Biology subjects

Nagashima, M.

Publications and source records attributed to Nagashima, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Spatially distinct microglia coordinate the response to photoreceptor injury in zebrafish

Microglia exhibit substantial molecular and functional heterogeneity, however, how the local tissue environment influences their responses to neuronal injury remains poorly understood. The zebrafish retina provides a unique opportunity to examine this relationship, because in addition to microglia within the retinal parenchyma, it contains a distinct population that resides within the subretinal space. In this study, we characterize the anatomical distribution and molecular heterogeneity of retinal microglia in zebrafish and examine their response to selective photoreceptor injury. Retinal microglia occupied distinct anatomical niches and exhibited diverse transcriptional states, including complement associated, proliferative, and apoc1/apoeb-enriched populations, suggesting that microglial heterogeneity reflects both tissue context and cellular. Following damage both subretinal and parenchymal microglia rapidly alter their morphology and migrate toward the injured site, resulting in their accumulation in the subretinal space. Microglia subsequently proliferate predominantly within this compartment. By 14 days post lesion, when photoreceptor regeneration is nearly completed, microglial morphology, distribution, and the number largely return to their unlesioned state. In contrast to the dynamic response of retinal microglia, response of microglia within the optic tectum was negligible. To investigate the mechanisms underlying the maintenance of these distinct microglial populations and their injury-induced responses, we examined retinal microglia in csf1ra mutants. In mutants lacking colony stimulating factor 1 receptor a (Csf1ra), parenchymal microglia are markedly reduced, whereas the number of subretinal microglia is preserved. Photoreceptor death following photolytic injury was comparable between csf1ra mutants and wildtype animals, and both parenchymal and subretinal microglia responded to the injury. However, proliferation of microglia in csf1ra mutants was severely impaired, and the normal redistribution of parenchymal microglia was not restored. These findings identify distinct anatomical and molecular features of retinal microglia and demonstrate that Csf1ra signaling differentially regulates microglial maintenance and injury-induced dynamics during photoreceptor regeneration.

neuroscience↗

bioRxiv2026

Muller glia mediated regeneration restores neuronal diversity and retinal circuit organization in the adult zebrafish

The ability to regenerate neurons with appropriate identities and circuit connectivity is a fundamental challenge in regenerative biology. Unlike mammals, adult zebrafish robustly regenerate retinal neurons after injury through the reprogramming of Muller glia. However, the extent to which regenerated neurons faithfully reconstruct molecular identity, cellular diversity, and circuit organization remains unclear. Here, we combined inducible lineage tracing, single-cell RNA sequencing and high-resolution morphological analysis to define the molecular identities and structural organization of regenerated neurons following photoreceptor-selective light lesion or NMDA-induced inner retinal injury. Both injury paradigms regenerated all major retinal cell classes, although the relative abundance of regenerated cell types reflected the pattern of neuronal loss. Across major neuronal classes and subtypes, regenerated neurons largely reestablished endogenous molecular identities, with the residual transcriptional differences primarily reflecting ongoing maturation. Regenerated amacrine and bipolar neurons recovered subtype diversity, characteristic dendritic morphologies, and laminar organization. Regenerated retinal ganglion cells likewise restored broad molecular diversity and appropriate retinotectal projections, while a subset underwent microglia-mediated refinement. Together, these findings demonstrate that Muller glia-mediated regeneration largely reconstructs neuronal identity, cellular diversity and key features of retinal circuit organization, providing insights into understanding how complex neuronal tissues are rebuilt after injury.

neuroscience↗

bioRxiv2024

Virological characteristics of the SARS-CoV-2 XEC variant

The SARS-CoV-2 JN.1 variant (BA.2.86.1.1), arising from BA.2.86.1 with spike protein (S) substitution S:L455S, outcompeted the previously predominant XBB lineages by the beginning of 2024. Subsequently, JN.1 subvariants including KP.2 (JN.1.11.1.2) and KP.3 (JN.1.11.1.3), which acquired additional S substitutions (e.g., S:R346T, S:F456L, and S:Q493E), have emerged concurrently. As of October 2024, KP.3.1.1 (JN.1.11.1.3.1.1), which acquired S:31del, outcompeted other JN.1 subvariants including KP.2 and KP.3 and is the most predominant SARS-CoV-2 variant in the world. Thereafter, XEC, a recombinant lineage of KS.1.1 (JN.13.1.1.1) and KP.3.3 (JN.1.11.1.3.3), was first identified in Germany on August 7, 2024. XEC acquired two S substitutions, S:T22N and S:F59S, compared with KP.3 through recombination, with a breakpoint at genomic position 21,738-22,599. We estimated the relative effective reproduction number (Re) of XEC using a Bayesian multinomial logistic model based on genome surveillance data from the USA, the United Kingdom, France, Canada, and Germany, where this variant has spread as of August 2024. In the USA, the Re of XEC is 1.13-fold higher than that of KP.3.1.1. Additionally, the other countries under investigation herein showed higher Re for XEC. These results suggest that XEC has the potential to outcompete the other major lineage including KP.3.1.1. We then assessed the virological properties of XEC using pseudoviruses. Pseudovirus infection assay showed that the infectivity of KP.3.1.1 and XEC was significantly higher than that of KP.3. Although S:T22N did not affect the infectivity of the pseudovirus based on KP.3, S:F59S significantly increased it. Neutralization assay was performed using three types of human sera: convalescent sera after breakthrough infection (BTI) with XBB.1.5 or KP.3.3, and convalescent sera after JN.1 infection. In all serum groups, XEC as well as KP.3.1.1 showed immune resistance when compared to KP.3 with statistically significant differences. In the cases of XBB.1.5 BTI sera and JN.1 infection sera, the 50% neutralization titers (NT50s) of XEC and KP.3.1.1 were comparable. However, we revealed that the NT50 of XEC was significantly (1.3-fold) lower than that of KP.3.1.1. Moreover, both S:T22N and S:F59S significantly (1.5-fold and 1.6-fold) increased the resistance to KP.3.3 BTI sera. Here we showed that XEC exhibited higher pseudovirus infectivity and higher immune evasion than KP.3. Particularly, XEC exhibited more robust immune resistance to KP.3.3 BTI sera than KP.3.1.1. Our data suggest that the higher Re of XEC than KP.3.1.1 is attributed to this property and XEC will be a predominant SARS-CoV-2 variant in the world in the near future.

microbiology↗

bioRxiv2024

Virological characteristics of the SARS-CoV-2 KP.2 variant

The JN.1 variant (BA.2.86.1.1), arising from BA.2.86(.1) with the S:L455S substitution, exhibited increased fitness and outcompeted the previous dominant XBB lineage by the biggening of 2024. JN.1 subsequently diversified, leading to the emergence of descendants with spike (S) protein substitutions such as S:R346T and S:F456L. Particularly, the KP.2 (JN.1.11.1.2) variant, a descendant of JN.1 bearing both S:R346T and S:F456L, is rapidly spreading in multiple regions as of April 2024. Here, we investigated the virological properties of KP.2. KP.2 has three substitutions in the S protein including the two above and additional one substitution in non-S protein compared with JN.1. We estimated the relative effective reproduction number (Re) of KP.2 based on the genome surveillance data from the USA, United Kingdom, and Canada where >30 sequences of KP.2 has been reported, using a Bayesian multinomial logistic model. The Re of KP.2 is 1.22-, 1.32-, and 1.26-times higher than that of JN.1 in USA, United Kingdom, and Canada, respectively. These results suggest that KP.2 has higher viral fitness and potentially becomes the predominant lineage worldwide. Indeed, as of the beginning of April 2024, the estimated variant frequency of KP.2 has already reached 20% in United Kingdom. The pseudovirus assay showed that the infectivity of KP.2 is significantly (10.5-fold) lower than that of JN.1. We then performed a neutralization assay using monovalent XBB.1.5 vaccine sera and breakthrough infection (BTI) sera with XBB.1.5, EG.5, HK.3 and JN.1 infections. In all cases, the 50% neutralization titer (NT50) against KP.2 was significantly lower than that against JN.1. Particularly, KP.2 shows the most significant resistance to the sera of monovalent XBB.1.5 vaccinee without infection (3.1-fold) as well as those who with infection (1.8-fold). Altogether, these results suggest that the increased immune resistance ability of KP.2 partially contributes to the higher Re more than previous variants including JN.1.

microbiology↗

bioRxiv2023

Virological characteristics of the SARS-CoV-2 Omicron HK.3 variant harboring the "FLip" substitution

In November 2023, SARS-CoV-2 XBB descendants, including EG.5.1 (XBB.1.9.2.5.1), the currently predominant lineage, are circulating worldwide according to Nextstrain. EG.5.1 has a characteristic amino acid substitution in the spike protein (S), S:F456L, which contributes to its escape from humoral immunity. EG.5.1 has further evolved, and its descendant lineage harboring S:L455F (i.e., EG.5.1+S:L455F) emerged and was named HK.3 (XBB.1.9.2.5.1.1.3). HK.3 was initially discovered in East Asia and is rapidly spreading worldwide. Notably, the XBB subvariants bearing both S:L455F and S:F456L substitutions, including HK.3, are called the "FLip" variants. These FLip variants, such as JG.3 (XBB.1.9.2.5.1.3.3), JF.1 (XBB.1.16.6.1) and GK.3 (XBB.1.5.70.3), have emerged convergently, suggesting that the acquisition of these two substitutions confers a growth advantage to XBB in the human population. Here, we investigated the virological properties of HK.3 as a representative of the FLip variants.

microbiology↗

bioRxiv2023

The effects of paroxetine-induced transient apoptosis and brain remodeling on social behavior in developing zebrafish

Autism spectrum disorder (ASD) is a neurodevelopmental condition caused by various genetic and environmental factors. This disorder has the cardinal symptoms including impaired social behavior involving the amygdala. Ingesting antidepressants such as paroxetine in early pregnancy increases the risk of ASD in offspring. However, a comprehensive picture of the underlying pathogenic mechanisms remains elusive. Here we demonstrate that early exposure of zebrafish embryos to paroxetine retards neurogenesis in the optic tectum and the telencephalon that includes a region corresponding to the mammalian amygdala. Paroxetine-treated embryos exhibit impaired growth, with small heads and short body lengths resulting from transient apoptosis. This is reminiscent of the early-onset fetal growth restriction (FGR) associated with ASD. Interestingly, the delayed neurogenesis in the small heads was found to be restored after the cessation of paroxetine. This restoration was accompanied by extended retinotectal projections, suggesting brain-preferential remodeling. Finally, social behavior of the paroxetine-treated fish was examined. Our findings imply a biological mechanism underlying early exposure to paroxetine, a risk factor associated with the pathogenesis of ASD.

pharmacology and toxicology↗

bioRxiv2023

Virological characteristics of the SARS-CoV-2 BA.2.86 variant

In late 2023, a lineage of SARS-CoV-2 emerged and was named the BA.2.86 variant. BA.2.86 is phylogenetically distinct from other Omicron sublineages identified so far, displaying an accumulation of over 30 amino acid mutations in its spike protein. Here, we performed multiscale investigations to reveal the virological characteristics of the BA.2.86 variant. Our epidemic dynamics modeling suggested that the relative reproduction number of BA.2.86 is significantly higher than that of EG.5.1. Experimental studies showed that four clinically-available antivirals were effective against BA.2.86. Although the fusogenicity of BA.2.86 spike is similar to that of the parental BA.2 spike, the intrinsic pathogenicity of BA.2.86 in hamsters was significantly lower than that of BA.2. Since the growth kinetics of BA.2.86 is significantly lower than that of BA.2 in both in vitro cell cultures and in vivo, it is suggested that the attenuated pathogenicity of BA.2.86 is due to its decreased replication capacity.

microbiology↗

bioRxiv2023

Virological characteristics of the SARS-CoV-2 Omicron EG.5.1 variant

In middle-late 2023, a sublineage of SARS-CoV-2 Omicron XBB, EG.5.1 (a progeny of XBB.1.9.2), is spreading rapidly around the world. Here, we performed multiscale investigations to reveal virological features of newly emerging EG.5.1 variant. Our phylogenetic-epidemic dynamics modeling suggested that two hallmark substitutions of EG.5.1, S:F456L and ORF9b:I5T, are critical to the increased viral fitness. Experimental investigations addressing the growth kinetics, sensitivity to clinically available antivirals, fusogenicity and pathogenicity of EG.5.1 suggested that the virological features of EG.5.1 is comparable to that of XBB.1.5. However, the cryo-electron microscopy reveals the structural difference between the spike proteins of EG.5.1 and XBB.1.5. We further assessed the impact of ORF9b:I5T on viral features, but it was almost negligible at least in our experimental setup. Our multiscale investigations provide the knowledge for understanding of the evolution trait of newly emerging pathogenic viruses in the human population.

microbiology↗

bioRxiv2023

Virological characteristics correlating with SARS-CoV-2 spike protein fusogenicity

The severe acute respiratory syndrome coronavirus (SARS-CoV-2) spike (S) protein is essential in mediating membrane fusion of the virus with the target cells. Several reports demonstrated that SARS-CoV-2 S protein fusogenicity is reportedly closely associated with the intrinsic pathogenicity of the virus determined using hamster models. However, the association between S protein fusogenicity and other virological parameters remains elusive. In this study, we investigated the virological parameters of eleven previous variants of concern (VOCs) and variants of interest (VOIs) correlating with S protein fusogenicity. S protein fusogenicity was found to be strongly correlated with S1/S2 cleavage efficiency and plaque size formed by clinical isolates. However, S protein fusogenicity was less associated with pseudoviral infectivity, pseudovirus entry efficiency, and viral replication kinetics. Taken together, our results suggest that S1/S2 cleavage efficiency and plaque size could be potential indicators to predict the intrinsic pathogenicity of newly emerged SARS-CoV-2 variants.

microbiology↗

bioRxiv2023

Antiviral efficacy of the SARS-CoV-2 XBB breakthrough infection sera against Omicron subvariants including EG.5

As of July 2023, EG.5.1 (a.k.a. XBB.1.9.2.5.1), a XBB subvariant bearing the S:Q52H and S:F456L substitutions, alongside the S:F486P substitution (Figure S1A), has rapidly spread in some countries. On July 19, 2023, the WHO classified EG.5 as a variant under monitoring. First, we showed that EG.5.1 exhibits a higher effective reproduction number compared with XBB.1.5, XBB.1.16, and its parental lineage (XBB.1.9.2), suggesting that EG.5.1 will spread globally and outcompete these XBB subvariants in the near future. We then addressed whether EG.5.1 evades from the antiviral effect of the humoral immunity induced by breakthrough infection (BTI) of XBB subvariants and performed a neutralization assay using XBB BTI sera. However, the 50% neutralization titer (NT50) of XBB BTI sera against EG.5.1 was comparable to those against XBB.1.5/1.9.2 and XBB.1.16. Moreover, the sensitivity of EG.5.1 to convalescent sera of XBB.1- and XBB.1.5-infected hamsters was similar to those of XBB.1.5/1.9 and XBB.1.16. These results suggest that the increased Re of EG.5.1 is attributed to neither increased infectivity nor immune evasion from XBB BTI, and the emergence and spread of EG.5 is driven by the other pressures. We previously demonstrated that Omicron BTI cannot efficiently induce antiviral humoral immunity against the variant infected. In fact, the NT50s of the BTI sera of Omicron BA.1, BA.2, and BA.5 against the variant infected were 3.0-, 2.2-, and 3.4-fold lower than that against the ancestral B.1.1 variant, respectively. However, strikingly, we found that the NT50 of the BTI sera of XBB1.5/1.9 and XBB.1.16 against the variant infected were 8.7- and 8.3-fold lower than that against the B.1.1 variant. These results suggest that XBB BTI cannot efficiently induce antiviral humoral immunity against XBB subvariants. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/552415v1_figs1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@f95376org.highwire.dtl.DTLVardef@d66fa8org.highwire.dtl.DTLVardef@3c8841org.highwire.dtl.DTLVardef@15824c_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure S1.C_FLOATNO Virological features of EG.5.1 and XBB BTI (A) Frequency of mutations of interest in the representative XBB sublineages. Only mutations with a frequency >0.5 in at least one but not all the representative sublineages are shown. Note that the S proteins of XBB.1.5 and XBB.1.9.2 are identical. (B) Estimated epidemic dynamics of the representative XBB sublineages in countries where >50 sequences of EG.5.1, XBB.1.5, XBB.1.9.2, and XBB.1.16 were detected from April 1, 2023 to July 13, 2023. Countries are ordered according to the number of detected sequences of EG.5.1. Line, posterior mean; ribbon, 95% Bayesian confidence interval. The dynamics for EG.5.1 is highlighted by a red arrowhead. (C) Estimated relative Re of the representative XBB sublineages in the six countries. The relative Re of XBB.1.5 is set to 1 (horizontal dashed line). Violin, posterior distribution; dot, posterior mean; line, 95% Bayesian confidence interval. (D) Lentivirus-based pseudovirus assay. HOS-ACE2-TMPRSS2 cells were infected with pseudoviruses bearing each S protein. The amount of input virus was normalized to the amount of HIV-1 p24 capsid protein. The percentage infectivity of XBB.1.5/1.9.2, XBB.1.5/1.9.2+Q52H, XBB.1.5/1.9.2+F456L, and EG.5.1 compared to that of XBB.1.5/1.9.2 are shown. The horizontal dash line indicates the mean value of the percentage infectivity of the XBB.1.5/1.9.2. Assays were performed in quadruplicate. The presented data are expressed as the average {+/-} SD. Each dot indicates the result of an individual replicate. (E-G) Neutralization assay. Assays were performed with pseudoviruses harboring the S proteins of B.1.1, BA.1, BA.2, BA.5, BQ.1.1, XBB.1, XBB.1.5/1.9.2, XBB.1.16, EG.5.1, XBB.1.5/1.9.2+Q52H, and XBB.1.5/1.9.2+F456L. The following sera were used: convalescent sera from fully vaccinated individuals who had been infected with XBB.1.5 (one 3-dose vaccinated. 1 donor in total), XBB.1.9 (one 3-dose vaccinated donor, one 4-dose vaccinated donor and one 5-dose vaccinated donor. 3 donors in total), and XBB.1.16 (one 2-dose vaccinated donor, two 3-dose vaccinated donors, and one 4-dose vaccinated donor. 4 donors in total) (E); sera from hamster infected with XBB.1 (left) or XBB.1.5 (right) (F); and convalescent sera from fully vaccinated individuals who had been infected with BA.1 (thirteen 2-dose vaccinated, 13 donors in total) (left)1, BA.2 (nine 2-dose vaccinated and four 3-dose vaccinated donors. 13 donors in total) (middle)19, and BA.5 (one 2-dose vaccinated, thirteen 3-dose vaccinated donors, and one 4-dose vaccinated. 15 donors in total) (right)19 (G). Each dot indicates the result of an individual replicate. Assays for each serum sample were performed in triplicate to determine the 50% neutralization titer (NT50). Each dot represents one NT50 value, and the geometric mean and 95% confidence interval are shown. The number in parenthesis indicates the mean of NT50 values. The horizontal dash line indicates the detection limit (120-fold). In D, statistically significant differences (**, P < 0.001, ***, P < 0.0001) versus XBB.1.5/1.9.2 were determined by two-sided Students t tests. Blue asterisks indicate decreased percentage of infectivity. In E and G, statistically significant differences versus B.1.1 were determined by two-sided Wilcoxon signed-rank tests. The fold change between B.1.1 and the variant indicated is shown in red. Background information on the convalescent donors is summarized in Table S1. In F, statistically significant differences (*, P < 0.01, **, P < 0.001) between B.1.1 and XBB.1 (left) or XBB.1.5/1.9.2 (right) were determined by two-sided Wilcoxon signed-rank tests and indicated with asterisks. Red asterisks indicate decreased NT50s. C_FIG

microbiology↗

bioRxiv2023

Common and divergent gene regulatory networks control injury-induced and developmental neurogenesis in zebrafish retina.

Following acute retinal damage, zebrafish possess the ability to regenerate all neuronal subtypes. This regeneration requires Muller glia (MG) to reprogram and divide asymmetrically to produce a multipotent Muller glia-derived neuronal progenitor cell (MGPC). This raises three key questions. First, does loss of different retinal cell subtypes induce unique MG regeneration responses? Second, do MG reprogram to a developmental retinal progenitor cell state? And finally, to what extent does regeneration recapitulate retinal development? We examined these questions by performing single-nuclear and single-cell RNA-Seq and ATAC-Seq in both developing and regenerating retinas. While MG reprogram to a state similar to late-stage retinal progenitors in developing retinas, there are transcriptional differences between reprogrammed MG/MGPCs and late progenitors, as well as reprogrammed MG in outer and inner retinal damage models. Validation of candidate genes confirmed that loss of different subtypes induces differences in transcription factor gene expression and regeneration outcomes. This work identifies major differences between gene regulatory networks activated following the selective loss of different subtypes of retina neurons, as well as between retinal regeneration and development.

neuroscience↗

bioRxiv2022

Virological characteristics of the SARS-CoV-2 XBB variant derived from recombination of two Omicron subvariants

In late 2022, the SARS-CoV-2 Omicron subvariants have highly diversified, and XBB is spreading rapidly around the world. Our phylogenetic analyses suggested that XBB emerged by recombination of two co-circulating BA.2 lineages, BJ.1 and BM.1.1.1 (a progeny of BA.2.75), during the summer of 2022 around India. In vitro experiments revealed that XBB is the most profoundly resistant variant to BA.2/5 breakthrough infection sera ever and is more fusogenic than BA.2.75. Notably, the recombination breakpoint is located in the receptor-binding domain of spike, and each region of recombined spike conferred immune evasion and augmented fusogenicity to the XBB spike. Finally, the intrinsic pathogenicity of XBB in hamsters is comparable to or even lower than that of BA.2.75. Our multiscale investigation provided evidence suggesting that XBB is the first documented SARS-CoV-2 variant increasing its fitness through recombination rather than single mutations.

microbiology↗

bioRxiv2022

Convergent evolution of the SARS-CoV-2 Omicron subvariants leading to the emergence of BQ.1.1 variant

In late 2022, although the SARS-CoV-2 Omicron subvariants have highly diversified, some lineages have convergently acquired amino acid substitutions at five critical residues in the spike protein. Here, we illuminated the evolutionary rules underlying the convergent evolution of Omicron subvariants and the properties of one of the latest lineages of concern, BQ.1.1. Our phylogenetic and epidemic dynamics analyses suggest that Omicron subvariants independently increased their viral fitness by acquiring the convergent substitutions. Particularly, BQ.1.1, which harbors all five convergent substitutions, shows the highest fitness among the viruses investigated. Neutralization assays show that BQ.1.1 is more resistant to breakthrough BA.2/5 infection sera than BA.5. The BQ.1.1 spike exhibits enhanced binding affinity to human ACE2 receptor and greater fusogenicity than the BA.5 spike. However, the pathogenicity of BQ.1.1 in hamsters is comparable to or even lower than that of BA.5. Our multiscale investigations provide insights into the evolutionary trajectory of Omicron subvariants.

microbiology↗

bioRxiv2022

Virological characteristics of the SARS-CoV-2 Omicron BA.2.75

SARS-CoV-2 Omicron BA.2.75 emerged in May 2022. BA.2.75 is a BA.2 descendant but is phylogenetically different from BA.5, the currently predominant BA.2 descendant. Here, we showed that the effective reproduction number of BA.2.75 is greater than that of BA.5. While the sensitivity of BA.2.75 to vaccination- and BA.1/2 breakthrough infection-induced humoral immunity was comparable to that of BA.2, the immunogenicity of BA.2.75 was different from that of BA.2 and BA.5. Three clinically-available antiviral drugs were effective against BA.2.75. BA.2.75 spike exhibited a profound higher affinity to human ACE2 than BA.2 and BA.5 spikes. The fusogenicity, growth efficiency in human alveolar epithelial cells, and intrinsic pathogenicity in hamsters of BA.2.75 were comparable to those of BA.5 but were greater than those of BA.2. Our multiscale investigations suggest that BA.2.75 acquired virological properties independently of BA.5, and the potential risk of BA.2.75 to global health is greater than that of BA.5.

microbiology↗

bioRxiv2022

Virological characteristics of the novel SARS-CoV-2 Omicron variants including BA.2.12.1, BA.4 and BA.5

After the global spread of SARS-CoV-2 Omicron BA.2 lineage, some BA.2-related variants that acquire mutations in the L452 residue of spike protein, such as BA.2.9.1 and BA.2.13 (L452M), BA.2.12.1 (L452Q), and BA.2.11, BA.4 and BA.5 (L452R), emerged in multiple countries. Our statistical analysis showed that the effective reproduction numbers of these L452R/M/Q-bearing BA.2-related Omicron variants are greater than that of the original BA.2. Neutralization experiments revealed that the immunity induced by BA.1 and BA.2 infections is less effective against BA.4/5. Cell culture experiments showed that BA.2.12.1 and BA.4/5 replicate more efficiently in human alveolar epithelial cells than BA.2, and particularly, BA.4/5 is more fusogenic than BA.2. Furthermore, infection experiments using hamsters indicated that BA.4/5 is more pathogenic than BA.2. Altogether, our multiscale investigations suggest that the risk of L452R/M/Q-bearing BA.2-related Omicron variants, particularly BA.4 and BA.5, to global health is potentially greater than that of original BA.2. HighlightsO_LISpike L452R/Q/M mutations increase the effective reproduction number of BA.2 C_LIO_LIBA.4/5 is resistant to the immunity induced by BA.1 and BA.2 infections C_LIO_LIBA.2.12.1 and BA.4/5 more efficiently spread in human lung cells than BA.2 C_LIO_LIBA.4/5 is more pathogenic than BA.2 in hamsters C_LI

microbiology↗

bioRxiv2022

Virological characteristics of SARS-CoV-2 BA.2 variant

Soon after the emergence and global spread of a new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron lineage, BA.1 (ref1, 2), another Omicron lineage, BA.2, has initiated outcompeting BA.1. Statistical analysis shows that the effective reproduction number of BA.2 is 1.4-fold higher than that of BA.1. Neutralisation experiments show that the vaccine-induced humoral immunity fails to function against BA.2 like BA.1, and notably, the antigenicity of BA.2 is different from BA.1. Cell culture experiments show that BA.2 is more replicative in human nasal epithelial cells and more fusogenic than BA.1. Furthermore, infection experiments using hamsters show that BA.2 is more pathogenic than BA.1. Our multiscale investigations suggest that the risk of BA.2 for global health is potentially higher than that of BA.1.

microbiology↗

bioRxiv2021

Transcriptional regulation of neonatal neural stem cells is a determinant of social behavior

Rare gene variants confer a high level of penetrance to neurodevelopmental disorders, but their developmental origin and cellular substrates remain poorly understood. To address this limitation, we explored the role of TBX1, a gene encoded in a rare copy number variant, in cell and mouse models. Here, we report that neonatal Tbx1 deficiency contributes to defective peripubertal social behavior and impairs the proliferation of neonatal neural stem/progenitor cells. Moreover, TBX1 transcriptionally regulates genes linked to post-embryonic neurogenesis and neurodevelopmental disorders associated with other rare gene variants. Our data indicate a precise time window and cell type through which the social dimension is altered by a gene encoded in a rare CNV and provide a potential common mechanistic basis for a group of neurodevelopmental disorders. One-Sentence SummaryTbx1, a gene affecting neonatal stem cell proliferation, influences peripubertal social behavior.

neuroscience↗

bioRxiv2021

SARS-CoV-2 spike P681R mutation enhances and accelerates viral fusion

During the current SARS-CoV-2 pandemic, a variety of mutations have been accumulated in the viral genome, and currently, four variants of concerns (VOCs) are considered as the hazardous SARS-CoV-2 variants to the human society1. The newly emerging VOC, the B.1.617.2/Delta variant, closely associates with a huge COVID-19 surge in India in Spring 20212. However, its virological property remains unclear. Here, we show that the B.1.617.2/Delta variant is highly fusogenic, and notably, more pathogenic than prototypic SARS-CoV-2 in infected hamsters. The P681R mutation in the spike protein, which is highly conserved in this lineage, facilitates the spike protein cleavage and enhances viral fusogenicity. Moreover, we demonstrate that the P681R-bearing virus exhibits higher pathogenicity than the parental virus. Our data suggest that the P681R mutation is a hallmark that characterizes the virological phenotype of the B.1.617.2/Delta variant and is closely associated with enhanced pathogenicity.

microbiology↗