Dysregulated splicing factors play critical roles in tumor progression. Here, we identify family with sequence similarity 50 member A (FAM50A) as a pivotal oncogenic splicing factor involved in esophageal squamous cell carcinoma (ESCC). Multi-omics and multi-cohort analyses revealed that FAM50A is upregulated in ESCC and correlates with a poor prognosis. Functional studies demonstrated that FAM50A promotes ESCC proliferation and migration both in vitro and in vivo, primarily through the activation of mitogen-activated protein kinases (MAPKs) and focal adhesion kinase (FAK). We further characterized the FAM50A-binding RNA motif and established its transcriptome-wide splicing landscape. Notably, we identified a novel FAM50A-dependent backsplicing event that generates circSDK1, which originates from exons 2–4 of the sidekick cell adhesion molecule 1 (SDK1) pre-mRNA. Mechanistically, circSDK1 binds to dual-specificity phosphatase 22 (DUSP22) and occupies its phosphatase domain, inhibiting the DUSP22-mediated dephosphorylation of MAPKs and FAK and thereby sustaining their activation. Furthermore, the transcription factor TFAP2C increased FAM50A expression. Finally, we identified rifabutin as a small-molecule inhibitor of FAM50A and confirmed its anti-tumor efficacy in cell-derived xenograft, patient-derived organoid, and patient-derived xenograft models. In summary, FAM50A promotes ESCC progression via the FAM50A/circSDK1/DUSP22 axis, leading to MAPKs and FAK activation. Genetic or pharmacological targeting of FAM50A with rifabutin represents a promising therapeutic strategy for ESCC.
Abstract Chronic pruritus is a debilitating condition with limited treatment options, particularly in cholestatic liver diseases, where bile acid dysregulation is a known trigger. Although Mas-related G protein-coupled receptor X4 (MRGPRX4) has recently been identified as a key mediator of bile acid-induced pruritus, the structural mechanisms underlying its inhibition remain poorly understood, hindering the development of therapeutic antagonists. Here, we report the cryo-electron microscopy structures of MRGPRX4 in three distinct states: agonist-bound state, antagonist-bound state, and apo state. Our structures reveal a previously unrecognized antagonist-binding site that is structurally distinct from those engaged by agonists. Complementary functional assays and molecular dynamics simulations further demonstrate that the extracellular pocket of MRGPRX4 undergoes pronounced ligand-dependent conformational rearrangements upon binding to both the agonist and the antagonist. Collectively, these findings elucidate the conformational plasticity underlying MRGPRX4 activity modulation and establish a structural framework for the rational design of MRGPRX4 antagonists that target chronic pruritus.
Early uterine development in humans is a critical determinant of reproductive health and disease susceptibility during adolescence. While single-cell analyses have extensively characterized the adult uterus, the developmental origins of this organ remain poorly understood. In this study, single-cell RNA sequencing and spatial transcriptomics of the human uterus from gestational week 12 (GW12) to GW24 and from adolescents revealed a population of hyaluronan-mediated motility receptor-expressing (HMMR+) stromal cells essential for uterine endometrial and myometrial development. These HMMR+ stromal cells were highly proliferative and differentiated into stromal- and muscle-like lineages upon in vitro induction. Following xenotransplantation into immunodeficient mice, they engrafted and formed mesenchymal-like tissue expressing both stromal and smooth muscle markers. We determined that HMMR+ stromal cells promote epithelial cell differentiation and development through pleiotrophin signaling. Notably, these HMMR+ stromal cells were significantly reduced in the thin endometrium. Collectively, our findings define the cellular ontogeny of the human uterus and identify a pivotal stromal progenitor-like population with implications for developmental disorders and endometrial pathologies.
Mpox virus (MPXV) poses an increasing global health threat, as underscored by two World Health Organization declarations of Public Health Emergencies of International Concern, particularly after the emergence of a novel Clade Ib strain that exhibited high human-to-human transmissibility in the Democratic Republic of the Congo. However, the treatment options for MPXV infection remain extremely limited. To address this unmet need, we established an integrated platform combining single-cell transcriptomics and deep learning-based structural prediction to discover effective human monoclonal antibodies against MPXV. By integrating computational prediction with experimental validation, we identified five neutralizing antibodies targeting the following distinct viral forms: BA345, MA42, and MA49, which engage the extracellular enveloped virus-associated A35R glycoprotein; BAL31, which binds intracellular mature virus (IMV) protein A29L; and HB05, which targets IMV antigen H3L. Importantly, the elite monoclonal antibody BA345 conferred effective protection against MPXV and vaccinia virus both in vitro and in vivo. Combined in silico structure prediction and X-ray crystallography revealed a highly conserved epitope shared across orthopoxviruses. Surface plasmon resonance measurements revealed nanomolar equilibrium dissociation constants of BA345 for A35R homologs, corroborating its cross-reactive, broad-spectrum neutralizing activity against orthopoxviruses. Moreover, the BA345/BAL31 and MA49/BAL31 antibody cocktails developed in this study conferred robust therapeutic protection in MPXV-infected animals, substantially reducing disease severity and viral load. Our findings not only establish a practical paradigm for antibody discovery through the integration of deep learning-driven structure prediction with single-cell multiomics but also inform next-generation biodefense countermeasures against MPXV and related orthopoxviruses.
