JCI insight最新文献

Fanconi anemia (FA) is the most common bone marrow failure (BMF) syndrome. Beyond a role in DNA repair, FA genes have a role in suppressing DNA-RNA hybrids, termed R-loops, which can be generated via RNA polymerase (RNAP)-mediated transcription. However, how these processes, including a role in fate determination of hematopoietic stem cells (HSCs), are related to BMF is largely unknown. Additionally, single FA gene knockouts in mice do not recapitulate most phenotypes observed in FA patients. Thus, we generated a mouse model for FA by introducing heterozygous Setd2, which restricts RNAP-dependent transcription. Here, we show that FA patient-derived cells and Setd2+/- Fanca-/- HSCs share increased R-loop as well as dsRNA levels, and a ribosomal biogenesis defect. Further, Setd2+/- Fanca-/- HSCs display cell cycle arrest, mitotic errors and BMF phenotypes. Importantly, utilizing our Setd2+/- Fanca-/- mice, we discovered that Juglone, a pan RNAP inhibitor, reduces R-loop and dsRNA and reverses ribosomal biogenesis defects and mitotic errors, thereby rescuing BMF. In conclusion, this study establishes a novel mouse model that underscores a key role for R-loop formation, ribosomal biogenesis defects and mitotic errors in HSCs in driving BMF in Fanconi anemia. We also introduce a potential therapeutic avenue based upon pan-inhibition of RNA polymerases utilizing Juglone.

Improper light focus on the retina, refractive error, is primarily caused by eye size differences and is the leading cause of vision loss worldwide. C-terminal variants in the Myelin regulatory factor (MYRF) gene, a retinal pigment epithelium-derived (RPE-derived) transcription factor, lead to isolated nanophthalmos characterized by a small, though structurally sound eye. However, other MYRF loss-of-function variants cause syndromic disease. To address this discrepancy, in vitro and animal studies were performed on a pathogenic C-terminal variant dG-MYRF (p.Gly1126fs30*, c.3376-1G>A). Human RPE cells or primary RPE transduced with dG-MYRF showed reduced target gene expression, with decreased steady-state levels of the C-terminal cleavage product, but normal cleavage and localization. A homozygous humanized MYRF C-terminal mouse model (MyrfhumdG/humdG) was embryonic lethal by E18.5, while WT (MyrfhumWT/humWT) mice were viable. Single-cell RNA-seq from E17.5 MyrfhumdG/humdG and KO RxCre;Myrffl/fl (E15.5 and P0) mice revealed shared differentially expressed genes, with decreased effect size in the MyrfhumdG/humdG eyes. These findings support dG-MYRF as a hypomorphic allele. Additionally, 2 MYRF splicing variants creating nonfunctional isoforms were found in families with isolated nanophthalmos. Overall, hypomorphic MYRF alleles underlie isolated nanophthalmos, supporting a tissue-specific threshold effect and highlighting unique roles for the MYRF C-terminus in the RPE.

Patients with COVID-19 who develop platelet-activating antibodies represent a subset at heightened thrombotic risk, yet the immune features associated with this response remains to be defined. We applied single-cell RNA sequencing of B- and T-cells, single B-cell V(D)J sequencing, and plasma cytokine and chemokine analysis to define immune signatures distinguishing patients who did (PEA+) or did not (PEA-) develop these antibodies. PEA⁺ patients showed prominent transcriptional enrichment of inflammatory, antigen-presentation, and B-cell receptor signaling pathways within antigen-experienced B-cell subsets. Expanded B-cell clones in PEA+ patients were disproportionately enriched within atypical memory B-cells and exhibited upregulated IFN-γ-response signatures, increased proliferative mutational patterns, limited class switching, and a significant overrepresentation of RKH/Y5 heavy-chain motifs associated with platelet-activating antibodies, consistent with an extrafollicular-biased response. Parallel T-cell profiling revealed IL-12 pathway enrichment across most T-cell subsets, increased IFN-γ transcription, and elevated plasma levels of Th1-associated cytokines in PEA+ patients. Collectively, these data highlight a coordinated inflammatory environment marked by Th1-skewed T-cell activation and selective expansion of atypical memory B-cell clones carrying RKH/Y5 motifs, defining immunologic features associated with platelet-activating antibody development in COVID-19.

The cardiac conduction system (CCS) develops asymmetrically along the body axes. In heterotaxy syndrome - resulting from aberrant left-right axis formation - atrial and atrioventricular conduction defects can cause life-threatening arrhythmias. However, the developmental mechanisms regulating the atrioventricular conduction system (AVCS) disposition and integrity remain unclear. To investigate the etiology of AVCS malformations in laterality defects, we analyzed CCS development and function in mouse mutants for Cryptic and Lefty1, which are key regulators of Pitx2 in the left-right axis formation. Cryptic-/- embryos exhibited bilateral sinoatrial nodes and an ectopic anterior AV node and bundle accompanied by reduced Pitx2 expression. In contrast, Lefty1-/- embryos showed a hypoplastic sinoatrial node and AV node-bundle dissociation with ectopic Pitx2 expression. Single-cell transcriptomic analysis of Pitx2-/- hearts revealed expansion of AV node and bundle populations, consistent with a repressive role of Pitx2 in AVCS specification. Genetic lineage tracing indicated that Pitx2-expressing cells from the left lateral plate mesoderm populate cranioventral cardiac regions, where AVCS development is suppressed. Together, these findings clarify how global left-right axis information is locally integrated to shape AVCS disposition and integrity, providing a mechanistic model for AVCS abnormalities in laterality-associated congenital heart disease.

Heart failure (HF) persists as the primary cause of death among patients recovering from acute myocardial infarction (AMI). Protein ubiquitination has been implicated as a key modulator of HF pathogenesis, yet the role of ubiquitination in the Aldh2 rs671 mutant-the most common single-nucleotide variant in human populations-remains poorly understood. We discovered TRIM21 as a previously unrecognized E3 ubiquitin ligase for the ALDH2 rs671 mutant and elucidated its mechanistic involvement in HF progression. Using Aldh2 bone marrow chimeric mice to model AMI, we observed that wild-type mice transplanted with Aldh2 rs671 donor bone marrow developed severe myocardial fibrosis and markedly reduced cardiac systolic function two weeks post-infarction compared to controls. This phenotype arose from defective macrophage efferocytosis caused by myeloid-specific Aldh2 rs671 mutation. Through high-resolution mass spectrometry proteomics, we identified TRIM21 as the E3 ligase targeting ALDH2. TRIM21 catalyzed K48-linked ubiquitination at ALDH2 lysine 73. Macrophage-specific Trim21 knockdown via AAV-shTrim21 reversed both the exacerbated cardiac fibrosis and systolic dysfunction by restoring macrophage efferocytosis. These findings delineate the upstream E3 ubiquitin ligase and the ubiquitination site of ALDH2, revealing a potential therapeutic target for HF.

Synthetic prostaglandin analogues, such as latanoprost, are first-line treatments to reduce intraocular pressure (IOP) in the management of glaucoma, treating millions of patients daily. Glaucoma is a leading cause of blindness, characterized by progressive optic neuropathy, with elevated IOP being the sole modifiable risk factor. Despite this importance, the underlying latanoprost mechanism of action is still not well defined, being associated with both acute and long term activities, and a growing list of ocular side effects. Prostaglandins are eicosanoid lipid mediators. Yet, there has not been a comprehensive assessment of small lipid mediators in glaucomatous eyes. Here we performed a lipidomic screen of aqueous humour sampled from glaucoma patients and healthy control eyes. The resulting signature was surprisingly focused on significantly elevated levels of arachidonic acid (AA) and its derivative, the ant-inflammatory and cytoprotective mediator, lipoxin A4 (LXA4) in glaucoma eyes. Subsequent experiments reveal that this response is drug-induced, due to latanoprost actions on trabecular meshwork cells, rather than a consequence of elevated IOP. We demonstrate that increased LXA4 inhibits pro-inflammatory cues and promotes TGF-β production in the anterior chamber. In concert, an autocrine prostaglandin circuit mediates canonical rapid IOP-lowering. This work reveals parallel mechanisms underlying acute and long-term latanoprost activities during glaucoma treatment.

Fontan-associated liver disease (FALD) is a frequent complication in single ventricle patients palliated with the Fontan operation. FALD severity can impact clinical decisions; however, the pathophysiology of FALD progression is unknown. Single-cell spatial transcriptomics (ST) was performed on liver explant tissue sections from FALD patients with early (n=1) and advanced fibrosis (n=1) using CosMxTM Spatial Molecular Imaging with in-situ hybridization of 6000 genes. Immunofluorescence for liver zonation and cellular stress markers was performed to confirm protein expression based on ST analysis in additional FALD tissues (n=18). Unbiased clustering yielded 12 liver cell types, comprising six subtypes of hepatocytes. FALD with advanced fibrosis demonstrated expansion of mid-zonal hepatocytes, accompanied by loss of zonal markers characteristic of canonical pericentral and periportal hepatocytes. A subset of hepatocytes in advanced FALD demonstrated increased cellular stress and a redundant zonal phenotype, which we have termed zonally ambiguous and stressed hepatocytes. CellChat analysis revealed that ectopic WNT2 signaling is likely driving disrupted hepatocyte zonation. To corroborate these bioinformatic findings, we performed immunofluorescence staining of FALD specimens, which confirmed a disruption of liver zonation, and a significant increase in heat shock protein 70 (HSP70). Lastly, HSP70 expression strongly correlated with the Congestive Hepatic Fibrosis (CHF) score. Thus, single-cell ST has identified a unique population of hepatocytes with features of cellular stress and redundant zonal gene expression specific to advanced FALD. Further studies on hepatocyte metabolic function in Fontan patients will lead to a greater understanding of FALD development and progression during chronic maladaptation.

Among the known genetic causes of syndromic autism spectrum disorders (ASDs) are transcription factor deficiencies. In this regard, haploinsufficiency of the zinc finger and broad complex, tramtrack, bric and brac domain-containing protein 20 (ZBTB20) leads to a prototypical clinical picture, referred to as Primrose syndrome, comprising severe ASD symptoms together with intellectual disability. Here, we present a comprehensive behavioral and phenotypical characterization of Zbtb20+/- mice, a construct valid model of this thus far untreatable human condition. Zbtb20+/- mice exhibited diminished sociability, reduced vocalization, distinct repetitive behaviors, impaired cognitive flexibility, hyperactivity, and hypoalgesia. Magnetic resonance imaging revealed increased volumes of hippocampus, cerebellum, brain matter, and whole brain, confirmed by postmortem brain weight measurements. Due to our previous observation of enhanced ZBTB20 expression in CA1 pyramidal neurons upon recombinant human erythropoietin (rhEPO) injections, we anticipated a mitigating effect through rhEPO treatment of Zbtb20 deficiency/Primrose syndrome. Indeed, after 3 weeks of alternate-day rhEPO injections, a remarkable improvement in the behavioral phenotype was observed. Our results highlight rhEPO as promising treatment for Primrose syndrome.