Biology subjects

Kohda, T.

Publications and source records attributed to Kohda, T..

7 recordsLinked to original sources

bioRxiv2026

A eutherian-specific metaviral gene, RTL6, coordinates microglial inflammatory responsiveness and state regulation

RTL6 (also known as SIRH3) is a eutherian-specific metavirus-derived gene highly conserved among placental mammals. We previously demonstrated that RTL6 is expressed in microglia and secreted into the brain extracellular space, where it mediates the trapping and clearance of bacterial lipopolysaccharide (LPS). However, its role in microglial TLR4 signaling remained unclear. To investigate the earliest LPS response, we performed RNA-seq analysis of wild-type and Rtl6-deficient primary microglia following 10 min of LPS stimulation. Rtl6-deficient microglia exhibited compensatory upregulation of residual transcripts derived from the untranslated region of Rtl6, suggesting feedback regulation of Rtl6 expression. Loss of RTL6 attenuated the induction of immediate-early response genes, including Fos, Jun, Nr4a1, Nr4a2, Egr2, and Egr3, together with broad suppression of interferon-responsive and inflammatory transcriptional programs. Altered neuronal and oligodendrocyte/myelin interaction pathways indicated remodeling of microglial communication networks. Strikingly, genes involved in cell-cycle progression, DNA replication, chromatin assembly, DNA repair, and genome maintenance were coordinately upregulated, including multiple disease-associated microglia (DAM)-related genes. Collectively, these findings indicate that RTL6 couples extracellular LPS sensing to inflammatory transcriptional responses while regulating microglial functional state transitions. Our results identify RTL6 as a previously unrecognized component of the regulatory network governing microglial functional states in placental mammals.

molecular biology↗

bioRxiv2025

PEG10-ORF1 programs trophoblast progenitor development for placental labyrinth formation

The emergence of the placenta was a significant event in mammalian evolution, enabling therian mammals to give birth to live young through viviparity. A key genomic change associated with this process was likely the acquisition of the therian-specific paternally expressed 10 (PEG10) from a metavirus, as Peg10-null mutant mice exhibit early embryonic lethality due to the absence of both the spongiotrophoblast and labyrinth layers in the placenta. PEG10 encodes a GAG-like open reading frame 1 (ORF1) and a POL-like ORF2, and produces two proteins, PEG10-ORF1 and PEG10-ORF1/2 fusion proteins, via the -1 frameshift mechanism conserved in retroviruses and metaviruses. Here, we demonstrate PEG10-ORF1 plays an essential and distinct role in labyrinth development. Mice lacking ORF1 but retaining the ORF1/2 protein initially developed normally in both embryos and placentas; however, later exhibited underdevelopment of the placental labyrinths complex microarchitecture, accompanied by mid-to late gestational growth retardation and lethality. These severe defects are most likely attributable to dysregulated development of labyrinth trophoblast precursor (LaTP) cells. Beyond its essential role in early placental formation, we previously demonstrated that the DSG protease domain within PEG10-ORF1/2--a metaviruse-derived feature--is critical for maintaining fetal capillaries during late gestation. Thus, PEG10 fulfills multiple indispensable functions in placental formation and maintenance by exploiting a metavirus-derived multi-protein and -peptide production system, despite being a single gene. This study provides additional evidence underscoring the profound role of PEG10 acquisition in therian placental evolution. Significance StatementThe placenta is an essential organ for viviparous reproduction in therian mammals; therefore, its evolutionary emergence is of significant interest. One key event may have been the acquisition of PEG10, a metavirus (retrovirus-like LTR retrotransposon)- derived gene, by the common therian ancestor. We previously showed that Peg10 is required for early placental development and that its protease domain is essential for late-gestational maintenance of fetal capillaries within the placental labyrinth. Here, we provide additional genetic evidence that Peg10 is also indispensable for mid-gestational development of the placental labyrinthine microvasculature. Together, these findings illustrate how multiple, stage-specific functions of a single metavirus-derived gene, PEG10, coordinate placental formation and maintenance, highlighting the evolutionary importance of PEG10 acquisition in therian placentation.

developmental biology↗

bioRxiv2025

Gut mucin fucosylation dictates the entry of botulinum toxin complexes

Botulinum toxins (BoNTs) are the most potent known bacterial toxins. The BoNT complex from Clostridium botulinum B-Okra (large progenitor toxin complex (L-PTC)/BOkra, hyper-oral-toxic) exerts at least 80-fold higher oral toxicity1 in mice compared with that from serotype A1 (L-PTC/A62A, non-hyper-oral-toxic). Here, we showed that L-PTC/BOkra was predominantly absorbed through enterocytes, whereas L-PTC/A62A targeted intestinal microfold cells. Furthermore, we demonstrated that 1,2-fucosylation of intestinal mucin determined the oral toxicity of L-PTCs as well as their entry routes; more specifically, these routes were governed by the carbohydrate-binding spectrum of hemagglutinin (HA) complex, which is one of the L-PTC components. Disruption of fucosylation in fucosyltrasferase-2 (Fut2)-null mice hindered the intestinal mucin penetration of L-PTC/BOkra via HA and reduced the susceptibility to its oral intoxication. Our data establish the molecular mechanism by which the oral toxicity of BoNTs is increased after they cross intestinal mucus layers.

microbiology↗

bioRxiv2024

Targeting of retrovirus-derived Rtl8a/8b reduces social response and increases apathy-like behavior associated with GABRB2 reduction

Retrotransposon Gag-like (RTL) 8A, 8B and 8C are eutherian-specific genes derived from a certain retrovirus. They clustered as a triplet of genes on the X chromosome, but their function remains unknown. Here, we demonstrate that Rtl8a and Rtl8b play important roles in the brain: their double knockout (DKO) mice not only exhibit reduced social responses and increased apathy-like behavior, but also become obese from young adulthood. Mouse RTL8A/8B proteins are expressed in the prefrontal cortex and hypothalamus and localize to both the nucleus and cytoplasm of neurons, presumably due to the N-terminal nuclear localization signal-like sequence at the N-terminus. An RNAseq study in the cerebral cortex revealed reduced expression of several GABA type A receptor subunits, in particular the {beta}2 subunit of Gabrb2, in DKO. We confirmed the reduction of GABRB2 protein in the DKO cerebral cortex by Western blotting. As GABRB2 has been implicated in the etiology of several neurodevelopmental disorders, it is likely that the reduction of GABRB2 is one of the major causes of the neuropsychiatric defects in the DKO mice.

molecular biology↗

bioRxiv2023

Targeting retrovirus-derived Rtl8a and 8b causes late onset obesity and neurodevelopmental defects

Retrotransposon Gag-like (RTL) 8A, 8B and 8C are triplet genes of uncertain function that form a cluster on the X chromosome. They are eutherian-specific genes presumably derived from a certain retrovirus. Here, we demonstrate that Rtl8a and Rtl8b play an important role in growth and behavior via brain functions in the hypothalamus and prefrontal cortex. Rtl8a and Rtl8b double knockout (DKO) mice exhibited overgrowth due to hyperphagia from young adulthood and reduced social responses, increased apathy-like behavior. RTL8A and RTL8B proteins are localized to both the nucleus and cytoplasm of neurons presumably due to an N-terminal nuclear localization signal-like sequence. An increment in nucleus size was also detected in the neurons in the prefrontal cortex, suggesting neuronal dysfunction. These data give another strong evidence that retrovirus-derived acquired genes contributed to the establishment of the current eutherian developmental system in a wide variety of ways. Summary statementRtl8a and Rtl8b double knockout mice exhibited late onset obesity and neurodevelopmental defects, demonstrating that these eutherian specific retrovirus-derived acquired genes encoding proteins with only 113 amino acids play important roles in the brain presumably via their functions in the hypothalamus and prefrontal cortex.

molecular biology↗

bioRxiv2021

PEG10 viral aspartic protease domain is essential for the maintenance of fetal capillary structure in the mouse placenta

The therian-specific gene paternally expressed 10 (Peg10) plays an essential role in placenta formation: Peg10 knockout (KO) mice exhibit early embryonic lethality due to severe placental defects. The PEG10 protein exhibits homology to long terminal repeat (LTR) retrotransposon GAG and POL proteins, therefore mice harboring a mutation in its highly conserved viral aspartic protease motif in the POL-like region were generated because it is essential for LTR retrotransposons/retroviruses. Intriguingly, frequent perinatal lethality, not early embryonic lethality, was observed with fetal and placental growth retardation starting mid-gestation. In the mutant placentas, severe defects were observed in the fetal vasculature, where PEG10 is expressed in the three trophoblast cell layers that surround fetal capillary endothelial cells. Thus, Peg10 has essential roles not only in early placenta formation, but also in placental vasculature maintenance from mid- to late-gestation. This implies that along the feto-maternal placenta interface an interaction occurs between two retrovirus-derived genes, Peg10 and retrotransposon Gag like 1 (Rtl1, also called Peg11), that is essential for the maintenance of fetal capillary endothelial cells. Summary statementDisruption of the highly conserved viral aspartic protease domain in PEG10 causes placental abnormality leading to perinatal lethality in mice.

developmental biology↗

bioRxiv2019

Fully Human Monoclonal Antibodies Effectively Neutralizing Botulinum Neurotoxin Serotype B

Botulinum neurotoxin (BoNT) is the most potent natural toxin known. Of the seven BoNT serotypes (A to G), types A, B, E, and F cause human botulism. Treatment of human botulism requires the development of effective toxin-neutralizing antibodies without side effects such as serum sickness and anaphylaxis. In this study, we generated fully human monoclonal antibodies (HuMAbs) against serotype B BoNT (BoNT/B1) using a murine-human chimera fusion partner cell line named SPYMEG. Of these HuMAbs, M2, which specifically binds to the light chain of BoNT/B1, showed neutralization activity in a mouse bioassay (approximately [≥] 100 i.p. LD50/mg of antibody), and M4, which binds to the C-terminal of heavy chain, showed partial protection. The combination of M2 and M4 was able to completely neutralize BoNT/B1 with a potency greater than 10,000 i.p. LD50/mg of antibodies, and was effective both prophylactically and therapeutically in the mouse model of botulism. Moreover, this combination showed broad neutralization activity against three type B subtypes, namely BoNT/B1, BoNT/B2, and BoNT/B6. These data demonstrate that the combination of M2 and M4 is promising in terms of a foundation for new human therapeutics for BoNT/B intoxication. IMPORTANCEBotulinum neurotoxins (BoNTs) produced by Clostridium botulinum and related species cause human botulism. Immunotherapy is the most effective treatment for botulism and equine immune serum formulations are used in cases of human botulism. However, these antisera may cause serum sickness or anaphylaxis. Additionally, the production of immune sera involves complicated and time-consuming manufacturing processes and quality management. Therefore, the development of safe, effective, and higher productive antibodies is required. Here we generated fully human monoclonal antibodies against serotype B BoNT (BoNT/B). We found that the combination of these antibodies (M2+M4) had potent and broad neutralization activity against BoNT/B, and showed therapeutic and preventive effects against botulism in mouse models. These data indicate that M2+M4 are promising candidates for the development of human therapeutics and prophylactics for BoNT/B intoxication.

microbiology↗