The Role of Leucine-Rich Repeat Containing Protein 10 (LRRC10) in Dilated Cardiomyopathy

Integrating molecular and clinical variables to predict myocardial recovery

Mechanical unloading and circulatory support with left ventricular assist devices (LVADs) mediate significant myocardial improvement in a subset of advanced heart failure (HF) patients. The clinical and biological phenomena associated with cardiac recovery are under intensive investigation. Left ventricular (LV) apical tissue, alongside clinical data, were collected from HF patients at the time of LVAD implantation (n=208). RNA was isolated and mRNA transcripts were identified through RNA sequencing and confirmed with RT-qPCR. To our knowledge this is the first study to combine transcriptomic and clinical data to derive predictors of myocardial recovery. We used a bioinformatic approach to integrate 59 clinical variables and 22,373 mRNA transcripts at the time of LVAD implantation for the prediction of post-LVAD myocardial recovery defined as LV ejection fraction (LVEF) ≥40% and LV end-diastolic diameter (LVEDD) ≤5.9cm, as well as functional and structural LV improvement independently by using LVEF and LVEDD as continuous variables, respectively. To substantiate the predicted variables, we used a multi-model approach with logistic and linear regressions. Combining RNA and clinical data resulted in a gradient boosted model with 80 features achieving an AUC of 0.731±0.15 for predicting myocardial recovery. Variables associated with myocardial recovery from a clinical standpoint included HF duration, pre-LVAD LVEF, LVEDD, and HF pharmacologic therapy, and LRRN4CL (ligand binding and programmed cell death) from a biological standpoint. Our findings could have diagnostic, prognostic, and therapeutic implications for advanced HF patients, and inform the care of the broader HF population.

Regulation of cardiomyocyte intracellular trafficking and signal transduction by protein palmitoylation

Despite the well-established functions of protein palmitoylation in fundamental cellular processes, the roles of this reversible post-translational lipid modification in cardiomyocyte biology remain poorly studied. Palmitoylation is catalyzed by a family of 23 zinc finger and Asp-His-His-Cys domain-containing S-acyltransferases (zDHHC enzymes) and removed by select thioesterases of the lysophospholipase and α/β-hydroxylase domain (ABHD)-containing families of serine hydrolases. Recently, studies utilizing genetic manipulation of zDHHC enzymes in cardiomyocytes have begun to unveil essential functions for these enzymes in regulating cardiac development, homeostasis, and pathogenesis. Palmitoylation co-ordinates cardiac electrophysiology through direct modulation of ion channels and transporters to impact their trafficking or gating properties as well as indirectly through modification of regulators of channels, transporters, and calcium handling machinery. Not surprisingly, palmitoylation has roles in orchestrating the intracellular trafficking of proteins in cardiomyocytes, but also dynamically fine-tunes cardiomyocyte exocytosis and natriuretic peptide secretion. Palmitoylation has emerged as a potent regulator of intracellular signaling in cardiomyocytes, with recent studies uncovering palmitoylation-dependent regulation of small GTPases through direct modification and sarcolemmal targeting of the small GTPases themselves or by modification of regulators of the GTPase cycle. In addition to dynamic control of G protein signaling, cytosolic DNA is sensed and transduced into an inflammatory transcriptional output through palmitoylation-dependent activation of the cGAS-STING pathway, which has been targeted pharmacologically in preclinical models of heart disease. Further research is needed to fully understand the complex regulatory mechanisms governed by protein palmitoylation in cardiomyocytes and potential emerging therapeutic targets.

Exploring the mechanism of artificial selection signature in Chinese indigenous pigs by leveraging multiple bioinformatics database tools

BACKGROUND

Chinese indigenous pigs in Yunnan exhibit considerable phenotypic diversity, but their population structure and the biological interpretation of signatures of artificial selection require further investigation. To uncover population genetic diversity, migration events, and artificial selection signatures in Chinese domestic pigs, we sampled 111 Yunnan pigs from four breeds in Yunnan which is considered to be one of the centres of livestock domestication in China, and genotyped them using Illumina Porcine SNP60K BeadChip. We then leveraged multiple bioinformatics database tools to further investigate the signatures and associated complex traits.

RESULTS

Population structure and migration analyses showed that Diannanxiaoer pigs had different genetic backgrounds from other Yunnan pigs, and Gaoligongshan may undergone the migration events from Baoshan and Saba pigs. Intriguingly, we identified a possible common target of sharing artificial selection on a 265.09 kb region on chromosome 5 in Yunnan indigenous pigs, and the genes on this region were associated with cardiovascular and immune systems. We also detected several candidate genes correlated with dietary adaptation, body size (e.g., PASCIN1, GRM4, ITPR2), and reproductive performance. In addition, the breed-sharing gene MMP16 was identified to be a human-mediated gene. Multiple lines of evidence at the mammalian genome, transcriptome, and phenome levels further supported the evidence for the causality between MMP16 variants and the metabolic diseases, brain development, and cartilage tissues in Chinese pigs. Our results suggested that the suppression of MMP16 would directly lead to inactivity and insensitivity of neuronal activity and skeletal development in Chinese indigenous pigs.

CONCLUSION

In this study, the population genetic analyses and identification of artificial selection signatures of Yunnan indigenous pigs help to build an understanding of the effect of human-mediated selection mechanisms on phenotypic traits in Chinese indigenous pigs. Further studies are needed to fully characterize the process of human-mediated genes and biological mechanisms.

Palmitoylation-dependent regulation of cardiomyocyte Rac1 signaling activity and minor effects on cardiac hypertrophy

S-palmitoylation is a reversible lipid modification catalyzed by 23 S-acyltransferases with a conserved zinc finger aspartate-histidine-histidine-cysteine (zDHHC) domain that facilitates targeting of proteins to specific intracellular membranes. Here we performed a gain-of-function screen in the mouse and identified the Golgi-localized enzymes zDHHC3 and zDHHC7 as regulators of cardiac hypertrophy. Cardiomyocyte-specific transgenic mice overexpressing zDHHC3 show cardiac disease, and S-acyl proteomics identified the small GTPase Rac1 as a novel substrate of zDHHC3. Notably, cardiomyopathy and congestive heart failure in zDHHC3 transgenic mice is preceded by enhanced Rac1 S-palmitoylation, membrane localization, activity, downstream hypertrophic signaling, and concomitant induction of all Rho family small GTPases whereas mice overexpressing an enzymatically dead zDHHC3 mutant show no discernible effect. However, loss of Rac1 or other identified zDHHC3 targets Gαq/11 or galectin-1 does not diminish zDHHC3-induced cardiomyopathy, suggesting multiple effectors and pathways promoting decompensation with sustained zDHHC3 activity. Genetic deletion of Zdhhc3 in combination with Zdhhc7 reduces cardiac hypertrophy during the early response to pressure overload stimulation but not over longer time periods. Indeed, cardiac hypertrophy in response to 2 weeks of angiotensin-II infusion is not diminished by Zdhhc3/7 deletion, again suggesting other S-acyltransferases or signaling mechanisms compensate to promote hypertrophic signaling. Taken together, these data indicate that the activity of zDHHC3 and zDHHC7 at the cardiomyocyte Golgi promote Rac1 signaling and maladaptive cardiac remodeling, but redundant signaling effectors compensate to maintain cardiac hypertrophy with sustained pathological stimulation in the absence of zDHHC3/7.

A Genetically Encoded Actuator Selectively Boosts L-type Calcium Channels in Diverse Physiological Settings

L-type Ca 2+ channels (Ca V 1.2/1.3) convey influx of calcium ions (Ca 2+ ) that orchestrate a bevy of biological responses including muscle contraction and gene transcription. Deficits in Ca V 1 function play a vital role in cardiac and neurodevelopmental disorders. Yet conventional pharmacological approaches to upregulate Ca V 1 are limited, as excessive Ca 2+ influx leads to cytotoxicity. Here, we develop a genetically encoded enhancer of Ca V 1.2/1.3 channels (GeeC) to manipulate Ca 2+ entry in distinct physiological settings. Specifically, we functionalized a nanobody that targets the Ca V macromolecular complex by attaching a minimal effector domain from a Ca V enhancer-leucine rich repeat containing protein 10 (Lrrc10). In cardiomyocytes, GeeC evoked a 3-fold increase in L-type current amplitude. In neurons, GeeC augmented excitation-transcription (E-T) coupling. In all, GeeC represents a powerful strategy to boost Ca V 1.2/1.3 function in distinct physiological settings and, in so doing, lays the groundwork to illuminate new insights on neuronal and cardiac physiology and disease.

A previously uncharacterized Factor Associated with Metabolism and Energy (FAME/C14orf105/CCDC198/1700011H14Rik) is related to evolutionary adaptation, energy balance, and kidney physiology

In this study we use comparative genomics to uncover a gene with uncharacterized function (1700011H14Rik/C14orf105/CCDC198), which we hereby name FAME (Factor Associated with Metabolism and Energy). We observe that FAME shows an unusually high evolutionary divergence in birds and mammals. Through the comparison of single nucleotide polymorphisms, we identify gene flow of FAME from Neandertals into modern humans. We conduct knockout experiments on animals and observe altered body weight and decreased energy expenditure in Fame knockout animals, corresponding to genome-wide association studies linking FAME with higher body mass index in humans. Gene expression and subcellular localization analyses reveal that FAME is a membrane-bound protein enriched in the kidneys. Although the gene knockout results in structurally normal kidneys, we detect higher albumin in urine and lowered ferritin in the blood. Through experimental validation, we confirm interactions between FAME and ferritin and show co-localization in vesicular and plasma membranes.

Construction of a diagnostic signature and immune landscape of pulmonary arterial hypertension

Background

Molecular biomarkers are widely used for disease diagnosis and exploration of pathogenesis. Pulmonary arterial hypertension (PAH) is a rapidly progressive cardiopulmonary disease with delayed diagnosis. Studies were limited regarding molecular biomarkers correlated with PAH from a broad perspective.

Methods

Two independent microarray cohorts comprising 73 PAH samples and 36 normal samples were enrolled in this study. The weighted gene co-expression network analysis (WGCNA) was performed to identify the key modules associated with PAH. The LASSO algorithm was employed to fit a diagnostic model. The latent biology mechanisms and immune landscape were further revealed via bioinformatics tools.

Results

The WGCNA approach ultimately identified two key modules significantly associated with PAH. For genes within the two models, differential expression analysis between PAH and normal samples further determined nine key genes. With the expression profiles of these nine genes, we initially developed a PAH diagnostic signature (PDS) consisting of LRRN4, PI15, BICC1, PDE1A, TSHZ2, HMCN1, COL14A1, CCDC80, and ABCB1 in GSE117261 and then validated this signature in GSE113439. The ROC analysis demonstrated outstanding AUCs with 0.948 and 0.945 in two cohorts, respectively. Besides, patients with high PDS scores enriched plenty of Th17 cells and neutrophils, while patients with low PDS scores were dramatically related to mast cells and B cells.

Conclusion

Our study established a robust and promising signature PDS for diagnosing PAH, with key genes, novel pathways, and immune landscape offering new perspectives for exploring the molecular mechanisms and potential therapeutic targets of PAH.

Integrative analysis of multiomics data identifies selenium-related gene ALAD associating with keshan disease

Keshan disease is an endemic fatal dilated cardiomyopathy that can cause heart enlargement, heart failure, and cardiogenic death. Selenium deficiency is considered to be the main cause of Keshan disease. However, the molecular mechanism underlying Keshan disease remains unclear. Our whole-exome sequencing from 68 patients with Keshan disease and 100 controls found 199 candidate genes by gene-level burden tests. Interestingly, using multiomics data, the selenium-related gene ALAD (δ-aminolevulinic acid dehydratase) was the only candidate causative gene identified by three different analysis approaches. Based on single-cell transcriptome data, ALAD was highly expressed in cardiomyocytes and double mutations of human ALAD dramatically reduced its enzyme activity in vitro compared to negative control. Functional analysis of ALAD inhibition in mice resulted in a Keshan phenotype with left ventricular enlargement and cardiac dysfunction, whereas administration of sodium selenite markedly reversed the changes caused by ALAD inhibition. In addition, sodium selenite reversed Keshan phenotypes by affecting energy metabolism and mitochondrial function in mice as shown by the transcriptomic and proteomic data and the ultrastructure of cardiac myocytes. Our findings are the first to demonstrate that the selenium-related gene ALAD is essential for cardiac function by maintaining normal mitochondrial activity, providing strong molecular evidence supporting the hypothesis of selenium deficiency in Keshan disease. These results identified ALAD as a novel target for therapeutic intervention in Keshan disease and Keshan disease-related dilated cardiomyopathy.

First report on genome wide association study in western Indian population reveals host genetic factors for COVID-19 severity and outcome

Different human races across the globe responded in a different way to the SARS-CoV-2 infection leading to different disease severity. Therefore, it is anticipated that host genetic factors have a straight association with the COVID-19. We identified a total 6, 7, and 6 genomic loci for deceased-recovered, asymptomatic-recovered, and deceased-asymptomatic group comparison, respectively. Unfavourable alleles of the markers nearby the genes which are associated with lung and heart diseases such as Tumor necrosis factor superfamily (TNFSF4&18), showed noteworthy association with the disease severity and outcome for the COVID-19 patients in the western Indian population. The markers found with significant association with disease prognosis or recovery are of value in determining the individual's response to SARS-CoV-2 infection and can be used for the risk prediction in COVID-19. Besides, GWAS study in other populations from India may help to strengthen the outcome of this study.

EGR1 Is Implicated in Right Ventricular Cardiac Remodeling Associated with Pulmonary Hypertension

Background: Pulmonary hypertension (PH) is a vasoconstrictive disease characterized by elevated mean pulmonary arterial pressure (mPAP) at rest. Idiopathic pulmonary arterial hypertension (iPAH) and chronic thromboembolic pulmonary hypertension (CTEPH) represent two distinct subtypes of PH. Persisting PH leads to right ventricular (RV) hypertrophy, heart failure, and death. RV performance predicts survival and surgical interventions re-establishing physiological mPAP reverse cardiac remodeling. Nonetheless, a considerable number of PH patients are deemed inoperable. The underlying mechanism(s) governing cardiac regeneration, however, remain largely elusive. Methods: In a longitudinal approach, we profiled the transcriptional landscapes of hypertrophic RVs and recovered hearts 3 months after surgery of iPAH and CTEPH patients. Results: Genes associated with cellular responses to inflammatory stimuli and metal ions were downregulated, and cardiac muscle tissue development was induced in iPAH after recovery. In CTEPH patients, genes related to muscle cell development were decreased, and genes governing cardiac conduction were upregulated in RVs following regeneration. Intriguingly, early growth response 1 (EGR1), a profibrotic regulator, was identified as a major transcription factor of hypertrophic RVs in iPAH and CTEPH. A histological assessment confirmed our biocomputational results, and suggested a pivotal role for EGR1 in RV vasculopathy. Conclusion: Our findings improved our understanding of the molecular events driving reverse cardiac remodeling following surgery. EGR1 might represent a promising candidate for targeted therapy of PH patients not eligible for surgical treatment.

The expression of LRRN4 was correlated with the progression and prognosis of colon adenocarcinoma (COAD) patients

Our present study aims to investigate the value of LRRN4 in the progression and prognosis of COAD patients. All COAD and adjacent sample data was downloaded from TCGA database. Survival analysis was performed according to Kaplan-Meier method. The real-time quantitative PCR and immunohistochemistry analysis were conducted for validation in cell lines and tissues. The GSEA was conducted to find functional KEGG pathways. Multivariate Cox regression proportional hazard mode was used to determine whether LRRN4 expression was an independent prognostic factor. The LRRN4 expression in COAD samples were significantly higher than that in adjacent samples, which was consistent with our experiments in cell lines and tissues. Along with the increase of TNM Stage, LRRN4 expression had an increasing tendency. The COAD patients with high LRRN4 expression showed undesirable prognoses. Additionally, the TGF-β signaling pathway, WNT signaling pathway and other 25 pathways were significantly activated in the high LRRN4 expression group. In conclusion, high LRRN4 expression was closely related to the onset of COAD and it was a poor prognostic factor for COAD patients.

Inhibition of G-protein signalling in cardiac dysfunction of intellectual developmental disorder with cardiac arrhythmia (IDDCA) syndrome

BACKGROUND

Pathogenic variants of GNB5 encoding the β5 subunit of the guanine nucleotide-binding protein cause IDDCA syndrome, an autosomal recessive neurodevelopmental disorder associated with cognitive disability and cardiac arrhythmia, particularly severe bradycardia.

METHODS

We used echocardiography and telemetric ECG recordings to investigate consequences of Gnb5 loss in mouse.

RESULTS

We delineated a key role of Gnb5 in heart sinus conduction and showed that Gnb5-inhibitory signalling is essential for parasympathetic control of heart rate (HR) and maintenance of the sympathovagal balance. Gnb5-/- mice were smaller and had a smaller heart than Gnb5+/+ and Gnb5+/- , but exhibited better cardiac function. Lower autonomic nervous system modulation through diminished parasympathetic control and greater sympathetic regulation resulted in a higher baseline HR in Gnb5-/- mice. In contrast, Gnb5-/- mice exhibited profound bradycardia on treatment with carbachol, while sympathetic modulation of the cardiac stimulation was not altered. Concordantly, transcriptome study pinpointed altered expression of genes involved in cardiac muscle contractility in atria and ventricles of knocked-out mice. Homozygous Gnb5 loss resulted in significantly higher frequencies of sinus arrhythmias. Moreover, we described 13 affected individuals, increasing the IDDCA cohort to 44 patients.

CONCLUSIONS

Our data demonstrate that loss of negative regulation of the inhibitory G-protein signalling causes HR perturbations in Gnb5-/- mice, an effect mainly driven by impaired parasympathetic activity. We anticipate that unravelling the mechanism of Gnb5 signalling in the autonomic control of the heart will pave the way for future drug screening.

Palmitoylation: A Fatty Regulator of Myocardial Electrophysiology

Regulation of cardiac physiology is well known to occur through the action of kinases that reversibly phosphorylate ion channels, calcium handling machinery, and signaling effectors. However, it is becoming increasingly apparent that palmitoylation or S-acylation, the post-translational modification of cysteines with saturated fatty acids, plays instrumental roles in regulating the localization, activity, stability, sorting, and function of numerous proteins, including proteins known to have essential functions in cardiomyocytes. However, the impact of this modification on cardiac physiology requires further investigation. S-acylation is catalyzed by the zDHHC family of S-acyl transferases that localize to intracellular organelle membranes or the sarcolemma. Recent work has begun to uncover functions of S-acylation in the heart, particularly in the regulation of cardiac electrophysiology, including modification of the sodium-calcium exchanger, phospholemman and the cardiac sodium pump, as well as the voltage-gated sodium channel. Elucidating the regulatory functions of zDHHC enzymes in cardiomyocytes and determination of how S-acylation is altered in the diseased heart will shed light on how these modifications participate in cardiac pathogenesis and potentially identify novel targets for the treatment of cardiovascular disease. Indeed, proteins with critical signaling roles in the heart are also S-acylated, including receptors and G-proteins, yet the dynamics and functions of these modifications in myocardial physiology have not been interrogated. Here, we will review what is known about zDHHC enzymes and substrate S-acylation in myocardial physiology and highlight future areas of investigation that will uncover novel functions of S-acylation in cardiac homeostasis and pathophysiology.

Heart Regeneration in the Mexican Cavefish

Although Astyanax mexicanus surface fish regenerate their hearts after injury, their Pachón cave-dwelling counterparts cannot and, instead, form a permanent fibrotic scar, similar to the human heart. Myocardial proliferation peaks at similar levels in both surface fish and Pachón 1 week after injury. However, in Pachón, this peak coincides with a strong scarring and immune response, and ultimately, cavefish cardiomyocytes fail to replace the scar. We identified lrrc10 to be upregulated in surface fish compared with Pachón after injury. Similar to cavefish, knockout of lrrc10 in zebrafish impairs heart regeneration without affecting wound cardiomyocyte proliferation. Furthermore, using quantitative trait locus (QTL) analysis, we have linked the degree of heart regeneration to three loci in the genome, identifying candidate genes fundamental to the difference between scarring and regeneration. Our study provides evidence that successful heart regeneration entails a delicate interplay between cardiomyocyte proliferation and scarring.

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Astyanax mexicanus surface fish regenerate their hearts, but Pachón cavefish cannot

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Successful regeneration is a delicate interplay between proliferation and scarring

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lrrc10 is required for heart regeneration

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Using QTL analysis, we have identified three genomic loci linked to heart regeneration

Leucine Rich Repeat Proteins: Sequences, Mutations, Structures and Diseases

Mutations in the genes encoding Leucine Rich Repeat (LRR) containing proteins are associated with over sixty human diseases; these include high myopia, mitochondrial encephalomyopathy, and Crohn's disease. These mutations occur frequently within the LRR domains and within the regions that shield the hydrophobic core of the LRR domain. The amino acid sequences of fifty-five LRR proteins have been published. They include Nod-Like Receptors (NLRs) such as NLRP1, NLRP3, NLRP14, and Nod-2, Small Leucine Rich Repeat Proteoglycans (SLRPs) such as keratocan, lumican, fibromodulin, PRELP, biglycan, and nyctalopin, and F-box/LRR-repeat proteins such as FBXL2, FBXL4, and FBXL12. For example, 363 missense mutations have been identified. Replacement of arginine, proline, or cysteine by another amino acid, or the reverse, is frequently observed. The diverse effects of the mutations are discussed based on the known structures of LRR proteins. These mutations influence protein folding, aggregation, oligomerization, stability, protein-ligand interactions, disulfide bond formation, and glycosylation. Most of the mutations cause loss of function and a few, gain of function.

Defective Flux of Thrombospondin-4 through the Secretory Pathway Impairs Cardiomyocyte Membrane Stability and Causes Cardiomyopathy

Thrombospondins are stress-inducible secreted glycoproteins with critical functions in tissue injury and healing. Thrombospondin-4 (Thbs4) is protective in cardiac and skeletal muscle, where it activates an adaptive endoplasmic reticulum (ER) stress response, induces expansion of the ER, and enhances sarcolemmal stability. However, it is unclear if Thbs4 has these protective functions from within the cell, from the extracellular matrix, or from the secretion process itself. In this study, we generated transgenic mice with cardiac cell-specific overexpression of a secretion-defective mutant of Thbs4 to evaluate its exclusive intracellular and secretion-dependent functions. Like wild-type Thbs4, the secretion-defective mutant upregulates the adaptive ER stress response and expands the ER and intracellular vesicles in cardiomyocytes. However, only the secretion-defective Thbs4 mutant produces cardiomyopathy with sarcolemmal weakness and rupture that is associated with reduced adhesion-forming glycoproteins in the membrane. Similarly, deletion of Thbs4 in the mdx mouse model of Duchenne muscular dystrophy enhances cardiomyocyte membrane instability and cardiomyopathy. Finally, overexpression of the secretion-defective Thbs4 mutant in Drosophila, but not wild-type Thbs4, impaired muscle function and sarcomere alignment. These results suggest that transit through the secretory pathway is required for Thbs4 to augment sarcolemmal stability, while ER stress induction and vesicular expansion mediated by Thbs4 are exclusively intracellular processes.

Pediatric Dilated Cardiomyopathy-Associated LRRC10 (Leucine-Rich Repeat-Containing 10) Variant Reveals LRRC10 as an Auxiliary Subunit of Cardiac L-Type Ca2+ Channels

BACKGROUND

Genetic causes of dilated cardiomyopathy (DCM) are incompletely understood. LRRC10 (leucine-rich repeat-containing 10) is a cardiac-specific protein of unknown function. Heterozygous mutations in LRRC10 have been suggested to cause DCM, and deletion of Lrrc10 in mice results in DCM.

METHODS AND RESULTS

Whole-exome sequencing was carried out on a patient who presented at 6 weeks of age with DCM and her unaffected parents, filtering for rare, deleterious, recessive, and de novo variants. Whole-exome sequencing followed by trio-based filtering identified a homozygous recessive variant in LRRC10, I195T. Coexpression of I195T LRRC10 with the L-type Ca2+ channel (Cav1.2, β2CN2, and α2δ subunits) in HEK293 cells resulted in a significant ≈0.5-fold decrease in ICa,L at 0 mV, in contrast to the ≈1.4-fold increase in ICa,L by coexpression of LRRC10 (n=9-12, P<0.05). Coexpression of LRRC10 or I195T LRRC10 did not alter the surface membrane expression of Cav1.2. LRRC10 coexpression with Cav1.2 in the absence of auxiliary β2CN2 and α2δ subunits revealed coassociation of Cav1.2 and LRRC10 and a hyperpolarizing shift in the voltage dependence of activation (n=6-9, P<0.05). Ventricular myocytes from Lrrc10-/- mice had significantly smaller ICa,L, and coimmunoprecipitation experiments confirmed association between LRRC10 and the Cav1.2 subunit in mouse hearts.

CONCLUSIONS

Examination of a patient with DCM revealed homozygosity for a previously unreported LRRC10 variant: I195T. Wild-type and I195T LRRC10 function as cardiac-specific subunits of L-type Ca2+ channels and exert dramatically different effects on channel gating, providing a potential link to DCM.

+mRNA expression of LRRC55 protein (leucine-rich repeat-containing protein 55) in the adult mouse brain

LRRC55 (leucine-rich repeat-containing protein 55) protein is an auxiliary γ subunit of BK (Big conductance potassium channel) channels, which leftward shifts GVs of BK channels around 50 mV in the absence of cytosolic Ca²⁺. LRRC55 protein is also the only γ subunit of BK channels that is expressed in mammalian nervous system. However, the expression pattern of LRRC55 gene in adult mammalian brain remains elusive. In this study, we investigated the distribution of LRRC55 mRNA in the adult mouse brain by using in situ hybridization. We found that LRRC55 mRNA is richly expressed in the adult mouse medial habenula nucleus (MHb), cerebellum and pons. However, the potential role of LRRC55 in MHb and cerebellum could be different based on the function of BK channels in these brain regions.

Leucine-rich repeat neuronal protein 4 (LRRN4) potentially functions in dilated cardiomyopathy

Leucine-rich repeat neuronal protein-4 (LRRN4 or NLRR4) has been identified as a new member of LRRN family, which is a group of proteins that contain leucine-rich repeat domains and functioned as regulators in a variety of pathologic processes including cardiac remodeling. However, the exact pattern of expression and function of LRRN4 in the human hearts is still unclear. In our study, the western blot test and real-time PCR were performed to detect the LRRN4 level in hearts of patients with dilated cardiomyopathy (DCM), ischemia heart disease (IHD) hearts respectively. Interestingly, the LRRN4 was highly expressed in donor hearts, but significantly reduced in hearts with DCM. While a comparable level of expression was detected in the IHD hearts when compared with donor hearts. Immunohistochemistry assay showed that LRRN4 was particularly expressed in cardiomyocytes and responsible for its decreased expression in the DCM hearts. Furthermore, we found LRRN4 was expressed in the ventricular cardiomyocytes of mice and apparently reduced after pressure overload treatment in the wild type mice. Therefore, our hitherto unrecognized findings provided the first evidence that the highly expressed LRRN4 is critical for maintaining morphology and function of heart. In addition to that, since its expression level decreased in DCM hearts but not IHD hearts, which indicated LRRN4 might be a therapeutic target clinically for DCM disease.

The role of miR-214 in cardiovascular diseases

Cardiovascular disease (CVD) is the leading cause of death throughout the world. The increase in new patients every year leads to a demand for the identification of valid and novel prognostic and diagnostic biomarkers for the prevention and treatment of cardiovascular diseases. MicroRNAs (miRNAs) are critical endogenous small noncoding RNAs that negatively modulate gene expression by regulating its translation. miRNAs are implicated in most physiological processes of the heart and in the pathological progression of cardiovascular diseases. miR-214 is a deregulated miRNA in many pathological conditions, and it contributes to the pathogenesis of multiple human disorders, including cancer and cardiovascular diseases. miR-214 has dual functions in different cardiac pathological circumstances. However, it is considered as a promising marker in the prognosis, diagnosis and treatment of cardiovascular diseases. In this review, we discuss the role of miR-214 in various cardiac disease conditions, including ischaemic heart diseases, cardiac hypertrophy, pulmonary arterial hypertension (PAH), angiogenesis following vascular injury and heart failure.