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Circulation. Genomic and Precision... Oct 2023Variants in the gene, that encodes the cytoskeletal protein, dystrophin, cause a severe form of dilated cardiomyopathy (DCM) associated with high rates of heart...
BACKGROUND
Variants in the gene, that encodes the cytoskeletal protein, dystrophin, cause a severe form of dilated cardiomyopathy (DCM) associated with high rates of heart failure, heart transplantation, and ventricular arrhythmias. Improved early detection of individuals at risk is needed.
METHODS
Genetic testing of 40 male probands with a potential X-linked genetic cause of primary DCM was undertaken using multi-gene panel sequencing, multiplex polymerase chain reaction, and array comparative genomic hybridization. Variant location was assessed with respect to dystrophin isoform patterns and exon usage. Telomere length was evaluated as a marker of myocardial dysfunction in left ventricular tissue and blood.
RESULTS
Four pathogenic/likely pathogenic variants were found in 5 probands (5/40: 12.5%). Only one rare variant was identified by gene panel testing with 3 additional multi-exon deletion/duplications found following targeted assays for structural variants. All of the pathogenic/likely pathogenic variants involved dystrophin exons that had percent spliced-in scores >90, indicating high levels of constitutive expression in the human adult heart. Fifteen variant-negative probands (15/40: 37.5%) had variants in autosomal genes including , , , and . Myocardial telomere length was reduced in patients with DCM irrespective of genotype. No differences in blood telomere length were observed between genotype-positive family members with/without DCM and controls.
CONCLUSIONS
Primary genetic testing using multi-gene panels has a low yield and specific assays for structural variants are required if -associated cardiomyopathy is suspected. Distinguishing X-linked causes of DCM from autosomal genes that show sex differences in clinical presentation is crucial for informed family management.
Topics: Adult; Humans; Male; Female; Dystrophin; Comparative Genomic Hybridization; Pedigree; Genotype; Phenotype; Adaptor Proteins, Signal Transducing; Apoptosis Regulatory Proteins
PubMed: 37671549
DOI: 10.1161/CIRCGEN.123.004221 -
Diabetologia Nov 2023Increased circulating levels of incompletely processed insulin (i.e. proinsulin) are observed clinically in type 1 and type 2 diabetes. Previous studies have suggested...
AIMS/HYPOTHESIS
Increased circulating levels of incompletely processed insulin (i.e. proinsulin) are observed clinically in type 1 and type 2 diabetes. Previous studies have suggested that Ca signalling within beta cells regulates insulin processing and secretion; however, the mechanisms that link impaired Ca signalling with defective insulin maturation remain incompletely understood.
METHODS
We generated mice with beta cell-specific sarcoendoplasmic reticulum Ca ATPase-2 (SERCA2) deletion (βS2KO mice) and used an INS-1 cell line model of SERCA2 deficiency. Whole-body metabolic phenotyping, Ca imaging, RNA-seq and protein processing assays were used to determine how loss of SERCA2 impacts beta cell function. To test key findings in human model systems, cadaveric islets were treated with diabetogenic stressors and prohormone convertase expression patterns were characterised.
RESULTS
βS2KO mice exhibited age-dependent glucose intolerance and increased plasma and pancreatic levels of proinsulin, while endoplasmic reticulum (ER) Ca levels and glucose-stimulated Ca synchronicity were reduced in βS2KO islets. Islets isolated from βS2KO mice and SERCA2-deficient INS-1 cells showed decreased expression of the active forms of the proinsulin processing enzymes PC1/3 and PC2. Additionally, immunofluorescence staining revealed mis-location and abnormal accumulation of proinsulin and proPC2 in the intermediate region between the ER and the Golgi (i.e. the ERGIC) and in the cis-Golgi in beta cells of βS2KO mice. Treatment of islets from human donors without diabetes with high glucose and palmitate concentrations led to reduced expression of the active forms of the proinsulin processing enzymes, thus phenocopying the findings observed in βS2KO islets and SERCA2-deficient INS-1 cells. Similar findings were observed in wild-type mouse islets treated with brefeldin A, a compound that perturbs ER-to-Golgi trafficking.
CONCLUSIONS/INTERPRETATION
Taken together, these data highlight an important link between ER Ca homeostasis and proinsulin processing in beta cells. Our findings suggest a model whereby chronic ER Ca depletion due to SERCA2 deficiency impairs the spatial regulation of prohormone trafficking, processing and maturation within the secretory pathway.
DATA AVAILABILITY
RNA-seq data have been deposited in the Gene Expression Omnibus (GEO; accession no.: GSE207498).
Topics: Mice; Humans; Animals; Proinsulin; Insulin-Secreting Cells; Diabetes Mellitus, Type 2; Sarcoplasmic Reticulum Calcium-Transporting ATPases; Insulin; Glucose; Islets of Langerhans
PubMed: 37537395
DOI: 10.1007/s00125-023-05979-4 -
Allergy, Asthma, and Clinical... Jan 2024Inborn errors of immunity (IEIs) are a group of conditions whereby parts of the immune system are missing or dysfunctional. Once thought to primarily be a pediatric... (Review)
Review
Inborn errors of immunity (IEIs) are a group of conditions whereby parts of the immune system are missing or dysfunctional. Once thought to primarily be a pediatric disorder, it is now estimated that more than 50% of worldwide incident IEI cases are accounted for by adults. Delayed diagnosis, late symptom onset, and IEI phenocopies can all lead to adult-onset recognition of IEIs. Lack of awareness regarding the diversity of IEI manifestations in adults contributes to diagnostic and treatment delays. Prompt referral to immunology is critical so that patients can receive a precise molecular diagnosis and targeted therapy when available. This article serves as a primer on IEIs in adulthood, highlighting the pathophysiology, epidemiology and clinical features. We present clinical vignettes of three key IEIs to assist clinicians in building illness scripts on their presentations. We provide a framework for the laboratory evaluation of IEIs and their initial treatment, with the aim of improving recognition and management of these conditions.
PubMed: 38233962
DOI: 10.1186/s13223-023-00862-8 -
Acta Pharmaceutica Sinica. B Nov 2023Osteoporosis (OP) is a systemic skeletal disease that primarily affects the elderly population, which greatly increases the risk of fractures. Here we report that...
Osteoporosis (OP) is a systemic skeletal disease that primarily affects the elderly population, which greatly increases the risk of fractures. Here we report that Kindlin-2 expression in adipose tissue increases during aging and high-fat diet fed and is accompanied by decreased bone mass. Kindlin-2 specific deletion (K2KO) controlled by mice or adipose tissue-targeting AAV (AAV-Rec2-CasRx-sgK2) significantly increases bone mass. Mechanistically, Kindlin-2 promotes peroxisome proliferator-activated receptor gamma (PPAR) activation and downstream fatty acid binding protein 4 (FABP4) expression through stabilizing fatty acid synthase (FAS), and increased FABP4 inhibits insulin expression and decreases bone mass. Kindlin-2 inhibition results in accelerated FAS degradation, decreased PPAR activation and FABP4 expression, and therefore increased insulin expression and bone mass. Interestingly, we find that FABP4 is increased while insulin is decreased in serum of OP patients. Increased FABP4 expression through PPAR activation by rosiglitazone reverses the high bone mass phenotype of K2KO mice. Inhibition of FAS by C75 phenocopies the high bone mass phenotype of K2KO mice. Collectively, our study establishes a novel Kindlin-2/FAS/PPAR/FABP4/insulin axis in adipose tissue modulating bone mass and strongly indicates that FAS and Kindlin-2 are new potential targets and C75 or AAV-Rec2-CasRx-sgK2 treatment are potential strategies for OP treatment.
PubMed: 37969743
DOI: 10.1016/j.apsb.2023.07.001 -
Nature Sep 2023AMPA glutamate receptors (AMPARs), the primary mediators of excitatory neurotransmission in the brain, are either GluA2 subunit-containing and thus Ca-impermeable, or...
AMPA glutamate receptors (AMPARs), the primary mediators of excitatory neurotransmission in the brain, are either GluA2 subunit-containing and thus Ca-impermeable, or GluA2-lacking and Ca-permeable. Despite their prominent expression throughout interneurons and glia, their role in long-term potentiation and their involvement in a range of neuropathologies, structural information for GluA2-lacking receptors is currently absent. Here we determine and characterize cryo-electron microscopy structures of the GluA1 homotetramer, fully occupied with TARPγ3 auxiliary subunits (GluA1/γ3). The gating core of both resting and open-state GluA1/γ3 closely resembles GluA2-containing receptors. However, the sequence-diverse N-terminal domains (NTDs) give rise to a highly mobile assembly, enabling domain swapping and subunit re-alignments in the ligand-binding domain tier that are pronounced in desensitized states. These transitions underlie the unique kinetic properties of GluA1. A GluA2 mutant (F231A) increasing NTD dynamics phenocopies this behaviour, and exhibits reduced synaptic responses, reflecting the anchoring function of the AMPAR NTD at the synapse. Together, this work underscores how the subunit-diverse NTDs determine subunit arrangement, gating properties and ultimately synaptic signalling efficiency among AMPAR subtypes.
Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Glutamic Acid; Cryoelectron Microscopy; Synaptic Transmission; Synapses
PubMed: 37704721
DOI: 10.1038/s41586-023-06528-0 -
Heart Failure Reviews Sep 2023The hypertrophic cardiomyopathy phenotype encompasses a heterogeneous spectrum of genetic and acquired diseases characterized by the presence of left ventricular... (Review)
Review
The hypertrophic cardiomyopathy phenotype encompasses a heterogeneous spectrum of genetic and acquired diseases characterized by the presence of left ventricular hypertrophy in the absence of abnormal cardiac loading conditions. This "umbrella diagnosis" includes the "classic" hypertrophic cardiomyopathy (HCM), due to sarcomere protein gene mutations, and its phenocopies caused by intra- or extracellular deposits, such as Fabry disease (FD) and cardiac amyloidosis (CA). All these conditions share a wide phenotypic variability which results from the combination of genetic and environmental factors and whose pathogenic mediators are poorly understood so far. Accumulating evidence suggests that inflammation plays a critical role in a broad spectrum of cardiovascular conditions, including cardiomyopathies. Indeed, inflammation can trigger molecular pathways which contribute to cardiomyocyte hypertrophy and dysfunction, extracellular matrix accumulation, and microvascular dysfunction. Growing evidence suggests that systemic inflammation is a possible key pathophysiologic process potentially involved in the pathogenesis of cardiac disease progression, influencing the severity of the phenotype and clinical outcome, including heart failure. In this review, we summarize current knowledge regarding the prevalence, clinical significance, and potential therapeutic implications of inflammation in HCM and two of its most important phenocopies, FD and CA.
Topics: Humans; Cardiomyopathy, Hypertrophic; Hypertrophy, Left Ventricular; Cardiomyopathies; Phenotype; Fabry Disease; Inflammation
PubMed: 37115472
DOI: 10.1007/s10741-023-10307-4 -
Nature Communications May 2024In diabetes, macrophages and inflammation are increased in the islets, along with β-cell dysfunction. Here, we demonstrate that galectin-3 (Gal3), mainly produced and...
In diabetes, macrophages and inflammation are increased in the islets, along with β-cell dysfunction. Here, we demonstrate that galectin-3 (Gal3), mainly produced and secreted by macrophages, is elevated in islets from both high-fat diet (HFD)-fed and diabetic db/db mice. Gal3 acutely reduces glucose-stimulated insulin secretion (GSIS) in β-cell lines and primary islets in mice and humans. Importantly, Gal3 binds to calcium voltage-gated channel auxiliary subunit gamma 1 (CACNG1) and inhibits calcium influx via the cytomembrane and subsequent GSIS. β-Cell CACNG1 deficiency phenocopies Gal3 treatment. Inhibition of Gal3 through either genetic or pharmacologic loss of function improves GSIS and glucose homeostasis in both HFD-fed and db/db mice. All animal findings are applicable to male mice. Here we show a role of Gal3 in pancreatic β-cell dysfunction, and Gal3 could be a therapeutic target for the treatment of type 2 diabetes.
Topics: Animals; Humans; Male; Mice; Calcium; Calcium Channels; Diabetes Mellitus, Type 2; Diet, High-Fat; Galectin 3; Glucose; Insulin; Insulin Secretion; Insulin-Secreting Cells; Macrophages; Mice, Inbred C57BL; Mice, Knockout
PubMed: 38693121
DOI: 10.1038/s41467-024-47959-1 -
ELife Oct 2023The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. Post-transcriptional regulation by microRNAs (miRNAs) is a key...
The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. Post-transcriptional regulation by microRNAs (miRNAs) is a key aspect of this program. Indeed, deletion of neuron-enriched miRNAs induces strong developmental phenotypes, and miRNA levels are altered in patients with neurodevelopmental disorders. However, the mechanisms used by miRNAs to instruct brain development remain largely unexplored. Here, we identified miR-218 as a critical regulator of hippocampal assembly. MiR-218 is highly expressed in the hippocampus and enriched in both excitatory principal neurons (PNs) and GABAergic inhibitory interneurons (INs). Early life inhibition of miR-218 results in an adult brain with a predisposition to seizures. Changes in gene expression in the absence of miR-218 suggest that network assembly is impaired. Indeed, we find that miR-218 inhibition results in the disruption of early depolarizing GABAergic signaling, structural defects in dendritic spines, and altered intrinsic membrane excitability. Conditional knockout of in INs, but not PNs, is sufficient to recapitulate long-term instability. Finally, de-repressing and , two miR-218 targets, phenocopies the effects on early synchronous network activity induced by miR-218 inhibition. Taken together, the data suggest that miR-218 orchestrates formative events in PNs and INs to produce stable networks.
Topics: Animals; Adult; Humans; MicroRNAs; Neurons; Hippocampus; Interneurons; Brain; Mammals
PubMed: 37862092
DOI: 10.7554/eLife.82729 -
Nature Communications Aug 2023In mitosis, most transcription factors detach from chromatin, but some are retained and bookmark genomic sites. Mitotic bookmarking has been implicated in lineage...
In mitosis, most transcription factors detach from chromatin, but some are retained and bookmark genomic sites. Mitotic bookmarking has been implicated in lineage inheritance, pluripotency and reprogramming. However, the biological significance of this mechanism in vivo remains unclear. Here, we address mitotic retention of the hemogenic factors GATA2, GFI1B and FOS during haematopoietic specification. We show that GATA2 remains bound to chromatin throughout mitosis, in contrast to GFI1B and FOS, via C-terminal zinc finger-mediated DNA binding. GATA2 bookmarks a subset of its interphase targets that are co-enriched for RUNX1 and other regulators of definitive haematopoiesis. Remarkably, homozygous mice harbouring the cyclin B1 mitosis degradation domain upstream Gata2 partially phenocopy knockout mice. Degradation of GATA2 at mitotic exit abolishes definitive haematopoiesis at aorta-gonad-mesonephros, placenta and foetal liver, but does not impair yolk sac haematopoiesis. Our findings implicate GATA2-mediated mitotic bookmarking as critical for definitive haematopoiesis and highlight a dependency on bookmarkers for lineage commitment.
Topics: Animals; Mice; Chromatin; Chromosomes; DNA; Hematopoiesis; Mitosis; GATA2 Transcription Factor
PubMed: 37580379
DOI: 10.1038/s41467-023-40391-x -
Journal of Clinical Medicine Nov 2023Fabry disease (FD) is a genetic lysosomal storage disease with frequent cardiovascular involvement, whose presence is a major determinant of adverse clinical outcomes.... (Review)
Review
Fabry disease (FD) is a genetic lysosomal storage disease with frequent cardiovascular involvement, whose presence is a major determinant of adverse clinical outcomes. As a potentially treatable cause of left ventricular hypertrophy (LVH) and heart failure with preserved ejection fraction, the early recognition of FD is crucial to initiate enzyme replacement therapy and improve long-term prognosis. Multimodality imaging plays a central role in the evaluation of patients with FD and helps in the differential diagnosis of other conditions presenting with LVH. In the present review, we explore the current applications of multimodality cardiac imaging, in particular echocardiography and cardiovascular magnetic resonance, in the diagnosis, prognostic assessment, and follow-up of patients with FD.
PubMed: 38002674
DOI: 10.3390/jcm12227061