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Cancer stem cells (CSCs) are a specific subpopulation of cancer cells with the ability of self‐renewal,infinite proliferation,multidifferentiation and tumorigenicity,and play critical roles in cancer progression and treatment resistance. CSCs are tightly regulated by the tumor microenvironment,such as hypoxia; however,how hypoxia regulates CSCs in non‐small cell lung cancer (NSCLC) remains unclear. The proportion of ALDH hi cells was examined using the Aldefluor assay. Tankyrase inhibitor XAV939 and siRNA were used to inhibit β‐catenin while pcDNA3‐β‐catenin (S33Y) plasmid enhanced the expression of β‐catenin. Western blot was administered for protein detection. The mRNA expression was measured by quantitative real‐time PCR. We found that hypoxia led to an increase in the proportion of ALDH hi cells in lung squamous carcinoma (LUSC) H520 cells,while causing a decrease in the ALDH hi cell proportion in lung adenocarcinoma (LUAD) A549 cells. Similarly,β‐catenin expression was upregulated in H520 cells but downregulated in A549 cells upon exposure to hypoxia. Mechanically,the proportion of ALDH hi cells in both cell lines was decreased by β‐catenin inhibitor or siRNA knockdown,whereas increased after β‐catenin overexpression. Furthermore,hypoxia treatment suppressed E‐cadherin expression in H520 cells and enhanced N‐cadherin and β‐catenin expression,while this effect was completely opposite in A549 cells. The hypoxia‐EMT‐β‐catenin axis functions as an important regulator for the proportion of CSCs in NSCLC and could potentially be explored as therapeutic targets in the future. View Publication

Leigh syndrome French Canadian type (LSFC) is a recessive neurodegenerative disease characterized by tissue-specific deficiency in cytochrome c oxidase (COX),the fourth complex in the oxidative phosphorylation system. LSFC is caused by mutations in the leucine rich pentatricopeptide repeat containing gene ( LRPPRC ). Most LSFC patients in Quebec are homozygous for an A354V substitution that causes a decrease in the expression of the LRPPRC protein. While LRPPRC is ubiquitously expressed and is involved in multiple cellular functions,tissue-specific expression of LRPPRC and COX activity is correlated with clinical features. In this proof-of-principle study,we developed human induced pluripotent stem cell (hiPSC)-based models from fibroblasts taken from a patient with LSFC,homozygous for the LRPPRC *354V allele,and from a control,homozygous for the LRPPRC *A354 allele. Specifically,for both of these fibroblast lines we generated hiPSC,hiPSC-derived cardiomyocytes (hiPSC-CMs) and hepatocyte-like cell (hiPSC-HLCs) lines,as well as the three germ layers. We observed that LRPPRC protein expression is reduced in all cell lines/layers derived from LSFC patient compared to control cells,with a reduction ranging from ∼70% in hiPSC-CMs to undetectable levels in hiPSC-HLC,reflecting tissue heterogeneity observed in patient tissues. We next performed exploratory analyses of these cell lines and observed that COX protein expression was reduced in all cell lines derived from LSFC patient compared to control cells. We also observed that mutant LRPPRC was associated with altered expression of key markers of endoplasmic reticulum stress response in hiPSC-HLCs but not in other cell types that were tested. While this demonstrates feasibility of the approach to experimentally study genotype-based differences that have tissue-specific impacts,this study will need to be extended to a larger number of patients and controls to not only validate the current observations but also to delve more deeply in the pathogenic mechanisms of LSFC. View Publication

The fine control of synaptic function requires robust trans-synaptic molecular interactions. However,it remains poorly understood how trans-synaptic bridges change to reflect the functional states of the synapse. Here,we develop optical tools to visualize in firing synapses the molecular behavior of two trans-synaptic proteins,LGI1 and ADAM23,and find that neuronal activity acutely rearranges their abundance at the synaptic cleft. Surprisingly,synaptic LGI1 is primarily not secreted,as described elsewhere,but exo- and endocytosed through its interaction with ADAM23. Activity-driven translocation of LGI1 facilitates the formation of trans-synaptic connections proportionally to the history of activity of the synapse,adjusting excitatory transmission to synaptic firing rates. Accordingly,we find that patient-derived autoantibodies against LGI1 reduce its surface fraction and cause increased glutamate release. Our findings suggest that LGI1 abundance at the synaptic cleft can be acutely remodeled and serves as a critical control point for synaptic function. View Publication

Kidney organoids are an innovative tool in transplantation research. The aim of the present study was to investigate whether kidney organoids are susceptible for allo-immune attack and whether they can be used as a model to study allo-immunity in kidney transplantation. Human induced pluripotent stem cell-derived kidney organoids were co-cultured with human peripheral blood mononuclear cells (PBMC),which resulted in invasion of allogeneic T-cells around nephron structures and macrophages in the stromal cell compartment of the organoids. This process was associated with the induction of fibrosis. Subcutaneous implantation of kidney organoids in immune-deficient mice followed by adoptive transfer of human PBMC led to the invasion of diverse T-cell subsets. Single cell transcriptomic analysis revealed that stromal cells in the organoids upregulated expression of immune response genes upon immune cell invasion. Moreover,immune regulatory PD-L1 protein was elevated in epithelial cells while genes related to nephron differentiation and function were downregulated. This study characterized the interaction between immune cells and kidney organoids,which will advance the use of kidney organoids for transplantation research. View Publication

The use of genetic engineering to generate point mutations in induced pluripotent stem cells (iPSCs) is essential for studying a specific genetic effect in an isogenic background. We demonstrate that a combination of p53 inhibition and pro-survival small molecules achieves a homologous recombination rate higher than 90% using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) in human iPSCs. Our protocol reduces the effort and time required to create isogenic lines. View Publication

CRISPR-Cas9 genome editing often induces unintended,large genomic rearrangements,posing potential safety risks. However,there are no methods for mitigating these risks. Using long-read individual-molecule sequencing (IDMseq),we found the microhomology-mediated end joining (MMEJ) DNA repair pathway plays a predominant role in Cas9-induced large deletions (LDs). We targeted MMEJ-associated genes genetically and/or pharmacologically and analyzed Cas9-induced LDs at multiple gene loci using flow cytometry and long-read sequencing. Reducing POLQ levels or activity significantly decreases LDs,while depleting or overexpressing RPA increases or reduces LD frequency,respectively. Interestingly,small-molecule inhibition of POLQ and delivery of recombinant RPA proteins also dramatically promote homology-directed repair (HDR) at multiple disease-relevant gene loci in human pluripotent stem cells and hematopoietic progenitor cells. Our findings reveal the contrasting roles of RPA and POLQ in Cas9-induced LD and HDR,suggesting new strategies for safer and more precise genome editing. The online version contains supplementary material available at 10.1186/s12915-024-01896-z. View Publication

The implementation of antiretroviral therapy (ART) has effectively restricted the transmission of Human Immunodeficiency Virus (HIV) and improved overall clinical outcomes. However,a complete cure for HIV remains out of reach,as the virus persists in a stable pool of infected cell reservoir that is resistant to therapy and thus a main barrier towards complete elimination of viral infection. While the mechanisms by which host proteins govern viral gene expression and latency are well-studied,the emerging regulatory functions of non-coding RNAs (ncRNA) in the context of T cell activation,HIV gene expression and viral latency have not yet been thoroughly explored. Here,we report the identification of the Cytoskeleton Regulator (CYTOR) long non-coding RNA (lncRNA) as an activator of HIV gene expression that is upregulated following T cell stimulation. Functional studies show that CYTOR suppresses viral latency by directly binding to the HIV promoter and associating with the cellular positive transcription elongation factor (P-TEFb) to activate viral gene expression. CYTOR also plays a global role in regulating cellular gene expression,including those involved in controlling actin dynamics. Depletion of CYTOR expression reduces cytoplasmic actin polymerization in response to T cell activation. In addition,treating HIV-infected cells with pharmacological inhibitors of actin polymerization reduces HIV gene expression. We conclude that both direct and indirect effects of CYTOR regulate HIV gene expression. View Publication

SARS-CoV-2 Omicron variant has evolved into sublineages. Here,we compared the neutralization susceptibility and viral fitness of EG.5.1 and XBB.1.9.1. Serum neutralization antibody titer against EG.5.1 was 1.71-fold lower than that for XBB.1.9.1. However,there was no significant difference in virus replication between EG.5.1 and XBB.1.9.1 in human nasal organoids and TMPRSS2/ACE2 over-expressing A549 cells. No significant difference was observed in competitive fitness and cytokine/chemokine response between EG.5.1 and XBB.1.9.1. Both EG.5.1 and XBB.1.9.1 replicated more robustly in the nasal organoid from a younger adult than that from an older adult. Our findings suggest that enhanced immune escape contributes to the dominance of EG.5.1 over earlier sublineages. The combination of population serum susceptibility testing and viral fitness evaluation with nasal organoids may hold promise in risk assessment of upcoming variants. Utilization of serum specimens and nasal organoid derived from older adults provides a targeted risk assessment for this vulnerable population. Subject areas: Immunology,Immune response,Virology View Publication

Telomeres as the protective ends of linear chromosomes,are synthesized by the enzyme telomerase (TERT). Critically short telomeres essentially contribute to aging-related diseases and are associated with a broad spectrum of disorders known as telomeropathies. In cardiomyocytes,telomere length is strongly correlated with cardiomyopathies but it remains ambiguous whether short telomeres are the cause or the result of the disease. In this study,we employed an inducible CRISPRi human induced pluripotent stem cell (hiPSC) line to silence TERT expression enabling the generation of hiPSCs and hiPSC-derived cardiomyocytes with long and short telomeres. Reduced telomerase activity and shorter telomere lengths of hiPSCs induced global transcriptomic changes associated with cardiac developmental pathways. Consequently,the differentiation potential towards cardiomyocytes was strongly impaired and single cell RNA sequencing revealed a shift towards a more smooth muscle cell like identity in the cells with the shortest telomeres. Poor cardiomyocyte function and increased sensitivity to stress directly correlated with the extent of telomere shortening. Collectively our data demonstrates a TERT dependent cardiomyogenic differentiation defect,highlighting the CRISPRi TERT hiPSCs model as a powerful platform to study the mechanisms and consequences of short telomeres in the heart and also in the context of telomeropathies. The online version contains supplementary material available at 10.1007/s00018-024-05239-7. View Publication

BCR::ABL1-independent pathways contribute to primary resistance to tyrosine kinase inhibitor (TKI) treatment in chronic myeloid leukemia (CML) and play a role in leukemic stem cell persistence. Here,we perform ex vivo drug screening of CML CD34 + leukemic stem/progenitor cells using 100 single drugs and TKI-drug combinations and identify sensitivities to Wee1,MDM2,and BCL2 inhibitors. These agents effectively inhibit primitive CD34 + CD38 − CML cells and demonstrate potent synergies when combined with TKIs. Flow-cytometry-based drug screening identifies mepacrine to induce differentiation of CD34 + CD38 − cells. We employ genome-wide CRISPR-Cas9 screening for six drugs,and mediator complex,apoptosis,and erythroid-lineage-related genes are identified as key resistance hits for TKIs,whereas the Wee1 inhibitor AZD1775 and mepacrine exhibit distinct resistance profiles. KCTD5,a consistent TKI-resistance-conferring gene,is found to mediate TKI-induced BCR::ABL1 ubiquitination. In summary,we delineate potential mechanisms for primary TKI resistance and non-BCR::ABL1-targeting drugs,offering insights for optimizing CML treatment. View Publication

AML is characterized by mutations in genes associated with growth regulation such as internal tandem duplications (ITD) in the receptor kinase FLT3. Inhibitors targeting FLT3 (FLT3i) are being used to treat patients with FLT3-ITD+ but most relapse and become resistant. To elucidate the resistance mechanism,we compared the gene regulatory networks (GRNs) of leukemic cells from patients before and after relapse,which revealed that the GRNs of drug-responsive patients were altered by rewiring their AP-1-RUNX1 axis. Moreover,FLT3i induces the upregulation of signaling genes,and we show that multiple cytokines,including interleukin-3 (IL-3),can overcome FLT3 inhibition and send cells back into cycle. FLT3i leads to loss of AP-1 and RUNX1 chromatin binding,which is counteracted by IL-3. However,cytokine-mediated drug resistance can be overcome by a pan-RAS inhibitor. We show that cytokines instruct AML growth via the transcriptional regulators AP-1 and RUNX1 and that pan-RAS drugs bypass this barrier. Subject area: Pharmacy,Molecular biology View Publication

Immune tolerance fails in autoimmune polyendocrine syndrome type 1 (APS-1) because of AIRE mutations. We have used single cell transcriptomics to characterize regulatory T cells (Tregs) sorted directly from blood and from in vitro expanded Tregs in APS-1 patients compared to healthy controls. We revealed only CD52 and LTB (down) and TXNIP (up) as consistently differentially expressed genes in the datasets. There were furthermore no large differences of the TCR-repertoire of expanded Tregs between the cohorts,but unique patients showed a more restricted use of specific clonotypes. We also found that in vitro expanded Tregs from APS-1 patients had similar suppressive capacity as controls in co-culture assays,despite expanding faster and having more exhausted cells. Our results suggest that APS-1 patients do not have intrinsic defects in their Treg functionality,and that their Tregs can be expanded ex vivo for potential therapeutic applications. Subject areas: Health sciences,Immunology,Components of the immune system,Proteomics,Transcriptomics View Publication