Biology subjects

Usuki, S.

Publications and source records attributed to Usuki, S..

7 recordsLinked to original sources

bioRxiv2026

MEIOSIN retains an intrinsic STRA8-independent activity that drives meiotic entry across vertebrate evolution

Meiotic entry in vertebrates has been viewed as a transcriptional switch driven by the MEIOSIN-STRA8 axis, but whether this represents the ancestral regulatory logic of meiosis has remained unclear. Here we combine comparative genomics with genetic and single-cell analyses in zebrafish and mice to show that MEIOSIN retains an intrinsic STRA8-independent activity. We identify Meiosin orthologs in zebrafish and hagfish, vertebrate lineages that lack Stra8, and show that these proteins retain the HMG domain but have lost the bHLH domain required for the canonical MEIOSIN-STRA8 interaction. In zebrafish, meiosin is transiently induced at meiotic entry in both sexes, yet its loss selectively disrupts the female germ line, causing failure of oogenesis and female-to-male sex reversal. In mice, MEIOSIN lacking the bHLH domain still initiates key features of meiotic entry and partially activates meiotic target genes, although it fails to support full meiotic progression. Together, these findings identify HMG-containing MEIOSIN as a conserved core regulator of meiotic entry and position STRA8 as a later-acting module that enhances the efficiency and robustness of meiotic gene activation.

developmental biology↗

bioRxiv2025

MAP7-driven cytoskeletal cross-talk establishes Sertoli cell polarity crucial for germ cell meiotic progression

How specialized apical membrane domains are assembled in vivo remains poorly understood. In the mouse testis, Sertoli cells build a luminal apical domain after birth that organizes the seminiferous epithelium and supports germ cell differentiation, distinct from fetal polarity established during cord formation. Here, we identify the microtubule-associated protein MAP7 as a key regulator of cytoskeletal organization during apical domain formation. MAP7 preferentially localizes to apical microtubules in Sertoli cells, showing limited overlap with stable microtubule markers. Native-tissue imaging indicates that MAP7-decorated microtubules, initially lacking obvious directionality, become increasingly aligned along the tubule axis as the apical domain matures. In Map7-deficient testes, microtubule abundance is maintained, but higher-order organization is disrupted and accompanied by persistent luminal F-actin accumulation. These defects compromise apical domain maturation and lumen formation during the first wave of spermatogenesis and are associated with altered tight-junction patterning. Proteomic analysis identifies the non-muscle myosin II heavy chains MYH9 and MYH10 among MAP7-associated proteins. MYH9 becomes enriched at luminal regions where microtubules and F-actin converge, but remains diffuse in Map7-deficient Sertoli cells despite ectopic luminal cytoskeletal assemblies, suggesting that MAP7 helps establish a cytoskeletal context that supports spatially restricted NMII enrichment. Single-cell RNA sequencing shows that Sertoli transcriptional differentiation largely proceeds without MAP7, whereas germ cells exhibit delayed meiotic progression with expansion of pachytene-stage subpopulations. Together, these findings establish MAP7-dependent microtubule remodeling as an organizing mechanism for postnatal apical domain maturation and suggest how epithelial cytoskeletal architecture shapes a niche that helps pace developmental progression of neighboring germ cells.

cell biology↗

bioRxiv2023

Atypical heat shock transcription factor HSF5 is critical for male meiotic prophase under non-stress conditions

Meiotic prophase progression is differently regulated in males and females. In males, pachytene transition during meiotic prophase is accompanied by robust alteration in gene expression. However, how gene expression is regulated differently to ensure meiotic prophase completion in males remains elusive. Herein, we identified HSF5 as a male germ cell-specific heat shock transcription factor (HSF) for meiotic prophase progression. Genetic analyses and single-cell RNA-sequencing demonstrated that HSF5 is essential for progression beyond the pachytene stage under non-stress conditions rather than heat stress. Chromatin binding analysis in vivo and DNA-binding assays in vitro suggested that HSF5 binds to promoters in a subset of genes associated with chromatin organization. HSF5 recognizes a DNA motif different from typical heat shock elements recognized by other canonical HSFs. This study suggests that HSF5 is an atypical HSF that enforces the gene expression program for pachytene transition during meiotic prophase in males.

developmental biology↗

bioRxiv2023

RNA G-quadruplexes forming scaffolds for alpha-synuclein aggregation lead to progressive neurodegeneration

Synucleinopathies, including Parkinsons disease, dementia with Lewy bodies, and multiple system atrophy, are triggered by the aggregation of -synuclein, leading to progressive neurodegeneration1,2,3,4,5,6,7,8. However, the intracellular mechanism of -synuclein aggregation remains unclear. Here we show that assembly of RNA G-quadruplexes forming scaffolds for -synuclein aggregation, contributing to neurodegeneration. Purified -synuclein binds RNA G-quadruplexes directly through the N-terminus. RNA G-quadruplex itself undergoes phase separation and assembly by Ca2+, accelerating the sol-gel phase transition of -synuclein. In -synuclein preformed fibrils-treated neurons, RNA G-quadruplexes assembly composed of synaptic mRNAs co-aggregates with -synuclein upon Ca2+ excess influx into cytoplasm, eliciting synaptic dysfunction. Forced assembly of RNA G-quadruplexes using an optogenetic approach evokes -synuclein aggregation, neuronal dysfunction and neurodegeneration. Administration of 5-aminolevulinic acid, a prodrug of protoporphyrin IX that prevents phase separation of RNA G-quadruplexes9, attenuating -synuclein aggregation, neurodegeneration, and progressive motor deficits in -synuclein preformed fibrils-injected synucleinopathy mice. Together, assembly of RNA G-quadruplexes due to dysregulation of intracellular Ca2+ homeostasis accelerates -synuclein phase transition and aggregation may contribute to pathogenesis of synucleinopathies.

molecular biology↗

bioRxiv2022

ROR1 plays a critical role in pancreatic tumor-initiating cells with a partial EMT signature.

Tumor-initiating cells are the major drivers of chemoresistance and relapse, making them attractive targets for cancer therapy. However, the identity of tumor- initiating cells in human pancreatic ductal adenocarcinoma (PDAC) and the key molecules underlying their traits remain poorly understood. Here, we show that a partial epithelial-mesenchymal transition (EMT)-like subpopulation marked by high expression of receptor tyrosine kinase-like orphan receptor 1 (ROR1) is the origin of heterogeneous tumor cells in PDAC. We demonstrate that ROR1 depletion suppresses tumor growth, recurrence after chemotherapy, and metastasis. Mechanistically, ROR1 induces the expression of AURKB by activating E2F to enhance PDAC proliferation. Furthermore, epigenomic analyses reveal that ROR1 is transcriptionally dependent on YAP/BRD4 binding at the enhancer region, and targeting this pathway reduces ROR1 expression and prevents PDAC growth. Collectively, our findings reveal a critical role of ROR1high cells as tumor-initiating cells and the functional importance of ROR1 in PDAC progression, thereby highlighting its therapeutic targetability. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=192 HEIGHT=200 SRC="FIGDIR/small/499868v2_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@167bf72org.highwire.dtl.DTLVardef@49df52org.highwire.dtl.DTLVardef@1e480a3org.highwire.dtl.DTLVardef@b987bf_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

Meiosis-specific ZFP541 repressor complex promotes meiotic prophase exit during spermatogenesis

During spermatogenesis, meiosis is accompanied by robust alteration in gene expression and chromatin status. However, it remained elusive how meiotic transcriptional program is established to ensure completion of meiotic prophase. Here, we identified a novel protein complex consisting of germ-cell-specific zinc-finger protein ZFP541 and its interactor KCTD19 as the key transcriptional regulator for meiotic prophase exit. Our genetic study showed that ZFP541 and KCTD19 are co-expressed from pachytene onward and play an essential role in the completion of meiotic prophase program in the testis. Furthermore, our ChIP-seq and transcriptome analyses revealed that ZFP541 binds to and suppresses a broad range of genes whose function is associated with biological processes of transcriptional regulation and covalent chromatin modification. The present study demonstrated that germ-cell specific ZFP541-KCTD19 containing complex promotes meiotic prophase exit in males, and triggers reconstruction of the transcription network and chromatin organization leading to post-meiotic development.

developmental biology↗

bioRxiv2019

Distinct transcriptional programs of SOX2 in different types of small cell lung cancers

SOX2 is an oncogene in human small cell lung cancer (SCLC), an aggressive neuroendocrine (NE) tumor. However, the roles of SOX2 in SCLC remain unclear, and strategies to selectively target SOX2 in SCLC cells have not yet been established. We herein demonstrated that SOX2 is involved in NE differentiation and tumorigenesis in cooperation with ASCL1, a lineage-specific transcriptional factor, in the classical subtype of SCLC cell lines. ASCL1 recruits SOX2, which promotes INSM1 expression. Precursor SCLC lesions were established in Trp53 (-/-); CCSPrtTA; tetOCre; floxedRb1; floxedHes1 mice, and the NE neoplasms induced were positive for Ascl1, Sox2, and Insm1. In contrast to the ASCL1-SOX2 signaling axis to control the SCLC phenotype in classical subtype SCLC, SOX2 targeted distinct genes, such as those related to the Hippo pathway, in ASCL1-negative, variant subtype SCLC. The present results support the importance of the ASCL1-SOX2 axis as a main subtype of SCLC, and suggest the therapeutic potential of targeting the ASCL1-SOX2 signaling axis and the clinical utility of SOX2 as a biological marker in the classical subtype of SCLC.

cancer biology↗