Inflammation is central to heart failure progression. Innate immune signaling increases expression of the transmembrane proteoglycan syndecan-4 in cardiac myocytes and fibroblasts, followed by shedding of its ectodomain. Circulating shed syndecan-4 is increased in heart failure patients, however the pathophysiological and molecular consequences associated with syndecan-4 shedding remain poorly understood. Here we used lipopolysaccharide (LPS) challenge to investigate the effects of syndecan-4 shedding in the heart. Wild-type mice (10mg/kg, 9h) and cultured neonatal rat cardiomyocytes and fibroblasts were subjected to LPS challenge. LPS increased cardiac syndecan-4 mRNA without altering full-length protein. Elevated levels of shedding fragments in the myocardium and blood from the heart confirmed syndecan-4 shedding in vivo. A parallel upregulation of ADAMTS1, ADAMTS4 and MMP9 mRNA suggested these shedding enzymes to be involved. Echocardiography revealed reduced ejection fraction, diastolic tissue velocity and prolonged QRS duration in mice unable to shed syndecan-4 (syndecan-4 KO) after LPS challenge. In line with syndecan-4 shedding promoting immune cell recruitment, expression of immune cell markers (CD8, CD11a, F4/80) and adhesion receptors (Icam1, Vcam1) were attenuated in syndecan-4 KO hearts after LPS. Cardiomyocytes and fibroblasts exposed to shed heparan sulfate-substituted syndecan-4 ectodomains showed increased Icam1, Vcam1, TNFα and IL-1β expression and NF-κB-activation, suggesting direct regulation of immune cell recruitment pathways. In cardiac fibroblasts, shed ectodomains regulated expression of extracellular matrix constituents associated with collagen synthesis, cross-linking and turnover. Higher syndecan-4 levels in the coronary sinus vs. the radial artery of open heart surgery patients suggested that syndecan-4 is shed from the human heart. Our data demonstrate that shedding of syndecan-4 ectodomains is part of the cardiac innate immune response, promoting immune cell recruitment, extracellular matrix remodeling and mitigating cardiac dysfunction in response to LPS.

Circulating biomarkers reflecting cardiac inflammation are needed to improve the diagnostics and guide the treatment of heart failure patients. The cardiac production and shedding of the transmembrane proteoglycan syndecan-4 is upregulated by innate immunity signaling pathways. Here, we investigated the potential of syndecan-4 as a blood biomarker of cardiac inflammation. Serum syndecan-4 was measured in patients with (i) non-ischemic, non-valvular dilated cardiomyopathy (DCM), with (n = 71) or without (n = 318) chronic inflammation; (ii) acute myocarditis (n = 15), acute pericarditis (n = 3) or acute perimyocarditis (23) and (iii) acute myocardial infarction (MI) at day 0, 3 and 30 (n = 119). Syndecan-4 was investigated in cultured cardiac myocytes and fibroblasts (n = 6–12) treated with the pro-inflammatory cytokines interleukin (IL)-1β and its inhibitor IL-1 receptor antagonist (IL-1Ra), or tumor necrosis factor (TNF)α and its specific inhibitor infliximab, an antibody used in treatment of autoimmune diseases. The levels of serum syndecan-4 were comparable in all subgroups of patients with chronic or acute cardiomyopathy, independent of inflammation. Post-MI, syndecan-4 levels were increased at day 3 and 30 vs. day 0. IL-1Ra attenuated IL-1β-induced syndecan-4 production and shedding in vitro, while infliximab had no effect. In conclusion, syndecan-4 shedding from cardiac myocytes and fibroblasts was attenuated by immunomodulatory therapy. Although its circulating levels were increased post-MI, syndecan-4 did not reflect cardiac inflammatory status in patients with heart disease.

In a model of reduced nephron mass combined with cardiac ischemia/reperfusion injury, proANP _31–67 prevented adverse cardiac remodeling independent of blood pressure. Vibrational spectroscopy identified coordinated biochemical alterations in cardiac and renal tissues not detected by conventional assays, providing molecular-level insight into cardiorenal remodeling.

We aimed to define the clinical and genetic basis of an autosomal recessive neurodevelopmental disorder identified in 3 unrelated families with an overlapping multisystem phenotype. Exome or genome sequencing was performed in 6 affected individuals from 3 families, revealing biallelic variants in SUPT4H1. Functional effects were evaluated using CRISPR and RNAi knockdown in C. elegans. Transcriptomic and proteomic profiling were conducted on patient-derived fibroblasts. Phylogenetic profiling assessed evolutionary conservation and coevolution. Dopamine response was evaluated in 2 affected siblings. All individuals carried biallelic SUPT4H1 variants-1 frameshift and 2 missense variants. Shared features included intellectual disability, dystonia, speech impairment, craniofacial dysmorphism, skeletal anomalies, and enamel hypoplasia. Functional modeling in C. elegans confirmed pathogenicity through neuromotor deficits. Multiomics analyses revealed dysregulation of developmental gene networks and the transcriptional machinery with disrupted RNA polymerase complexes and cell-cycle regulators. Dopamine treatment improved motor symptoms and normalized cerebrospinal neurotransmitter levels in 2 siblings. Biallelic variants in SUPT4H1 cause a previously unrecognized multisystem neurodevelopmental disorder. These findings underscore the importance of disrupted transcription in human disease and demonstrate how integrated multiomics and cross-species modeling can reveal underlying mechanisms and provide a foundation for future studies of transcriptional regulation.

Whole‐genome sequencing identifies intronic variants whose pathogenicity can be predicted with tools like SpliceAI. However, an actionable classification of such variants may require RNA‐based validation, which can be limited by low expression in clinically accessible tissues. We report two fetuses from one family with Arthrogryposis multiplex congenita 6 (AMC6 [OMIM # 619334]) and biallelic NEB variants: a paternally inherited likely pathogenic frameshift variant, Chr2(GRCh38):g.151579391del; NM_001164508.2:c.16653del; NP_001157980.2:p.(Asp5552ThrfsTer5), and a maternally inherited intronic variant of uncertain clinical significance, Chr2(GRCh38):g.151496267G>A; NM_001164508.2:c.24486+9C>T; NP_001157980.2:p.(?). Because NEB is poorly expressed in fibroblasts, we used CRISPR activation to induce its expression in fibroblasts from the heterozygous mother. RNA‐sequencing subsequently confirmed that the intronic variant generated a novel splice donor site associated with inferred loss of splicing at the canonical donor site. After NMD‐inhibition, we could thus identify 45.5% of NEB transcripts with a 7 bp exon extension, predicted to result in a protein‐coding frameshift. The intronic variant was classified as likely pathogenic, allowing a genetic diagnosis.

Background: The contribution of intronic variants to the etiology of Mendelian diseases is still underrecognized, impacting the diagnostic yield. Whole genome sequencing (WGS) detects intronic variants, but beside canonical splice-sites, intronic variants are frequently excluded from the interpretation step or are classified as variants of uncertain significance (VUS). In fact, assessing their clinical significance often requires validation via RNA-sequencing or in vitro studies. Methods: We studied a 31-year-old patient with spinocerebellar ataxia who lacked a molecular diagnosis after WGS analysis. We applied the Detection of RNA Outliers Pipeline (DROP) to analyze RNA-sequencing (RNA-seq) data from patient fibroblasts. DROP integrates OUTRID-ER and FRASER 2.0 algorithms designed to identify aberrant gene expression and splicing, respectively. Results: DROP identified SNX14 as an outlier with significantly reduced gene expression and aberrant splicing. Retrospective WGS data inspection revealed a homozygous deep intronic variant NM_153816.6(SNX14):c.867+288A>G, which caused the splicing defect. Biallelic loss of function variants in SNX14 cause autosomal recessive spinocerebellar ataxia type 20 (SCAR20; OMIM 616354), and the patient’s clinical presentation was compatible with this disease. Conclusion: We present a deep intronic SNX14 variant as the cause of SCAR20. Integration of RNA-sequencing increases the diagnostic yield specifically by identifying and resolving the pathogenicity of deep intronic variants. Identification of aberrant splicing events can be therapeutically relevant, as these mechanisms are targets for antisense oligonucleotide (ASO) based interventions.