A change of heart: new roles for cilia in cardiac development and disease

Genome-Wide Association Studies of Down Syndrome Associated Congenital Heart Defects Suggests a Genetically Heterogeneous Risk for CHD in DS

Congenital heart defects (CHDs) are the most common structural birth defect and are present in 40%-50% of children born with Down syndrome (DS). To characterize the genetic architecture of DS-associated CHD, we sequenced genomes of a multiethnic group of children with DS and a CHD (n = 886: atrioventricular septal defects (AVSD), n = 438; atrial septal defects (ASD), n = 122; ventricular septal defects (VSD), n = 170; other types of CHD, n = 156) and DS with a structurally normal heart (DS + NH, n = 572). We performed four genome-wide association study (GWAS) for common variants (MAF > 0.05) comparing DS with CHD, stratified by CHD-subtype, to DS + NH controls. Although no SNP achieved genome-wide significance, multiple loci in each analysis achieved suggestive significance (p < 2 × 10-6). Of these, the 1p35.1 locus (near RBBP4) was specifically associated with ASD risk, and the 5q35.2 locus (near MSX2) was associated with any type of CHD. Each of the suggestive loci contained one or more plausible candidate genes expressed in the developing heart. While no SNP replicated (p < 2 × 10-6) in an independent cohort of DS + CHD (DS + CHD: n = 229; DS + NH: n = 197), most SNPs that were suggestive in our GWASs remained suggestive when meta-analyzed with the GWASs from the replication cohort. These results build on previous work to identify genetic modifiers of DS-associated CHD.

Pathogenic variants in the IFT140 gene and an intriguing clinical presentation in two pediatric patients. Cases report and review of literature

BACKGROUND

The IFT140 gene is one of many genes involved in the synthesis of proteins needed for cilium function. Ciliopathies are a group of disorders associated with the dysfunction of ciliary structures and express as an individual organ system disease as well as multisystem disorders. Dysfunctional cilia typically manifest as pleiotropic clinical features, reflecting their widespread distribution and varied functionality.

CASES PRESENTATION

We present two cases: Case 1, a male with two pathological variations in IFT140 gene, a compound heterozygote, with kidney failure, retinal dystrophy, cardiomyopathy, and situs inversus and Case 2, a female with an IFT140 pathogenic homozygous variant, presented with nephrotic range proteinuria, retinitis pigmentosa, and pseudotumor cerebri.

CONCLUSIONS

As cilia dysfunction is known to cause pleiotropic clinical features due to the presence of cilia in different organs in the body, the clinical picture of the IFT140 mutation is also very heterogeneous. Our cases reveal unprecedented manifestations - LVNC, situs inversus, and pseudotumor cerebri - not previously documented in IFT140 mutation. These findings underscore the importance of genetic screening in ciliopathies.

Modulating biomechanical and integrating biochemical cues to foster adaptive remodeling of tissue engineered matrices for cardiovascular implants

Cardiovascular disease remains one of the leading causes of mortality in the Western world. Congenital heart disease affects nearly 1 % of newborns, with approximately one-fourth requiring reconstructive surgery during their lifetime. Current cardiovascular replacement options have significant limitations. Their inability to grow poses particular challenges for pediatric patients. Tissue Engineered Matrix (TEM)-based in situ constructs, with their self-repair and growth potential, offer a promising solution to overcome the limitations of current clinically used replacement options. Various functionalization strategies, involving the integration of biomechanical or biochemical components to enhance biocompatibility, have been developed for Tissue Engineered Vascular Grafts (TEVG) and Tissue Engineered Heart Valves (TEHV) to foster their capacity for in vivo remodeling. In this review, we present the current state of clinical translation for TEVG and TEHV, and provide a comprehensive overview of biomechanical and biochemical functionalization strategies for TEVG and TEHV. We discuss the rationale for functionalization, the implementation of functionalization cues in TEM-based TEVG and TEHV, and the interrelatedness of biomechanical and biochemical cues in the in vivo response. Finally, we address the challenges associated with functionalization and discuss how interdisciplinary research, especially when combined with in silico models, could enhance the translation of these strategies into clinical applications. STATEMENT OF SIGNIFICANCE: Cardiovascular disease remains one of the leading causes of mortality, with current replacements being unable to grow and regenerate. In this review, we present the current state of clinical translation for tissue engineered vascular grafts (TEVG) and heart valves (TEHV). Particularly, we discuss the rationale and implementation for functionalization cues in tissue engineered matrix-based TEVGs and TEHVs, and for the first time we introduce the interrelatedness of biomechanical and biochemical cues in the in-vivo response. These insights pave the way for next-generation cardiovascular implants that promise better durability, biocompatibility, and growth potential. Finally, we address the challenges associated with functionalization and discuss how interdisciplinary research, especially when combined with in silico models, could enhance the translation of these strategies into clinical applications .

Recessive genetic contribution to congenital heart disease in 5,424 probands

Variants with large effect contribute to congenital heart disease (CHD). To date, recessive genotypes (RGs) have commonly been implicated through anecdotal ascertainment of consanguineous families and candidate gene-based analysis; the recessive contribution to the broad range of CHD phenotypes has been limited. We analyzed whole exome sequences of 5,424 CHD probands. Rare damaging RGs were estimated to contribute to at least 2.2% of CHD, with greater enrichment among laterality phenotypes (5.4%) versus other subsets (1.4%). Among 108 curated human recessive CHD genes, there were 66 RGs, with 54 in 11 genes with >1 RG, 12 genes with 1 RG, and 85 genes with zero. RGs were more prevalent among offspring of consanguineous union (4.7%, 32/675) than among nonconsanguineous probands (0.7%, 34/4749). Founder variants in GDF1 and PLD1 accounted for 74% of the contribution of RGs among 410 Ashkenazi Jewish probands. We identified genome-wide significant enrichment of RGs in C1orf127, encoding a likely secreted protein expressed in embryonic mouse notochord and associated with laterality defects. Single-cell transcriptomes from gastrulation-stage mouse embryos revealed enrichment of RGs in genes highly expressed in the cardiomyocyte lineage, including contractility-related genes MYH6, UNC45B, MYO18B, and MYBPC3 in probands with left-sided CHD, consistent with abnormal contractile function contributing to these malformations. Genes with significant RG burden account for 1.3% of probands, more than half the inferred total. These results reveal the recessive contribution to CHD, and indicate that many genes remain to be discovered, with each likely accounting for a very small fraction of the total.

A splicing variant in EFCAB7 hinders ciliary transport and disrupts cardiac development

The Tetralogy of Fallot (TOF), the most prevalent form of cyanotic congenital heart disease, stems from abnormal development of the outflow tract during embryogenesis. Despite the crucial role played by primary cilia in heart development, there is currently insufficient evidence to establish a causal relationship between defects in genes related to primary cilia and non-syndromic TOF. Here, we performed Sanger sequencing on 131 Chinese patients diagnosed with TOF and identified a splicing variant (c.683-1G > C) in the EFCAB7 gene. This splicing variant triggered exon skipping, leading to the production of a non-functional protein both in vitro and in vivo. Mice carrying this variant exhibited abnormal cardiac development, impaired ciliogenesis, disrupted Hedgehog signaling, and hindered Shh/Gli pathway activity. Through the integration of CUT&Tag data on Glis and bulk RNA-seq profiles of embryonic hearts at E10.5, we found that transcriptional downregulation of Gli target genes, including Myh6, Zfpm1, and Nkx2-5, is a consequence of Shh signaling inhibition. Our findings implicate EFCAB7 as a potential causative gene for TOF, underscoring the indispensable function of primary cilia in the intricate process of cardiac septation during heart development.

A method for dyadic cardiac rhythmicity analysis: Preliminary evidence on bilateral interactions in fetal-maternal cardiac dynamics

Cardiac activity responds dynamically to metabolic demands and neural regulation. However, little is known about this process during pregnancy. Reports show occasional fetal-maternal heart rate couplings, but it has remained unclear whether these couplings extend to more complex oscillatory patterns of the heart rhythm. We developed a framework of time-varying measures of heart rate and rhythm, to test the presence of co-varying patterns in concurrent maternal and fetal measures (late pregnancy dataset, n = 10, and labour dataset, n = 12). These measures were derived from first and second-order Poincaré plots, with the aim to describe changes in short- and long-term rhythmicity, but also the dynamic shifts in acceleration and deceleration of heart rate. We found episodes of maternal-fetal co-varying patterns of cardiac rhythm in all the measures explored, in both datasets (at least 90% of the dataset presented a significant maternal-fetal correlation in each measure, with P < 0.001), with dynamic delays suggesting bilateral interactions at different time scales. We also found that these couplings intensify during labour (test between late pregnancy vs. labour datasets, P < 0.0015 in all second-order Poincaré plot-derived measures). While most literature suggests that the fetal heart responds to maternal breathing patterns or contractions, we propose the possibility that the fetal heart may also have a signalling function in the context of co-regulatory mechanisms and maternal inter-organ interactions. Understanding these complex visceral oscillations in utero may enhance the assessment of a healthy fetal development.

Cryo-electron tomography of eel sperm flagella reveals a molecular "minimum system" for motile cilia

Cilia and flagella play a crucial role in the development and function of eukaryotes. The activity of thousands of dyneins is precisely regulated to generate flagellar motility. The complex proteome (600+ proteins) and architecture of the structural core of flagella, the axoneme, have made it challenging to dissect the functions of the different complexes, like the regulatory machinery. Previous reports suggested that the flagellum of American eel sperm lacks many of the canonical axonemal complexes yet is still motile. Here, we use cryo-electron tomography for molecular characterization of this proposed "minimal" motile flagellum. We observed different diameters for the eel sperm flagellum: narrow at the base and wider toward the flagellar tip. Subtomogram averaging revealed the three-dimensional (3D) structure of the eel sperm flagellum. As expected, major complexes were missing, for example, outer dynein arms, radial spokes, and the central pair complex, but we found molecular remnants of most complexes. We also identified bend direction-specific patterns in the inter-DMT distance in actively beating eel sperm flagella and we propose a model for the regulation of dynein activity during their motility. Together, our results shed light on the structure and function of the eel sperm flagellum and provide insight into the minimum requirements for ciliary beating.

Convergence of autism proteins at the cilium

Hundreds of high-confidence autism genes have been identified, yet the relevant etiological mechanisms remain unclear. Gene ontology analyses have repeatedly identified enrichment of proteins with annotated functions in gene expression regulation and neuronal communication. However, proteins are often pleiotropic and these annotations are inherently incomplete. Our recent autism functional genetics work has suggested that these genes may share a common mechanism at the cilium, a membrane-bound organelle critical for neurogenesis, brain patterning, and neuronal activity-all processes strongly implicated in autism. Moreover, autism commonly co-occurs with conditions that are known to involve ciliary-related pathologies, including congenital heart disease, hydrocephalus, and blindness. However, the role of autism genes at the cilium has not been systematically investigated. Here we demonstrate that autism proteins spanning disparate functional annotations converge in expression, localization, and function at cilia, and that patients with pathogenic variants in these genes have cilia-related co-occurring conditions and biomarkers of disrupted ciliary function. This degree of convergence among genes spanning diverse functional annotations strongly suggests that cilia are relevant to autism, as well as to commonly co-occurring conditions, and that this organelle should be explored further for therapeutic potential.

Canopy elastic turbulence: Insights and analogies to canopy inertial turbulence

Canopy flows occur when a moving fluid encounters a matrix of free-standing obstacles and are found in diverse systems, from forests and marine ecology to urban landscapes and biology (e.g. cilia arrays). In large-scale systems, involving Newtonian fluids (like water or air), canopy flows typically exhibit inertial turbulence due to high Reynolds numbers (Re). However, in small-scale systems like cilia, where Re is low, but the fluid can be viscoelastic (like mucus), the relevant control parameter is the Weissenberg number (Wi), quantifying elastic stresses in the flow. Here, we investigate the flow of a viscoelastic polymer solution over a microscopic canopy within a microfluidic device. As the Weissenberg number increases, the flow undergoes distinct transitions, eventually becoming unstable beyond a critical Wi. At high Wi, we observe the emergence of elastic turbulence (ET), a chaotic flow regime that, despite differing underlying mechanisms, exhibits striking similarities to large-scale canopy inertial turbulence. Similar to canopy inertial turbulence, ET within the canopy can be spatially divided into distinct regions: a porous layer within the canopy, a mixing layer at the canopy tips, a transitional region just above the canopy, and a Poiseuille-like flow further up. The separation of the flow into different regions reveals a new analogy between inertial turbulence and ET, providing a fresh insight into ET flows and expanding their potential for innovative microfluidic designs and real-world applications.

Cardiac Localized Polycystin-2 in the Natriuretic Peptide Signaling Pathway and Hypertension

Key Points

Cardiac localized polycystin facilitates natriuretic peptide signaling pathways. Hypertension associated with autosomal dominant polycystic kidney disease may arise from impaired cardiac natriuretic peptide signaling.

Background

Hypertension is seen in 70% of patients with autosomal dominant polycystic kidney disease by age of 30 years before decline in kidney function. However, cardiac origins of hypertension, such as the natriuretic peptide signaling pathway, have not been fully investigated. We hypothesized that cardiomyocyte localized polycystin proteins contribute to production of natriuretic peptides, and loss of this pathway would contribute to hypertension.

Methods

Telemetry, echocardiography, and a molecular analysis of the natriuretic peptide pathway from left ventricular tissue of cardiomyocyte specific knockout models of polycystin-2 (cPC2-KO) mice and Cre control littermates were conducted. Complementary studies were conducted in ex vivo murine hearts, engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 knockout of PKD2 and in in vitro cell lines.

Results

cPC2-KO mice demonstrated diurnal hypertension. Circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide were unchanged between cPC2-KO and Cre mice. Analysis of the pathways involved in production, maturation, and activity of natriuretic peptides identified decreased transcription of chromogranin B, PCSK6, NPR1, and NFAT genes in cPC2-KOs. Human iPSC-derived cardiomyocytes with PC2-KO failed to produce ANP. Re-expression of polycystin-2 in a myoblast cell line, but not pathogenic forms of polycystin-2, restored ANP production.

Conclusions

Natriuretic peptide production required cardiac localized polycystin-2, and loss of this pathway may contribute to the development of hypertension in autosomal dominant polycystic kidney disease.

Podcast

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The molecular mechanisms of cardiac development and related diseases

Cardiac development is a complex and intricate process involving numerous molecular signals and pathways. Researchers have explored cardiac development through a long journey, starting with early studies observing morphological changes and progressing to the exploration of molecular mechanisms using various molecular biology methods. Currently, advancements in stem cell technology and sequencing technology, such as the generation of human pluripotent stem cells and cardiac organoids, multi-omics sequencing, and artificial intelligence (AI) technology, have enabled researchers to understand the molecular mechanisms of cardiac development better. Many molecular signals regulate cardiac development, including various growth and transcription factors and signaling pathways, such as WNT signaling, retinoic acid signaling, and Notch signaling pathways. In addition, cilia, the extracellular matrix, epigenetic modifications, and hypoxia conditions also play important roles in cardiac development. These factors play crucial roles at one or even multiple stages of cardiac development. Recent studies have also identified roles for autophagy, metabolic transition, and macrophages in cardiac development. Deficiencies or abnormal expression of these factors can lead to various types of cardiac development abnormalities. Nowadays, congenital heart disease (CHD) management requires lifelong care, primarily involving surgical and pharmacological treatments. Advances in surgical techniques and the development of clinical genetic testing have enabled earlier diagnosis and treatment of CHD. However, these technologies still have significant limitations. The development of new technologies, such as sequencing and AI technologies, will help us better understand the molecular mechanisms of cardiac development and promote earlier prevention and treatment of CHD in the future.

Genetic and phenotypic architecture of human myocardial trabeculation

Cardiac trabeculae form a network of muscular strands that line the inner surfaces of the heart. Their development depends on multiscale morphogenetic processes and, while highly conserved across vertebrate evolution, their role in the pathophysiology of the mature heart is not fully understood. Here we report variant associations across the allele frequency spectrum for trabecular morphology in 47,803 participants of the UK Biobank using fractal dimension analysis of cardiac imaging. We identified an association between trabeculation and rare variants in 56 genes that regulate myocardial contractility and ventricular development. Genome-wide association studies identified 68 loci in pathways that regulate sarcomeric function, differentiation of the conduction system and cell fate determination. We found that trabeculation-associated variants were modifiers of cardiomyopathy phenotypes with opposing effects in hypertrophic and dilated cardiomyopathy. Together, these data provide insights into mechanisms that regulate trabecular development and plasticity, and identify a potential role in modifying monogenic disease expression.

Ciliopathy interacts with neonatal anesthesia to cause non-apoptotic caspase-mediated motor deficits

Increasing evidence suggests that anesthesia may induce developmental neurotoxicity, yet the influence of genetic predispositions associated with congenital anomalies on this toxicity remains largely unknown. Children with congenital heart disease often exhibit mutations in cilia-related genes and ciliary dysfunction, requiring sedation for their catheter or surgical interventions during the neonatal period. Here we demonstrate that briefly exposing ciliopathic neonatal mice to ketamine causes motor skill impairments, which are associated with a baseline deficit in neocortical layer V neuron apical spine density and their altered dynamics during motor learning.. These neuromorphological changes were linked to augmented non-apoptotic neuronal caspase activation. Neonatal caspase suppression rescued the spine density and motor deficits, confirming the requirement for sublethal caspase signaling in appropriate spine formation and motor learning. Our findings suggest that ciliopathy interacts with ketamine to induce motor impairments, which is reversible through caspase inhibition. Furthermore, they underscore the potential for ketamine- induced sublethal caspase responses in shaping neurodevelopmental outcomes.

Rare homozygous cilia gene variants identified in consanguineous congenital heart disease patients

Congenital heart defects (CHD) appear in almost one percent of live births. Asian countries have the highest birth prevalence of CHD in the world. Recessive genotypes may represent a CHD risk factor in Asian populations with a high degree of consanguineous marriages. Genetic analysis of consanguineous families may represent a relatively unexplored source for investigating CHD etiology. To obtain insight into the contribution of recessive genotypes in CHD we analysed a cohort of forty-nine Pakistani CHD probands, originating from consanguineous unions. The majority (82%) of patient's malformations were septal defects. We identified protein altering, rare homozygous variants (RHVs) in the patient's coding genome by whole exome sequencing. The patients had a median of seven damaging RHVs each, and our analysis revealed a total of 758 RHVs in 693 different genes. By prioritizing these genes based on variant severity, loss-of-function intolerance and specific expression in the developing heart, we identified a set of 23 candidate disease genes. These candidate genes were significantly enriched for genes known to cause heart defects in recessive mouse models (P < 2.4e-06). In addition, we found a significant enrichment of cilia genes in both the initial set of 693 genes (P < 5.4e-04) and the 23 candidate disease genes (P < 5.2e-04). Functional investigation of ADCY6 in cell- and zebrafish-models verified its role in heart development. Our results confirm a significant role for cilia genes in recessive forms of CHD and suggest important functions of cilia genes in cardiac septation.

PKD2: An Important Membrane Protein in Organ Development

PKD2 was first identified as the pathogenic protein for autosomal dominant polycystic kidney disease (ADPKD) and is widely recognized as an ion channel. Subsequent studies have shown that PKD2 is widely expressed in various animal tissues and plays a crucial role in tissue and organ development. Additionally, PKD2 is conserved from single-celled organisms to vertebrates. Here, we provide an overview of recent advances in the function of PKD2 in key model animals, focusing on the establishment of left-right organ asymmetry, renal homeostasis, cardiovascular development, and signal transduction in reproduction and mating. We specifically focus on the roles of PKD2 in development and highlight future prospects for PKD2 research.

Olfactory Bulb Volume and Asymmetry as Predictors of Executive Dysfunction in Adolescents with Congenital Heart Disease

Background and Purpose

Common sequelae for patients with congenital heart disease (CHD) are neurodevelopmental disabilities including executive function, attention, and socio-emotional deficits. Although these are common diagnoses for patients with CHD, limited research has investigated the mechanistic underpinnings of these findings. Our previous research examined the association between abnormal respiratory ciliary motion and brain abnormalities in infants with CHD. Results suggested that abnormal ciliary motion correlated to a spectrum of subtle dysplasia, notably within the olfactory bulb (OB)1. Our current study investigates whether OB anomalies predict neurodevelopmental outcomes for pediatric patients with CHD. We hypothesize that adolescents with CHD who exhibit aberrant morphological measurements in the OB are more likely to suffer from executive functional deficits.

Materials and Methods

A prospective, observational study of 54 CHD and 75 healthy subjects, ages 6-25 years old, was completed under the supervision of a senior pediatric neuroradiologist. T2 3D Space and T2 Blade 2MM MRI images were manually segmented to extract volumetric bilateral regions of the OB and cerebrospinal fluid (CSF) using ITK-SNAP. Imaging metrics were correlated to OB asymmetry, CSF to OB ratio, total CSF volume, total OB volume, and independent left and right CSF and OB volumes. Linear regression was used to evaluate MRI morphologic measurements with co-variates: CHD status, sex, MRI age, and segmenter. Executive function was determined by the Behavioral Rating Inventory of Executive Function (BRIEF) Parent Report and Delis-Kaplan Executive Function System (D-KEFS) for subjects ages 6-16. Cognition and olfactory function were measured with the NIH Toolbox Cognitive Battery and Odor Identification Test, respectively.

Results

No statistically significant results were reported between cohorts for asymmetry of OB, CSF to OB ratio, total CSF volume, total OB volume, nor between independent left and right CSF and OB volumes. Increased OB volume was associated with worse outcomes on the BRIEF Parent Report (p≤0.03). Asymmetry of OB predicted poorer executive functioning as reported by parents on the BRIEF (p≤0.05). Overall, the CHD cohort demonstrated worse scores on the BRIEF Parent Report compared to controls. Across groups, no significant association was reported for olfaction function measured by the NIH Toolbox Odor Identification Test on a limited subset of participants.

Conclusion

As survival rates for CHD improve, there is an increased risk of long-term neurodevelopmental impairments. Our findings identify adolescents who are at risk for executive dysfunction, particularly those showing increased OB volume and/or asymmetry of the OB. This is particularly concerning for the CHD population with atypical OB morphology, who also exhibit significantly poorer outcomes on the BRIEF Parent Report and face a higher overall risk. Increased OB volume and OB asymmetry are olfactory-based biomarkers that may help identify at-risk CHD patients earlier, enabling more timely intervention and support.

Genome-wide association studies of Down syndrome associated congenital heart defects

Congenital heart defects (CHDs) are the most common structural birth defect and are present in 40-50% of children born with Down syndrome (DS). To characterize the genetic architecture of DS-associated CHD, we sequenced genomes of a multiethnic group of children with DS and a CHD (n=886: atrioventricular septal defects (AVSD), n=438; atrial septal defects (ASD), n=122; ventricular septal defects (VSD), n=170; other types of CHD, n=156) and DS with a structurally normal heart (DS+NH, n=572). We performed four GWAS for common variants (MAF>0.05) comparing DS with CHD, stratified by CHD-subtype, to DS+NH controls. Although no SNP achieved genome-wide significance, multiple loci in each analysis achieved suggestive significance (p<2×10-6). Of these, the 1p35.1 locus (near RBBP4) was specifically associated with ASD risk and the 5q35.2 locus (near MSX2) was associated with any type of CHD. Each of the suggestive loci contained one or more plausible candidate genes expressed in the developing heart. While no SNP replicated (p<2×10-6) in an independent cohort of DS+CHD (DS+CHD: n=229; DS+NH: n=197), most SNPs that were suggestive in our GWASs remained suggestive when meta-analyzed with the GWASs from the replication cohort. These results build on previous work to identify genetic modifiers of DS-associated CHD.

ccdc141 is required for left-right axis development by regulating cilia formation in the Kupffer's vesicle of zebrafish

Laterality is a crucial physiological process intricately linked to the cilium-centrosome complex during embryo development. Defects in the process can result in severe organ mispositioning. Coiled-coil domain containing 141 (CCDC141) has been previously known as a centrosome-related gene, but its role in left-right (LR) asymmetry has not been characterized. In this study, we utilize the zebrafish model and human exome analysis to elucidate the function of ccdc141 in laterality defects. The knockdown of ccdc141 in zebrafish disrupts early LR signaling pathways, cilia function, and Kupffer's vesicle formation. Unlike ccdc141-knockdown embryos exhibiting aberrant LR patterns, ccdc141-null mutants show no apparent abnormality, suggesting a genetic compensation response effect. In parallel, we observe a marked reduction in α-tubulin acetylation levels in the ccdc141 crispants. The treatment with histone deacetylase (HDAC) inhibitors, particularly the HDAC6 inhibitor, rescues the ccdc141 crispant phenotypes. Furthermore, exome analysis of 70 patients with laterality defects reveals an increased burden of CCDC141 mutations, with in-vivo studies verifying the pathogenicity of the patient mutation CCDC141-R123G. Our findings highlight the critical role of ccdc141 in ciliogenesis and demonstrate that CCDC141 mutations lead to abnormal LR patterns, identifying it as a candidate gene for laterality defects.

Ciliary biology intersects autism and congenital heart disease

Autism spectrum disorder (ASD) commonly co-occurs with congenital heart disease (CHD), but the molecular mechanisms underlying this comorbidity remain unknown. Given that children with CHD come to clinical attention by the newborn period, understanding which CHD variants carry ASD risk could provide an opportunity to identify and treat individuals at high risk for developing ASD far before the typical age of diagnosis. Therefore, it is critical to delineate the subset of CHD genes most likely to increase the risk of ASD. However, to date there is relatively limited overlap between high confidence ASD and CHD genes, suggesting that alternative strategies for prioritizing CHD genes are necessary. Recent studies have shown that ASD gene perturbations commonly dysregulate neural progenitor cell (NPC) biology. Thus, we hypothesized that CHD genes that disrupt neurogenesis are more likely to carry risk for ASD. Hence, we performed an in vitro pooled CRISPR interference (CRISPRi) screen to identify CHD genes that disrupt NPC biology similarly to ASD genes. Overall, we identified 45 CHD genes that strongly impact proliferation and/or survival of NPCs. Moreover, we observed that a cluster of physically interacting ASD and CHD genes are enriched for ciliary biology. Studying seven of these genes with evidence of shared risk (CEP290, CHD4, KMT2E, NSD1, OFD1, RFX3, TAOK1), we observe that perturbation significantly impacts primary cilia formation in vitro. While in vivo investigation of TAOK1 reveals a previously unappreciated role for the gene in motile cilia formation and heart development, supporting its prediction as a CHD risk gene. Together, our findings highlight a set of CHD risk genes that may carry risk for ASD and underscore the role of cilia in shared ASD and CHD biology.

Endocardial primary cilia and blood flow are required for regulation of EndoMT during endocardial cushion development

Blood flow is critical for heart valve formation, and cellular mechanosensors are essential to translate flow into transcriptional regulation of development. Here, we identify a role for primary cilia in vivo in the spatial regulation of cushion formation, the first stage of valve development, by regionally controlling endothelial to mesenchymal transition (EndoMT) via modulation of Kruppel-like Factor 4 (Klf4) . We find that high shear stress intracardiac regions decrease endocardial ciliation over cushion development, correlating with KLF4 downregulation and EndoMT progression. Mouse embryos constitutively lacking cilia exhibit a blood-flow dependent accumulation of KLF4 in these regions, independent of upstream left-right abnormalities, resulting in impaired cushion cellularization. snRNA-seq revealed that cilia KO endocardium fails to progress to late-EndoMT, retains endothelial markers and has reduced EndoMT/mesenchymal genes that KLF4 antagonizes. Together, these data identify a mechanosensory role for endocardial primary cilia in cushion development through regional regulation of KLF4.

Cardiovascular perspectives of the TRP channel polycystin 2

Calcium release from the endoplasmic reticulum (ER) is predominantly driven by two key ion channel receptors, inositol 1, 4, 5-triphosphate receptor (InsP3R) in non-excitable cells and ryanodine receptor (RyR) in excitable and muscle-based cells. These calcium transients can be modified by other less-studied ion channels, including polycystin 2 (PC2), a member of the transient receptor potential (TRP) family. PC2 is found in various cell types and is evolutionarily conserved with paralogues ranging from single-cell organisms to yeasts and mammals. Interest in the mammalian form of PC2 stems from its disease relevance, as mutations in the PKD2 gene, which encodes PC2, result in autosomal dominant polycystic kidney disease (ADPKD). This disease is characterized by renal and liver cysts, and cardiovascular extrarenal manifestations. However, in contrast to the well-defined roles of many TRP channels, the role of PC2 remains unknown, as it has different subcellular locations, and the functional understanding of the channel in each location is still unclear. Recent structural and functional studies have shed light on this channel. Moreover, studies on cardiovascular tissues have demonstrated a diverse role of PC2 in these tissues compared to that in the kidney. We highlight recent advances in understanding the role of this channel in the cardiovascular system and discuss the functional relevance of PC2 in non-renal cells.

Nontuberculous Mycobacteria, Mucociliary Clearance, and Bronchiectasis

Nontuberculous mycobacteria (NTM) are environmental and ubiquitous, but only a few species are associated with disease, often presented as nodular/bronchiectatic or cavitary pulmonary forms. Bronchiectasis, airways dilatations characterized by chronic productive cough, is the main presentation of NTM pulmonary disease. The current Cole's vicious circle model for bronchiectasis proposes that it progresses from a damaging insult, such as pneumonia, that affects the respiratory epithelium and compromises mucociliary clearance mechanisms, allowing microorganisms to colonize the airways. An important bronchiectasis risk factor is primary ciliary dyskinesia, but other ciliopathies, such as those associated with connective tissue diseases, also seem to facilitate bronchiectasis, as may occur in Lady Windermere syndrome, caused by M. avium infection. Inhaled NTM may become part of the lung microbiome. If the dose is too large, they may grow excessively as a biofilm and lead to disease. The incidence of NTM pulmonary disease has increased in the last two decades, which may have influenced the parallel increase in bronchiectasis incidence. We propose that ciliary dyskinesia is the main promoter of bronchiectasis, and that the bacteria most frequently involved are NTM. Restoration of ciliary function and impairment of mycobacterial biofilm formation may provide effective therapeutic alternatives to antibiotics.

Genetic effects of sequence-conserved enhancer-like elements on human complex traits

BACKGROUND

The vast majority of findings from human genome-wide association studies (GWAS) map to non-coding sequences, complicating their mechanistic interpretations and clinical translations. Non-coding sequences that are evolutionarily conserved and biochemically active could offer clues to the mechanisms underpinning GWAS discoveries. However, genetic effects of such sequences have not been systematically examined across a wide range of human tissues and traits, hampering progress to fully understand regulatory causes of human complex traits.

RESULTS

Here we develop a simple yet effective strategy to identify functional elements exhibiting high levels of human-mouse sequence conservation and enhancer-like biochemical activity, which scales well to 313 epigenomic datasets across 106 human tissues and cell types. Combined with 468 GWAS of European (EUR) and East Asian (EAS) ancestries, these elements show tissue-specific enrichments of heritability and causal variants for many traits, which are significantly stronger than enrichments based on enhancers without sequence conservation. These elements also help prioritize candidate genes that are functionally relevant to body mass index (BMI) and schizophrenia but were not reported in previous GWAS with large sample sizes.

CONCLUSIONS

Our findings provide a comprehensive assessment of how sequence-conserved enhancer-like elements affect complex traits in diverse tissues and demonstrate a generalizable strategy of integrating evolutionary and biochemical data to elucidate human disease genetics.

Cardiac Localized Polycystin-2 plays a Functional Role in Natriuretic Peptide Production and its Absence Contributes to Hypertension

Cardiovascular complications are the most common cause of mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Hypertension is seen in 70% of patients by the age of 30 prior to decline in kidney function. The natriuretic peptides (NPs), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are released by cardiomyocytes in response to membrane stretch, increasing urinary excretion of sodium and water. Mice heterozygous for Pkd2 have attenuated NP responses and we hypothesized that cardiomyocyte-localized polycystin proteins contribute to production of NPs. Cardiomyocyte-specific knock-out models of polycystin-2 (PC2), one of the causative genes of ADPKD, demonstrate diurnal hypertension. These mice have decreased ANP and BNP expression in the left ventricle. Analysis of the pathways involved in production, maturation, and activity of NPs identified decreased transcription of CgB, PCSK6, and NFAT genes in cPC2-KOs. Engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 KO of PKD2 failed to produce ANP. These results suggest that PC2 in cardiomyocytes are involved in NP production and lack of cardiac PC2 predisposes to a hypertensive volume expanded phenotype, which may contribute to the development of hypertension in ADPKD.

Functions of cilia in cardiac development and disease

Errors in embryonic cardiac development are a leading cause of congenital heart defects (CHDs), including morphological abnormalities of the heart that are often detected after birth. In the past few decades, an emerging role for cilia in the pathogenesis of CHD has been identified, but this topic still largely remains an unexplored area. Mouse forward genetic screens and whole exome sequencing analysis of CHD patients have identified enrichment for de novo mutations in ciliary genes or non-ciliary genes, which regulate cilia-related pathways, linking cilia function to aberrant cardiac development. Key events in cardiac morphogenesis, including left-right asymmetric development of the heart, are dependent upon cilia function. Cilia dysfunction during left-right axis formation contributes to CHD as evidenced by the substantial proportion of heterotaxy patients displaying complex CHD. Cilia-transduced signaling also regulates later events during heart development such as cardiac valve formation, outflow tract septation, ventricle development, and atrioventricular septa formation. In this review, we summarize the role of motile and non-motile (primary cilia) in cardiac asymmetry establishment and later events during heart development.

Valvular heart disease and cardiomyopathy: reappraisal of their interplay

Cardiomyopathies and valvular heart diseases are typically considered distinct diagnostic categories with dedicated guidelines for their management. However, the interplay between these conditions is increasingly being recognized and they frequently coexist, as in the paradigmatic examples of dilated cardiomyopathy and hypertrophic cardiomyopathy, which are often complicated by the occurrence of mitral regurgitation. Moreover, cardiomyopathies and valvular heart diseases can have a shared aetiology because several genetic or acquired diseases can affect both the cardiac valves and the myocardium. In addition, the association between cardiomyopathies and valvular heart diseases has important prognostic and therapeutic implications. Therefore, a better understanding of their shared pathophysiological mechanisms, as well as of the prevalence and predisposing factors to their association, might lead to a different approach in the risk stratification and management of these diseases. In this Review, we discuss the different scenarios in which valvular heart diseases and cardiomyopathies coexist, highlighting the need for an improved classification and clustering of these diseases with potential repercussions in the clinical management and, particularly, personalized therapeutic approaches.

ALS-linked C9orf72-SMCR8 complex is a negative regulator of primary ciliogenesis

Massive GGGGCC (G4C2) repeat expansion in C9orf72 and the resulting loss of C9orf72 function are the key features of ~50% of inherited amyotrophic lateral sclerosis and frontotemporal dementia cases. However, the biological function of C9orf72 remains unclear. We previously found that C9orf72 can form a stable GTPase activating protein (GAP) complex with SMCR8 (Smith-Magenis chromosome region 8). Herein, we report that the C9orf72-SMCR8 complex is a major negative regulator of primary ciliogenesis, abnormalities in which lead to ciliopathies. Mechanistically, the C9orf72-SMCR8 complex suppresses the primary cilium as a RAB8A GAP. Moreover, based on biochemical analysis, we found that C9orf72 is the RAB8A binding subunit and that SMCR8 is the GAP subunit in the complex. We further found that the C9orf72-SMCR8 complex suppressed the primary cilium in multiple tissues from mice, including but not limited to the brain, kidney, and spleen. Importantly, cells with C9orf72 or SMCR8 knocked out were more sensitive to hedgehog signaling. These results reveal the unexpected impact of C9orf72 on primary ciliogenesis and elucidate the pathogenesis of diseases caused by the loss of C9orf72 function.

The role of cilia during organogenesis in zebrafish

Cilia are hair-like organelles that protrude from the surface of eukaryotic cells and are present on the surface of nearly all human cells. Cilia play a crucial role in signal transduction, organ development and tissue homeostasis. Abnormalities in the structure and function of cilia can lead to a group of human diseases known as ciliopathies. Currently, zebrafish serves as an ideal model for studying ciliary function and ciliopathies due to its relatively conserved structure and function of cilia compared to humans. In this review, we will summarize the different types of cilia that present in embryonic and adult zebrafish, and provide an overview of the advantages of using zebrafish as a vertebrate model for cilia research. We will specifically focus on the roles of cilia during zebrafish organogenesis based on recent studies. Additionally, we will highlight future prospects for ciliary research in zebrafish.

Cardiovascular Manifestations and Management in ADPKD

Cardiovascular disease (CVD) is the major cause of mortality in autosomal dominant polycystic kidney disease (ADPKD) and contributes to significant burden of disease. The manifestations are varied, including left ventricular hypertrophy (LVH), intracranial aneurysms (ICAs), valvular heart disease, and cardiomyopathies; however, the most common presentation and a major modifiable risk factor is hypertension. The aim of this review is to detail the complex pathogenesis of hypertension and other extrarenal cardiac and vascular conditions in ADPKD drawing on preclinical, clinical, and epidemiological evidence. The main drivers of disease are the renin-angiotensin-aldosterone system (RAAS) and polycystin-related endothelial cell dysfunction, with the sympathetic nervous system (SNS), nitric oxide (NO), endothelin-1 (ET-1), and asymmetric dimethylarginine (ADMA) likely playing key roles in different disease stages. The reported rates of some manifestations, such as LVH, have decreased likely due to the use of antihypertensive therapies; and others, such as ischemic cardiomyopathy, have been reported with increased prevalence likely due to longer survival and higher rates of chronic disease. ADPKD-specific screening and management guidelines exist for hypertension, LVH, and ICAs; and these are described in this review.

Which side are they on? Diagnosing primary ciliary dyskinesias in low- or middle-income countries: A review and case series

Background

Primary ciliary dyskinesia (PCD) is a rare genetic condition with a variable clinical presentation, making its diagnosis a challenge. We describe two unrelated sibling pairs with PCD: adult siblings in the first and perinatal/neonatal in the second. Both families highlight the more common and rarer clinical manifestations of PCD. We use these cases to highlight: (i) current understanding of the underlying genetic and pathophysiological mechanisms of PCD; (ii) the diversity of cardiac and respiratory features of PCD across a wide age range; (iii) aspects of the history and clinical examination that should raise suspicion of PCD; and (iv) the role of next-generation sequencing gene panel testing in confirmation of the diagnosis. We note genomic evidence predicting that PCD is relatively common in black African populations.

Study synopsis

What the study adds. This review of two sibling pairs illustrates the variable histories, presentations, diagnostic processes and clinical courses of primary ciliary dyskinesia (PCD) in low- or middle-income countries (LMICs), highlighting the diagnostic challenges faced when encountering such patients in settings where there may not be access to specialised resources. Possible diagnostic tools that can be used are discussed, weighing up their pros and cons in an LMIC setting, and a potential diagnostic approach that can be adapted to the treating clinician's own context is provided.Implications of the findings. Confirmation of the diagnosis of primary ciliary dyskinesia is no longer limited to well-resourced institutions, but can be done in less specialised environments using novel, highly accurate next-generation sequencing gene panel testing, reducing the need to transport patients as well as the overall cost to the healthcare system. Well-resourced institutions that see high volumes of patients with PCD can invest in new highly sensitive diagnostic tools such as high-speed video microscopy. There is a need for research investigating the validity of tools such as ciliary immunofluorescence in the South African population.

Integrated analysis of copy number variation-associated lncRNAs identifies candidates contributing to the etiologies of congenital kidney anomalies

Congenital anomalies of the kidney and urinary tract (CAKUT) are disorders resulting from defects in the development of the kidneys and their outflow tract. Copy number variations (CNVs) have been identified as important genetic variations leading to CAKUT, whereas most CAKUT-associated CNVs cannot be attributed to a specific pathogenic gene. Here we construct coexpression networks involving long noncoding RNAs (lncRNAs) within these CNVs (CNV-lncRNAs) using human kidney developmental transcriptomic data. The results show that CNV-lncRNAs encompassed in recurrent CAKUT associated CNVs have highly correlated expression with CAKUT genes in the developing kidneys. The regulatory effects of two hub CNV-lncRNAs (HSALNG0134318 in 22q11.2 and HSALNG0115943 in 17q12) in the module most significantly enriched in known CAKUT genes (CAKUT_sig1, P = 1.150 × 10^-6) are validated experimentally. Our results indicate that the reduction of CNV-lncRNAs can downregulate CAKUT genes as predicted by our computational analyses. Furthermore, knockdown of HSALNG0134318 would downregulate HSALNG0115943 and affect kidney development related pathways. The results also indicate that the CAKUT_sig1 module has function significance involving multi-organ development. Overall, our findings suggest that CNV-lncRNAs play roles in regulating CAKUT genes, and the etiologies of CAKUT-associated CNVs should take account of effects on the noncoding genome.

Primary cilia as dynamic and diverse signalling hubs in development and disease

Primary cilia, antenna-like sensory organelles protruding from the surface of most vertebrate cell types, are essential for regulating signalling pathways during development and adult homeostasis. Mutations in genes affecting cilia cause an overlapping spectrum of >30 human diseases and syndromes, the ciliopathies. Given the immense structural and functional diversity of the mammalian cilia repertoire, there is a growing disconnect between patient genotype and associated phenotypes, with variable severity and expressivity characteristic of the ciliopathies as a group. Recent technological developments are rapidly advancing our understanding of the complex mechanisms that control biogenesis and function of primary cilia across a range of cell types and are starting to tackle this diversity. Here, we examine the structural and functional diversity of primary cilia, their dynamic regulation in different cellular and developmental contexts and their disruption in disease.

Insights into the genetic architecture of congenital heart disease from animal modeling

Congenital heart disease (CHD) is observed in up to 1% of live births and is one of the leading causes of mortality from birth defects. While hundreds of genes have been implicated in the genetic etiology of CHD, their role in CHD pathogenesis is still poorly understood. This is largely a reflection of the sporadic nature of CHD, as well as its variable expressivity and incomplete penetrance. We reviewed the monogenic causes and evidence for oligogenic etiology of CHD, as well as the role of de novo mutations, common variants, and genetic modifiers. For further mechanistic insight, we leveraged single-cell data across species to investigate the cellular expression characteristics of genes implicated in CHD in developing human and mouse embryonic hearts. Understanding the genetic etiology of CHD may enable the application of precision medicine and prenatal diagnosis, thereby facilitating early intervention to improve outcomes for patients with CHD.

Post-myocardial infarction fibrosis: Pathophysiology, examination, and intervention

Cardiac fibrosis plays an indispensable role in cardiac tissue homeostasis and repair after myocardial infarction (MI). The cardiac fibroblast-to-myofibroblast differentiation and extracellular matrix collagen deposition are the hallmarks of cardiac fibrosis, which are modulated by multiple signaling pathways and various types of cells in time-dependent manners. Our understanding of the development of cardiac fibrosis after MI has evolved in basic and clinical researches, and the regulation of fibrotic remodeling may facilitate novel diagnostic and therapeutic strategies, and finally improve outcomes. Here, we aim to elaborate pathophysiology, examination and intervention of cardiac fibrosis after MI.

Evaluating High-Confidence Genes in Conotruncal Cardiac Defects by Gene Burden Analyses

Background In nonsyndromic conotruncal cardiac defects, the use of next-generation sequencing for clinical diagnosis is increasingly adopted, but gene-disease associations in research are only partially translated to diagnostic panels, suggesting a need for evidence-based consensus. Methods and Results In an exome data set of 245 patients with conotruncal cardiac defects, we performed burden analysis on a high-confidence congenital heart disease gene list (n=132) with rare (<0.01%) and ultrarare (absent in the Genome Aggregation Database) protein-altering variants. Overall, we confirmed an excess of rare variants compared with ethnicity-matched controls and identified 2 known genes (GATA6, NOTCH1) and 4 candidate genes supported by the literature (ANKRD11, DOCK6, NPHP4, and STRA6). Ultrarare variant analysis was performed in combination with 3 other published studies (n=1451) and identified 3 genes (FLT4, NOTCH1, TBX1) to be significant, whereas a subgroup analysis involving 391 Chinese subjects identified only GATA6 as significant. Conclusions We suggest that these significant genes in our rare and ultrarare burden analyses warrant prioritization for clinical testing implied for rare inherited and de novo variants. Additionally, associations on ClinVar for these genes were predominantly variants of uncertain significance. Therefore, a more stringent assessment of gene-disease associations in a larger and ethnically diverse cohort is required to be prudent for future curation of conotruncal cardiac defect genes.

Cilia function as calcium-mediated mechanosensors that instruct left-right asymmetry

The breaking of bilateral symmetry in most vertebrates is critically dependent upon the motile cilia of the embryonic left-right organizer (LRO), which generate a directional fluid flow; however, it remains unclear how this flow is sensed. Here, we demonstrated that immotile LRO cilia are mechanosensors for shear force using a methodological pipeline that combines optical tweezers, light sheet microscopy, and deep learning to permit in vivo analyses in zebrafish. Mechanical manipulation of immotile LRO cilia activated intraciliary calcium transients that required the cation channel Polycystin-2. Furthermore, mechanical force applied to LRO cilia was sufficient to rescue and reverse cardiac situs in zebrafish that lack motile cilia. Thus, LRO cilia are mechanosensitive cellular levers that convert biomechanical forces into calcium signals to instruct left-right asymmetry.

Genetics and pathophysiology of mitral valve prolapse

Mitral valve prolapse (MVP) is a common condition affecting 2-3% of the general population, and the most complex form of valve pathology, with a complication rate up to 10-15% per year in advanced stages. Complications include mitral regurgitation which can lead to heart failure and atrial fibrillation, but also life-threatening ventricular arrhythmia and cardiovascular death. Sudden death has been recently brought to the forefront of MVP disease, increasing the complexity of management and suggesting that MVP condition is not properly understood. MVP can occur as part of syndromic conditions such as Marfan syndrome, but the most common form is non-syndromic, isolated or familial. Although a specific X-linked form of MVP was initially identified, autosomal dominant inheritance appears to be the primary mode of transmission. MVP can be stratified into myxomatous degeneration (Barlow), fibroelastic deficiency, and Filamin A-related MVP. While FED is still considered a degenerative disease associated with aging, myxomatous MVP and FlnA-MVP are recognized as familial pathologies. Deciphering genetic defects associated to MVP is still a work in progress; although FLNA, DCHS1, and DZIP1 have been identified as causative genes in myxomatous forms of MVP thanks to familial approaches, they explain only a small proportion of MVP. In addition, genome-wide association studies have revealed the important role of common variants in the development of MVP, in agreement with the high prevalence of this condition in the population. Furthermore, a potential genetic link between MVP and ventricular arrhythmia or a specific type of cardiomyopathy is considered. Animal models that allow to advance in the genetic and pathophysiological knowledge of MVP, and in particular those that can be easily manipulated to express a genetic defect identified in humans are detailed. Corroborated by genetic data and animal models, the main pathophysiological pathways of MVP are briefly addressed. Finally, genetic counseling is considered in the context of MVP.

Biallelic mutations of TTC12 and TTC21B were identified in Chinese patients with multisystem ciliopathy syndromes

Background

Abnormalities in cilia ultrastructure and function lead to a range of human phenotypes termed ciliopathies. Many tetratricopeptide repeat domain (TTC) family members have been reported to play critical roles in cilium organization and function.

Results

Here, we describe five unrelated family trios with multisystem ciliopathy syndromes, including situs abnormality, complex congenital heart disease, nephronophthisis or neonatal cholestasis. Through whole-exome sequencing and Sanger sequencing confirmation, we identified compound heterozygous mutations of TTC12 and TTC21B in six affected individuals of Chinese origin. These nonsynonymous mutations affected highly conserved residues and were consistently predicted to be pathogenic. Furthermore, ex vivo cDNA amplification demonstrated that homozygous c.1464 + 2 T > C of TTC12 would cause a whole exon 16 skipping. Both mRNA and protein levels of TTC12 were significantly downregulated in the cells derived from the patient carrying TTC12 mutation c.1464 + 2 T > C by real-time qPCR and immunofluorescence assays when compared with two healthy controls. Transmission electron microscopy analysis further identified ultrastructural defects of the inner dynein arms in this patient. Finally, the effect of TTC12 deficiency on cardiac LR patterning was recapitulated by employing a morpholino-mediated knockdown of ttc12 in zebrafish.

Conclusions

To the best of our knowledge, this is the first study reporting the association between TTC12 variants and ciliopathies in a Chinese population. In addition to nephronophthisis and laterality defects, our findings demonstrated that TTC21B should also be considered a candidate gene for biliary ciliopathy, such as TTC26, which further expands the phenotypic spectrum of TTC21B deficiency in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40246-022-00421-z.

Hedgehog Morphogens Act as Growth Factors Critical to Pre- and Postnatal Cardiac Development and Maturation: How Primary Cilia Mediate Their Signal Transduction

Primary cilia are crucial for normal cardiac organogenesis via the formation of cyto-architectural, anatomical, and physiological boundaries in the developing heart and outflow tract. These tiny, plasma membrane-bound organelles function in a sensory-integrative capacity, interpreting both the intra- and extra-cellular environments and directing changes in gene expression responses to promote, prevent, and modify cellular proliferation and differentiation. One distinct feature of this organelle is its involvement in the propagation of a variety of signaling cascades, most notably, the Hedgehog cascade. Three ligands, Sonic, Indian, and Desert hedgehog, function as growth factors that are most commonly dependent on the presence of intact primary cilia, where the Hedgehog receptors Patched-1 and Smoothened localize directly within or at the base of the ciliary axoneme. Hedgehog signaling functions to mediate many cell behaviors that are critical for normal embryonic tissue/organ development. However, inappropriate activation and/or upregulation of Hedgehog signaling in postnatal and adult tissue is known to initiate oncogenesis, as well as the pathogenesis of other diseases. The focus of this review is to provide an overview describing the role of Hedgehog signaling and its dependence upon the primary cilium in the cell types that are most essential for mammalian heart development. We outline the breadth of developmental defects and the consequential pathologies resulting from inappropriate changes to Hedgehog signaling, as it pertains to congenital heart disease and general cardiac pathophysiology.

Tubulin Post-translational Modifications: Potential Therapeutic Approaches to Heart Failure

In recent decades, advancing insights into the mechanisms of cardiac dysfunction have focused on the involvement of microtubule network. A variety of tubulin post-translational modifications have been discovered to fine-tune the microtubules’ properties and functions. Given the limits of therapies based on conserved structures of the skeleton, targeting tubulin modifications appears to be a potentially promising therapeutic strategy. Here we review the current understanding of tubulin post-translational modifications in regulating microtubule functions in the cardiac system. We also discussed how altered modifications may lead to a range of cardiac dysfunctions, many of which are linked to heart failure.