Biology subjects

Maezawa, S.

Publications and source records attributed to Maezawa, S..

12 recordsLinked to original sources

bioRxiv2026

Digital Chromosome Banding Reveals Distinct Spatiotemporal Dynamics and Sexual Dimorphism in Meiotic Silencing

In mammals, meiotic silencing of unsynapsed chromatin (MSUC) is initiated by the DNA damage response (DDR) pathway, as marked by {gamma}H2AX. During normal male meiosis, MSUC is restricted to the unsynapsed sex chromosomes, a process known as meiotic sex chromosome inactivation (MSCI). While the initiation of MSCI has been well studied, its full silencing dynamics and underlying structural mechanisms remain unclear. In contrast to MSCI, broader MSUC can occur on autosomes in response to synapsis failure, but its cell-to-cell variability obscures its quantification. To address these challenges, we introduce "digital-chromosome-banding", a single-cell-based approach that allows quantitative analysis of MSCI and MSUC at chromosomal resolution. Using this approach, we identified two distinct silencing transitions during MSCI, occurring from zygonema to early pachynema and from early to mid-pachynema. The latter step coincides with mature sex body formation and involves a gel-like diffusion barrier to enforce transcriptional repression. Applying this approach to synapsis-defective mouse models (Spo11-/-, Tardbp cKO, and Nelfb cKO), we observed divergent MSUC patterns that correlate with the severity of asynapsis. Comparative analysis between sexes also uncovered notable sexual dimorphisms in meiotic silencing. Together, our data provide a quantitative framework to dissect the spatiotemporal dynamics and sexual differences of meiotic silencing.

cell biology↗

bioRxiv2026

Folate-dependent one-carbon metabolism controls meiotic and post-meiotic epigenome remodeling in the male germline

Environmental exposures can influence offspring health through epigenetic alterations in the male germline. Folate deficiency, a dietary perturbation that disrupts one-carbon metabolism and S-adenosylmethionine (SAM) production, has been linked to altered histone methylation and developmental abnormalities in offspring. However, when and how folate availability shapes the germline epigenome during spermatogenesis remains unclear. In this study, unbiased metabolomic profiling of spermatogenic cells uncovers stage-specific metabolic remodeling, including downregulation of serine- glycine-one-carbon (SGOC) metabolism in meiotic spermatocytes. Using a post-weaning folate-deficient mouse model, we investigate how folate availability influences germline epigenome establishment during spermatogenesis. Consistent with this metabolic transition, genome-wide chromatin accessibility profiling demonstrates extensive, stage-dependent remodeling under folate-deficient conditions, particularly in meiotic spermatocytes and post-meiotic spermatids. These accessibility changes display cell-type-specific genomic distributions and preferential localization to repressive chromatin compartments in post-meiotic cells. Histone modification analyses further reveal bidirectional redistribution of the active histone mark H3K4me3 in round spermatids. Although genome-wide distribution of the repressive mark H3K27me3 remains largely stable, folate deficiency alters its nuclear organization. Notably, a subset of H3K4me3 alterations established in post-meiotic cells is retained in mature sperm, providing a mechanistic link between paternal metabolic perturbation and the germline epigenome. Together, these findings demonstrate that folate availability shapes germline epigenome establishment through stage-specific metabolic and chromatin remodeling during spermatogenesis, revealing a metabolic basis for paternal environmental effects on the germline epigenome.

developmental biology↗

bioRxiv2026

Paternal folate deficiency reveals meiosis as a metabolic sensing window in the male germline

Folate-dependent one-carbon metabolism supplies methyl donors required for chromatin modification, yet how metabolic conditions shape epigenome establishment in the male germline remains poorly understood. Here, using a folate-deficient mouse model, we identify meiotic prophase I as a metabolically sensitive window in the male germline. By integrating in vivo germline analysis with bulk and single-cell transcriptomic and epigenomic profiling, we show that folate deficiency disturbs transcriptional programs in pachytene spermatocytes and preferentially perturbs CpG island (CGI)-associated promoters, which are characterized by bivalent H3K4me3 and H3K27me3 during meiosis. Consistent with this selective vulnerability, active chromatin marks, including H3K4me3 and H3K27ac, are markedly reduced at CGI-associated promoters under folate-deficient conditions. Notably, loci that later exhibit altered H3K4me3 enrichment in mature sperm show earlier chromatin perturbations during meiosis, suggesting that these sperm epigenomic alterations may originate during meiotic development. Together, these findings establish a mechanistic link between paternal folate deficiency and dynamic epigenomic remodeling of CGI-associated chromatin in the male germline.

developmental biology↗

bioRxiv2025

Site-specific DNA demethylation during spermatogenesis presets the sites of nucleosome retention in mouse sperm

DNA methylation patterns are inherited from the parental germline to the embryo. In mature sperm, the sites of unmethylated DNA are tightly coupled to sites of histone retention at gene regulatory elements that are implicated in paternal epigenetic inheritance. The timing and mechanism of site-specific DNA demethylation in the male germline remains unknown. Here, we perform genome-wide profiling of DNA methylation during spermatogenesis by capturing methylated DNA through interaction with a methyl-DNA binding protein domain (MBD). Our data demonstrate a site-specific change in DNA methylation during the mitosis-to-meiosis transition. Importantly, demethylation at these genomic sites during this transition precedes nucleosome retention in spermatozoa. These results suggest that site-specific DNA demethylation during the mitosis-to-meiosis transition of spermatogenesis contributes to the establishment of sperm epigenetic states associated with embryonic gene expression. We therefore propose DNA demethylation during spermatogenesis as a novel phase of epigenetic reprogramming that contributes to embryonic gene regulation.

developmental biology↗

bioRxiv2024

Adaptive decision-making by ants in response to past, imminent, and predicted adversity

Many animals exhibit innate behaviours, which are often interpreted as hard-wired, reflex-like responses, particularly in insects. Among these behaviours, beacon-aiming--an approach towards dark areas or objects--is observed in many animals; however, its functional significance remains unclear, and some ant species do not exhibit it. Here we show that in one such species, Camponotus japonicus, the behaviour was triggered only under adverse substrate conditions, such as during the crossing of liquid-covered surfaces, regardless of the locomotor patterns like walking or swimming, or the mere presence of water, or when walking upside-down. Once initiated, beacon-aiming persists even under normal substrate conditions, as demonstrated by ants transitioning from water-covered to dry substrates suitable for comfortable walking. This behavioural flexibility indicates that the innate behaviour is not hard-wired but modulated by internal states. Furthermore, changes in internal states may serve adaptive decision-making, potentially allowing ants to prepare for future adverse conditions. The isolated ants on a water-surrounded platform gradually established an attraction to the direction of the beacon before ultimately swimming towards it. These findings suggest that beacon-aiming is regulated by internal states, especially anxiety-like states formed in response to past, imminent, and predicted adverse substrate conditions in ants.

animal behavior and cognition↗

bioRxiv2024

Inter-cellular mRNA Transfer Alters Human Pluripotent Stem Cell State

Inter-cellular transmission of mRNA is being explored in mammalian species using immortal cell lines (1-3). Here, we uncover an inter-cellular mRNA transfer phenomenon that allows for the adaptation and reprogramming of human primed pluripotent stem cells (hPSCs). This process is induced by the direct cell contact-mediated coculture with mouse embryonic stem cells (mESCs) under the condition impermissible for human primed PSC culture. Mouse-derived mRNA contents are transmitted into adapted hPSCs only in the coculture. Transfer-specific mRNA analysis show the enrichment for divergent biological pathways involving transcription/translational machinery and stress-coping mechanisms, wherein such transfer is diminished when direct cell contacts are lost. After 5 days of mESC culture, surface marker analysis, and global gene profiling confirmed that mRNA transfer-prone hPSC efficiently gains a naive-like state. Furthermore, transfer-specific knockdown experiments targeting mouse-specific transcription factor-coding mRNAs in hPSC show that mouse-derived Tfcp2l1, Tfap2c, and Klf4 are indispensable for human naive-like conversion. Thus, inter-species mRNA transfer triggers cellular reprogramming in mammalian cells. Our results support that episodic mRNA transfer can occur in cell cooperative and competitive processes(4), which provides a fresh perspective on understanding the roles of mRNA mobility for intra- and inter-species cellular communications.

cell biology↗

bioRxiv2023

CTCF-mediated 3D chromatin predetermines the gene expression program in the male germline

Spermatogenesis is a unidirectional differentiation process that generates haploid sperm, but how the gene expression program that directs this process is established is largely unknown. Here we determine the high-resolution 3D chromatin architecture of male germ cells during spermatogenesis and show that CTCF-mediated 3D chromatin predetermines the gene expression program required for spermatogenesis. In undifferentiated spermatogonia, CTCF-mediated chromatin contacts on autosomes pre-establish meiosis-specific super-enhancers (SE). These meiotic SE recruit the master transcription factor A-MYB in meiotic spermatocytes, which strengthens their 3D contacts and instructs a burst of meiotic gene expression. We also find that at the mitosis-to-meiosis transition, the germline-specific Polycomb protein SCML2 resolves chromatin loops that are specific to mitotic spermatogonia. Moreover, SCML2 and A-MYB establish the unique 3D chromatin organization of sex chromosomes during meiotic sex chromosome inactivation. We propose that CTCF-mediated 3D chromatin organization enforces epigenetic priming that directs unidirectional differentiation, thereby determining the cellular identity of the male germline.

developmental biology↗

bioRxiv2023

PRC1 directs PRC2-H3K27me3 deposition to shield adult spermatogonial stem cells from differentiation

Spermatogonial stem cell functionality resides in the slow-cycling and heterogeneous undifferentiated spermatogonia cell population. This pool of cells supports lifelong fertility in adult males by balancing self-renewal and differentiation to produce haploid gametes. However, the molecular mechanisms underpinning long-term stemness of undifferentiated spermatogonia during adulthood remain unclear. Here, we discover that an epigenetic regulator, Polycomb repressive complex 1 (PRC1), shields adult undifferentiated spermatogonia from differentiation, maintains slow cycling, and directs commitment to differentiation during steady-state spermatogenesis in adults. We show that PRC2-mediated H3K27me3 is an epigenetic hallmark of adult undifferentiated spermatogonia. Indeed, spermatogonial differentiation is accompanied by a global loss of H3K27me3. Disruption of PRC1 impairs global H3K27me3 deposition, leading to precocious spermatogonial differentiation. Therefore, PRC1 directs PRC2-H3K27me3 deposition to maintain the self-renewing state of undifferentiated spermatogonia. Importantly, in contrast to its role in other tissue stem cells, PRC1 negatively regulates the cell cycle to maintain slow cycling of undifferentiated spermatogonia. Our findings have implications for how epigenetic regulators can be tuned to regulate the stem cell potential, cell cycle, and differentiation to ensure lifelong fertility in adult males.

developmental biology↗

bioRxiv2023

KRAB-zinc-finger proteins regulate endogenous retroviruses to sculpt germline transcriptomes and genome evolution

As transposable elements (TEs) coevolved with the host genome, the host genome exploited TEs as functional regulatory elements. What remains largely unknown are how the activity of TEs, namely, endogenous retroviruses (ERVs), are regulated and how TEs evolved in the germline. Here we show that KRAB domain-containing zinc-finger proteins (KZFPs), which are highly expressed in mitotically dividing spermatogonia, bind to suppressed ERVs that function following entry into meiosis as active enhancers. These features are observed for independently evolved KZFPs and ERVs in mice and humans, i.e., are evolutionarily conserved in mammals. Further, we show that meiotic sex chromosome inactivation (MSCI) antagonizes the coevolution of KZFPs and ERVs in mammals. Our study uncovers a mechanism by which KZFPs regulate ERVs to sculpt germline transcriptomes. We propose that epigenetic programming in the mammalian germline during the mitosis-to-meiosis transition facilitates coevolution of KZFPs and TEs on autosomes and is antagonized by MSCI.

genomics↗

bioRxiv2021

Polycomb suppresses a female gene regulatory network in Sertoli cells

Gonadal sex determination is controlled by the support cells of testes and ovaries. In testes, the epigenetic mechanism that maintains cellular memory to suppress female sexual differentiation remains unknown. Here, we show that Polycomb suppresses a female gene regulatory network in Sertoli cells, the specific support cells for postnatal testes. Through genetic ablation, we removed Polycomb repressive complex 1 (PRC1) from embryonic Sertoli cells after sex determination. PRC1-depleted postnatal Sertoli cells exhibited defective proliferation and cell death, leading to the degeneration of adult testes. In adult Sertoli cells, PRC1 suppressed the specific, critical genes required for granulosa cells, the support cells of ovaries, thereby inactivating the female gene regulatory network. The underlying chromatin of female genes was coated with Polycomb-mediated repressive modifications: PRC1-mediated H2AK119ub and PRC2-mediated H3K27me3. Taken together, we identify a critical mechanism centered on Polycomb that maintains the male fate in adult testes.

developmental biology↗

bioRxiv2020

Super-enhancer switching drives a burst in germline gene expression at the mitosis-to-meiosis transition

The testis has the most diverse and complex transcriptome of all organs due to bursts in expression of thousands of germline-specific genes. Much of this unique gene expression takes place when mitotic germ cells differentiate and enter into meiotic prophase. Here, we demonstrate that the genome-wide reorganization of super-enhancers (SEs) drives bursts of germline genes after the mitosis-to-meiosis transition. At the mitosis-to-meiosis transition, mitotic SEs dissolve while meiotic SEs are established. Meiotic SEs are associated with the activation of key germline genes, defining the cellular identity of germ cells. This SE switching is regulated by the establishment of meiotic SEs via A-MYB (MYBL1), a key transcription factor for germline genes, and by the resolution of mitotic SEs via SCML2, a germline-specific Polycomb protein required for spermatogenesis-specific gene expression. Prior to the entry into meiosis, meiotic SEs are preprogrammed in mitotic spermatogonia, serving to direct the unidirectional differentiation of spermatogenesis. We identify key regulatory factors for both mitotic and meiotic enhancers, revealing a molecular logic for the concurrent activation of mitotic enhancers and suppression of meiotic enhancers in the somatic and/or mitotically proliferating phase.

developmental biology↗

bioRxiv2020

Endogenous retroviruses drive species-specific germline transcriptomes in mammals

Gene regulation in the germline ensures the production of high-quality gametes, long-term maintenance of the species, and speciation. Germline transcriptomes undergo dynamic changes after the mitosis-to-meiosis transition in males and have been subject to evolutionary divergence among mammals. However, the mechanism that underlies germline regulatory divergence remains undetermined. Here, we show that endogenous retroviruses influence species-specific germline transcriptomes in mammals. We show that the expression of endogenous retroviruses, particularly the evolutionarily young K family (ERVK), is associated with gene activation after the mitosis-to-meiosis transition in male mice. We demonstrate that accessible chromatin and H3K27ac, a marker of active enhancers, are tightly associated with ERVK loci as well as with the activation of neighboring evolutionarily young germline genes. Thus, ERVKs serve as evolutionarily novel enhancers in mouse spermatogenesis. These ERVK loci bear binding motifs for critical regulators of spermatogenesis such as A-MYB. The genome-wide transposition of ERVKs might have rewired germline gene expression in a species-specific manner. Notably, these features are present in human spermatogenesis, but independently evolved ERVs are associated with expression of germline genes, demonstrating the prevalence of ERV-driven mechanisms in mammals. Together, we propose a model whereby species-specific transcriptomes are fine-tuned by endogenous retroviruses in the mammalian germline.

developmental biology↗