Xudong Zhao

Polycomb Repressive Complex 1 (PRC1) and its antagonistic H2A deubiquitinase USP16 have been regarded as nuclear proteins acting on chromatin. However, our recent studies revealed that a fraction of PRC1 and USP16 also localizes to mitochondria, where PRC1 plays a critical role in maintaining mitochondrial function. The role of USP16 in this context, however, has not yet been investigated. This study shows that USP16 interacts with and stabilizes TOM40, the core subunit of the TOM complex. USP16 deubiquitinates K48-linked ubiquitin chains from lysine 175, 184, and 309 of TOM40. USP16 knockout disrupts mitochondrial homeostasis, resulting in impaired membrane potential, elevated reactive oxygen species, reduced ATP synthesis, and altered oxygen consumption rates. Expression of FLAG-tagged USP16 restores TOM40 protein levels and rescues mitochondrial function. TOM40 re-expression in USP16 KO cells partially restores mitochondrial function, confirming its essential role. In summary, this study reveals that USP16 regulates mitochondrial function through TOM40.

The lack of hormone-responsive follicles is a major challenge in treating infertility/subfertility in women with premature ovarian insufficiency or diminished ovarian reserve. In this study, we demonstrate that securinine, a neurological drug, can be repurposed to promote small follicle growth. In aged mice, intraovarian injection of securinine significantly enhances follicular development and improves fertility, yielding healthy offspring. Mechanistically, single-cell RNA sequencing reveals that securinine promotes follicular development by alleviating the negative regulation from the stromal extracellular matrix on granulosa cells. Furthermore, intraovarian injection of securinine in aged cynomolgus macaques effectively stimulates the development of small follicles into large antral follicles. Our findings highlight securinine as a promising candidate for ultrasound-guided ovarian injection for treating infertility/subfertility in women with premature ovarian insufficiency, diminished ovarian reserve, or advanced maternal age. As a small molecule drug, intraovarian securinine injection offers clinical advantages that avoid complex preparation procedures required for platelet-rich plasma or stem cell-based therapies.

Currently, no effective treatment exists for infertility associated with premature ovarian insufficiency (POI) because affected patients lack hormone-responsive antral follicles. By screening a Food and Drug Administration (FDA)–approved drug library, we identified finerenone, a kidney disease medication, as a promising drug for restoring fertility in POI. Finerenone stimulated follicle development in aged mice and restored antral follicle development in patients with POI following oral administration, resulting in mature oocytes and embryos. Mechanistically, finerenone reduced fibrotic deposition in the ovarian stroma, alleviating collagen-mediated suppression of follicular development. Building on this insight, we identified additional FDA-approved oral antifibrotic drugs as potential treatments for POI-related infertility. Our findings highlight the ovarian stroma—rather than the follicles themselves—as the key therapeutic target and offer potential therapeutic leads for POI-related infertility.

In mouse early pachytene spermatocytes, the X and Y chromosomes undergo rapid non-homologous (NH) synapsis and desynapsis, but the functional significance remains unknown. Here, we report that pachynema-specific knockout of Speedy A (SpdyA) from telomeres caused persistent Y-X NH synapsis , with the entire Y axis synapsed onto the X axis. This persistent Y-X NH synapsis did not interrupt meiotic sex chromosome inactivation, recombination, or sex body formation, but it disrupted X-Y loop-axis organization and homologous X-Y desynapsis, leading to spermatocyte death. Similarly, persistent Y-X NH synapsis was also observed in pachytene spermatocytes lacking TRF1, where SpdyA was frequently lost from the X-Y non-pseudoautosomal region (non-PAR) telomeres. Mechanistic studies revealed that Serine 48 of SUN1 is a key SpdyA/CDK2 phosphorylation site required for Y-X NH desynapsis. We propose that SpdyA governs Y-X NH desynapsis by stabilizing the linkage between the X-Y non-PAR telomeres and their LINC complexes, and that this process is regulated independently from other aspects of pachynema progression. Our findings suggest a key role for Y-X NH desynapsis in establishing proper X-Y loop-axis organization.

Esophageal squamous cell carcinoma (ESCC) is a prevalent malignancy, ranking eleventh in incidence and seventh in mortality globally. Remodeling and Spacing factor 1 (RSF1), a chromatin remodeling factor, is frequently overexpressed in various tumors and correlates with poor prognosis. This study, combining public database analysis and clinical sample validation, reveals significantly elevated RSF1 expression in ESCC tumor tissues, confirmed further in an ESCC orthotopic model. Functional assays show that RSF1 knockout (KO) significantly inhibits ESCC cell proliferation, migration, invasion, and in vivo tumor growth, while reintroducing RSF1 restores its oncogenic effects. Proteomic analysis highlights that RSF1 KO disrupts pathways associated with cell cycle control, apoptosis, and focal adhesion. Experimentally, RSF1 KO induces apoptosis and G2/M arrest, establishing its essential role in ESCC progression. Collectively, these findings establish RSF1 as an oncogenic driver and a promising therapeutic target in ESCC.

Esophageal cancer (ESCA) is the sixth leading cause of cancer-related mortality worldwide. Despite the significant impact, the molecular mechanisms underlying its initiation and progression remain poorly understood. In this study, we identified mircoRNA miR-193b-3p as a critical regulator of ESCA progression and the Remodeling and Spacing Factor 1 (RSF1) as an essential target of miR-193b-3p. Analysis of the TCGA_ESCA dataset and RT-qPCR experiments revealed that RSF1 levels are significantly elevated in ESCA and inversely correlated with miR-193b-3p levels. Using a dual-luciferase reporter assay, as well as transfection of miR-193-3p mimics or inhibitors, we confirmed RSF1 as a direct target of miR-193b-3p in ESCA cells. Transfection of miR-193b-3p suppresses ESCA cell proliferation, migration, and invasion. These effects were partially reversed by exogenous RSF1 expression. Injection of AgomiR-193b-3p into mice bearing ESCA xenografts impeded tumor growth. These findings underscore the critical role of the miR-193b-3p/RSF1 axis in esophageal cancer progression.