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Ataxia with oculomotor apraxia type 1 (AOA1) is a rare, autosomal recessive, early-onset, progressive cerebellar ataxia caused by mutations in the APTX gene, which encodes aprataxin, a DNA-adenylate hydrolase involved in DNA damage repair. The pathogenesis of AOA1 remains unclear. The purpose of this study was to investigate the pathogenesis of a novel mutation, p.H201P/H201R, carried by our AOA1 patient and the mechanism of AOA1 in an induced pluripotent stem cells (iPSCs) model. We edited iPSCs derived from a healthy individual to carry the APTX homozygous mutation p.H201P (H201P-iPSCs) or p.H201R (H201R-iPSCs) via CRISPR/Cas9. We found that aprataxin expression was absent in both H201P- and H201R-iPSCs. The capacity of these APTX-mutant iPSCs to differentiate into neural progenitor cells (NPCs) and mature neurons was diminished. We observed an increase in DNA single-strand breaks (SSB) via a comet assay and poly(ADP-ribose) staining, and an increase in the ratio of cleaved PARP-1/total PARP-1 in APTX-mutant NPCs and early immature neurons (EiNs), in addition of a heightened sensitivity to tert-butyl hydroperoxide in APTX-mutant EiNs. Moreover, a decrease of APE1 expression was observed in APTX-mutant NPCs and H201R-EiNs during neural differentiation. Our study established a practical iPSCs model to investigate AOA1 disease. We found that mutant aprataxin leads to defective neural differentiation, accompanied by the accumulation of DNA SSBs with increased cleaved PARP-1 and reduced APE1 expression of the base excision repair pathway.

Chagas disease, caused by the parasite Trypanosoma cruzi, affects millions of people globally. Unfortunately, the available treatment options, especially for the chronic stage of the disease, are suboptimal. Given the chronic nature of the disease and the elusive nature of the parasite, there is a high need for new and safer drugs that deliver sterile cure. Posaconazole was a promising lead in the drug discovery pipeline but ultimately failed in clinical trials due to patient relapses. This failure illustrates the need for a drug screening assay that can predict sterile cure by assessing recrudescence after treatment. Here, we used human induced pluripotent stem cell (iPSC)-derived macrophages (iMACs) as host cells for T. cruzi. The iMACs were highly susceptible to infection by the parasites. By combining red fluorescent protein (RFP)-expressing iMACs with mNeonGreen-expressing T. cruzi, we were able to monitor the dynamics of the infection through live cell imaging. The activity of the compounds benznidazole and posaconazole was consistent with the results of an established infection system using mouse primary macrophages. The post-mitotic nature of iMACs makes them suitable host cells for long-term assays needed to assess recrudescence of parasites. Moreover, their human origin, stable genetic background, and capacity for genetic modification make the iMACs excellent host cells for studying host-pathogen interaction. Author summaryThe parasite Trypanosoma cruzi, the causative agent of Chagas disease, is a global health concern affecting millions each year. Infection with T. cruzi can cause chronic disease, often remaining asymptomatic for decades before resulting in severe cardiac or gastro-intestinal pathologies. To date, only benznidazole and nifurtimox are used for treatment of the infection, but both drugs are suboptimal for curing the chronic stage. Posaconazole showed great promise in preclinical studies but failed to achieve sterile cure in clinical trials, causing patient relapses. These disappointing results underline the need for drug screening assays able to predict sterile cure by evaluating recrudescence post-treatment. We used human induced pluripotent stem cell derived macrophages as host cells for T. cruzi and testing of trypanocidal compounds. This model can be used for long-term in vitro screening assays to find new drug candidates against Chagas disease. The human origin of these cells combined with the possibility of upscaling their production make them great host cells for drug screening campaigns.

In stem cell biology, a long-held structure–function relationship is the domed colony morphology and naïve pluripotency for mouse or human pluripotent stem cells. This link has provided a convenient way to recognize bona fide naïve pluripotent cells during derivation, passaging and characterization. However, the molecular basis of this link remains poorly understood. Results: We show that a loss of domed morphology may not impact the overall genetic architecture of naïve pluripotency in mouse embryonic stem cells (mESCs). We first generated stable mESC lines by knocking out Myh9 that encodes non-muscle myosin heavy chain IIA, resulting in colonies deprived of the typical domed morphology, but competent to differentiate into the three germ layers and chimeric mice. Modulating cell morphologies with inhibitors against kinases known to regulate myosin pathway also phenocopy the knockout in wild type mESCs. Conclusions: These results provide evidence that the domed morphology and potency can be uncoupled and suggest that domed structure is not a pre-requisite for acquiring and maintaining naïve pluripotency.

EVI1-rearranged acute myeloid leukemia (AML) with inv(3)(q21q26) or t(3;3)(q21q26) represents a distinct and aggressive subtype characterized by poor prognosis and limited treatment options. However, the optimal strategy to overcome resistance to conventional therapy remains elusive. Building upon observations correlating EVI1 overexpression with reduced sensitivity to venetoclax, a BH3-mimetic BCL-2 inhibitor, we investigated the mechanisms of resistance to venetoclax in combination with hypomethylating agents in inv(3)/t(3;3) AML cells. Utilizing novel murine models recapitulating inv(3) AML with concomitant SF3B1 mutations, we conducted comprehensive phenotypic and transcriptomic analyses in the presence or absence of venetoclax-containing therapy. Despite initial therapeutic responses, manifested as partially prolonged survival and myeloid differentiation, resistant leukemic cells demonstrated enhanced dependency on BRD4 and MYB pathways with a dormant phenotype. Notably, inhibition of either BRD4 or MYB significantly augmented the efficacy of venetoclax and hypomethylating agents in both murine and patient-derived AML models harboring inv(3) and SF3B1 mutations. These findings elucidate the transcriptional dynamics underlying venetoclax resistance and propose alternative therapeutic strategies targeting BRD4 and MYB as promising avenues for improving outcomes in patients with EVI1-rearranged AML. Our work highlights the necessity for innovative combination therapies to address the multifaceted mechanisms of resistance in this high-risk leukemia subtype.

Chimeric antigen receptor (CAR) T cell therapy has transformed the treatment landscape of hematologic cancers by engineering T cells to specifically target and destroy cancer cells. Monitoring CAR T cell activity and function is essential for optimizing therapeutic outcomes, but existing tools for CAR detection are often limited in specificity and functional assessment capability. Methods: We developed dextran multimers by conjugating multiple CAR-specific antigens to a dextran backbone. The multimers were compared to previously reported antigen tetramers for their ability to stain and detect CAR T cells. Because these multimers incorporate the CAR target antigen, they uniquely enable assessment of CAR T cell functionality. We tested the staining and functional properties of the multimers across a range of CAR constructs with different affinities, using flow cytometry and microscopy. Results: The dextran multimers demonstrated high specificity and sensitivity in staining CAR T cells, with adjustable antigen density to optimize binding. Dextran multimers also enabled effective clustering and subsequent activation of CARs, showing their utility as both a staining and functional assessment tool. The multimers revealed that CARs with different affinities and clustering tendencies displayed varied binding and activation in response to different antigen densities. Conclusions: Dextran multimers offer a dual advantage as versatile reagents for both staining and functional analysis of CAR T cells. Their capacity to engage CARs with the specific antigen provides a valuable platform for evaluating CAR functionality, informing CAR design improvements, and enhancing therapeutic precision.

Assessment of Fc receptors and immune cells in breast cancer enables development of tailored engineering strategies for tumor-targeting monoclonal antibodies with enhanced immune-stimulating and anticancer attributes by combining glycoengineering and Fc mutations. AbstractFc engineering to enhance antibody effector functions harbors the potential to improve therapeutic effects. Understanding FcγR expression and distribution in the tumor microenvironment prior to and following treatment may help guide immune-engaging antibody design and patient stratification. In this study, we investigated FcR-expressing immune effector cells in HER2+ and triple-negative breast cancers (TNBC), including neoadjuvant chemotherapy–resistant disease. FcγRIIIa expression, FcγRIIIa+ NK cells, and classically activated (M1-like) macrophages correlated with improved anti-HER2 antibody efficacy. FcγRIIIa protein and FcγRIIIa+ NK cells and macrophages were present in primary TNBC and retained in treatment-resistant tumors. FcγRIIIa was spatially associated with folate receptor alpha–positive (FRα+) tumor areas at baseline and in residual tumors following neoadjuvant chemotherapy. Wild-type and Fc-engineered antibodies recognizing two breast cancer–associated antigens, HER2 and the emerging TNBC target FRα, were designed and generated to have increased FcγRIIIa-expressing effector cell engagement. The combination of glycoengineering, including fucose removal from the N-linked Fc glycan, and Fc point mutations greatly increased antibody affinity for and retention on FcγRIIIa. The Fc-engineered antibodies enhanced immune effector activity against HER2+ breast cancer and TNBC, altering proinflammatory cytokine production by NK cells and tumor-conditioned macrophages and skewing macrophages toward proinflammatory states. Furthermore, the Fc-engineered antibodies restricted orthotopic HER2+ and FRα+ breast cancer xenograft growth at doses suboptimal for equivalent wild-type antibodies and recruited FcγRIIIa-expressing cells into tumors. Antibody design through combined glycoengineering and Fc point mutations to enhance FcγRIIIa engagement of tumor-infiltrating effector cells may be a promising strategy for developing therapies for patients with aggressive and treatment-resistant breast cancers.Significance:Assessment of Fc receptors and immune cells in breast cancer enables development of tailored engineering strategies for tumor-targeting monoclonal antibodies with enhanced immune-stimulating and anticancer attributes by combining glycoengineering and Fc mutations.

MEF2C encodes a transcription factor that is critical in nervous system development. Here, to examine disease-associated functions of MEF2C in human microglia, we profiled microglia differentiated from isogenic MEF2C-haploinsufficient and MEF2C-knockout induced pluripotent stem cell lines. Complementary transcriptomic and functional analyses revealed that loss of MEF2C led to a hyperinflammatory phenotype with broad phagocytic impairment, lipid accumulation, lysosomal dysfunction and elevated basal inflammatory cytokine secretion. Genome-wide profiling of MEF2C-bound sites coupled with the active regulatory landscape enabled inference of its transcriptional functions and potential mechanisms for MEF2C-associated cellular functions. Transcriptomic and epigenetic approaches identified substantial overlap with idiopathic autism datasets, suggesting a broader role of human microglial MEF2C dysregulation in idiopathic autism. In a mouse xenotransplantation model, loss of MEF2C led to morphological, lysosomal and lipid abnormalities in human microglia in vivo. Together, these studies reveal mechanisms by which reduced microglial MEF2C could contribute to the development of neurological diseases. Coufal and colleagues generated microglia from human iPS cells to examine mechanistic roles of the transcription factor MEF2C and how these roles might relate to the autism phenotype seen following the loss of MEF2C in human microglia.

Triple-negative breast cancer (TNBC) is an aggressive and clinically challenging subtype defined by the absence of estrogen receptor, progesterone receptor, and HER2 amplification, resulting in poor prognosis and limited therapeutic options. Targeting alternative molecular pathways is urgently needed to overcome resistance and improve patient outcomes. CD147 has emerged as surface marker associated with tumor progression and immune evasion. In this study, CD147 and MHC class I—a key inhibitory ligand for natural killer cells—were analyzed in breast cancer cell lines (MCF7, MDA-MB-453, MDA-MB-231, and HCC38) using flow cytometry. The therapeutic efficacy of a humanized anti-CD147 monoclonal antibody (HuM6-1B9) was evaluated for its capacity to potentiate antibody-dependent cellular cytotoxicity (ADCC). HuM6-1B9 demonstrated the strong binding to MDA-MB-231 (KD = 4.982 nM) and HCC38 (KD = 4.523 nM), which are representative TNBC cell lines. In 3D spheroid models, HuM6-1B9 significantly enhanced PBMC-mediated ADCC, leading to a marked reduction in TNBC spheroid viability. Co-culture of CFSE-labeled MDA-MB-231 and HCC38 cells with primary NK cells confirmed robust ADCC, achieving 50% and 70% cytotoxicity, respectively, despite high MHC class I expression. Live-cell imaging demonstrated caspase-3/7 activation consistent with apoptosis in NK-targeted tumor cells, while CD107a degranulation and IFN-γ secretion confirmed the functional contribution of HuM6-1B9 to ADCC enhancement. Importantly, HuM6-1B9 did not promote migration or invasion in MDA-MB-231 cells, supporting its safety profile regarding metastasis. Collectively, these findings establish HuM6-1B9 as a promising immunotherapeutic candidate that overcomes immune resistance and selectively eliminates TNBC cells through ADCC without enhancing metastatic potential. By integrating mechanistic assays of NK cytotoxicity, apoptosis, and 3D tumor spheroids, this study provides clinically relevant insights underscoring the translational potential of HuM6-1B9 in TNBC immunotherapy.