Biology subjects

Ogawa, T.

Publications and source records attributed to Ogawa, T..

At least 19 recordsLinked to original sources

bioRxiv2026

Medullary epithelium-free areas in the rat thymus are specialized niches enriched for mature thymocytes and distinct stromal subsets

The thymic medulla provides the microenvironment for negative selection, late thymocyte maturation, and thymocyte egress, and is generally characterized by widespread distribution of medullary thymic epithelial cells (mTECs). In contrast, rat thymic medulla contains medullary epithelium-free areas (mEFAs), but the cellular composition and functional significance of these regions remain unclear. Here, we combined spatial transcriptomics and scRNA-seq, using robust cell-type decomposition (RCTD) to characterize mEFAs in Lewis-strain rat thymus. These analyses revealed that more mature-phenotypes of CD4SP, CD8SP, and regulatory T-cell-lineage thymocytes were preferentially localized in mEFAs, whereas immature SP subsets were enriched in medullary epithelium-containing areas. Newly found rat thymic mesenchymal cell-3 and -4 (TMC3 and TMC4) subsets were also enriched in mEFAs. These subsets were broadly similar to mouse medullary fibroblasts but displayed distinct predicted interactions with SP thymocytes, including costimulatory molecule- receptor, chemokine-receptor, and ECM-integrin axes. In addition, the venous endothelial cells (vECs) expressing portal endothelial cell markers were accumulated in mEFAs. The S1P transporter gene Spns2 was preferentially expressed in both TMC4 and vEC subsets, suggesting increased local concentration in mEFAs. These findings indicate that rat mEFAs are specialized medullary niches linking stromal organization, thymocyte maturation, and thymic egress.

immunology↗

bioRxiv2026

Antiviral activity of anisomycin against chikungunya virus

Chikungunya virus (CHIKV) is a globally prevalent arbovirus transmitted by Aedes mosquitoes, which causes acute fever accompanied by debilitating joint pain that can persist for extended periods. Despite the significant public health impact and an increasing incidence worldwide, antiviral treatment targeting CHIKV has not been clinically approved. In this study, we screened compounds using a newly developed In-Cell ELISA-based assay and CHIKV Indian Ocean Lineage (IOL) and found that an antibiotic derived from Streptomyces bacteria, anisomycin, potentially inhibited CHIKV. The selectivity index of anisomycin was favorable for anti-CHIKV activity, with 50% effective concentration (EC50) of 200 pM and 50% cytotoxic concentration (CC50) of 390 nM in Vero cells. This robust inhibitory activity against CHIKV was confirmed in a human cell line and against a CHIKV East/Central/South African (ECSA) lineage. These effects of anisomycin were apparently independent of its functions as a translation inhibitor and mitogen-activated protein kinase (MAPK) pathway stimulator. These findings, together with the finding that anisomycin suppressed the production of infectious CHIKV virions, suggested that anisomycin inhibits CHIKV via a distinct mechanism. Further mechanistic insights were gained through genetic analyses of anisomycin-resistant mutants, which revealed that a single amino acid substitution (G117R) in the macrodomain of CHIKV nsP3 confers resistance to anisomycin. Importantly, anisomycin reduced footpad swelling and viremia in mice during the early days of CHIKV infection, indicating its therapeutic potential. Given its inhibitory activity against other arboviruses, our study positions anisomycin as a promising lead inhibitor for the future development of broad-spectrum antiviral drugs, including CHIKV. Author summaryChikungunya fever (CHIKF) is a mosquito-borne disease caused by the chikungunya virus (CHIKV) and is characterized by fever, rash, and arthralgia. Although most persons infected with CHIKV recover within days, joint pain and severe complications can persist. However, the management of CHIKF is limited to symptom relief, and specific antiviral treatments are not available. Our study focused on identifying potential inhibitors of CHIKV infection. We found that the natural alkaloid, anisomycin, inhibited CHIKV replication in cultured cells in vitro using a novel screening assay and a chemical compound library. Interestingly, the mechanism by which anisomycin blocks CHIKV infection likely differs from its currently known effects, suggesting a distinct mode of inhibition. We also identified an amino acid change in a nonstructural protein that conferred resistance to anisomycin, providing insights into a viral target of anisomycin. Importantly, anisomycin reduced disease symptoms and viremia in mouse models of CHIKV in vivo. Because anisomycin inhibits other mosquito-borne viruses, our findings suggest that it could serve as a basis for developing broad-acting antiviral drugs.

microbiology↗

bioRxiv2026

AtPUP5 functions as a plasma membrane flavin transporter regulating localized riboflavin distribution in Arabidopsis

Riboflavin (vitamin B{square}; RF) and its derivatives flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are indispensable cofactors for redox reactions in plants. While higher plants possess a conserved pathway for de novo riboflavin biosynthesis, how flavins are transported and spatially distributed between tissues remains unresolved. In particular, the molecular identity of plasma membrane transporters involved in flavin transport in plants remains largely unknown. Here, we identify Arabidopsis purine permease 5 (AtPUP5) as a plasma membrane-localized protein associated with riboflavin transport and its distribution in plants. Using a riboflavin-auxotrophic yeast mutant, we show that AtPUP5 enhances intracellular accumulation of RF and, to a lesser extent, FMN, whereas FAD accumulation is inefficient under the conditions tested. In planta, AtPUP5 overexpression increases RF accumulation following external application. In contrast, loss-of-function mutants do not display defects in bulk RF uptake at the whole-plant level, indicating that AtPUP5 is not essential for global riboflavin acquisition. Notably, AtPUP5 deficiency results in RF overaccumulation in reproductive organs, including inflorescences, siliques, and seeds, irrespective of external RF supply. This organ-specific phenotype is fully suppressed by genetic complementation and coincides spatially with strong AtPUP5 promoter activity in reproductive tissues. These findings suggest that AtPUP5 contributes to the regulation of localized riboflavin distribution in reproductive tissues. Together, our study provides a molecular framework for plasma membrane-mediated regulation of riboflavin distribution in plants and highlights spatial regulation as an important component of flavin homeostasis.

plant biology↗

bioRxiv2026

Segmented wavetrains and sites of reversal in the mouse seminiferous tubules

Mammalian spermatogenesis occurs in the seminiferous tubules, which exhibit unique spatiotemporal differentiation patterns known as cellular association patterns. In mice, these patterns can be regarded as one-dimensional wavetrains that consistently propagate inward from both ends, resulting in one or more "sites of reversal." Segmented wavetrain pattern, in which the wave propagation direction spatially switches, was observed in our previous three-species reaction-diffusion model for interspecific species difference in spermatogenic waves (Kawamura et al., 2021). However, the biological mechanisms of the formation of sites of reversal and of this directional bias, as well as the principle of pattern formation, remain unknown. Here, we refined our previous model to match the actual biological spatiotemporal scale and examined its dynamics through extensive numerical simulations. The modified model frequently generated segmented wavetrain patterns, corresponding to the sites of reversal, but without directional bias. We systematically examined possible biological mechanisms for the bias and found that tubule elongation, especially near the rete testis, most effectively accounts for the bias among the tested. Extensive simulations revealed that the segmented pattern is numerically stable, emerges more frequently in longer domains, and shows an exponential segment size distribution with a lower limit for the stably existing segment length. These explorations imply that locally emerged unidirectional wavetrains serve as building blocks to generate the stable segmented wavetrains through their interactions. HighlightsO_LISegmented wavetrains reflect sites of reversal in seminiferous tubules. C_LIO_LISegmented patterns frequently emerge but show no inherent directional bias. C_LIO_LITubule elongation may contribute to inward propagation near the rete testis. C_LIO_LISegmented wavetrains are numerically stable and more frequent in longer domains. C_LIO_LIInteractions of local unidirectional wavetrains generate stable segmented structures. C_LI

developmental biology↗

bioRxiv2025

Leveraging the salivary microbiome profile to stratify REM sleep behavior disorder and synucleinopathies

Few studies have explored noninvasive biomarkers of synucleinopathies, including Parkinsons disease (PD), and rapid-eye-movement behavior disorder (RBD), a prodromal stage for these conditions. Human oral/salivary microbiomes are altered in PD, highlighting their potential role in both PD pathogenesis and diagnosis. We analyzed 249 salivary microbiomes of controls and patients with idiopathic RBD and various synucleinopathies, including two subgroups divided based on the presence of RBD symptoms, through both cross-sectional and longitudinal studies. The microbiome composition was strikingly similar between patients with RBD and early PD exhibiting RBD symptoms. The area under the curve range for distinguishing RBD from controls and each synucleinopathy was 0.85-0.94. We further performed pseudotime trajectory analysis of the microbiome compositional space; populations with low diversity, enriched Streptococcus, and depleted Neisseria exhibited a brief pseudotime transition from RBD to early PD. Our findings suggest that early PD-like salivary dysbiosis manifests during RBD, allowing for the stratification of synucleinopathies through the innovative use of salivary microbiome profiles.

neuroscience↗

bioRxiv2025

Metabolic cell death of labile iron deficiency as a vulnerability of head and neck squamous cancer cells evaded by BACH1

Head and neck squamous cell carcinoma (HNSCC) remains difficult to treat due to the lack of molecularly targeted drugs with high anti-tumor efficacy and safety. To investigate the involvement of the transcription factor BACH1, which is known to promote the metastasis of various cancers, in the malignant properties of HNSCC cells, we examined the effects of BACH1 depletion with short interfering RNAs in human HNSCC cell lines. We found that knockdown of BACH1 induced cell death due to depletion of intracellular labile iron which is not tightly bound to protein. Mitochodrial electron transfer chain activity was severely reduced but efficiently resuced with supplementation of iron in the medium. By combining chromatin immunoprecipitation-sequence and RNA-sequence analyses, we found that BACH1 represses ferritin genes in HNSCC cells. BACH1 knockdown was found to enhance the effect of tipifarnib, a selective inhibitor of farnesyltransferase required for HRAS activation, resulting in efficient inhibition of proliferation of HNSCC cell lines in vitro. These results indicate that BACH1 is essential for maintaining the amount of labile iron in HNSCC cells to evade metabolic cell death of iron deficiency and to proliferate. BACH1 can be a target for conferring Tipifarnib sensitivity to HNSCC cells.

cancer biology↗

bioRxiv2025

Bordetella BcrH1 and BcrH2 are specific chaperones for the pore-forming complex.

Bordetella has a type III secretion system that secretes virulence proteins crucial to the establishment of infection. The genes encoding components of the Bordetella type III secretion system are located in the bsc region on the chromosome. This region includes the bcrH1 and bcrH2 genes, which respectively encode the proteins BcrH1 and BcrH2. In this study, we analyzed the roles of BcrH1 and BcrH2 in Bordetella infection. First, we created a BcrH1/BcrH2-double deficient strains, and analyzed the amounts of the type III secreted proteins BopB and BopD, which make a complex that forms pores in the host membrane, in bacterial cells of each protein-deficient strain. The results showed that the BopB and BopD signals were weakened in the whole cell fraction of the BcrH1/BcrH2-double deficient strains, respectively. The hemolytic activity and cell toxicity of each BcrH protein-deficient strain were significantly lower than those of the wild-type strain. When anti-BcrH1 and anti-BcrH2 antibodies were used for the immunoprecipitation assay, the BopB and BopD signals were detected in the precipitated fractions, respectively. These results strongly suggest that BcrH1 and BcrH2 are specific chaperones for maintaining the stability of BopB and BopD, respectively.

microbiology↗

bioRxiv2024

Newly found rat CD103- dendritic cells are the highly immunogenic conventional DC2 subpopulation, corresponding to the known DC subsets in mice and humans.

Dendritic cells (DCs), the primary antigen-presenting cells, have traditionally been identified by CD103 molecules in rats, whereas mouse and human DCs are identified by CD11c molecules. However, this history does not preclude the existence of CD103- DCs in rats. To explore this possibility, we examined MHCII+ cells in rat spleen and thymus, identifying a novel population of CD103-MHCII+CD45R-CD172a+ cells. These cells are negative for CD103 and B cell marker CD45R, but positive for the type-2 conventional DC (cDC2) marker CD172a. Transcriptomic analyses revealed that they represent a subpopulation of cDC2. Additionally, gene set enrichment analysis predicted enhanced immunogenic activities for this novel population compared to known rat cDC2s. Mixed leukocyte reaction assays confirmed that the rat CD103- cDC2s induce T cell proliferation more effectively than other DC subsets, suggesting enhanced immunogenic potential. In reaggregated thymic organ culture assays, both the rat CD103- and CD103+ cDC2 subsets suppressed the total number of generated thymocytes and skewed the differentiation toward CD8 single-positive cells. Comparisons with previously published single-cell RNA-sequencing datasets showed that the rat CD103- cDC2 subset shares markers and GO terms of known mouse and human cDC2 subpopulations: cDC2a, cDC2b, inf-cDC2, and moDC. In contrast, the classic rat CD103+ cDC2 subset expresses only cDC2a markers. These findings provide new insights into DC subpopulations, particularly in species other than mice and humans, where much remains to be uncovered.

immunology↗

bioRxiv2024

Self-organization of spermatogenic wave coordinates sustained sperm production in the mouse testis

Spermatogenesis takes place in the testis, relying on the ordered turnover of differentiating cells supplied from stem cells. Classic histological analyses have revealed that this process shows hierarchical spatiotemporal patterning known as the spermatogenic cycle, wave, and descent of segmental order, indicative of currently underexplored mechanisms of tissue- and organ-scale homeostasis. Here, using mice, we conducted high-resolution, wide-field, and ultra long-term live imaging studies in vivo and ex vivo, combined with whole-organ mapping of differentiation stages. Such trans-scale measures demonstrate how stereotypic local cell turnover is coordinated into characteristic phase waves propagating along the seminiferous tubules, further organized into organ-scale patterning over the tubule loops. Minimal mathematical modeling shows that such higher-order dynamics can emerge from the local coupling of autonomous oscillators, which are rooted in delayed feedback interplay between stem and differentiating cells via retinoic acid signaling. These findings highlight a self-organization mechanism underpinning organ-scale homeostasis and constant sperm production.

developmental biology↗

bioRxiv2024

Tuning of ribosome levels mediated by RNase I and hibernating ribosomes

Protein biosynthesis is an energy-hungry intracellular process that requires the stringent regulation of ribosome abundance under environmental conditions. In response to stress, some active ribosomes are degraded while others, in bacteria, enter a hibernation state to protect against degradation. RNase I, a conserved T2 family ribonuclease in Escherichia coli, degrades ribosomal RNA to suppress biofilm formation, whereas it interacts with ribosomes. However, how and why RNase I binds to ribosomes remains elusive. Here, we show that hibernating ribosomes bind to RNase I and inhibit its activity, thereby promoting biofilm formation. We determined the cryo-electron microscopy structure of the hibernating ribosome complexed with RNase I. RNase I interacts with helix 41 of the 16S rRNA and the ribosomal protein uS14 in the head domain of the 30S subunit of the hibernating ribosome and positions its active centre away from helix 41, resulting in its catalytic inactivation. Hibernating ribosomes are protected from RNase I-mediated cleavage, and our in vivo and in vitro analyses revealed that RNase I targets dissociated large and small ribosomal subunits for rRNA degradation. These findings reveal a previously uncharacterized regulatory strategy that ribosomes modulate RNase I activity, ensuring both the preservation and timely degradation of ribosomes during environmental stress adaptation.

molecular biology↗

bioRxiv2024

Silicon Nitride Induces Osteoconduction Via Activated Mitochondrial Oxidative Phosphorylation and Neovascularization

Silicon nitride (Si3N4: SiN) is a thermodynamically stable ceramic material with excellent mechanical properties, and wear and corrosion resistance for industrial applications. SiN has been proposed for orthopedic and dental implant applications owing to its enhanced osteoconduction. However, the biological mechanisms underlying SiN-induced bone formation have not been fully elucidated. In this study, SiN significantly increased in vitro mineralization of human bone marrow mesenchymal stromal cells (BM-MSC) and in vivo peri-implant bone volume in mouse femurs compared to conventionally used titanium (Ti) implants. RNA sequencing of BM-MSC cultured on SiN disks revealed that functional gene clusters associated with mitochondrial oxidative phosphorylation were significantly elevated. SiN in an aqueous solution has been shown to release ammonium/ammonia, which may provide a source for glutamine-dependent energy production, and BM-MSC upregulated the expression of a key enzyme, glutamate-ammonia ligase under osteogenic conditions. Additionally, SiN increased the expression of functional gene clusters involved in vascular formation. The upregulation of HIF1a in vitro and increased VEGFR3-positive blanching vascular structures in vivo implied that SiN induced neovascularization. This study revealed an important mechanism through which SiN stimulated osteoconduction by unique glutamine-driven mitochondrial oxidative phosphorylation and established oxygen and nutrient supply by neovascularization, leading to stable osseointegration.

bioengineering↗

bioRxiv2024

Rapid screening and identification of genes involved in bacterial extracellular membrane vesicle production using a curvature-sensing peptide

Bacteria secrete extracellular membrane vesicles (EMVs). Physiology and biotechnological applications of these lipid nanoparticles have been attracting significant attention. However, the molecular basis of EMV biogenesis has not yet been fully elucidated. In the previous research, an N-terminus-substituted FAAV peptide labeled with NBD (nFAAV5-NBD) was developed, which can sense a curvature of a lipid bilayer and selectively bind to EMVs in the presence of the cells. Herein, we applied nFAAV5-NBD to a screening of hyper- and hypo-vesiculation transposon mutants of a Gram-negative bacterium, Shewanella vesiculosa HM13, to identify the genes involved in EMV production. As a result, for 16 and six genes, we found that transposon insertion within or near the gene caused hyper- and hypo-vesiculation, respectively. Targeted gene-disrupted mutants of the identified genes demonstrated that the lack of putative dipeptidyl carboxypeptidase, glutamate synthase {beta}-subunit, LapG protease, metallohydrolase, RNA polymerase sigma-54 factor, inactive transglutaminase, PepSY domain-containing protein, and Rhs-family protein caused EMV overproduction. On the other hand, disruption of the genes encoding putative phosphoenolpyruvate synthase, D-hexose-6-phosphate epimerase, NAD-specific glutamate dehydrogenase, and sensory box histidine kinase/response regulator decreased EMV production. This study shows the utility of a novel screening method using a curvature-sensing peptide and fundamental information on the genes related to EMV production. IMPORTANCEConventional methods for isolation and quantification of EMVs are generally time-consuming. nFAAV5-NBD can detect EMVs in the culture without separating EMVs from cells. In situ detection of EMVs using this peptide facilitated screening of the genes related to EMV production. We succeeded in identifying a number of genes involved in the EMV production of S. vesiculosa HM13, and the strains obtained in this study would contribute to the elucidation of bacterial EMV formation mechanisms. Additionally, the hyper-vesiculating mutants obtained in this study would be useful in the application of this bacterium, such as in the production of useful substances as cargoes of EMVs and in the production of surface-engineered vesicles.

microbiology↗

bioRxiv2024

The cochlear hook region detects harmonics beyond the canonical hearing range

Ultrasound, or sound at frequencies exceeding the conventional range of human hearing, is not only audible to mice, microbats, and dolphins, but also creates an auditory sensation when delivered through bone conduction in humans. Although ultrasound is utilized for brain activation and in hearing aids, the physiological mechanism of ultrasonic hearing remains unknown. In guinea pigs, we found that ultrasound above the hearing range delivered through ossicles of the middle ear evokes an auditory brainstem response and a mechano-electrical transduction current through hair cells, as shown by the local field potential called the cochlear microphonic potential (CM). The CM synchronizes with ultrasound, and like the response to audible sounds is actively and nonlinearly amplified. In vivo optical nano-vibration analysis revealed that the sensory epithelium in the hook region, the basal extreme of the cochlear turns, resonates in response both to ultrasound within the hearing range and to harmonics beyond the hearing range. The results indicate that hair cells can respond to stimulation at the optimal frequency and its harmonics, and the hook region detects ultrasound stimuli with frequencies more than two octaves higher than the upper limit of the ordinary hearing range.

physiology↗

bioRxiv2024

The Architecture of Sponge Choanocyte Chambers Maximizes Mechanical Pumping Efficiency

Sponges, the basalmost members of the animal kingdom, exhibit a range of complex architectures in which microfluidic channels connect multitudes of spherical chambers lined with choanocytes, flagellated filter-feeding cells. Choanocyte chambers can possess scores or even hundreds of such cells, which drive complex flows entering through porous walls and exiting into the sponge channels. One of the mysteries of the choanocyte chamber is its spherical shape, as it seems inappropriate for inducing directional transport since many choanocyte flagella beat in opposition to such a flow. Here we combine direct imaging of choanocyte chambers in living sponges with computational studies of many-flagella models to understand the connection between chamber architecture and directional flow. We find that those flagella that beat against the flow play a key role in raising the pressure inside the choanocyte chamber, with the result that the mechanical pumping efficiency, calculated from the pressure rise and flow rate, reaches a maximum at a small outlet opening angle. Comparison between experimental observations and the results of numerical simulations reveal that the chamber diameter, flagellar wave number and the outlet opening angle of the freshwater sponge E. muelleri, as well as several other species, are related in a manner that maximizes the mechanical pumping efficiency. These results indicate the subtle balances at play during morphogenesis of choanocyte chambers, and give insights into the physiology and body design of sponges.

biophysics↗

bioRxiv2023

Testis organ culture system capable of evaluating testicular toxicity

Successful treatment of pediatric cancers often results in long-term health complications, including potential effects on fertility. Therefore, assessing the male reproductive toxicity of anti-cancer drug treatments and the potential for recovery is of paramount importance. However, in vivo evaluations are time-intensive and require large numbers of animals. To overcome these constraints, we utilized an innovative organ culture system that supports long-term spermatogenesis by placing the testis tissue between a base agarose gel and a polydimethylsiloxane ceiling, effectively mirroring the in vivo testicular environment. The present study aimed to determine the efficacy of this organ culture system for accurately assessing testicular toxicity induced by cisplatin, using acrosin-green fluorescent protein (GFP) transgenic neonatal mouse testes. The testis fragments were treated with different concentrations of cisplatin-containing medium for 24 hours and incubated in fresh medium for up to 70 days. The changes in tissue volume and GFP fluorescence over time were evaluated to monitor the progression of spermatogenesis, in addition to the corresponding histopathology. Cisplatin treatment caused tissue volume shrinkage and reduced GFP fluorescence in a concentration-dependent manner. Recovery from testicular toxicity was also dependent on the concentration of cisplatin received. The results demonstrated that this novel in vitro system can be a faithful replacement for animal experiments to assess the testicular toxicity of anti-cancer drugs and their reversibility, providing a useful method for drug development. Short AbstractAssessing the male reproductive toxicity of anti-cancer drugs and the potential for recovery is of paramount importance, however, in vivo evaluations are time-intensive and require large numbers of animals. We utilized an innovative organ culture system that mirrors the in vivo testicular environment to determine its efficacy in accurately assessing testicular toxicity induced by cisplatin. The results demonstrate that this system can be a faithful replacement for animal experiments to assess the testicular toxicity of anti-cancer drugs and their reversibility.

developmental biology↗

bioRxiv2023

RudLOV-a new optically synchronized cargo transport method reveals unexpected effect of dynasore

Live imaging of secretory cargoes is a powerful method for understanding the mechanisms of membrane trafficking. Inducing the synchronous release of cargoes from an organelle is a key for enhancing microscopic observation. We developed an optical cargo-releasing method named as retention using dark state of LOV2 (RudLOV), which enables exceptional spatial, temporal, and quantity control during cargo release. A limited amount of cargo-release using RudLOV successfully visualized cargo cisternal-movement and cargo-specific exit sites on the Golgi/trans-Golgi network. Moreover, by controlling the timing of cargo-release using RudLOV, we revealed the canonical and non-canonical effects of the well-known dynamin inhibitor dynasore, which inhibits early-Golgi but not late-Golgi transport and exit from the trans-Golgi network where dynamin-2 is active. Accumulation of COPI vesicles at the cis-side of the Golgi stacks in dynasore-treated cells suggests that dynasore targets COPI-uncoating/tethering/fusion machinery in the early-Golgi cisternae or endoplasmic reticulum but not in the late-Golgi cisternae. These results provide insight into the cisternal maturation of Golgi stacks.

cell biology↗

bioRxiv2023

In vitro pigmentation of human iPSC-derived retinal pigment epithelium cells does not indicate their quality for cell transplantation

Retinal pigment epithelium (RPE) cells show heterogeneous level of pigmentation when cultured in vitro. To know whether their color in appearance is correlated with the function of the RPE, we analyzed the color intensities of human-induced pluripotent stem cell-derived RPE cells (iPSC-RPE) together with the gene expression profile at the single cell level. For this purpose, we utilized our recent invention, Automated Live imaging and cell Picking System (ALPS), which enabled photographing each cell before RNA-sequencing analysis to profile the gene expression of each cell. While our iPSC-RPE were categorized in 4 clusters by gene expression, the color intensity of iPSC-RPE did not project any specific gene expression profiles. We reasoned this by less correlation between the actual color and the gene expressions that directly define the level of pigmentation, from which we hypothesized the color of RPE cells may be a temporal condition not strongly indicating the functional characteristics of the RPE.

cell biology↗

bioRxiv2023

AtDREB2G is a novel regulator of riboflavin biosynthesis under low-temperature stress and abscisic acid treatment in Arabidopsis thaliana

Riboflavin (RF) serves as a precursor to FMN and FAD, crucial cofactors in various metabolic processes. Strict regulation of cellular flavin homeostasis is imperative, yet information regarding the factors governing this regulation remains largely elusive. In this study, we first examined the impact of external flavin treatment on the Arabidopsis transcriptome to identify novel regulators of cellular flavin levels. Our analysis revealed alterations in the expression of 49 putative transcription factors. Subsequent reverse genetic screening highlighted a member of the Dehydration-Responsive Element Binding (DREB) family, AtDREB2G, as a potential regulator of cellular flavin levels. Knockout mutants of AtDREB2G (dreb2g) exhibited reduced flavin levels and decreased expression of RF biosynthetic genes compared to wild-type plants. Conversely, conditional overexpression of AtDREB2G led to an increase in the expression of RF biosynthetic genes and elevated flavin levels. In wild-type plants, exposure to low temperatures and abscisic acid treatment stimulated enhanced flavin levels and upregulated the expression of RF biosynthetic genes, concomitant with the induction of AtDREB2G. Notably, these responses were significantly attenuated in dreb2g mutants. Our findings establish AtDREB2G as a novel positive regulator of flavin biosynthesis in Arabidopsis, particularly under conditions of low temperature and abscisic acid treatment.

plant biology↗