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Background: During cardiomyocyte maturation, the centrosome, which functions as a microtubule organizing center in cardiomyocytes, undergoes dramatic structural reorganization where its components reorganize from being localized at the centriole to the nuclear envelope. This developmentally programmed process, referred to as centrosome reduction, has been previously associated with cell cycle exit. However, understanding of how this process influences cardiomyocyte cell biology, and whether its disruption results in human cardiac disease, remains unknown. We studied this phenomenon in an infant with a rare case of infantile dilated cardiomyopathy (iDCM) who presented with left ventricular ejection fraction of 18% and disrupted sarcomere and mitochondria structure. Methods: We performed an analysis beginning with an infant who presented with a rare case of iDCM. We derived induced pluripotent stem cells from the patient to model iDCM in vitro. We performed whole exome sequencing on the patient and his parents for causal gene analysis. CRISPR/Cas9-mediated gene knockout and correction in vitro were used to confirm whole exome sequencing results. Zebrafish and Drosophila models were used for in vivo validation of the causal gene. Matrigel mattress technology and single-cell RNA sequencing were used to characterize iDCM cardiomyocytes further. Results: Whole exome sequencing and CRISPR/Cas9 gene knockout/correction identified RTTN , the gene encoding the centrosomal protein RTTN (rotatin), as the causal gene underlying the patient’s condition, representing the first time a centrosome defect has been implicated in a nonsyndromic dilated cardiomyopathy. Genetic knockdowns in zebrafish and Drosophila confirmed an evolutionarily conserved requirement of RTTN for cardiac structure and function. Single-cell RNA sequencing of iDCM cardiomyocytes showed impaired maturation of iDCM cardiomyocytes, which underlie the observed cardiomyocyte structural and functional deficits. We also observed persistent localization of the centrosome at the centriole, contrasting with expected programmed perinuclear reorganization, which led to subsequent global microtubule network defects. In addition, we identified a small molecule that restored centrosome reorganization and improved the structure and contractility of iDCM cardiomyocytes. Conclusions: This study is the first to demonstrate a case of human disease caused by a defect in centrosome reduction. We also uncovered a novel role for RTTN in perinatal cardiac development and identified a potential therapeutic strategy for centrosome-related iDCM. Future study aimed at identifying variants in centrosome components may uncover additional contributors to human cardiac disease.

Congenital heart disease (CHD) is the most common birth defect, and the leading cause of death due to birth defects, yet causative molecular mechanisms remain mostly unknown. We previously implicated a novel CHD candidate gene, SHROOM3, in a patient with CHD. Using a Shroom3 gene trap knockout mouse (Shroom3(gt/gt)) we demonstrate that SHROOM3 is downstream of the noncanonical Wnt planar cell polarity signaling pathway (PCP) and loss-of-function causes cardiac defects. We demonstrate Shroom3 expression within cardiomyocytes of the ventricles and interventricular septum from E10.5 onward, as well as within cardiac neural crest cells and second heart field cells that populate the cardiac outflow tract. We demonstrate that Shroom3(gt/gt) mice exhibit variable penetrance of a spectrum of CHDs that include ventricular septal defects, double outlet right ventricle, and thin left ventricular myocardium. This CHD spectrum phenocopies what is observed with disrupted PCP. We show that during cardiac development SHROOM3 interacts physically and genetically with, and is downstream of, key PCP signaling component Dishevelled 2. Within Shroom3(gt/gt) hearts we demonstrate disrupted terminal PCP components, actomyosin cytoskeleton, cardiomyocyte polarity, organization, proliferation and morphology. Together, these data demonstrate SHROOM3 functions during cardiac development as an actomyosin cytoskeleton effector downstream of PCP signaling, revealing SHROOM3’s novel role in cardiac development and CHD.

DA closure is crucial for the transition from fetal to neonatal life. This closure is supported by changes to the DA's signaling and structural properties that distinguish it from neighboring vessels. Examining transcriptional differences between these vessels is key to identifying genes or pathways responsible for DA closure. Several microarray studies have explored the DA transcriptome in animal models but varied experimental designs have led to conflicting results. Thorough transcriptomic analysis of the human DA has yet to be performed. A clear picture of the DA transcriptome is key to guiding future research endeavors, both to allow more targeted treatments in the clinical setting, and to understand the basic biology of DA function. In this review, we use a cross-species cross-platform analysis to consider all available published rodent microarray data and novel human RNAseq data in order to provide high priority candidate genes for consideration in future DA studies.

The study of disease pathophysiology has long relied on model systems, including animal models and cultured cells. In 2006, Shinya Yamanaka achieved a breakthrough by reprogramming somatic cells into induced pluripotent stem cells (iPSCs). This revolutionary discovery provided new opportunities for disease modeling and therapeutic intervention. With established protocols, investigators can generate iPSC lines from patient blood, urine, and tissue samples. These iPSCs retain ability to differentiate into every human cell type. Advances in differentiation and organogenesis move cellular in vitro modeling to a multicellular model capable of recapitulating physiology and disease. Here, we discuss limitations of traditional animal and tissue culture models, as well as the application of iPSC models. We highlight various techniques, including reprogramming strategies, directed differentiation, tissue engineering, organoid developments, and genome editing. We extensively summarize current established iPSC disease models that utilize these techniques. Confluence of these technologies will advance our understanding of pediatric diseases and help usher in new personalized therapies for patients.

Congenital heart disease (CHD) is the most common cause of death due to birth defects. Despite CHD frequency, the etiology remains mostly unknown. Understanding CHD genetics and elucidating disease mechanism will help establish prognosis, identify comorbidity risks, and develop targeted therapies. CHD often results from disrupted cytoarchitecture and signaling pathways. We have identified a novel CHD candidate SHROOM3, a protein associated with the actin cytoskeleton and the Wnt/Planar Cell Polarity (PCP) signaling pathway. SHROOM3 induces actomyosin constriction within the apical side of cells and is implicated in neural tube defects and chronic renal failure in humans. A recent study demonstrated that SHROOM3 interacts with Dishevelled2 (DVL2), a component of the PCP signaling pathway, suggesting that SHROOM3 serves as an important link between acto-myosin constriction and PCP signaling. PCP signaling establishes cell polarity required for multiple developmental processes, and is required for cardiac development. In Preliminary data we utilized a Shroom3 gene-trap mouse (Shroom3gt/gt) to demonstrated that SHROOM3 disruption leads to cardiac defects phenocopy PCP disruption. We also demonstrate that patients with CHD phenotypes have rare and potentially damaging SHROOM3 variants within SHROOM3’s PCP-binding domain. We hypothesize SHROOM3 is a novel terminal effector of PCP signaling, and disruption is a novel contributor to CHD. To test this, we assessed genetic interaction between SHROOM3 and PCP during cardiac development and the ultimate effect on cell structure and movement. Heterozygous Shroom3+/gt mice and heterozygous Dvl2 +/- mice are phenotypically normal. We demonstrated genetic interaction between SHROOM3 and PCP signaling by generating compound heterozygous Shroom3+/gt ;Dvl2 +/- mice and identifying a Double Outlet Right Ventricle and Ventricular Septal Defect in one embryo. We also observed fewer compound heterozygous mice than anticipated by Mendelian rations (observed: 18.4%; expected: 25%; n=76), suggesting potential lethality in utero. Immunohistochemistry demonstrates disrupted actomyosin in the SHROOM3gt/gt mice, characteristic of PCP disruption. These data help strengthen SHROOM3 as a novel CHD candidate gene and a component of the PCP Signaling pathway. Further characterization of this gene is important for CHD diagnosis and therapeutic development.

Background and Hypothesis: Congenital heart disease(CHD) is the most common birth defect, but most genetic contributors remain unknown. We recently identified CHD patients with variants in a gene called SHROOM3. The SHROOM3 protein impacts the actin cytoskeleton by binding ActinF and Rho-kinase, causing actomyosin constriction. SHROOM3 also binds Dishevelled2(Dvl2), a component of Wnt/Planar cell polarity(PCP) signaling pathway, suggesting a connection between PCP signaling and actin-myosin contraction. We hypothesize SHROOM3 disruption alters PCP signaling and actin cytoskeleton during cardiac development, and is a novel contributor to CHD. Project Methods: We analyzed the cardiac phenotype of Shroom3 gene trap knockout mice at embryonic day 14.5. We characterized the expression of Shroom3 during cardiac development using LacZ staining at important stages of cardiac development. Using IHC, we measured actomyosin disruption in Shroom3 knockout embryos. We preformed in silico analysis on previously identified SHROOM3 variants from patients with CHD. Results: Shroom3 null mice had Ventricular Septal Defects (0.73, p=0.0006), Double Outlet Right Ventricle (0.33, p=0.04), Left Ventricular Noncompaction, and other CHD. Shroom3 mutant mice left ventricular wall thickness was 36% thinner compared to wild type mice (99.0±8.6µm, 63.0±8.4µm, p=0.005). LacZ shows the expression of Shroom3 through important stages of cardiac development, and IHC shows actomyosin disruption. In silico analysis demonstrates CHD patients have SHROOM3 variants in highly conserved nucleic acid and protein sequences, and significant protein structural changes. Conclusion and Potential Impact: Shroom3 null mice have cardiac defects resembling a Wnt/PCP disruption phenotype. Similarly, patients with CHD have likely pathogenic variants in SHROOM3. These data support a role for SHROOM3 in CHD pathogenesis and begin to elucidate mechanisms. Identifying SHROOM3’s role in CHD is critical to understanding cardiac development as well as the diagnosis, management and treatment of CHD.

PURPOSE OF REVIEW: The goal of this review is to highlight the potential of induced pluripotent stem cell (iPSC)-based modeling as a tool for studying human cardiovascular diseases. We present some of the current cardiovascular disease models utilizing genome editing and patient-derived iPSCs. RECENT FINDINGS: The incorporation of genome-editing and iPSC technologies provides an innovative research platform, providing novel insight into human cardiovascular disease at molecular, cellular, and functional level. In addition, genome editing in diseased iPSC lines holds potential for personalized regenerative therapies. SUMMARY: The study of human cardiovascular disease has been revolutionized by cellular reprogramming and genome editing discoveries. These exceptional technologies provide an opportunity to generate human cell cardiovascular disease models and enable therapeutic strategy development in a dish. We anticipate these technologies to improve our understanding of cardiovascular disease pathophysiology leading to optimal treatment for heart diseases in the future.

This unit describes the published Matrigel mattress method. Briefly, we describe the preparation of the mattress, replating of the human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) on the Matrigel mattress, and hiPSC-CM mattress maintenance. Adherence to this protocol will yield individual, robustly shortening hiPSC-CMs, which can be used for downstream applications. © 2017 by John Wiley & Sons, Inc.

Hypoplastic left heart syndrome (HLHS) has been associated with germline mutations in 12 candidate genes and a recurrent somatic mutation in HAND1 gene. Using targeted and whole exome sequencing (WES) of heart tissue samples from HLHS patients, we sought to estimate the prevalence of somatic and germline mutations associated with HLHS. We performed Sanger sequencing of the HAND1 gene on 14 ventricular (9 LV and 5 RV) samples obtained from HLHS patients, and WES of 4 LV, 2 aortic, and 4 matched PBMC samples, analyzing for sequence discrepancy. We also screened for mutations in the 12 candidate genes implicated in HLHS. We found no somatic mutations in our HLHS cohort. However, we detected a novel germline frameshift/stop-gain mutation in NOTCH1 in a HLHS patient with a family history of both HLHS and hypoplastic right heart syndrome (HRHS). Our study, involving one of the first familial cases of single ventricle defects linked to a specific mutation, strengthens the association of NOTCH1 mutations with HLHS and suggests that the two morphologically distinct single ventricle conditions, HLHS and HRHS, may share a common molecular and cellular etiology. Finally, somatic mutations in the LV are an unlikely contributor to HLHS.

Background: Although the role of microbes in disease pathogenesis is well established, data describing the variability of the vast microbiome in children diagnosed with ulcerative colitis (UC) are lacking. This study characterizes the gut microbiome in hospitalized children with severe UC and determines the relationship between microbiota and response to steroid therapy. Methods: Fecal samples were collected from 26 healthy controls and 27 children hospitalized with severe UC as part of a prospective multicenter study. DNA extraction, polymerase chain reaction (PCR) amplification of bacterial 16S rRNA, and microarray hybridization were performed. Results were analyzed in GeneSpring GX 11.0 comparing healthy controls with children with UC, and steroid responsive (n = 17) with nonresponsive patients (n = 10). Results: Bacterial signal strength and distribution showed differences between UC and healthy controls (adjusted P < 0.05) for Phylum, Class, Order, Family, Genus, and Phylospecies levels with reduction in Clostridia and an increase in Gamma-proteobacteria. The number of microbial phylospecies was reduced in UC (266 ± 69) vs. controls (758 ± 3, P < 0.001), as was the Shannon Diversity Index (6.1 ± 0.23 vs. 6.49 ± 0.04, respectively; P < 0.0001). Steroid nonresponders harbored fewer phylospecies than responders (142 ± 49 vs. 338 ± 62, P = 0.013). Conclusions: Richness, evenness, and biodiversity of the gut microbiome were remarkably reduced in children with UC compared with healthy controls. Children who did not respond to steroids harbored a microbiome that was even less rich than steroid responders. This study is the first to characterize the gut microbiome in a large cohort of pediatric patients with severe UC and describes changes in the gut microbiome as a potential prognostic feature. (Inflamm Bowel Dis 2012)

Mutation is a central biological process whose rates and spectra are influenced by a variety of complex and interacting forces. Although DNA repair pathways are generally known to play key roles in maintaining genetic stability, much remains to be understood about the relative roles of different pathways in preventing the accumulation of mutations and the extent of heterogeneity in pathway-specific repair efficiencies across different genomic regions. In this study we examine mutation processes in base excision repair-deficient (nth-1) and nucleotide excision repair-deficient (xpa-1) Caenorhabditis elegans mutation-accumulation (MA) lines across 24 regions of the genome and compare our observations to previous data from mismatch repair-deficient (msh-2 and msh-6) and wild-type (N2) MA lines. Drastic variation in both average and locus-specific mutation rates, ranging two orders of magnitude for the latter, was detected among the four sets of repair-deficient MA lines. Our work provides critical insights into the relative roles of three DNA repair pathways in preventing C. elegans mutation accumulation and provides evidence for the presence of pathway-specific DNA repair territories in the C. elegans genome.