinoma.

cancer biology↗