Casz1 is required for cardiomyocyte G1-to-S phase progression during mammalian cardiac development

CASZ1 upregulates PI3K-AKT-mTOR signaling and promotes T-cell acute lymphoblastic leukemia

CASZ1 is a conserved transcription factor involved in neural development, blood vessel assembly and heart morphogenesis. CASZ1 has been implicated in cancer, either suppressing or promoting tumor development depending on the tissue. However, the impact of CASZ1 on hematological tumors remains unknown. Here, we show that the T-cell oncogenic transcription factor TAL1 is a direct positive regulator of CASZ1, that T-cell acute lymphoblastic leukemia (T-ALL) samples at diagnosis overexpress CASZ1b isoform, and that CASZ1b expression in patient samples correlates with PI3K-AKT-mTOR signaling pathway activation. In agreement, overexpression of CASZ1b in both Ba/F3 and T-ALL cells leads to the activation of PI3K signaling pathway, which is required for CASZ1b-mediated transformation of Ba/F3 cells in vitro and malignant expansion in vivo. We further demonstrate that CASZ1b cooperates with activated NOTCH1 to promote T-ALL development in zebrafish, and that CASZ1b protects human T-ALL cells from serum deprivation and treatment with chemotherapeutic drugs. Taken together, our studies indicate that CASZ1b is a TAL1-regulated gene that promotes T-ALL development and resistance to chemotherapy.

Role of the CASZ1 transcription factor in tissue development and disease

The zinc finger transcription factor gene, CASZ1/Castor (Castor zinc finger 1), initially identified in Drosophila, plays a critical role in neural, cardiac, and cardiovascular development, exerting a complex, multifaceted influence on cell fate and tissue morphogenesis. During neurogenesis, CASZ1 exhibits dynamic expression from early embryonic development to the perinatal period, constituting a key regulator in this process. Additionally, CASZ1 controls the transition between neurogenesis and gliomagenesis. During human cardiovascular system development, CASZ1 is essential for cardiomyocyte differentiation, cardiac morphogenesis, and vascular morphology homeostasis and formation. The deletion or inactivation of CASZ1 mutations can lead to human developmental diseases or tumors, including congenital heart disease, cardiovascular disease, and neuroblastoma. CASZ1 can be used as a biomarker for disease prevention and diagnosis as well as a prognostic indicator for cancer. This review explores the unique functions of CASZ1 in tissue morphogenesis and associated diseases, offering new insights for elucidating the molecular mechanisms underlying diseases and identifying potential therapeutic targets for disease prevention and treatment.

The Tbx20-TLE interaction is essential for the maintenance of the second heart field

T-box transcription factor 20 (Tbx20) plays a multifaceted role in cardiac morphogenesis and controls a broad gene regulatory network. However, the mechanism by which Tbx20 activates and represses target genes in a tissue-specific and temporal manner remains unclear. Studies show that Tbx20 directly interacts with the Transducin-like Enhancer of Split (TLE) family of proteins to mediate transcriptional repression. However, a function for the Tbx20-TLE transcriptional repression complex during heart development has yet to be established. We created a mouse model with a two amino acid substitution in the Tbx20 EH1 domain, thereby disrupting the Tbx20-TLE interaction. Disruption of this interaction impaired crucial morphogenic events, including cardiac looping and chamber formation. Transcriptional profiling of Tbx20EH1Mut hearts and analysis of putative direct targets revealed misexpression of the retinoic acid pathway and cardiac progenitor genes. Further, we show that altered cardiac progenitor development and function contribute to the severe cardiac defects in our model. Our studies indicate that TLE-mediated repression is a primary mechanism by which Tbx20 controls gene expression.

Association of CASZ1 genetic variants with stroke risk in the Chinese population

BACKGROUND

Stroke is a heterogeneous disease with multiple etiologies, placing a heavy burden on the world. Our purpose was to clarify the association between CASZ1 genetic variants and stroke risk in the Chinese population.

METHODS

The Agena MassARRAY platform effectively genotyped three single nucleotide polymorphisms of CASZ1 in recruited 591 stroke patients and 553 healthy controls. Logistic regression genetic models were employed to evaluate the relationship between CASZ1 polymorphisms and stroke risk through odds ratios (ORs) and 95% confidence intervals (CIs). Then, the interaction between CASZ1 variants was detected by multifactor dimensionality reduction (MDR). Moreover, functional enrichment analyses of the CASZ1 gene were performed by Metascape.

RESULTS

In this study, CASZ1 rs4845941 and rs778228 were significantly associated with an increased risk of stroke. In particular, the gender-stratified analysis also showed that rs778228 of CASZ1 had an association with higher stroke risk in females. The relationship between stroke susceptibility and the interaction models of rs4845941, rs778228, and rs17035539 forecasted by MDR were analyzed to improve the ability to predict stroke risk. Furthermore, we found CASZ1 and related genes might facilitate the occurrence of stroke.

CONCLUSIONS

This study demonstrated that CASZ1 genetic variants (rs4845941 and rs778228) contribute to the occurrence of stroke in the Chinese population, and therefore has important implications for treating and preventing stroke.

CASZ1: Current Implications in Cardiovascular Diseases and Cancers

Castor zinc finger 1 (CASZ1) is a C2H2 zinc finger family protein that has two splicing variants, CASZ1a and CASZ1b. It is involved in multiple physiological processes, such as tissue differentiation and aldosterone antagonism. Genetic and epigenetic alternations of CASZ1 have been characterized in multiple cardiovascular disorders, such as congenital heart diseases, chronic venous diseases, and hypertension. However, little is known about how CASZ1 mechanically participates in the pathogenesis of these diseases. Over the past decades, at first glance, paradoxical influences on cell behaviors and progressions of different cancer types have been discovered for CASZ1, which may be explained by a "double-agent" role for CASZ1. In this review, we discuss the physiological function of CASZ1, and focus on the association of CASZ1 aberrations with the pathogenesis of cardiovascular diseases and cancers.

Missense Mutation in Human CHD4 Causes Ventricular Noncompaction by Repressing ADAMTS1

BACKGROUND

Left ventricular noncompaction (LVNC) is a prevalent cardiomyopathy associated with excessive trabeculation and thin compact myocardium. Patients with LVNC are vulnerable to cardiac dysfunction and at high risk of sudden death. Although sporadic and inherited mutations in cardiac genes are implicated in LVNC, understanding of the mechanisms responsible for human LVNC is limited.

METHODS

We screened the complete exome sequence database of the Pediatrics Cardiac Genomics Consortium and identified a cohort with a de novo CHD4 (chromodomain helicase DNA-binding protein 4) proband, CHD4M202I, with congenital heart defects. We engineered a humanized mouse model of CHD4M202I (mouse CHD4M195I). Histological analysis, immunohistochemistry, flow cytometry, transmission electron microscopy, and echocardiography were used to analyze cardiac anatomy and function. Ex vivo culture, immunopurification coupled with mass spectrometry, transcriptional profiling, and chromatin immunoprecipitation were performed to deduce the mechanism of CHD4M195I-mediated ventricular wall defects.

RESULTS

CHD4M195I/M195I mice developed biventricular hypertrabeculation and noncompaction and died at birth. Proliferation of cardiomyocytes was significantly increased in CHD4M195I hearts, and the excessive trabeculation was associated with accumulation of ECM (extracellular matrix) proteins and a reduction of ADAMTS1 (ADAM metallopeptidase with thrombospondin type 1 motif 1), an ECM protease. We rescued the hyperproliferation and hypertrabeculation defects in CHD4M195I hearts by administration of ADAMTS1. Mechanistically, the CHD4M195I protein showed augmented affinity to endocardial BRG1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4). This enhanced affinity resulted in the failure of derepression of Adamts1 transcription such that ADAMTS1-mediated trabeculation termination was impaired.

CONCLUSIONS

Our study reveals how a single mutation in the chromatin remodeler CHD4, in mice or humans, modulates ventricular chamber maturation and that cardiac defects associated with the missense mutation CHD4M195I can be attenuated by the administration of ADAMTS1.

Identification of a Novel de Novo Variant in the CASZ1 Causing a Rare Type of Dilated Cardiomyopathy

A new de novo frameshift variant has been identified in the CASZ1 gene leading to severe dilated cardiomyopathy. Methods: The proband was analyzed with WES NGS, post-mortem, using dried blood spots on filters. The variant was verified with Sanger sequencing for the proband and her parents. Results: We reported a proband with a new de novo frameshift mutation, c.3781del (p.(Trp1261GlyfsTer29)), in the CASZ1 gene. The clinical presentation was similar to the severe phenotype described in previous studies. Conclusions: In this study, we described a new case with a frameshift mutation in CASZ1 causing a severe phenotype of dilated cardiomyopathy.

Exome sequencing in multiplex families with left-sided cardiac defects has high yield for disease gene discovery

Congenital heart disease (CHD) is a common group of birth defects with a strong genetic contribution to their etiology, but historically the diagnostic yield from exome studies of isolated CHD has been low. Pleiotropy, variable expressivity, and the difficulty of accurately phenotyping newborns contribute to this problem. We hypothesized that performing exome sequencing on selected individuals in families with multiple members affected by left-sided CHD, then filtering variants by population frequency, in silico predictive algorithms, and phenotypic annotations from publicly available databases would increase this yield and generate a list of candidate disease-causing variants that would show a high validation rate. In eight of the nineteen families in our study (42%), we established a well-known gene/phenotype link for a candidate variant or performed confirmation of a candidate variant’s effect on protein function, including variants in genes not previously described or firmly established as disease genes in the body of CHD literature: BMP10, CASZ1, ROCK1 and SMYD1. Two plausible variants in different genes were found to segregate in the same family in two instances suggesting oligogenic inheritance. These results highlight the need for functional validation and demonstrate that in the era of next-generation sequencing, multiplex families with isolated CHD can still bring high yield to the discovery of novel disease genes.

Congenital heart disease is a common group of birth defects that are a leading cause of death in children under one year of age. There is strong evidence that genetics plays a role in causing congenital heart disease. While studies using individual cases have identified causative genes for those with a heart defect when accompanied by other birth defects or intellectual disabilities, for individuals who have only a heart defect without other problems, a genetic cause can be found in fewer than 10%. In this study, we enrolled families where there was more than one individual with a heart defect. This allowed us to take advantage of inheritance by searching for potential disease-causing genetic variants in common among all affected individuals in the family. Among 19 families studied, we were able to find a plausible disease-causing variant in eight of them and identified new genes that may cause or contribute to the presence of a heart defect. Two families had potential disease-causing variants in two different genes. We designed assays to test if the variants led to altered function of the protein coded by the gene, demonstrating a functional consequence that support the gene and variant as contributing to the heart defect. These findings show that studying families may be more effective than using individuals to find causes of heart defects. In addition, this family-based method suggests that changes in more than one gene may be required for a heart defect to occur.

CHD4 is recruited by GATA4 and NKX2-5 to repress noncardiac gene programs in the developing heart

The nucleosome remodeling and deacetylase (NuRD) complex is one of the central chromatin remodeling complexes that mediates gene repression. NuRD is essential for numerous developmental events, including heart development. Clinical and genetic studies have provided direct evidence for the role of chromodomain helicase DNA-binding protein 4 (CHD4), the catalytic component of NuRD, in congenital heart disease (CHD), including atrial and ventricular septal defects. Furthermore, it has been demonstrated that CHD4 is essential for mammalian cardiomyocyte formation and function. A key unresolved question is how CHD4/NuRD is localized to specific cardiac target genes, as neither CHD4 nor NuRD can directly bind DNA. Here, we coupled a bioinformatics-based approach with mass spectrometry analyses to demonstrate that CHD4 interacts with the core cardiac transcription factors GATA4, NKX2-5, and TBX5 during embryonic heart development. Using transcriptomics and genome-wide occupancy data, we characterized the genomic landscape of GATA4, NKX2-5, and TBX5 repression and defined the direct cardiac gene targets of the GATA4-CHD4, NKX2-5-CHD4, and TBX5-CHD4 complexes. These data were used to identify putative cis-regulatory elements controlled by these complexes. We genetically interrogated two of these silencers in vivo: Acta1 and Myh11 We show that deletion of these silencers leads to inappropriate skeletal and smooth muscle gene misexpression, respectively, in the embryonic heart. These results delineate how CHD4/NuRD is localized to specific cardiac loci and explicates how mutations in the broadly expressed CHD4 protein lead to cardiac-specific disease states.

Single-cell transcriptomic landscapes of the otic neuronal lineage at multiple early embryonic ages

Inner ear vestibular and spiral ganglion neurons (VGNs and SGNs) are known to play pivotal roles in balance control and sound detection. However, the molecular mechanisms underlying otic neurogenesis at early embryonic ages have remained unclear. Here, we use single-cell RNA sequencing to reveal the transcriptomes of mouse otic tissues at three embryonic ages, embryonic day 9.5 (E9.5), E11.5, and E13.5, covering proliferating and undifferentiated otic neuroblasts and differentiating VGNs and SGNs. We validate the high quality of our studies by using multiple assays, including genetic fate mapping analysis, and we uncover several genes upregulated in neuroblasts or differentiating VGNs and SGNs, such as Shox2, Myt1, Casz1, and Sall3. Notably, our findings suggest a general cascaded differentiation trajectory during early otic neurogenesis. The comprehensive understanding of early otic neurogenesis provided by our study holds critical implications for both basic and translational research.

Cardiac proteomics reveals sex chromosome-dependent differences between males and females that arise prior to gonad formation

Sex disparities in cardiac homeostasis and heart disease are well documented, with differences attributed to actions of sex hormones. However, studies have indicated sex chromosomes act outside of the gonads to function without mediation by gonadal hormones. Here, we performed transcriptional and proteomics profiling to define differences between male and female mouse hearts. We demonstrate, contrary to current dogma, cardiac sex disparities are controlled not only by sex hormones but also through a sex-chromosome mechanism. Using Turner syndrome (XO) and Klinefelter (XXY) models, we find the sex-chromosome pathway is established by X-linked gene dosage. We demonstrate cardiac sex disparities occur at the earliest stages of heart formation, a period before gonad formation. Using these datasets, we identify and define a role for alpha-1B-glycoprotein (A1BG), showing loss of A1BG leads to cardiac defects in females, but not males. These studies provide resources for studying sex-biased cardiac disease states.

Targeting cardiomyocyte proliferation as a key approach of promoting heart repair after injury

Cardiovascular diseases such as myocardial infarction (MI) is a major contributor to human mortality and morbidity. The mammalian adult heart almost loses its plasticity to appreciably regenerate new cardiomyocytes after injuries, such as MI and heart failure. The neonatal heart exhibits robust proliferative capacity when exposed to varying forms of myocardial damage. The ability of the neonatal heart to repair the injury and prevent pathological left ventricular remodeling leads to preserved or improved cardiac function. Therefore, promoting cardiomyocyte proliferation after injuries to reinitiate the process of cardiomyocyte regeneration, and suppress heart failure and other serious cardiovascular problems have become the primary goal of many researchers. Here, we review recent studies in this field and summarize the factors that act upon the proliferation of cardiomyocytes and cardiac repair after injury and discuss the new possibilities for potential clinical treatment strategies for cardiovascular diseases.

Epigenome-Wide Association Study for All-Cause Mortality in a Cardiovascular Cohort Identifies Differential Methylation in Castor Zinc Finger 1 (CASZ1)

Background DNA methylation is implicated in many chronic diseases and may contribute to mortality. Therefore, we conducted an epigenome-wide association study (EWAS) for all-cause mortality with whole-transcriptome data in a cardiovascular cohort (CATHGEN [Catheterization Genetics]). Methods and Results Cases were participants with mortality≥7 days postcatheterization whereas controls were alive with≥2 years of follow-up. The Illumina Human Methylation 450K and EPIC arrays (Illumina, San Diego, CA) were used for the discovery and validation sets, respectively. A linear model approach with empirical Bayes estimators adjusted for confounders was used to assess difference in methylation (Δβ). In the discovery set (55 cases, 49 controls), 25 629 (6.5%) probes were differently methylated (P<0.05). In the validation set (108 cases, 108 controls), 3 probes were differentially methylated with a false discovery rate-adjusted P<0.10: cg08215811 (SLC4A9; log2 fold change=-0.14); cg17845532 (MATK; fold change=-0.26); and cg17944110 (castor zinc finger 1 [CASZ1]; FC=0.26; P<0.0001; false discovery rate-adjusted P=0.046-0.080). Meta-analysis identified 6 probes (false discovery rate-adjusted P<0.05): the 3 above, cg20428720 (intergenic), cg17647904 (NCOR2), and cg23198793 (CAPN3). Messenger RNA expression of 2 MATK isoforms was lower in cases (fold change=-0.24 [P=0.007] and fold change=-0.61 [P=0.009]). The CASZ1, NCOR2, and CAPN3 transcripts did not show differential expression (P>0.05); the SLC4A9 transcript did not pass quality control. The cg17944110 probe is located within a potential regulatory element; expression of predicted targets (using GeneHancer) of the regulatory element, UBIAD1 (P=0.01) and CLSTN1 (P=0.03), were lower in cases. Conclusions We identified 6 novel methylation sites associated with all-cause mortality. Methylation in CASZ1 may serve as a regulatory element associated with mortality in cardiovascular patients. Larger studies are necessary to confirm these observations.

Conservation and divergence of protein pathways in the vertebrate heart

Heart disease is the leading cause of death in the western world. Attaining a mechanistic understanding of human heart development and homeostasis and the molecular basis of associated disease states relies on the use of animal models. Here, we present the cardiac proteomes of 4 model vertebrates with dual circulatory systems: the pig (Sus scrofa), the mouse (Mus musculus), and 2 frogs (Xenopus laevis and Xenopus tropicalis). Determination of which proteins and protein pathways are conserved and which have diverged within these species will aid in our ability to choose the appropriate models for determining protein function and to model human disease. We uncover mammalian- and amphibian-specific, as well as species-specific, enriched proteins and protein pathways. Among these, we find and validate an enrichment in cell-cycle–associated proteins within Xenopus laevis. To further investigate functional units within cardiac proteomes, we develop a computational approach to profile the abundance of protein complexes across species. Finally, we demonstrate the utility of these data sets for predicting appropriate model systems for studying given cardiac conditions by testing the role of Kielin/chordin-like protein (Kcp), a protein found as enriched in frog hearts compared to mammals. We establish that germ-line mutations in Kcp in Xenopus lead to valve defects and, ultimately, cardiac failure and death. Thus, integrating these findings with data on proteins responsible for cardiac disease should lead to the development of refined, species-specific models for protein function and disease states.

Comparison of cardiac proteomes across four vertebrate model systems reveals species-specific differentially enriched proteins and pathways, including the Xenopus-enriched Kielin/chordin-like protein (Kcp), which is shown to be important for proper heart development.

A novel de novo CASZ1 heterozygous frameshift variant causes dilated cardiomyopathy and left ventricular noncompaction cardiomyopathy

Background

Dilated cardiomyopathy (DCM) is the most common cardiomyopathy with a common presentation of heart failure. It has been reported that CASZ1 loss‐of‐function mutation contributes to familial DCM and congenital ventricular septal defect (VSD). To date, only two pathogenic variants in CASZ1 have been previously reported worldwide.

Methods

To identify the causative variant in an 11‐month‐old Chinese boy with DCM and left ventricular noncompaction cardiomyopathy (LVNC), trio‐whole‐exome sequencing was performed followed by mutational analysis and Sanger sequencing.

Results

An unreported de novo heterozygous frameshift variant (c.2443_2459delGTGGGCACCCCCAGCCT, p.Val815Profs*14) in CASZ1 was idenitified in the proband. The frameshift mutation in CASZ1 not only led to DCM but also presented an LVNC phenotype.

Conclusion

We have identified a novel CASZ1 variant in a patient with combined DCM and LVNC for the first time, thus broadening the phenotypic spectrum of CASZ1 variants. Furthermore, this study emphasized the usefulness of whole‐exome sequencing for genetic diagnosis of cardiomyopathy.

Proteomic-based approaches to cardiac development and disease

Congenital malformations, or structural birth defects, are now the leading cause of infant mortality in the United States and Europe (Dolk et al., 2010; Heron et al., 2009). Of the congenital malformations, congenital heart disease (CHD) is the most common (Dolk et al., 2010; Heron et al., 2009). Thus, a molecular understanding of heart development is an essential goal for improving clinical approaches to CHD. However, CHDs are commonly a result of genetic defects that manifest themselves in a spatial and temporal manner during the early stages of embryogenesis, leaving them mostly intractable to mass spectrometry-based analysis. Here, we describe the technologies and advancements in the field of mass spectrometry over the past few years that have begun to provide insights into the molecular and cellular basis of CHD and prospects for these types of approaches in the future.

Zinc and Zinc Transporters: Novel Regulators of Ventricular Myocardial Development

Ventricular myocardial development is a well-orchestrated process involving different cardiac structures, multiple signal pathways, and myriad proteins. Dysregulation of this important developmental event can result in cardiomyopathies, such as left ventricle non-compaction, which affect the pediatric population and the adults. Human and mouse studies have shed light upon the etiology of some cardiomyopathy cases and highlighted the contribution of both genetic and environmental factors. However, the regulation of ventricular myocardial development remains incompletely understood. Zinc is an essential trace metal with structural, enzymatic, and signaling function. Perturbation of zinc homeostasis has resulted in developmental and physiological defects including cardiomyopathy. In this review, we summarize several mechanisms by which zinc and zinc transporters can impact the regulation of ventricular myocardial development. Based on our review, we propose that zinc deficiency and mutations of zinc transporters may underlie some cardiomyopathy cases especially those involving ventricular myocardial development defects.

Identification of Casz1 as a Regulatory Protein Controlling T Helper Cell Differentiation, Inflammation, and Immunity

While T helper (Th) cells play a crucial role in host defense, an imbalance in Th effector subsets due to dysregulation in their differentiation and expansion contribute to inflammatory disorders. Here, we show that Casz1, whose function is previously unknown in CD4+ T cells, coordinates Th differentiation in vitro and in vivo. Casz1 deficiency in CD4+ T cells lowers susceptibility to experimental autoimmune encephalomyelitis, consistent with the reduced frequency of Th17 cells, despite an increase in Th1 cells in mice. Loss of Casz1 in the context of mucosal Candida infection severely impairs Th17 and Treg responses, and lowers the ability of the mice to clear the secondary infection. Importantly, in both the models, absence of Casz1 causes a significant diminution in IFN-γ+IL-17A+ double-positive inflammatory Th17 cells (Th1* cells) in tissues in vivo. Transcriptome analyses of CD4+ T cells lacking Casz1 show a signature consistent with defective Th17 differentiation. With regards to Th17 differentiation, Casz1 limits repressive histone marks and enables acquisition of permissive histone marks at Rorc, Il17a, Ahr, and Runx1 loci. Taken together, these data identify Casz1 as a new Th plasticity regulator having important clinical implications for autoimmune inflammation and mucosal immunity.

The Role of a Novel Long Noncoding RNA TUC40- in Cardiomyocyte Induction and Maturation in P19 Cells

BACKGROUND

In previous studies, TUC40-, a new long noncoding RNA, was found to be overexpressed in human ventricular septal defect (VSD) embryonic heart samples. In this article, we carried out experiments on the P19 cell line to elucidate the effects of TUC40- overexpression on cardiomyocyte development relevant to VSD pathogenesis.

METHODS

We established the overexpression cell model by plasmid transfection, and explored the expression profile of Pbx1, the sense gene of TUC40-, and the marker genes of cardiomyocyte linage commitment (Nkx2.5 and GATA4) and maturation (cardiac troponin T). In addition, we combined cell cycle and Cell Counting Kit-8 analysis to detect cell proliferation and used flow cytometry and caspase-3 assays to test apoptosis. At last, bioinformatics analysis was performed to show the possible role of TUC40-.

RESULTS

In the control group, Pbx1 elevated steadily during cardiomyocyte induction; whereas in the overexpression group, it showed significantly lower expression at day 6, 8 and 10 of induction. Cells in the overexpression group failed to induce cardiomyocytes indicated by GATA4 and cardiac troponin T. Proliferation was inhibited possibly owing to G2/M cell cycle arrest and the induced apoptosis rate was higher in the overexpression group.

CONCLUSIONS

TUC40- overexpression reduced Pbx1 expression, cardiomyocyte induction and differentiation, inhibited proliferation and promoted apoptosis. Combining the results and previous studies, we propose TUC40- as a potential pathologic factor for VSD.

Formation of a TBX20-CASZ1 protein complex is protective against dilated cardiomyopathy and critical for cardiac homeostasis

By the age of 40, one in five adults without symptoms of cardiovascular disease are at risk for developing congestive heart failure. Within this population, dilated cardiomyopathy (DCM) remains one of the leading causes of disease and death, with nearly half of cases genetically determined. Though genetic and high throughput sequencing-based approaches have identified sporadic and inherited mutations in a multitude of genes implicated in cardiomyopathy, how combinations of asymptomatic mutations lead to cardiac failure remains a mystery. Since a number of studies have implicated mutations of the transcription factor TBX20 in congenital heart diseases, we investigated the underlying mechanisms, using an unbiased systems-based screen to identify novel, cardiac-specific binding partners. We demonstrated that TBX20 physically and genetically interacts with the essential transcription factor CASZ1. This interaction is required for survival, as mice heterozygous for both Tbx20 and Casz1 die post-natally as a result of DCM. A Tbx20 mutation associated with human familial DCM sterically interferes with the TBX20-CASZ1 interaction and provides a physical basis for how this human mutation disrupts normal cardiac function. Finally, we employed quantitative proteomic analyses to define the molecular pathways mis-regulated upon disruption of this novel complex. Collectively, our proteomic, biochemical, genetic, and structural studies suggest that the physical interaction between TBX20 and CASZ1 is required for cardiac homeostasis, and further, that reduction or loss of this critical interaction leads to DCM. This work provides strong evidence that DCM can be inherited through a digenic mechanism.

A molecular understanding of cardiomyocyte development is an essential goal for improving clinical approaches to CHD. While TBX20 is an essential transcription factor for heart development and its disease relevance is well established, many fundamental questions remain about the mechanism of TBX20 function. Principle among these is how TBX20 mutations associated with adult dilated cardiomyopathy circumvent (DCM) the essential embryonic requirement for TBX20 in heart development. Here we report using an integrated approach that TBX20 complexes with the cardiac transcription factor CASZ1 in vivo. We confirmed TBX20 and CASZ1 interact biochemically and genetically, and show mice heterozygous for both Tbx20 and Casz1 die, beginning at 4 to 8 weeks post birth, exhibiting hallmarks of DCM. Interestingly, the human mutant TBX20^F256I bypasses the early essential requirement for TBX20 but leads to DCM. We report here that TBX20^F256I disrupts the TBX20-CASZ1 interaction, ascribing clinical relevance to this protein complex. Further, by using quantitative proteomics we have identified the molecular pathways altered in TBX20-CASZ1-mediated DCM. Together, these results identify a novel interaction between TBX20 and CASZ1 that is essential for maintaining cardiac homeostasis and imply that DCM can be inherited through a digenic mechanism.

Understanding cardiomyocyte proliferation: an insight into cell cycle activity

Cardiomyocyte proliferation and regeneration are key to the functional recovery of myocardial tissue from injury. In the recent years, studies on cardiomyocyte proliferation overturned the traditional belief that adult cardiomyocytes permanently withdraw from the cell cycle activity. Hence, targeting cardiomyocyte proliferation is one of the potential therapeutic strategies for myocardial regeneration and repair. To achieve this, a deep understanding of the fundamental mechanisms involved in cardiomyocyte cell cycle as well as differences between neonatal and adult cardiomyocytes' cell cycle activity is required. This review focuses on the recent progress in understanding of cardiomyocyte cell cycle activity at different life stages viz., gestation, birth, and adulthood. The temporal expression/activities of major cell cycle activators (cyclins and CDKs), inhibitors (p21, p27, p57, p16, and p18), and cell-cycle-associated proteins (Rb, p107, and p130) in cardiomyocytes during gestation and postnatal life are described in this review. The influence of different transcription factors and microRNAs on the expression of cell cycle proteins is demonstrated. This review also deals major pathways (PI3K/AKT, Wnt/β-catenin, and Hippo-YAP) associated with cardiomyocyte cell cycle progression. Furthermore, the postnatal alterations in structure and cellular events responsible for the loss of cell cycle activity are also illustrated.

CASZ1 loss-of-function mutation contributes to familial dilated cardiomyopathy

Background:

The zinc finger transcription factor CASZ1 plays a key role in cardiac development and postnatal adaptation, and in mice, deletion of the

Methods:

The coding exons and splicing junction sites of the

Results:

A novel heterozygous CASZ1 mutation, p.K351X, was identified in an index patient with DCM. Genetic analysis of the mutation carrier’s family showed that the mutation co-segregated with DCM, which was transmitted in an autosomal dominant pattern with complete penetrance. The nonsense mutation, which was absent in 400 referential chromosomes, altered the amino acid that was highly conserved evolutionarily. Biological investigations revealed that the mutant CASZ1 had no transcriptional activity.

Conclusions:

The current study reveals

CASZ1 loss-of-function mutation associated with congenital heart disease

As the most common form of birth defect in humans, congenital heart disease (CHD) is associated with substantial morbidity and mortality in both children and adults. Increasing evidence demonstrates that genetic defects play a pivotal role in the pathogenesis of CHD. However, CHD is of great heterogeneity, and in an overwhelming majority of cases, the genetic determinants underpinning CHD remain elusive. In the present investigation, the coding exons and flanking introns of the CASZ1 gene, which codes for a zinc finger transcription factor essential for the cardiovascular morphogenesis, were sequenced in 172 unrelated patients with CHD. As a result, a novel heterozygous CASZ1 mutation, p.L38P, was identified in an index patient with congenital ventricular septal defect (VSD). Genetic scanning of the mutation carrier's available family members revealed that the mutation was present in all affected patients but absent in unaffected individuals. Analysis of the proband's pedigree showed that the mutation co-segregated with VSD, which was transmitted as an autosomal dominant trait with complete penetrance. The missense mutation, which altered the amino acid that was highly conserved evolutionarily, was absent in 200 unrelated, ethnically-matched healthy subjects used as controls. Functional deciphers by using a dual-luciferase reporter assay system unveiled that the mutant CASZ1 had significantly reduced transcriptional activity as compared with its wild-type counterpart. To the best of our knowledge, the current study firstly identifies CASZ1 as a new gene predisposing to CHD in humans, which provides novel insight into the molecular mechanisms underlying CHD and a potential therapeutic target for CASZ1-associated CHD, suggesting potential implications for personalized prophylaxis and therapy of CHD.

Anacardic acid and thyroid hormone enhance cardiomyocytes production from undifferentiated mouse ES cells along functionally distinct pathways

The epigenetics of early commitment to embryonal cardiomyocyte is poorly understood. In this work, we compared the effect of thyroid hormone and that of anacardic acid, a naturally occurring histone acetylase inhibitor, or both in combination, on mouse embryonic stem cells (mES) differentiating into embryonal cardiomyocyte by embryoid bodies (EBs) formation. Although the results indicated that anacardic acid (AA) and thyroid hormone were both efficient in promoting cardiomyocyte differentiation, we noticed that a transient exposure of mES to AA alone was sufficient to enlarge the beating areas of EBs compared to those of untreated controls. This effect was associated with changes in the chromatin structure at the promoters of specific cardiomyogenic genes. Among them, a rapid induction of the transcription factor Castor 1 (CASZ1), important for cardiomyocytes differentiation and maturation during embryonic development, was observed in the presence of AA. In contrast, thyroid hormone (T 3) was more effective in stimulating spontaneous firing, thus suggesting a role in the production of a population of cardiomyocyte with pacemaker properties. In conclusion, AA and thyroid hormone both enhanced cardiomyocyte formation along in apparently distinct pathways.

The Cardiac TBX5 Interactome Reveals a Chromatin Remodeling Network Essential for Cardiac Septation

Human mutations in the cardiac transcription factor gene TBX5 cause congenital heart disease (CHD), although the underlying mechanism is unknown. We report characterization of the endogenous TBX5 cardiac interactome and demonstrate that TBX5, long considered a transcriptional activator, interacts biochemically and genetically with the nucleosome remodeling and deacetylase (NuRD) repressor complex. Incompatible gene programs are repressed by TBX5 in the developing heart. CHD mis-sense mutations that disrupt the TBX5-NuRD interaction cause depression of a subset of repressed genes. Furthermore, the TBX5-NuRD interaction is required for heart development. Phylogenetic analysis showed that the TBX5-NuRD interaction domain evolved during early diversification of vertebrates, simultaneous with the evolution of cardiac septation. Collectively, this work defines a TBX5-NuRD interaction essential to cardiac development and the evolution of the mammalian heart, and when altered may contribute to human CHD.

Age-driven developmental drift in the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and usually lethal disease of unknown aetiology. A growing body of evidence supports that IPF represents an epithelial-driven process characterised by aberrant epithelial cell behaviour, fibroblast/myofibroblast activation and excessive accumulation of extracellular matrix with the subsequent destruction of the lung architecture. The mechanisms involved in the abnormal hyper-activation of the epithelium are unclear, but we propose that recapitulation of pathways and processes critical to embryological development associated with a tissue specific age-related stochastic epigenetic drift may be implicated. These pathways may also contribute to the distinctive behaviour of IPF fibroblasts. Genomic and epigenomic studies have revealed that wingless/Int, sonic hedgehog and other developmental signalling pathways are reactivated and deregulated in IPF. Moreover, some of these pathways cross-talk with transforming growth factor-β activating a profibrotic feedback loop. The expression pattern of microRNAs is also dysregulated in IPF and exhibits a similar expression profile to embryonic lungs. In addition, senescence, a process usually associated with ageing, which occurs early in alveolar epithelial cells of IPF lungs, likely represents a conserved programmed developmental mechanism. Here, we review the major developmental pathways that get twisted in IPF, and discuss the connection with ageing and potential therapeutic approaches.

CASZ1 is a novel promoter of metastasis in ovarian cancer

Epithelial ovarian cancer (EOC) carries the highest mortality rate of all gynecologic malignancies. This high mortality rate is attributed to the fact that most cases of ovarian cancer are detected at late stages when metastases are already present. Through microarray analysis, we previously demonstrated that castor zinc finger 1 (CASZ1) is up-regulated in EOC cells. In contrast to its role in EOC, CASZ1 functions a tumor suppressor in neuroblastoma. Human CASZ1 is predominantly expressed in 2 alternatively spliced isoforms: CASZ1a and CASZ1b. In the present study, we investigated the role of CASZ1 in ovarian cancer cell migration and invasion and assessed the value of CASZ1 expression as a prognostic indicator of metastasis in human ovarian cancer. We used a lentivirus expressing CASZ1-shRNA and a plasmid expressing CASZ1 from a CMV promoter to knockdown and overexpress CASZ1, respectively, in the MCAS, RMUG-S, TOV21G, and A2780(CP70) ovarian cancer cell lines. mRNA expression levels in tumor tissues and cell lines were measured using quantitative real-time PCR, and CASZ1 protein expression in EOC and paired metastatic tumor tissues was analyzed using immunohistochemistry. We found that CASZ1 was highly expressed in EOC tissues and ovarian cancer cell lines and that CASZ1 knockdown suppressed cell migration and invasion in EOC cells. CASZ1a and CASZ1b exerted similar effects on cell migration and invasion in EOC cells. In addition, CASZ1 promoted the epithelial-mesenchymal transition in EOC cells, and CASZ1 knockdown suppressed cancer metastasis in vivo. Furthermore, CASZ1 protein levels were elevated in human metastatic ovarian tumor tissues. Together, these results indicate that CASZ1 is a novel promoter of EOC metastasis and is highly up-regulated in metastatic EOC tumors.

Zinc finger transcription factor Casz1 expression is regulated by homeodomain transcription factor Prrxl1 in embryonic spinal dorsal horn late-born excitatory interneurons

The transcription factor Casz1 is required for proper assembly of vertebrate vasculature and heart morphogenesis as well as for temporal control of Drosophila neuroblasts and mouse retina progenitors in the generation of different cell types. Although Casz1 function in the mammalian nervous system remains largely unexplored, Casz1 is expressed in several regions of this system. Here we provide a detailed spatiotemporal characterization of Casz1 expression along mouse dorsal root ganglion (DRG) and dorsal spinal cord development by immunochemistry. In the DRG, Casz1 is broadly expressed in sensory neurons since they are born until perinatal age. In the dorsal spinal cord, Casz1 displays a more dynamic pattern being first expressed in dorsal interneuron 1 (dI1) progenitors and their derived neurons and then in a large subset of embryonic dorsal late-born excitatory (dILB) neurons that narrows gradually to become restricted perinatally to the inner portion. Strikingly, expression analyses using Prrxl1-knockout mice revealed that Prrxl1, a key transcription factor in the differentiation of dILB neurons, is a positive regulator of Casz1 expression in the embryonic dorsal spinal cord but not in the DRG. By performing chromatin immunoprecipitation in the dorsal spinal cord, we identified two Prrxl1-bound regions within Casz1 introns, suggesting that Prrxl1 directly regulates Casz1 transcription. Our work reveals that Casz1 lies downstream of Prrxl1 in the differentiation pathway of a large subset of dILB neurons and provides a framework for further studies of Casz1 in assembly of the DRG-spinal circuit.

Mechanisms of temporal identity regulation in mouse retinal progenitor cells

While much progress has been made in recent years toward elucidating the transcription factor codes controlling how neural progenitor cells generate the various glial and neuronal cell types in a particular spatial domain, much less is known about how these progenitors alter their output over time. In the past years, work in the developing mouse retina has provided evidence that a transcriptional cascade similar to the one used in Drosophila neuroblasts might control progenitor temporal identity in vertebrates. The zinc finger transcription factor Ikzf1 (Ikaros), an ortholog of Drosophila hunchback, was reported to confer early temporal identity in retinal progenitors and, more recently, the ortholog of Drosophila castor, Casz1, was found to function as a mid/late temporal identity factor that is negatively regulated by Ikzf1. The molecular mechanisms by which these temporal identity factors function in retinal progenitors, however, remain unknown. Here we briefly review previous work on the vertebrate temporal identity factors in the retina, and propose a model by which they might operate.

Innervating sympathetic neurons regulate heart size and the timing of cardiomyocyte cell cycle withdrawal

Sympathetic drive to the heart is a key modulator of cardiac function and interactions between heart tissue and innervating sympathetic fibres are established early in development. Significant innervation takes place during postnatal heart development, a period when cardiomyocytes undergo a rapid transition from proliferative to hypertrophic growth. The question of whether these innervating sympathetic fibres play a role in regulating the modes of cardiomyocyte growth was investigated using 6-hydroxydopamine (6-OHDA) to abolish early sympathetic innervation of the heart. Postnatal chemical sympathectomy resulted in rats with smaller hearts, indicating that heart growth is regulated by innervating sympathetic fibres during the postnatal period. In vitro experiments showed that sympathetic interactions resulted in delays in markers of cardiomyocyte maturation, suggesting that changes in the timing of the transition from hyperplastic to hypertrophic growth of cardiomyocytes could underlie changes in heart size in the sympathectomized animals. There was also an increase in the expression of Meis1, which has been linked to cardiomyocyte cell cycle withdrawal, suggesting that sympathetic signalling suppresses cell cycle withdrawal. This signalling involves β-adrenergic activation, which was necessary for sympathetic regulation of cardiomyocyte proliferation and hypertrophy. The effect of β-adrenergic signalling on cardiomyocyte hypertrophy underwent a developmental transition. While young postnatal cardiomyocytes responded to isoproterenol (isoprenaline) with a decrease in cell size, mature cardiomyocytes showed an increase in cell size in response to the drug. Together, these results suggest that early sympathetic effects on proliferation modulate a key transition between proliferative and hypertrophic growth of the heart and contribute to the sympathetic regulation of adult heart size.