Biology subjects

Ohira, T.

Publications and source records attributed to Ohira, T..

7 recordsLinked to original sources

bioRxiv2025

Insulin-like androgenic gland factor regulates the development of internal and external secondary sexual characteristics in juvenile male kuruma prawn Marsupenaeus japonicus

In decapod crustaceans, insulin-like androgenic gland factor (IAG) is a well-known peptide hormone produced by the androgenic gland, a male-specific endocrine organ. In certain species classified within Pleocyemata, experimental manipulation of IAG signaling has successfully altered both internal and external sexual characteristics, leading to sex reversal. Therefore, IAG is considered a key regulator of male sexual differentiation and maturation and is thought to be a crustacean androgen. In the kuruma prawn Marsupenaeus japonicus (Dendrobranchiata), an important fishery species in Japan, a homologous molecule known as Maj-IAG has been identified. However, its physiological function in males remains poorly understood. In this context, we conducted Maj-IAG knockdown (KD) via RNA interference in juvenile male M. japonicus. Over a 9-week period, Maj-IAG KD significantly inhibited the development of the petasma, male-specific external copulatory structure, and parts of the internal reproductive organs, such as the vas deferens and seminal vesicles. In contrast, somatic growth and testicular development were unaffected by Maj-IAG KD. Histological analysis of the testes revealed no evident abnormalities such as degeneration of testicular structures or abnormal arrest of germ cell differentiation. These findings indicate that Maj-IAG partially governs the development of male secondary sexual characteristics in juveniles and further suggest that once testicular differentiation is initiated, the maintenance and development of the testis proceeds without dependence on Maj-IAG. Our study provides fundamental insights that may contribute to the advancement of functional sex reversal technologies in penaeid shrimps. HighlightsO_LILong-term gene knockdown of the insulin-like androgenic gland factor gene (Maj-IAG) was successfully achieved in Marsupenaeus japonicus. C_LIO_LISomatic growth and spermatogenesis were not affected by Maj-IAG knockdown. C_LIO_LIMaj-IAG is involved in the development of male secondary sexual characteristics in juvenile prawns, including the external male copulatory structures and certain parts of the internal male reproductive organs. C_LI

zoology↗

bioRxiv2025

Characterization of a crustacean hyperglycemic hormone of the horsehair crab Erimacrus isenbeckii

The horsehair crab Erimacrus isenbeckii is widely distributed from Alaska and the Bering Sea through Southern Sakhalin, and in Japan from the coastal areas of Hokkaido to the Sea of Japan. In the Hokkaido area, although strict resource management has been promoted by setting an allowable catch limit, the catch amount has remained at a low level. While knowledge on larval rearing methods is accumulating in relation to seedling production techniques, information on adult growth and molting is limited, due to a deep-sea species that requires a long period for growth. In decapod crustaceans, the sinus-gland/X-organ complex in the eyestalk ganglion synthesizes and secrets various neuropeptides such as crustacean hyperglycemic hormone (CHH) to regulate the homeostasis of blood glucose levels. In this study, combined isolation of sinus gland peptides by reverse-phase high-performance liquid chromatography (RP-HPLC) and amino acid sequencing, and transcriptome analyses using male and female eyestalk ganglion has been successfully identified EiCHHa. The in vivo assays of EiCHHa using the blue swimming crab Portunus pelagicus revealed EiCHHa has a hyperglycemic effect, as well as CHHs in other decapod crustaceans. Additionally, we successfully demonstrated the sexual differences in the transcriptomic profiles between males and females. Especially, two sinus gland-derived neuropeptides (EiCHHb and a crustacean female sex hormone (EiCFSH)) were isolated as female-biased transcripts, suggesting that both hormones may have female-specific roles such as the development of female characteristics and reproduction.

molecular biology↗

bioRxiv2024

Toxic Small Alarmone Synthetase FaRel2 inhibits translation by pyrophosphorylating tRNAGly and tRNAThr

Translation-targeting toxic Small Alarmone Synthetases (toxSAS) are effectors of bacterial Toxin-Antitoxin systems that pyrophosphorylate the 3-CCA end of tRNA to prevent aminoacylation. toxSAS are implicated in antiphage immunity: phage detection triggers the toxSAS activity to shut down viral production. We show that the toxSAS FaRel2 inspects the tRNA acceptor stem to specifically select tRNAGly and tRNAThr. The 1st, 2nd, 4th and 5th base pairs the stem act as the specificity determinants. We show that the toxSASs PhRel2 and CapRelSJ46 differ in tRNA specificity from FaRel2, and rationalise this through structural modelling: while the universal 3-CCA end slots into a highly conserved CCA recognition groove, the acceptor stem recognition region is variable across toxSAS diversity. As phages use tRNA isoacceptors to overcome tRNA-targeting defences, we hypothesise that highly evolvable modular tRNA recognition allows for the escape of viral countermeasures through tRNA substrate specificity switching.

microbiology↗

bioRxiv2023

Dengue virus exploits the host tRNA epitranscriptome to promote viral replication

The 40-50 RNA modifications of the epitranscriptome regulate posttranscriptional gene expression. Here we show that flaviviruses hijack the host tRNA epitranscriptome to promote expression of pro-viral proteins, with tRNA-modifying ALKBH1 acting as a host restriction factor in dengue virus infection. Early in the infection of human Huh-7 cells, ALKBH1 and its tRNA products 5-formylcytidine (f5C) and 2-O-methyl-5-formylcytidine (f5Cm) were reduced. ALKBH1 knockdown mimicked viral infection, but caused increased viral NS3 protein levels during infection, while ALKBH1 overexpression reduced NS3 levels and viral replication, and increased f5C and f5Cm. Viral NS5, but not host FTSJ1, increased f5Cm levels late in infection. Consistent with reports of impaired decoding of leucine UUA codon by f5Cm-modified tRNALeu(CAA), ALKBH1 knockdown induced translation of UUA-deficient transcripts, most having pro-viral functions. Our findings support a dynamic ALKBH1/f5Cm axis during dengue infection, with virally-induced remodeling of the proteome by tRNA reprogramming and codon-biased translation.

microbiology↗

bioRxiv2023

Dual roles of crustacean female sex hormone during juvenile stage in the kuruma prawn Marsupenaeus japonicus

The crustacean female sex hormone (CFSH) has been identified as a female-specific hormone that plays a crucial role in female phenotype developments in the blue crab Callinectes sapidus. To date, its homologous genes have been reported in various decapod species. Additionally, unlike the blue crab, several species have two different CFSH subtypes. The kuruma prawn Marsupenaeus japonicus is a representative example species of this phenomenon, having two CFSH subtypes identified from the eyestalk (MajCFSH) and ovary (MajCFSH-ov). Eyestalk-type MajCFSH is expressed predominantly in the eyestalk at the same level in both sexes, indicating no female-specificity. Here, we conducted gene knockdown analysis of eyestalk-type MajCFSH using sexually immature juveniles of kuruma prawn (average body length: [~]10 mm) to elucidate its physiological functions. As a result, MajCFSH-knockdown did not affect the development of sex-specific characteristics such as external reproductive organs, while it induced apparent growth suppression in male juveniles, implying that MajCFSH may play a male-specific juvenile growth role. Moreover, MajCFSH-knockdown female and male juveniles changed their body color to become brighter, indicating that MajCFSH has the ability to change body color by dispersing the pigment granules in the chromatophore. Overall, our present study improved our understanding of the physiological roles of CFSH using kuruma prawn. Highlights- MajCFSH-knockdown was conducted using sexually immature juveniles of kuruma prawn. - MajCFSH-knockdown male juveniles showed significant growth suppression. - MajCFSH-knockdown female and male juveniles changed their body color to become brighter.

physiology↗

bioRxiv2021

Endothelial metastasis-associated protein 1 (MTA1) is an essential molecule for angiogenesis

Our previous study revealed that metastasis-associated protein 1 (MTA1), expressed in endothelial cells acts as a factor promoting tube formation. In this study, we aimed to clarify the importance of MTA1 in tube formation using MTA1-knockout endothelial cells (MTA1-KO MSS31 cells). Tube formation was strongly suppressed in MTA1-KO MSS31 cells, whereas MTA1-overexpressed MTA1-KO MSS31 cells regained the ability to form tube-like structures. Furthermore, MTA1-KO MSS31 cells showed higher phosphorylation of non-muscle myosin heavy chain IIa (NMIIa), which resulted in suppression of tube formation; this was attributed to a decrease of MTA1- S100 calcium-binding protein A4 (S100A4) complex formation. Moreover, inhibition of tube formation in MTA1-KO MSS31 cells could not be rescued by stimulation with vascular endothelial growth factor (VEGF). These results demonstrated that MTA1 is an essential molecule for angiogenesis, and that it may be involved in different steps of the angiogenic process compared to the VEGF-VEGF receptor 2 (VEGFR2) pathway. Our findings showed that endothelial MTA1 and its pathway are promising targets for inhibiting tumor angiogenesis, supporting the development of MTA1-based anti-angiogenic therapies.

cell biology↗

bioRxiv2019

PITX1 protein interacts with ZCCHC10 to regulate hTERT mRNA transcription

Telomerase is a ribonucleoprotein ribonucleic enzyme that is essential for cellular immortalization via elongation of telomere repeat sequences at the end of chromosomes. Human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase holoenzyme, is a key regulator of telomerase activity. Telomerase activity, which has been detected in the majority of cancer cells, is accompanied by hTERT expression, resulting in continuous cell division that is a crucial factor for malignant transformation. Thus, hTERT is an attractive target for cancer-specific treatments. We previously reported that pared-like homeodomain 1 (PITX1) is a negative regulator of hTERT through direct binding to the hTERT promoter. However, the mechanism by which the function of PITX1 contributes to transcriptional silencing of the hTERT gene remains to be clarified. Here, we show that PITX1 and zinc finger CCHC-type containing 10 (ZCCHC10) proteins cooperate to facilitate the transcriptional regulation of the hTERT gene by functional studies via FLAG pull-down assay. Co-expression of PITX1 and ZCCHC10 resulted in inhibition of hTERT transcription, in melanoma cell lines, whereas mutate-deletion of homeodomain in PITX1 that interact with ZCCHC10 did not induce similar phenotypes. In addition, ZCCHC10 expression levels showed marked decrease in the majority of melanoma cell lines and tissues. Taken together, these results suggest that ZCCHC10-PITX1 complex is a new functional unit that suppresses hTERT transcription, and plays a crucial role in cancer development through regulation of telomerase activity.

cancer biology↗