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MEIS1 knockdown upregulates WNT signaling pathway genes in esophageal squamous cell carcinoma.

BACKGROUND: The transcription factor MEIS1 belongs to the 3-amino acid loop extension (TALE) family of homeodomain proteins which plays various functions in normal and tumor cell progression. The canonical WNT/β-catenin pathway governs a plethora of biological processes including cell proliferation, differentiation, and tumor development. In the present study, the effect of MEIS1 gene silencing was assessed on WNT pathway genes in esophageal squamous cell carcinoma (ESCC) cells. MATERIALS AND METHODS: Along with the packaging plasmids, the pLKO.1-MEIS1 plasmid was cotransfected into HEK293T to generate lentiviral particles, followed by transduction of a semi-confluent KYSE-30 cell culture. After total RNA extraction and cDNA synthesis, comparative real-time PCR was applied to assess the efficiency of MEIS1 knockdown and the expression of genes related to the WNT signaling pathway. RESULTS: The results revealed effective downregulation of MEIS1 in KYSE-30 cells. Interestingly, MEIS1 silencing led to a substantial overexpression of WNT pathway key components while the expression of negative regulators of this pathway was substantially decreased. CONCLUSIONS: Our data suggest that MEIS1 gene probably induces WNT/β-catenin pathway deactivation in ESCC cells. Consequently, the inverse correlation of MEIS1 expression and WNT signaling pathway activation may introduce a new molecular linkage through ESCC progression and aggressiveness.

Humans

Integrated Clinicopathologic and Multiomic Profiling Reveals MEIS1-Rearranged Sarcoma as a Distinct Entity With 2 Prognostic Subgroups.

Sarcomas with MEIS1 fusions represent a rare, recently recognized group of mesenchymal neoplasms with a predilection for genitourinary and gynecologic sites. A subset exhibits skeletal muscle differentiation resembling spindle cell rhabdomyosarcoma. Existing literature is limited to case reports and small series, with scant comprehensive clinicopathologic, molecular, and outcome data. In this study, we analyzed a multi-institutional cohort of 20 MEIS1-rearranged sarcomas using integrated clinicopathologic review, genomic profiling, and DNA methylation analysis. The tumors occurred in 17 females and 3 males (median age, 41 years; range, 6-58 years), arising mainly in the uterus/vagina (n = 12), vulva/perineum (n = 4), bone (n = 2), and kidney (n = 2), with a median size of 9 cm (range, 2.5-20 cm). Histology showed mostly bland spindle cells in fascicles/storiform patterns, alternating cellularity, fibromyxoid stroma, prominent vascularity, and adipose metaplasia (45%). A subset of cases featured high-grade morphology with epithelioid cells and increased mitotic activity. Skeletal muscle markers were variably positive in 9 cases. Fusions involved MEIS1 with NCOA2 (16/20), NCOA1 (3/20), or FOXO1 (1/20). Recurrent additional genomic alterations included CTNNB1 mutations (31.6%) and MDM2 amplification (15%). DNA methylation profiling showed that MEIS1-rearranged sarcomas formed a unifying cluster comprising 2 subgroups, regardless of rhabdomyosarcomatous phenotype, clearly separated from other mesenchymal neoplasms, including various rhabdomyosarcoma subtypes and uterine sarcomas. The 2 DNA methylation (Meth) subgroups correlated with differences in genome-wide copy number variation (CNV) status (Meth-CNV high vs Meth-CNV low), with Meth-CNV high tumors characterized by high mitotic rate, frequent tumor necrosis, recurrent co-occurring CTNNB1 and MDM2 alterations, and recurrent chromosomal arm-level changes. Most importantly, this subgroup exhibited significantly worse overall survival (P = .027) and disease-free survival (median, 5 vs 99 months; P = .017). This study establishes MEIS1-rearranged sarcoma as a distinct entity with generally indolent but potentially aggressive behavior. The 2 methylation/CNV subgroups provide potential utility for prognostic stratification and highlight actionable molecular targets in high-risk cases.

Humans

Cross-species variant-to-function analyses implicate MEIS1 in conferring sleep abnormalities and impaired cerebellar development.

Genome-wide association studies (GWAS) have identified numerous loci for insomnia, yet functional validation of effector genes remains limited because most risk variants lie in noncoding regions, and the true causal gene is not known. Here, we use prior human cell-based variant-to-gene mapping to nominate six insomnia effector genes and test them in zebrafish, a tractable diurnal vertebrate model well suited for sleep phenotyping. Our CRISPR-based behavioral screening identifies the MEIS1 ortholog, meis1b, as a regulator of sleep maintenance, with crispants displaying impaired nighttime-specific sleep maintenance and increased sleep latency. Comparative chromatin analyses reveal conserved regulatory architecture spanning the human insomnia-associated locus and selectively implicate meis1b, whereas the duplicated ohnolog meis1a was dispensable. Developmental profiling further shows that meis1b is expressed in cerebellar granule progenitors, paralleling human MEIS1 expression, and that its disruption impairs cerebellar development. Together, these findings establish zebrafish as an efficient vertebrate platform for functional interrogation of GWAS candidates and support an evolutionarily conserved cerebellar role for MEIS1 in sleep maintenance.

Animals

A conserved Notch-Meis1-Pbx cascade specifies secretory progenitors into spatially diverse intestinal best4 + cells.

best4 + cells are a recently described vertebrate intestinal epithelial cell type. best4 + cells are altered in inflammatory bowel disease and colorectal cancer, suggesting that stimulation of their homeostatic replenishment may have therapeutic potential. However, the development and function of best4 + cells remain unclear. Since mice lack best4 + cells, we established zebrafish as a tractable in vivo model to observe, manipulate, and remove best4 + cells in an organismal context. We dissected best4 + cell developmental regulation in vivo from birth to differentiation and specialization, focusing on factors conserved in best4 + cells across vertebrates. Lineage tracing demonstrated that best4 + cells arise from secretory progenitors, where Notch/Dll4 signaling mediates a decision between best4 + and enterochromaffin cells by triggering meis1b expression. Following specification by meis1b, pbx3a spatially diversifies best4 + cells, which develop regional heterogeneity in gene expression, intracellular pH, and function. In vivo live imaging and removal of best4 + cells showed that best4+ cells sense luminal pH changes and extend dynamic luminal and stromal projections, but are not required to restore global luminal pH after challenge. Altogether, this study experimentally delineates best4 + cell developmental regulation and develops a genetic toolkit to examine their function in vivo, both of which will aid investigating how best4 + cells are altered or can be restored during disease.

Animals

Systematic decoding of functional enhancer connectomes and risk variants in human glioma.

Genetic and epigenetic variations contribute to the progression of glioma, but the mechanisms underlying these effects, particularly for enhancer-associated genetic variations in non-coding regions, still remain unclear. Here we performed high-throughput CRISPR interference screening to identify pro-tumour enhancers in glioma cells. By integrating genome-wide H3K27ac HiChIP data, we identified the target genes of these pro-tumour enhancers and revealed the essential role of enhancer connectomes in promoting glioma progression. Through systematic analysis of enhancers carrying glioma risk-associated single-nucleotide polymorphisms (SNPs), we found that these SNPs can promote glioma progression through the enhancer connectome. Using CRISPR-Cas9-mediated enhancer interference and SNP editing, we demonstrated that glioma-specific enhancer carrying the risk SNP rs2297440 regulates SOX18 expression by specifically recruiting transcription factor MEIS1 binding, thereby contributing to glioma progression. Our study sheds light on the molecular mechanisms underlying glioma susceptibility and provides potential therapeutic targets to treat glioma.

Humans

KAT6A and KAT7 Histone Acetyltransferase Complexes Are Molecular Dependencies and Therapeutic Targets in NUP98-Rearranged Acute Myeloid Leukemia.

UNLABELLED: NUP98 fusion oncoproteins (FO) are a hallmark of childhood acute myeloid leukemia. NUP98 FOs drive leukemogenesis through phase-separated condensate formation and maintenance of an active chromatin landscape at stem cell-associated genes in cooperation with epigenetic regulators. In this study, we show that MYST family histone acetyltransferase (HAT) complex proteins, including KAT6A/MOZ, KAT7/HBO1, and the common KAT6A/7 complex subunit BRPF1, associate with NUP98 FOs on chromatin and within condensates. MYST HATs are molecular dependencies in NUP98-rearranged (NUP98-r) leukemia, and genetic inactivation or pharmacologic inhibition of KAT6A and KAT7 impairs NUP98-r cell fitness. KAT6A/7 inhibition decreased global H3K23ac levels, displaced NUP98::HOXA9 from chromatin at the Meis1 locus, and led to myeloid cell differentiation. Additionally, KAT6A/7 inhibition decreased leukemic burden in multiple NUP98-r leukemia xenograft mouse models, synergized with menin inhibitor treatment, and was efficacious in menin inhibitor-resistant cells. In summary, we show that MYST family HATs are therapeutically actionable dependencies in NUP98-r acute myeloid leukemia. SIGNIFICANCE: KAT6A and KAT7 associate with NUP98 FOs to drive leukemogenesis. Inhibition of their HAT activity is an effective therapeutic strategy in NUP98-r leukemias, including those resistant to menin inhibition. Moreover, combined KAT6A/7 and menin inhibition is synergistic, supporting clinical translation to improve outcomes for NUP98 FO-driven leukemias.

Humans

Ex vivo long-term expansion of human hematopoietic stem and progenitor cells as a tool for modeling vector integration sites and clonality.

BACKGROUND: Gene therapy (GT) using retroviral vectors (RVs) is efficacious in treating monogenic diseases. However, there is an inherent risk for severe adverse effects due to insertional mutagenesis. Preclinical safety assessment and patient monitoring are inevitable in GT. To assess the genotoxic risk of novel RV vectors, mainly murine hematopoietic stem and progenitor cells (HPSCs) are routinely used, because human HSPCs cannot be immortalized in vitro using mutagenic vectors. In this study, we aim to identify early signs of clonal outgrowth by performing integration site analyses (ISA). METHODS: The small molecules A83-01, pomalidomide, and UM171 (APU) were used for the ex vivo expansion, lentiviral transduction, and long-term cultivation of umbilical cord blood-derived HSPCs. We determined the influence of APU on the stemness of HSPCs and their differentiation capacity via single-cell RNA sequencing (scRNA seq) and in xenotransplantation studies. To track vector insertion site dynamics, we transduced 7-day expanded HSPCs with a mutagenic or a safer RV. ISA was conducted in human HSPCs over a 5-week cultivation in vitro and compared to the bone marrow of xenotransplanted mice to assess clonal skewings. RESULTS: APU supported the expansion of CD34+CD38-CD45RA-CD90+EPCR+ HSPCs. scRNA seq confirmed the enrichment of HSC signature genes in APU-expanded HSPCs compared to the clinically used medium SFT3 (SCF, FLT3-L, TPO, IL-3). After RV transduction, APU still maintained around 30% of CD34+ cells for 5 more weeks. Without the compounds, already 2 weeks post-transduction, less than 10% of cells were CD34+. The long-term culture allowed the detection of high-risk integrations of the mutagenic SIN-LV.SF in MEIS1 or SUSD6 due to their increasing abundance over time. Bone marrow of xenotransplanted mice was less clonal but did not support the outgrowth of insertional mutants. Overall, APU increased clonal diversity. CONCLUSIONS: Our findings propose that long-term cultivation of transduced HSPC in APU allows for outgrowth of clonal integration sites. The decrease of clonality has been observed in gene therapy patient's years after treatment. Thus, the in vitro model could be used to develop novel human HSPC-based genotoxicity assays that predict insertional mutagenesis, in addition to existing preclinical biosafety assays.

Humans