Biology subjects

Nakahara, T.

Publications and source records attributed to Nakahara, T..

4 recordsLinked to original sources

bioRxiv2025

Impaired store-operated Ca2+ entry in mouse epidermis leads to reduced epidermal barrier function via Klk activation.

Store-operated Ca2+ entry (SOCE) is a mechanism by which STIM1/2 detect calcium depletion in the endoplasmic reticulum (ER) and activate ORAI1/TRPC channels on the cell membrane to induce calcium influx into the cytoplasm. This study aimed to investigate SOCEs role in the skin epidermis in vivo, using female mice with epithelial tissue-specific Stim1 and Stim2 knockout (Stim1/2 cKO) and control mice (Stim1/2fl/fl). Keratinocytes from Stim1/2 cKO mice exhibited reduced Stim1 and Stim2 gene expression levels and impaired SOCE function compared with the controls. Histological analysis revealed hyperkeratosis in the Stim1/2 cKO tissues; however, no significant changes were observed in the proliferation or migration of keratinocytes or wound healing of the back skin. RNA-seq analysis indicated altered keratinization and cell-to-cell adhesion in the Stim1/2 cKO mice. Additionally, transepidermal water loss (TEWL) was increased significantly, and a biotinylated reagent diffused from the subcutaneous area into the granular layer, signifying compromised barrier function in the Stim1/2 cKO mice. The Stim1/2 cKO mice exhibited alterations in desmoglein 1 (Dsg1) and elevated levels of Kallikrein-related peptidase (Klk) 6 and Klk7, leading to increased trypsin- and chymotrypsin-like serine protease activities, respectively. These results suggest that SOCE dysfunction leads to hyperkeratosis and impaired epidermal barrier function via Klk activation without affecting skin cell proliferation in vivo. These novel findings improve understanding of the molecular mechanisms underlying calcium signaling in the epidermis barrier and suggest potential avenues for investigating related skin pathologies linked to calcium homeostasis, such as Hailey-Hailey disease (HHD) and Darier disease (DD).

cell biology↗

bioRxiv2025

REFEE Shapes ZGA Through Post-Transcriptional Regulation of Repetitive RNAs in Mouse Embryos

During early mammalian embryonic development, repetitive elements such as transposons and duplicated genes are transcriptionally active and play key roles in embryogenesis. MERVL, an endogenous retrovirus, is essential for shaping the early transcriptome, particularly during the transition from totipotency to pluripotency. However, the function of many repetitive elements remains poorly understood. Here, we add a new repetitive player, REFEE, that regulates repetitive RNAs and contributes to totipotency regulation through post-transcriptional mechanisms. REFEE was initially identified as a paralogue of Alyref, a nucleocytoplasmic RNA exporter, transiently expressed during the 2-cell stage of mouse embryogenesis. REFEE preferentially binds and stabilizes MERVL RNA, promoting its export. REFEE knockdown embryos fail to complete zygotic genome activation (ZGA), accompanied by a significant reduction in MERVL RNA levels. REFEE primarily influences transcript levels of ZGA genes, upregulating or downregulating them in a manner correlated with their genomic proximity to MERVL. Proteomic analysis further revealed that REFEE knockdown also decreases protein levels of its RNA targets, indicating an additional layer of post-transcriptional regulation beyond RNA stability. Our findings identify REFEE as an essential post-transcriptional regulator of early embryonic development and highlight the functional interplay between repetitive elements in shaping the zygotic transcriptome.

developmental biology↗

bioRxiv2025

Functional redundancy between UTY and UTX in regulating the localization of transcription factors involved in pluripotency

The Y chromosome harbors few protein-coding genes, and their roles in early human development remain largely unclear. Here, we demonstrate that UTY, a Y-linked homolog of the histone demethylase UTX, plays a critical, demethylase-independent role in maintaining pluripotency in human embryonic stem cells (hESCs). Despite its low expression and weak enzymatic activity, UTY co-occupies active cis-regulatory elements with UTX and promotes the transcription of key pluripotency genes, including NODAL and LEFTY. Integrated genomic analyses of single and double knockout hESCs reveal that UTY and UTX function redundantly to maintain chromatin accessibility and ensure proper recruitment of core transcription factors such as OCT4 and SOX2. The combined loss of UTY and UTX disrupts transcription factor localization, induces widespread gene expression changes, and leads to a collapse of the pluripotent state, without detectable changes in H3K27 methylation. Instead, these defects are associated with impaired recruitment of ATP-dependent chromatin remodelers and reduced histone acetylation, suggesting a demethylase-independent mechanism. Our findings uncover an essential role for the evolutionarily conserved UTY in safeguarding enhancer function and transcription factor occupancy, highlighting Y-linked regulatory mechanisms that are critical for maintaining human pluripotency. Summary statementThis study reveals how UTX and UTY cooperate to maintain stable gene regulation in human stem cells and guide proper developmental programs.

developmental biology↗

bioRxiv2023

Delivering mRNAs to mouse tissues using the SEND system

mRNAs produced in a cell are almost always translated within the same cell. Some mRNAs are transported to other cells of the organism through processes involving membrane nanotubes or extracellular vesicles. A recent report describes a surprising new phenomenon of encapsulating mRNAs inside virus-like particles (VLPs) to deliver them to other cells in a process that was named SEND (Selective Endogenous eNcapsidation for cellular Delivery). Although the seminal work demonstrates the SEND process in cultured cells, it is unknown whether this phenomenon occurs in vivo. Here, we demonstrate the SEND process in living organisms using specially designed genetically engineered mouse models. Our proof of principle study lays a foundation for the SEND-VLP system to potentially be used as a gene therapy tool to deliver therapeutically important mRNAs to tissues.

genomics↗