Biology subjects

Horie, M.

Publications and source records attributed to Horie, M..

26 records · Page 2Linked to original sources

bioRxiv2021

The mechanism underlying the organization of Borna disease virus inclusion bodies is unique among mononegaviruses

Inclusion bodies (IBs) are characteristic biomolecular condensates organized by mononegaviruses. Here, we characterize the IBs of Borna disease virus 1 (BoDV-1), a unique mononegavirus that forms IBs in the nucleus, in terms of liquid-liquid phase separation (LLPS). The BoDV-1 phosphoprotein (P) alone induces LLPS and the nucleoprotein (N) is incorporated into the P droplet in vitro. In contrast, co-expression of N and P is required for the formation of IB-like structure in cells. Furthermore, while BoDV-1 P binds to RNA, an excess amount of RNA dissolves the liquid droplets formed by N and P. Notably, the N-terminal intrinsically disordered region of BoDV-1 P is essential to drive LLPS and bind to RNA, suggesting that both abilities could compete with one another. These features are unique among mononegaviruses, and thus this study will contribute to a deeper understanding of LLPS-driven organization and RNA-mediated regulation of biomolecular condensates.

microbiology↗

bioRxiv2021

Hidden viral sequences in public sequencing data and warning for future emerging diseases

RNA viruses cause numerous emerging diseases, mostly due to transmission from mammalian and avian reservoirs. Large-scale surveillance of RNA viral infections in these animals is a fundamental step for controlling viral infectious diseases. Metagenomic analysis is a powerful method for virus identification with low bias and has substantially contributed to the discovery of novel viruses. Deep sequencing data have been collected from diverse animals and accumulated in public databases, which can be valuable resources for identifying unknown viral sequences. Here, we screened for infections of 33 RNA viral families in publicly available mammalian and avian sequencing data and found approximately 900 hidden viral infections. We also discovered six nearly complete viral genomes in livestock, wild, and experimental animals: hepatovirus in a goat, hepeviruses in blind mole-rats and a galago, astrovirus in macaque monkeys, parechovirus in a cow, and pegivirus in tree shrews. Some of these viruses were phylogenetically close to human pathogenic viruses, suggesting the potential risk of causing disease in humans upon infection. Furthermore, the infections of five novel viruses were identified in several different individuals, indicating that their infections may have already spread in the natural host population. Our findings demonstrate the reusability of public sequencing data for surveying viral infections and identifying novel viral sequences, presenting a warning about a new threat of viral infectious disease to public health. ImportanceMonitoring the spread of viral infections and identifying novel viruses capable of infecting humans through animal reservoirs are necessary to control emerging viral diseases. Massive amounts of sequencing data collected from various animals are publicly available, and these data may contain sequences originating from a wide variety of viruses. Here, we analyzed more than 46,000 public sequencing data and identified approximately 900 hidden RNA viral infections in mammalian and avian samples. Some viruses discovered in this study were genetically similar to pathogens that cause hepatitis, diarrhea, or encephalitis in humans, suggesting the presence of new threats to public health. Our study demonstrates the effectiveness of reusing public sequencing data to identify known and unknown viral infections, indicating that future continuous monitoring of public sequencing data by metagenomic analyses would help prepare and mitigate future viral pandemics.

microbiology↗

bioRxiv2021

Enhanced CICR activity reduces ER Ca2+ level in cells expressing CPVT-linked mutant RyR2

Type 2 ryanodine receptor (RyR2) is a cardiac Ca2+ release channel in the endoplasmic reticulum (ER). Mutations in RyR2 are linked to catecholaminergic polymorphic ventricular tachycardia (CPVT), which is considered to be associated with enhanced spontaneous Ca2+ release. This spontaneous Ca2+ release tends to occur when ER Ca2+ ([Ca2+]ER) reaches a certain threshold level, and CPVT mutations are reported to lower this threshold. There are two explanations for this lowered threshold: the mutations increase sensitivity to luminal Ca2+ or they enhance cytosolic [Ca2+] ([Ca2+]cyt)-induced Ca2+ release (CICR) activity. However, no quantitative analysis of this issue has been performed so far. Here, we quantitatively explored how the change in CICR activity of RyR2 affects the threshold [Ca2+]ER experimentally and by model-based simulation. Wild-type (WT) and CPVT-linked mutant RyR2s were expressed in HEK293 cells. [Ca2+]cyt and [Ca2+]ER measurements with Ca2+ indicators revealed that CPVT RyR2 cells showed higher oscillation frequency and lower threshold [Ca2+]ER in a mutation-specific manner compared with WT cells. The CICR activity of mutant RyR2s was assessed by Ca2+-dependent [3H]ryanodine binding and parameter analysis. CICR activity at resting [Ca2+]cyt, A7.0, was higher in CPVT mutants than in WT and a strong inverse correlation was found between threshold [Ca2+]ER and A7.0. Interestingly, lowering RyR2 expression increased threshold [Ca2+]ER, suggesting that the threshold [Ca2+]ER depends on net Ca2+ release rate via RyR2, a product of A7.0 for each mutant and the density of RyR2 molecules. A model-based simulation successfully reproduced the [Ca2+]cyt and [Ca2+]ER changes. Interestingly, the CICR activity associated with specific mutations correlated well with the age of onset of the disease in CPVT patients carrying the mutations. Our data suggest that the reduction in threshold [Ca2+]ER for spontaneous Ca2+ release by CPVT mutation is explained by enhanced CICR activity without considering a change in the [Ca2+]ER sensitivity of RyR2. SummaryCPVT-linked RyR2 mutations are prone to induce spontaneous Ca2+ release from ER, which is strongly associated with arrhythmias. Kurebayashi et al. quantitatively explore how the changes in CICR activity by RyR2 mutations affect spontaneous Ca2+ experimentally and by model simulation.

physiology↗

bioRxiv2020

One hundred million years history of bornavirus infections hidden in vertebrate genomes

Although viruses have threatened our ancestors for millions of years, prehistoric epidemics of viruses are largely unknown. Endogenous bornavirus-like elements (EBLs) are ancient viral sequences that have been integrated into animal genomes. These elements can be used as molecular fossil records to trace past bornaviral infections. In this study, we systematically identified EBLs in vertebrate genomes and revealed the history of bornavirus infections over nearly 100 million years. We found that ancient bornaviral infections have occurred in diverse vertebrate lineages, especially in primate ancestors. Phylogenetic analyses indicated that primate ancestors had been infected with various bornaviral lineages during evolution. Moreover, EBLs in primate genomes formed clades according to their integration ages, suggesting that epidemic lineages of bornaviruses had changed chronologically. However, we found that some bornaviral lineages coexisted with primate ancestors and underwent repeated endogenizations for tens of millions of years. Furthermore, this viral lineage that coexisted with primate ancestors was also endogenized in some ancestral bats. Notably, the geographic distributions of these bat ancestors have been reported to overlap with the migration route of primate ancestors, suggesting that long-term virus-host coexistence could have expanded the geographic distributions of the viral lineage and might have spread their infections to new hosts. Thus, our findings describe hidden virus-host co-evolutionary history over geological timescales, including chronological change in epidemic bornaviral lineages, long-term virus-host coexistence, and expansion of viral infections.

microbiology↗

bioRxiv2020

Identifications of novel avian and mammalian deltaviruses filled the large evolutionally gaps and revealed inter-family transmission of deltaviruses

Hepatitis delta virus (HDV) is a satellite virus that requires hepadnavirus envelope proteins for its transmission. Although recent studies identified HDV-related deltaviruses in certain animals, the evolution of deltaviruses, such as the origin of HDV and the mechanism of its coevolution with its helper viruses, is unknown, mainly because of the phylogenetic gaps among deltaviruses. Here we identified novel deltaviruses of passerine birds, woodchucks, and white-tailed deer by extensive database searches and molecular surveillance. Phylogenetic and molecular epidemiological analyses suggest that HDV originated from mammalian deltaviruses and the past interspecies transmission of mammalian and passerine deltaviruses. Further, metaviromic and experimental analyses suggest that the satellite-helper relationship between HDV and hepadnavirus was established after the divergence of the HDV lineage from non-HDV mammalian deltaviruses. Our findings enhance our understanding of deltavirus evolution, diversity, and transmission, indicating the importance of further surveillance for deltaviruses.

microbiology↗

bioRxiv2019

Reciprocal connectivity between secondary auditory cortical field and amygdala in mice

Recent studies have examined the feedback pathway from the amygdala to the auditory cortex in conjunction with the feedforward pathway from the auditory cortex to the amygdala. However, these connections have not been fully characterized. Here, to visualize the comprehensive connectivity between the auditory cortex and amygdala, we injected cholera toxin subunit b (CTB), a bidirectional tracer, into multiple subfields in the mouse auditory cortex after identifying the location of these subfields using flavoprotein fluorescence imaging. After injecting CTB into the secondary auditory field (A2), we found densely innervated CTB-positive axon terminals that were mainly located in the lateral amygdala (La), and slight innervations in other divisions such as the basal amygdala. Moreover, we found a large number of retrogradely-stained CTB-positive neurons in La after injecting CTB into A2. When injecting CTB into the primary auditory cortex (A1), a small number of CTB-positive neurons and axons were visualized in the amygdala. Finally, we found a near complete absence of connections between the other auditory cortical fields and the amygdala. These data suggest that reciprocal connections between A2 and La are main conduits for communication between the auditory cortex and amygdala in mice.

neuroscience↗

bioRxiv2018

Nell2 regulates the contralateral-versus-ipsilateral visual projection as a layer-specific positional cue

SUMMARY STATEMENTNell2 is an ipsilateral layer-specific axon guidance cue in the visual thalamus and contributes to establishment of the eye-specific retinogeniculate projection by specifically inhibiting contralateral retinal axons.\n\nABSTRACTIn mammals with binocular vision, retinal ganglion cell (RGC) axons from each eye project to eye-specific layers in the contralateral and ipsilateral dorsal lateral geniculate nucleus (dLGN). Although layer-specific axon guidance cues that discriminate contralateral and ipsilateral RGC axons have long been postulated as a key mechanism for development of the eye-specificretinogeniculate projection, the molecular nature of such cues has remained elusive. Here we show that the extracellular glycoprotein Nell2 (also known as Nel) is expressed in the dorsomedial region of the dLGN, which corresponds to the layer receiving ipsilateral RGC axons. In Nell2 mutant mice, contralateral RGC axons invaded the ipsilateral layer of the dLGN, and ipsilateral axons terminated in partially fragmented patches, forming a mosaic pattern of contralateral and ipsilateral axon termination zones. In vitro, Nell2 exerted inhibitory effects on contralateral, but not ipsilateral, RGC axons. These results provide evidence that Nell2 acts as a layer-specific positional label in the dLGN that discriminates contralateral and ipsilateral RGC axons, and that it plays essential roles in establishment of the eye-specific projection patterns in the retinogeniculate system.

developmental biology↗

bioRxiv2017

Thalamocortical Projectional Divergence Leads to Complexity in Functional Organizations in Mouse Auditory Cortex

Frequency-related topological projections from the ventral division of the medial geniculate body (MGv) relay the tonotopic organization found in primary auditory cortex (A1). However, relaying circuits of the functional organization to higher-order, secondary auditory field (A2) have not been identified so far. Here, using tracing, we found that A2 receives dense topological projections from MGv in mice, and that tonotopy was established in A2 even when primary fields including A1 were removed. These indicate that thalamic inputs to A2 are sufficient for generating its tonotopy. Moreover, neuronal responses in the thalamocortical recipient layer of A2 showed wider bandwidth and greater heterogeneity of the best frequency distribution than those of A1, which was attributed to larger divergence of thalamocortical projections from MGv to A2 than those from MGv to A1. The current study identifies that the functional organization in the auditory cortex can be determined by the structure of thalamocortical input.\n\nSignificant StatementAlthough peripheral input patterns to the primary auditory cortex (A1) of the brain are well understood, how tonal information is relayed to higher-order regions such as the secondary auditory field (A2) remains unclear. This work revealed a new source of auditory information to A2; the tonal map in mouse A2 is primarily produced by orderly projections from the primary auditory thalamus. We also found that the complex behaviour and organization of neurons in A2 is generated by divergent projections from the primary thalamus that converge on neurons in A2. Our findings indicate that thalamocortical projections constitute a major factor that determines the regional properties and functional organization of mouse A2.

neuroscience↗