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Results for “Adaptor Proteins, Signal Transducing”

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PubMed2003

Complexes between the LKB1 tumor suppressor, STRAD alpha/beta and MO25 alpha/beta are upstream kinases in the AMP-activated protein kinase cascade.

BACKGROUND: The AMP-activated protein kinase (AMPK) cascade is a sensor of cellular energy charge that acts as a 'metabolic master switch' and inhibits cell proliferation. Activation requires phosphorylation of Thr172 of AMPK within the activation loop by upstream kinases (AMPKKs) that have not been identified. Recently, we identified three related protein kinases acting upstream of the yeast homolog of AMPK. Although they do not have obvious mammalian homologs, they are related to LKB1, a tumor suppressor that is mutated in the human Peutz-Jeghers cancer syndrome. We recently showed that LKB1 exists as a complex with two accessory subunits, STRAD alpha/beta and MO25 alpha/beta. RESULTS: We report the following observations. First, two AMPKK activities purified from rat liver contain LKB1, STRAD alpha and MO25 alpha, and can be immunoprecipitated using anti-LKB1 antibodies. Second, both endogenous and recombinant complexes of LKB1, STRAD alpha/beta and MO25 alpha/beta activate AMPK via phosphorylation of Thr172. Third, catalytically active LKB1, STRAD alpha or STRAD beta and MO25 alpha or MO25 beta are required for full activity. Fourth, the AMPK-activating drugs AICA riboside and phenformin do not activate AMPK in HeLa cells (which lack LKB1), but activation can be restored by stably expressing wild-type, but not catalytically inactive, LKB1. Fifth, AICA riboside and phenformin fail to activate AMPK in immortalized fibroblasts from LKB1-knockout mouse embryos. CONCLUSIONS: These results provide the first description of a physiological substrate for the LKB1 tumor suppressor and suggest that it functions as an upstream regulator of AMPK. Our findings indicate that the tumors in Peutz-Jeghers syndrome could result from deficient activation of AMPK as a consequence of LKB1 inactivation.

AMP-Activated Protein Kinase Kinases↗

PubMed2026

PDLIM4 promotes dephosphorylation of STAT transcription factors by recruiting PTP-BL and inhibits Th1, Th2, and Th17 cell differentiation.

STAT (signal transducers and activators of transcription) transcription factors are activated by tyrosine phosphorylation after cytokine stimulation and are critical for the differentiation of T-helper (Th) cells into particular Th lineage subsets. How STAT-mediated Th cell differentiation is negatively regulated, however, is not fully understood. Here, we report that PDLIM4 binds to STAT3, 4, and 6 and suppresses gene activation mediated by these STATs. PDLIM4 acts as an adaptor that recruits PTP-BL, a protein tyrosine phosphatase, through its LIM (abnormal cell lineage 11-islet 1-mechanosensory abnormal 3) domain, facilitating dephosphorylation of STAT proteins. PDLIM4-deficiency in CD4+ T cells resulted in augmented tyrosine phosphorylation of these STAT proteins and consequently enhanced Th1, Th2, and Th17 cell differentiation, suggesting that PDLIM4 regulates the differentiation of multiple lineages of Th cells by suppressing STAT signaling. We further found that a non-synonymous single-nucleotide polymorphism in PDLIM4, which causes the substitution of a glycine residue with a cysteine in the LIM domain, is associated with susceptibility to rheumatoid arthritis and Graves' disease, both of which are known to be Th17 cell-driven autoimmune diseases. Notably, PDLIM4 containing this amino acid substitution in the LIM domain showed reduced binding to PTP-BL and was therefore partially impaired in its ability to dephosphorylate STAT3 and suppress STAT3 signaling. Our findings define an essential role of PDLIM4 in negatively regulating STAT-mediated Th-cell differentiation and preventing the onset of human autoimmune diseases.

Animals↗

PubMed2024

Bidirectional Risk Modulator and Modifier Variant of Dilated and Hypertrophic Cardiomyopathy in BAG3.

IMPORTANCE: The genetic factors that modulate the reduced penetrance and variable expressivity of heritable dilated cardiomyopathy (DCM) are largely unknown. BAG3 genetic variants have been implicated in both DCM and hypertrophic cardiomyopathy (HCM), nominating BAG3 as a gene that harbors potential modifier variants in DCM. OBJECTIVE: To interrogate the clinical traits and diseases associated with BAG3 coding variation. DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study in the Penn Medicine BioBank (PMBB) enrolling patients of the University of Pennsylvania Health System's clinical practice sites from 2014 to 2023. Whole-exome sequencing (WES) was linked to electronic health record (EHR) data to associate BAG3 coding variants with EHR phenotypes. This was a health care population-based study including individuals of European and African genetic ancestry in the PMBB with WES linked to EHR phenotypes, with replication studies in BioVU, UK Biobank, MyCode, and DCM Precision Medicine Study. EXPOSURES: Carrier status for BAG3 coding variants. MAIN OUTCOMES AND MEASURES: Association of BAG3 coding variation with clinical diagnoses, echocardiographic traits, and longitudinal outcomes. RESULTS: In PMBB (n = 43 731; median [IQR] age, 65 [50-76] years; 21 907 female [50.1%]), among 30 324 European and 11 198 African individuals, the common C151R variant was associated with decreased risk for DCM (odds ratio [OR], 0.85; 95% CI, 0.78-0.92) and simultaneous increased risk for HCM (OR, 1.59; 95% CI, 1.25-2.02), which was confirmed in the replication cohorts. C151R carriers exhibited improved longitudinal outcomes compared with noncarriers as assessed by age at death (hazard ratio [HR], 0.85; 95% CI, 0.74-0.96; median [IQR] age, 71.8 [63.1-80.7] in carriers and 70.3 [61.6-79.2] in noncarriers) and heart transplant (HR, 0.81; 95% CI, 0.66-0.99; median [IQR] age, 56.7 [46.1-63.1] in carriers and 55.6 [45.2-62.9] in noncarriers). C151R was associated with reduced risk of DCM (OR, 0.42; 95% CI, 0.24-0.74) and heart failure (OR, 0.27; 95% CI, 0.14-0.50) among individuals harboring truncating TTN variants in exons with high cardiac expression (n = 358). CONCLUSIONS AND RELEVANCE: BAG3 C151R was identified as a bidirectional modulator of risk along the DCM-HCM spectrum, as well as an important genetic modifier variant in TTN-mediated DCM. This work expands on the understanding of the etiology and penetrance of DCM, suggesting that BAG3 C151R is an important genetic modifier variant contributing to the variable expressivity of DCM, warranting further exploration of its mechanisms and of genetic modifiers in DCM more broadly.

Humans↗

PubMed2024

Association of common and rare variants with Alzheimer's disease in more than 13,000 diverse individuals with whole-genome sequencing from the Alzheimer's Disease Sequencing Project.

INTRODUCTION: Alzheimer's disease (AD) is a common disorder of the elderly that is both highly heritable and genetically heterogeneous. METHODS: We investigated the association of AD with both common variants and aggregates of rare coding and non-coding variants in 13,371 individuals of diverse ancestry with whole genome sequencing (WGS) data. RESULTS: Pooled-population analyses of all individuals identified genetic variants at apolipoprotein E (APOE) and BIN1 associated with AD (p < 5 × 10-8). Subgroup-specific analyses identified a haplotype on chromosome 14 including PSEN1 associated with AD in Hispanics, further supported by aggregate testing of rare coding and non-coding variants in the region. Common variants in LINC00320 were observed associated with AD in Black individuals (p = 1.9 × 10-9). Finally, we observed rare non-coding variants in the promoter of TOMM40 distinct of APOE in pooled-population analyses (p = 7.2 × 10-8). DISCUSSION: We observed that complementary pooled-population and subgroup-specific analyses offered unique insights into the genetic architecture of AD. HIGHLIGHTS: We determine the association of genetic variants with Alzheimer's disease (AD) using 13,371 individuals of diverse ancestry with whole genome sequencing (WGS) data. We identified genetic variants at apolipoprotein E (APOE), BIN1, PSEN1, and LINC00320 associated with AD. We observed rare non-coding variants in the promoter of TOMM40 distinct of APOE.

Humans↗

PubMed2022

Insights on the pathogenesis of type 2 diabetes as revealed by signature genomic classifiers in an African American population in the Washington, DC area.

AIMS: African Americans (AA) in the United States have a high risk of type 2 diabetes mellitus (T2DM) and suffer from disparities in the prevalence, mortality, and comorbidities of the disease compared to other Americans. The present study aimed to shed light on the molecular mechanisms of disease pathogenesis of T2DM among AA in the Washington, DC region. METHODS: We performed TaqMan Low Density Arrays (TLDA) on 24 genes of interest that belong to three categories: metabolic disease and disorders, cancer-related genes, and neurobehavioural disorders genes. The 18 genes, viz. ARNT, CYP2D6, IL6, INSR, RRAD, SLC2A2 (metabolic disease and disorders), APC, BCL2, CSNK1D, MYC, SOD2, TP53 (Cancer-related), APBA1, APBB2, APOC1, APOE, GSK3B, and NAE1 (neurobehavioural disorders), were differentially expressed in T2DM participants compared to controls. RESULTS: Our results suggest that factors including gender, smoking habits, and the severity or lack of control of T2DM (as indicated by HbA1c levels) were significantly associated with differential gene expression. APBA1 was significantly (p-value <0.05) downregulated in all diabetes participants. Upregulation of APOE and CYP2D6 genes and downregulation of the INSR gene were observed in the majority of diabetes patients. CONCLUSIONS: Tobacco smoking and gender were significantly associated with case-control differences in expression of the APBA1 and APOE genes (connected with Alzheimer's disease) and the INSR and CYP2D6 (associated with metabolic disorders). The results highlight the need for more effective management of T2DM and for tobacco smoking cessation interventions in this community, and further research on the associations of T2DM with other disease processes, including cancer and neurobehavioral pathways.

Humans↗

PubMed2026

The Germline SH2B3rs111340708 Splicing Variant Drives Intron Retention and Protein Instability by Impacting Clinical Outcomes in Core Binding Factor AML.

The SH2B3 gene, also known as LNK, encodes an adaptor protein that negatively regulates key hematopoietic signaling pathways, including JAK-STAT, MAPK, and PI3K/AKT, thereby maintaining hematopoietic homeostasis. SH2B3 interacts with major signaling regulators such as JAK2, MPL, FLT3, and KIT. Loss-of-function alterations have been reported in several hematologic malignancies, supporting its role as a leukemia predisposition gene. We previously identified a germline start-loss mutation (c.3G > A) in SH2B3 in a family with early-onset myeloproliferative neoplasm, demonstrating that this variant causes SH2B3 haploinsufficiency. In the present study, next-generation sequencing of 149 de novo AML patients identified a frequent intronic polymorphism (rs111340708), located within intron 6 (IVS6) of SH2B3. Although this variant has a reported minor allele frequency (MAF) of approximately 12% in European populations, it was enriched in our AML cohort, reaching 34.2% in Core Binding Factor leukemias (CBFLs). The presence of the rs111340708 variant was associated with inferior overall survival, whereas no significant association with progression-free survival was observed. Functional analyses demonstrated that this polymorphism promotes aberrant IVS6 intron retention in AML cells, resulting in reduced abundance of correctly spliced SH2B3 transcripts and predicted generation of truncated peptides and/or nonsense-mediated decay. Consistently, immunoblot analyses of AML patient samples and hematologic cell lines revealed heterogeneous SH2B3 protein expression, including additional SH2B3-immunoreactive species in variant carriers, together with reduced levels of the canonical SH2B3 protein. Collectively, these findings identify a common germline splicing polymorphism as a novel mechanism contributing to SH2B3 functional impairment in AML and highlight the potential relevance of non-coding variants in leukemia pathogenesis, with possible implications for risk stratification and future therapeutic strategies.

Humans↗

PubMed2025

Comprehensive proteomic and pathological profiling identifies PRAS40 as a novel biomarker and mediator of primary immune checkpoint blockade resistance in non-small cell lung cancer.

BACKGROUND: Immune checkpoint blockade (ICB) has revolutionized the treatment landscape of non-small cell lung cancer (NSCLC), yet primary resistance remains a significant clinical challenge. Recent evidence implicates PRAS40 (AKT1S1) in regulating cellular survival and immune responses, but its role in immunotherapy resistance is not fully understood. METHODS: Transcriptomic data from TCGA and GTEx cohorts were analyzed to assess PRAS40 expression. Prognostic value was evaluated using Cox regression. Immune microenvironment features were characterized with CIBERSORT and TIMER. Predictive efficacy for ICB response was examined using TIDE and IPS. Plasma PRAS40 levels in 66 NSCLC patients receiving ICB were quantified by proximity extension assay (PEA), and multiplex immunohistochemistry assessed associations among PRAS40, PD-L1, and CD8+ T cells in tumor tissues. RESULTS: High PRAS40 expression was associated with poor prognosis, reduced CD8+ T cell infiltration, and downregulation of immune checkpoint genes. Elevated circulating PRAS40 predicted primary ICB resistance and shorter progression-free survival, independent of PD-L1 or CD8+ T cell status. CONCLUSION: PRAS40 is strongly associated with primary ICB resistance in NSCLC and may serve as a novel predictive biomarker. These findings support its potential to guide personalized immunotherapy in lung cancer.

Humans↗

PubMed2026

Age-associated chromatin repression of Hippo-Yap signaling drives oogonial stem cell decline in chicken.

Oogonial stem cells (OSCs) are a type of reproductive germline stem cell present in the ovaries of adult animals after birth. They have been proposed to contribute to follicle renewal and could be associated with reproductive longevity, yet the molecular mechanism contribute to OSC malfunction during aging in chicken remain unclear. Here, we show that OSC number and proliferative capacity decline significantly from pre-laying to late-laying stages, accompanied by increased follicular atresia. RNA-seq analysis revealed a global reduction in transcriptional activity in aged OSCs. ChIP-seq demonstrated elevated H3K27me3 deposition, particularly at promoter regions, which correlated with repression of proliferation-related genes in the Hippo pathway including YAP1 and TEAD1. Pharmacological inhibition of H3K27me3 reduced repressive chromatin marks, restored Hippo pathway gene expression, and significantly enhanced OSC proliferation. Conversely, YAP1 knockdown attenuated proliferation-associated gene expression. These findings indicate that age-dependent H3K27me3 accumulation suppresses OSC proliferation through epigenetic repression of the Hippo-YAP axis, providing mechanistic insight into ovarian aging and a potential strategy to extend the laying cycle in poultry.

Animals↗

PubMed2026

Role of IFIT1 and IFIT3 in systemic lupus erythematosus: modeling a diagnosis and exploring immune regulation.

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder characterized by multi-organ involvement and a protracted clinical course. Current diagnostic strategies, which rely heavily on clinical symptoms and serology, are often insufficient for early detection. Therefore, highly accurate diagnostic biomarkers are urgently needed to facilitate early intervention and optimize personalized treatment strategies. D atasets GSE61635 and GSE135779 were integrated to identify differentially expressed genes. Weighted gene co-expression network analysis (WGCNA) was performed to isolate the module with the strongest clinical relevance. Mendelian randomization and single‑cell RNA‑seq were used to identify key disease‑relevant genes. A diagnostic model was then constructed, and gene set variation analysis (GSVA), along with gene set enrichment analysis (GSEA), was conducted to elucidate the underlying molecular pathways. IFIT1 and IFIT3 were identified as 2 core genes highly expressed in monocytes and T cells of SLE patients. Functional enrichment analysis revealed that these genes were enriched in immune-related pathways, metabolic pathways related to inflammation and genomic stability. The diagnostic model showed good accuracy, with an area under the curve (AUC) of 0.974 on the training set and 0.912 on the validation set. IFIT1 and IFIT3 represent promising biomarkers for diagnosing SLE and appear to mediate key immune and metabolic disturbances. Furthermore, the developed model serves as an accurate and reliable instrument for early diagnosis and personalized therapy. Large-scale clinical studies are warranted to further validate these findings and evaluate their clinical application.

Humans↗

PubMed2026

Role of semaphorin 4f in cardiac fibroblasts to regulate matrix production through actin remodeling and YAP/TAZ activation.

Cardiac fibrosis remains a critical determinant of adverse outcomes in heart disease, yet effective anti-fibrotic therapies are lacking. While multiple semaphorin family members participate in cardiovascular pathophysiology, the role of semaphorin 4f (Sema4f) in cardiac fibrosis remains unexplored. This study investigates the role and mechanisms of Sema4f in fibrotic remodeling post-myocardial infarction (MI). We employed flow cytometry to characterize cell type-specific Sema4f expression patterns in post-MI hearts. Lineage-specific knockout mice (fibroblast vs. myeloid) were subjected to left anterior descending ligation to assess functional consequences. Proteomic analysis of Sema4f-deficient cardiac fibroblasts was conducted to identify downstream effectors. Key pathways were subsequently validated using pharmacological inhibitors. We found that Sema4f expression was markedly upregulated during the fibrotic phase post-MI, primarily due to fibroblast activation. Fibroblast-, but not myeloid-, specific Sema4f deletion significantly reduced fibrosis and improved cardiac function. Proteomic profiling revealed that Sema4f deficiency led to downregulation of pro-fibrotic gene expression, which was associated with impaired actin cytoskeletal remodeling and decreased nuclear translocation of YAP/TAZ. Pharmacological inhibition of either actin remodeling or YAP/TAZ activity attenuated fibrosis, whereas YAP/TAZ activation abolished the anti-fibrotic effects of Sema4f knockout. Our study provides the first evidence demonstrating the functional role of Sema4f in cardiac fibroblast activation and fibrosis progression. We have identified a fibroblast-specific mechanism mediated by the Sema4f-actin cytoskeleton-YAP/TAZ axis, offering novel mechanistic insights into fibrosis regulation and revealing a promising therapeutic target for cardiac fibrosis with potential clinical applications.

Animals↗

PubMed2025

The functional study of novel KLHL3 missense mutations associated with pseudohypoaldosteronism type II.

BACKGROUND: Pseudohypoaldosteronism type II (PHA II) is an inherited tubulopathy, clinically defined by three hallmark features, including secondary hypertension, hyperchloremic metabolic acidosis, and persistent hyperkalemia occurring despite maintained glomerular filtration function. Herein, we aim to investigate the association of kelch like family member 3 (KLHL3) gene mutations with PHA II. METHODS: Compound heterozygous KLHL3 mutations were identified through whole-exome sequencing and Sanger validation. AlphaFold-based structural modeling, site-directed mutagenesis of Flag-tagged plasmids, and co-immunoprecipitation (Co-IP)/immunoblotting in vivo were combined to analyze mutant protein interactions and ubiquitination effects. RESULTS: A Chinese patient was identified with two previously unreported KLHL3 variants (c.131G > A [p.R44Q] and c.744 C > G [p.Y248*]), exhibiting a biochemical triad of asymptomatic hyperkalemia, mild metabolic acidosis, and borderline hypertension. Administration of thiazide diuretics effectively normalized the patient’s hyperkalemia and hypertension. A p.R44Q missense mutation predicted as variants of uncertain significance (VOUS) by American College of Medical Genetics and Genomics (ACMG) guidelines, and a p.Y248* nonsense mutation predicted as variants of likely pathogenic. Functional study revealed that the two KLHL3 mutations impair its ubiquitination of with-no-lysine kinase 1 (WNK1) and with-no-lysine kinase 4 (WNK4), and further increase phosphorylation of both SPAK (sterile20/sporulation-specific protein-1 related proline/alanine-rich kinase)/OSR1 (oxidative stress response kinase-1) and Na-Cl-cotransporter (NCC). CONCLUSIONS: Our study characterized two previously unreported KLHL3 mutations, followed by comprehensive in vitro functional analyses to elucidate their pathophysiological contributions at the molecular level.

Humans↗

PubMed2020

LINC00922 regulates epithelial-mesenchymal transition, invasive and migratory capacities in breast cancer through promoting NKD2 methylation.

Breast cancer ranks as the major reason for mortality in women populations, accounting for 23% of all cancer deaths. One in every three Asian women encounters the risk of this cancer in their lifetime. Long intergenic non-coding RNAs (lincRNAs) have emerged as tumor promoters and suppressors. The molecular mechanism of breast cancer remains elusive. Therefore, the current study aimed to explore the role lincRNA LINC00922 plays in the development of breast cancer. Breast cancer tissues and adjacent tissues were obtained from 109 patients with breast cancer. The RNA extraction and quantification and immunohistochemical staining characterized the high expression of LINC00922 and low expression of NKD2 in breast cancer tissues in comparison to its adjacent counterparts. Furthermore, the ectopic expression and knockdown experiments were conducted to figure out the in vivo and in vitro effects of LINC00922 on breast cancer progression. The ectopically expressed LINC00922 activated the Wnt signaling pathway, promoted epithelial-mesenchymal transition, cell proliferative, invasive and migratory capacities, tumor growth and metastasis. Additionally, the RIP and ChIP assay identified that LINC00922 recruited DNMT1, DNMT3A and DNMT3B proteins in the promoter region of NKD2 to promote NKD2 promoter methylation, thus reducing the NKD2 expression. Moreover, the Wnt signaling pathway was activated subsequent to NKD2 silencing, which was reversed by LINC00922 silencing. Lastly, the anti-oncogenic effects of LINC00922 inhibition was antagonized after NKD2 knocked down. The current study provides evidence that LINC00922 acts as a tumor promoter by promoting NKD2 methylation. Hopefully, it provides a novel potential gene target for the treatment of breast cancer.

Adaptor Proteins, Signal Transducing↗

PubMed2025

HnRNPR promotes non-small cell lung cancer progression by protecting XB130 mRNA from XRN1- and DIS3L2-mediated degradation.

The adaptor protein XB130 is critically implicated in tumorigenesis. However, the mechanisms regulating its expression in tumors are not well understood. Our previous studies have identified hnRNPR as a potential binding protein of XB130 3'UTR in non-small cell lung cancer (NSCLC). This study aimed to clarify hnRNPR's role in NSCLC progression and its specific mechanisms regulating XB130 expression. The expression of hnRNPR in NSCLC and normal tissues was assessed using NSCLC tissue microarray and the TCGA database. Subsequently, in vitro and in vivo experiments were conducted to investigate the impact of hnRNPR on NSCLC cell proliferation and epithelial-mesenchymal transition (EMT) by modulating XB130 expression. The underlying molecular mechanisms of hnRNPR regulating XB130 expression were explored utilizing a range of molecular biology techniques including Western blotting, Real-time quantitative PCR, Immunohistochemistry, Dual-luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation. We identified the overexpression of hnRNPR in NSCLC, with heightened hnRNPR levels significantly associated with poor prognosis in patients with lung adenocarcinoma. Functionally, hnRNPR overexpression promoted NSCLC cell proliferation and EMT and activated the Akt signaling pathway. Mechanistically, hnRNPR protected XB130 mRNA from XRN1- and DIS3L2-mediated degradation by binding to specific regions within XB130 3'UTR, consequently elevating XB130 expression. Lastly, XB130 overexpression counteracted the effects of hnRNPR silencing on NSCLC cells. Overall, our study unveils the potential of targeting the hnRNPR/XB130 axis as a promising therapeutic strategy for NSCLC.

Humans↗

PubMed2025

Mutant RIT1 cooperates with YAP to drive an EMT-like lung cancer state.

Mutations in "Ras-like in all tissues" (RIT1) occur in up to 2% of lung adenocarcinomas and are mutually exclusive with KRAS and EGFR mutations, suggesting that RIT1 may act as a non-canonical driver oncogene in lung cancer. However, the lack of a RIT1-mutant lung cancer model has hindered the development and testing of RIT1-targeted therapeutics. Here, we report a mouse model with conditional regulation of the cancer-associated RIT1M90I variant. We show that autochthonous expression of RIT1M90I and combined inactivation of Nf2 and p53 drives an aggressive lung cancer with 100% penetrance and short latency. Oncogenic cooperation between RIT1M90I and p53/Nf2 loss is driven by synergistic activation of AP-1 transcription factors and can be reversed by the combined inhibition of MEK and TEAD. These data identify YAP/TEAD as a mediator of RIT1's oncogenic capability and nominate TEAD as a potential drug target in RIT1-mutant lung cancer.

Animals↗

PubMed2025

A method for the detection and enrichment of endogenous cereblon substrates.

C-terminal cyclic imides are posttranslational modifications (PTMs) on proteins that are recognized and removed by the E3 ligase substrate adapter cereblon (CRBN). Despite the observation of these modifications across the proteome by mass spectrometry-based proteomics, an orthogonal and generalizable method to visualize the C-terminal cyclic imide would enhance detection, sensitivity, and throughput of endogenous CRBN substrate characterization. Here, we develop an antibody-like reagent, termed "cerebody," for visualizing and enriching C-terminal cyclic imide-modified proteins. We describe the engineering of CRBN derivatives to produce cerebody and use it to identify CRBN substrates by western blot and enrichment from whole-cell and tissue lysates. CRBN substrates identified by cerebody enrichment are mapped, validated, and further characterized for dependence on the C-terminal cyclic imide modification. These methods will accelerate the characterization of endogenous CRBN substrates and their regulation.

Humans↗

PubMed2025

Severe hypercholesterolemia in a pediatric cohort: Familial homozygous and autosomal recessive hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic disorder characterized by impaired clearance of low-density lipoprotein cholesterol (LDL-C), leading to severe hypercholesterolemia and increased risk of premature cardiovascular disease (CVD). Our study aims to describe and compare the clinical, biochemical, and genetic profiles of pediatric patients diagnosed with FH based on LDL-C levels exceeding 400 mg/dL (10.4 mmol/L) and confirmed by biallelic pathogenic variants in low-density lipoprotein receptor (LDLR) or low-density lipoprotein receptor adapter protein-1 (LDLRAP1) genes. METHODS: This retrospective cohort study included 39 pediatric patients diagnosed with FH at a tertiary care center. Clinical data were analyzed, including age at diagnosis, family history, lipid profile, presence of xanthomas, and cardiovascular complications. Molecular analysis was conducted using next-generation sequencing (NGS) and Sanger sequencing to confirm pathogenic variants. Statistical comparisons were performed between the LDLR and LDLRAP1 variant groups regarding lipid profiles, treatment response, and cardiovascular outcomes. RESULTS: Among 39 patients, 32 and 7 had pathogenic variants in LDLR and LDLRAP1 genes, respectively. Genetic analysis identified 27 unique pathogenic variants in LDLR (including 5 novel mutations) and 4 in LDLRAP1 causal for autosomal recessive hypercholesterolemia (ARH), highlighting the molecular diversity of FH. Compared to the LDLR variant group, LDLRAP1 variant patients had significantly lower untreated LDL-C levels (640.0 ± 155.6 mg/dL [16.6 ± 4.0 mmol/L] vs 506.9 ± 130.1 mg/dL [13.1 ± 3.4 mmol/L], P = .026] and showed a superior response to lipid-lowering therapy (LLT), with a greater percentage (70.6% ± 12.0%) reduction in LDL-C levels (P = .015). While xanthomas were present in 62.5% of LDLR variant patients, they were less frequent (42.9%) in the LDLRAP1 group (P = .107). Cardiovascular complications were observed exclusively in LDLR variant patients. Fourteen patients required lipoprotein apheresis (LA), and one underwent liver transplantation due to severe aortic stenosis. CONCLUSION: This study highlights the importance of genetic testing in differentiating classical semidominant homozygous FH from ARH, given their phenotypic overlap but distinct treatment responses. LDLRAP1 variant patients with ARH exhibit better LDL-C reductions with conventional LLT, suggesting a milder phenotype. Early diagnosis, aggressive LLT, and novel treatments are essential to mitigate cardiovascular risk. Future studies with larger cohorts and long-term follow-ups are needed to refine treatment strategies for pediatric FH.

Humans↗

PubMed2025

The common murine retroviral integration site activating Hhex marks a distal regulatory enhancer co-opted in human early T-cell precursor leukemia.

The Hhex gene encodes a transcription factor that is important for both embryonic and post-natal development, especially of hematopoietic tissues. Hhex is one of the most common sites of retroviral integration in mouse models. We found the most common integrations in AKXD (recombinant inbred strains) T-ALLs occur 57-61kb 3' of Hhex and activate Hhex gene expression. The genomic region of murine leukemia virus (MLV) integrations has features of a developmental stage-specific cis regulatory element (CRE), as evidenced by ATAC-seq in murine progenitor cells and high H3K27 acetylation at the syntenic CRE in human hematopoietic cell lines. With ChIP-exonuclease, we describe occupancy of LIM domain binding protein 1 (LDB1), the constitutive partner of the LIM Only-2 (LMO2), GATA1, and TAL1 transcription factors at GATA sites and at a composite GATA-E box within the CRE. With virtual 4C analysis, we observed looping between this +65kb CRE and the proximal intron one enhancer of HHEX in primary human ETP-ALLs and in normal progenitor cells. Our results show that retroviral integrations at intergenic sites can mark and take advantage of CREs. Specifically, in the case of HHEX activation, this newly described +65kb CRE is co-opted in the pathogenesis of ETP-ALL by the LMO2/LDB1 complex.

Humans↗

PubMed2026

Genome-wide CRISPR interference screen identifies Clip2 as a novel regulator of osteocyte maturation and morphology.

Osteocytes play critical roles in bone, making them attractive targets for therapeutics aimed at improving bone mass and strength. The genes driving osteocyte maturation and function are not fully understood. Here, we aimed to identify novel genes responsible for osteocyte differentiation and dendrite development by performing a genome-wide CRISPR-interference (CRISPRi) screen in the Ocy454 osteocyte-like cell line. We identify CD61 (integrin β3) as a marker of osteocyte maturation: surface CD61 expression increases during osteocyte maturation, and CD61high cells express higher levels of osteocyte marker genes. We then developed a flow cytometry-based assay to quantify surface CD61 protein levels as a phenotypic endpoint for functional genomic screening. In a genome-wide screen, we identified Clip2, which encodes a microtubule-binding protein, as one of dozens of genes necessary for CD61 expression. Clip2 inhibition decreased surface CD61 expression, reduced expression of osteocyte-specific genes Dmp1 and Sost, and impaired dendrite morphology in vitro. Together, these results highlight the utility of surface CD61 as a marker of osteocyte maturity and identify the role of the microtubule cytoskeleton for osteocyte differentiation, form, and function.

Osteocytes↗