CHD7 regulates cardiovascular development through ATP-dependent and -independent activities

Naturally occurring genetic diseases caused by de novo variants in domestic animals

With the advent of next-generation sequencing, an increasing number of cases of de novo variants in domestic animals have been reported in scientific literature primarily associated with clinically severe phenotypes. The emergence of new variants at each generation is a crucial aspect in understanding the pathology of early-onset diseases in animals and can provide valuable insights into similar diseases in humans. With the aim of collecting deleterious de novo variants in domestic animals, we searched the scientific literature and compiled reports on 42 de novo variants in 31 genes in domestic animals. No clear disease-associated phenotype has been established in humans for three of these genes (NUMB, ANKRD28 and KCNG1). For the remaining 28 genes, a strong similarity between animal and human phenotypes was recognized from available information in OMIM and OMIA, revealing the importance of comparative studies and supporting the use of domestic animals as natural models for human diseases, in line with the One Health approach.

Zebrafish Congenital Heart Disease Models: Opportunities and Challenges

Congenital heart defects (CHDs) are common human birth defects. Genetic mutations potentially cause the exhibition of various pathological phenotypes associated with CHDs, occurring alone or as part of certain syndromes. Zebrafish, a model organism with a strong molecular conservation similar to humans, is commonly used in studies on cardiovascular diseases owing to its advantageous features, such as a similarity to human electrophysiology, transparent embryos and larvae for observation, and suitability for forward and reverse genetics technology, to create various economical and easily controlled zebrafish CHD models. In this review, we outline the pros and cons of zebrafish CHD models created by genetic mutations associated with single defects and syndromes and the underlying pathogenic mechanism of CHDs discovered in these models. The challenges of zebrafish CHD models generated through gene editing are also discussed, since the cardiac phenotypes resulting from a single-candidate pathological gene mutation in zebrafish might not mirror the corresponding human phenotypes. The comprehensive review of these zebrafish CHD models will facilitate the understanding of the pathogenic mechanisms of CHDs and offer new opportunities for their treatments and intervention strategies.

Single-cell RNA analysis of chromodomain-encoding genes in mesenchymal stromal cells of the mouse dental pulp

The chromodomain helicase DNA-binding (CHD) and chromobox (CBX) families of proteins play crucial roles in cell fate decisions, differentiation, and cell proliferation in a broad variety of tissues and cell types. CHD proteins are ATP-dependent epigenetic enzymes actively engaged in transcriptional regulation, DNA replication, and DNA damage repair, whereas CBX proteins are transcriptional repressors mainly involved in the formation of heterochromatin. The pleiotropic effects of CHD and CBX proteins are largely dependent on their versatility to interact with other key components of the epigenetic and transcriptional machinery. Although the function and regulatory modes of CHD and CBX factors are well established in many cell types, little is known about their roles during osteogenic differentiation. A single-cell RNA-sequencing analysis of the mouse incisor dental pulp revealed distinct spatiotemporal expression patterns of CHD- and CBX-encoding genes within different clusters of mesenchymal stromal cells (MSCs) representing various stages of osteogenic differentiation. Additionally, genes encoding interaction partners of CHD and CBX proteins, such as subunits of the trithorax-COMPASS and polycomb chromatin remodeling complexes, exhibited differential co-expression behaviors within MSC subpopulations. Thus, CHD- and CBX-encoding genes show partially overlapping but distinct expression patterns in MSCs, suggesting their differential roles in osteogenic cell fate decisions.

CHD7 Disorder-Not CHARGE Syndrome-Presenting as Isolated Cochleovestibular Dysfunction

CHARGE syndrome, characterized by a distinct set of clinical features, has been linked primarily to mutations in the CHD7 gene. Initially defined by specific clinical criteria, including coloboma, heart defects, choanal atresia, delayed growth, and ear anomalies, CHARGE syndrome's diagnostic spectrum has broadened since the identification of CHD7. Variants in this gene exhibit considerable phenotypic variability, leading to the adoption of the term "CHD7 disorder" to encompass a wider range of associated symptoms. Recent research has identified CHD7 variants in individuals with isolated features such as autism spectrum disorder or gonadotropin-releasing hormone deficiency. In this study, we present three cases from two different families exhibiting audiovestibular impairment as the primary manifestation of a CHD7 variant. We discuss the expanding phenotypic variability observed in CHD7-related disorders, highlighting the importance of considering CHD7 in nonsyndromic hearing loss cases, especially when accompanied by inner ear malformations on MRI. Additionally, we underscore the necessity of genetic counseling and comprehensive clinical evaluation for individuals with CHD7 variants to ensure appropriate management of associated health concerns.

Chromatin modifiers in human disease: from functional roles to regulatory mechanisms

The field of transcriptional regulation has revealed the vital role of chromatin modifiers in human diseases from the beginning of functional exploration to the process of participating in many types of disease regulatory mechanisms. Chromatin modifiers are a class of enzymes that can catalyze the chemical conversion of pyrimidine residues or amino acid residues, including histone modifiers, DNA methyltransferases, and chromatin remodeling complexes. Chromatin modifiers assist in the formation of transcriptional regulatory circuits between transcription factors, enhancers, and promoters by regulating chromatin accessibility and the ability of transcription factors to acquire DNA. This is achieved by recruiting associated proteins and RNA polymerases. They modify the physical contact between cis-regulatory factor elements, transcription factors, and chromatin DNA to influence transcriptional regulatory processes. Then, abnormal chromatin perturbations can impair the homeostasis of organs, tissues, and cells, leading to diseases. The review offers a comprehensive elucidation on the function and regulatory mechanism of chromatin modifiers, thereby highlighting their indispensability in the development of diseases. Furthermore, this underscores the potential of chromatin modifiers as biomarkers, which may enable early disease diagnosis. With the aid of this paper, a deeper understanding of the role of chromatin modifiers in the pathogenesis of diseases can be gained, which could help in devising effective diagnostic and therapeutic interventions.

Human Genetics of Atrial Septal Defect

Although atrial septal defects (ASD) can be subdivided based on their anatomical location, an essential aspect of human genetics and genetic counseling is distinguishing between isolated and familiar cases without extracardiac features and syndromic cases with the co-occurrence of extracardiac abnormalities, such as developmental delay. Isolated or familial cases tend to show genetic alterations in genes related to important cardiac transcription factors and genes encoding for sarcomeric proteins. By contrast, the spectrum of genes with genetic alterations observed in syndromic cases is diverse. Currently, it points to different pathways and gene networks relevant to the dysregulation of cardiomyogenesis and ASD pathogenesis. Therefore, this chapter reflects the current knowledge and highlights stable associations observed in human genetics studies. It gives an overview of the different types of genetic alterations in these subtypes, including common associations based on genome-wide association studies (GWAS), and it highlights the most frequently observed syndromes associated with ASD pathogenesis.

Whole-Exome Sequencing Analysis of Idiopathic Hypogonadotropic Hypogonadism: Comparison of Varicocele and Nonobstructive Azoospermia

As a rare disease leading to male infertility, idiopathic hypogonadotropic hypogonadism (IHH) has strong heterogeneity of clinical phenotype and gene mutation. At present, there is no effective diagnosis and treatment method for this disease. This study is to explore the possible new pathogenic gene of idiopathic hypogonadotrophic hypogonadism and the pathological mechanism affecting its occurrence. We performed a whole-exome sequencing on 9 patients with normosmic idiopathic hypogonadotropic hypogonadism (nIHH), 19 varicocele patients with asthenospermia, oligospermia, or azoospermia, 5 patients with simple nonobstructive azoospermia, and 13 normal healthy adult males and carried out comparative analysis, channel analysis, etc. After preliminary sequencing screening, 309-431 genes harbouring variants, including SNPs and indels, were predicted to be harmful per single patient in each group. In genetic variations of nIHH patients' analysis, variants were detected in 10 loci and nine genes in nine patients. And in co-analysis of the three patient groups, nine nIHH patients, 19 VC patients, and five SN patients shared 116 variants, with 28 variant-harbouring genes detected in five or more patients. We found that the NEFH, CCDC177, and PCLO genes and the Gene Ontology pathways GO:0051301: cell division and GO:0090066: regulation of anatomical structure size may be key factors in the pathogenic mechanism of IHH. Our results suggest that the pathogenic mechanism of IHH is not limited to the central nervous system effects of GnRH but may involve other heterogeneous pathogenic genetic variants that affect peripheral organs.

CHARGE syndrome-associated CHD7 acts at ISL1-regulated enhancers to modulate second heart field gene expression

AIMS

Haploinsufficiency of the chromo-domain protein CHD7 underlies most cases of CHARGE syndrome, a multisystem birth defect including congenital heart malformation. Context specific roles for CHD7 in various stem, progenitor, and differentiated cell lineages have been reported. Previously, we showed severe defects when Chd7 is absent from cardiopharyngeal mesoderm (CPM). Here, we investigate altered gene expression in the CPM and identify specific CHD7-bound target genes with known roles in the morphogenesis of affected structures.

METHODS AND RESULTS

We generated conditional KO of Chd7 in CPM and analysed cardiac progenitor cells using transcriptomic and epigenomic analyses, in vivo expression analysis, and bioinformatic comparisons with existing datasets. We show CHD7 is required for correct expression of several genes established as major players in cardiac development, especially within the second heart field (SHF). We identified CHD7 binding sites in cardiac progenitor cells and found strong association with histone marks suggestive of dynamically regulated enhancers during the mesodermal to cardiac progenitor transition of mESC differentiation. Moreover, CHD7 shares a subset of its target sites with ISL1, a pioneer transcription factor in the cardiogenic gene regulatory network, including one enhancer modulating Fgf10 expression in SHF progenitor cells vs. differentiating cardiomyocytes.

CONCLUSION

We show that CHD7 interacts with ISL1, binds ISL1-regulated cardiac enhancers, and modulates gene expression across the mesodermal heart fields during cardiac morphogenesis.

Deletion of the chd7 Hinders Oligodendrocyte Progenitor Cell Development and Myelination in Zebrafish

CHD7, an encoding ATP-dependent chromodomain helicase DNA-binding protein 7, has been identified as the causative gene involved in CHARGE syndrome (Coloboma of the eye, Heart defects, Atresia choanae, Retardation of growth and/or development, Genital abnormalities and Ear abnormalities). Although studies in rodent models have expanded our understanding of CHD7, its role in oligodendrocyte (OL) differentiation and myelination in zebrafish is still unclear. In this study, we generated a chd7-knockout strain with CRISPR/Cas9 in zebrafish. We observed that knockout (KO) of chd7 intensely impeded the oligodendrocyte progenitor cells' (OPCs) migration and myelin formation due to massive expression of chd7 in oilg2+ cells, which might provoke upregulation of the MAPK signal pathway. Thus, our study demonstrates that chd7 is critical to oligodendrocyte migration and myelination during early development in zebrafish and describes a mechanism potentially associated with CHARGE syndrome.

Expanding the reproductive organ phenotype of CHD7-spectrum disorder

CHD7 disorder is a multiple congenital anomaly syndrome with a highly variable phenotypic spectrum, and includes CHARGE syndrome. Internal and external genital phenotypes frequently seen in CHD7 disorder include cryptorchidism and micropenis in males, and vaginal hypoplasia in females, both thought to be secondary to hypogonadotropic hypogonadism. Here, we report 14 deeply phenotyped individuals with known CHD7 variants (9 pathogenic/likely pathogenic and 5 VOUS) and a range of reproductive and endocrine phenotypes. Reproductive organ anomalies were observed in 8 of 14 individuals and were more commonly noted in males (7/7), most of whom presented with micropenis and/or cryptorchidism. Kallmann syndrome was commonly observed among adolescents and adults with CHD7 variants. Remarkably, one 46,XY individual presented with ambiguous genitalia, cryptorchidism with Müllerian structures including uterus, vagina and fallopian tubes, and one 46,XX female patient presented with absent vagina, uterus and ovaries. These cases expand the genital and reproductive phenotype of CHD7 disorder to include two individuals with genital/gonadal atypia (ambiguous genitalia), and one with Müllerian aplasia.

The Genetics of Neurodevelopment in Congenital Heart Disease

Congenital heart disease (CHD) is the most common birth anomaly, affecting almost 1% of infants. Neurodevelopmental delay is the most common extracardiac feature in people with CHD. Many factors may contribute to neurodevelopmental risk, including genetic factors, CHD physiology, and the prenatal/postnatal environment. Damaging variants are most highly enriched among individuals with extracardiac anomalies or neurodevelopmental delay in addition to CHD, indicating that genetic factors have an impact beyond cardiac tissues in people with CHD. Potential sources of genetic risk include large deletions or duplications that affect multiple genes, such as 22q11 deletion syndrome, single genes that alter both heart and brain development, such as CHD7, and common variants that affect neurodevelopmental resiliency, such as APOE. Increased use of genome-sequencing technologies in studies of neurodevelopmental outcomes in people with CHD will improve our ability to detect relevant genes and variants. Ultimately, such knowledge can lead to improved and more timely intervention of learning support for affected children.

Chromatin remodeler CHD7 targets active enhancer region to regulate cell type-specific gene expression in human neural crest cells

A mutation in the chromatin remodeler chromodomain helicase DNA-binding 7 (CHD7) gene causes the multiple congenital anomaly CHARGE syndrome. The craniofacial anomalies observed in CHARGE syndrome are caused by dysfunctions of neural crest cells (NCCs), which originate from the neural tube. However, the mechanism by which CHD7 regulates the function of human NCCs (hNCCs) remains unclear. We aimed to characterize the cis-regulatory elements governed by CHD7 in hNCCs by analyzing genome-wide ChIP-Seq data and identifying hNCC-specific CHD7-binding profiles. We compared CHD7-binding regions among cell types, including human induced pluripotent stem cells and human neuroepithelial cells, to determine the comprehensive properties of CHD7-binding in hNCCs. Importantly, analysis of the hNCC-specific CHD7-bound region revealed transcription factor AP-2α as a potential co-factor facilitating the cell type-specific transcriptional program in hNCCs. CHD7 was strongly associated with active enhancer regions, permitting the expression of hNCC-specific genes to sustain the function of hNCCs. Our findings reveal the regulatory mechanisms of CHD7 in hNCCs, thus providing additional information regarding the transcriptional programs in hNCCs.

Diagnostic potential of the amniotic fluid cells transcriptome in deciphering mendelian disease: a proof-of-concept

RNA sequencing (RNA-seq) is emerging in genetic diagnoses as it provides functional support for the interpretation of variants of uncertain significance. However, the use of amniotic fluid (AF) cells for RNA-seq has not yet been explored. Here, we examined the expression of clinically relevant genes in AF cells (n = 48) compared with whole blood and fibroblasts. The number of well-expressed genes in AF cells was comparable to that in fibroblasts and much higher than that in blood across different disease categories. We found AF cells RNA-seq feasible and beneficial in prenatal diagnosis (n = 4) as transcriptomic data elucidated the molecular consequence leading to the pathogenicity upgrade of variants in CHD7 and COL1A2 and revising the in silico prediction of a variant in MYRF. AF cells RNA-seq could become a reasonable choice for postnatal patients with advantages over fibroblasts and blood as it prevents invasive procedures.

Craniofacial and cardiac defects in chd7 zebrafish mutants mimic CHARGE syndrome

Congenital heart defects occur in almost 80% of patients with CHARGE syndrome, a sporadically occurring disease causing craniofacial and other abnormalities due to mutations in the CHD7 gene. Animal models have been generated to mimic CHARGE syndrome; however, heart defects are not extensively described in zebrafish disease models of CHARGE using morpholino injections or genetic mutants. Here, we describe the co-occurrence of craniofacial abnormalities and heart defects in zebrafish chd7 mutants. These mutant phenotypes are enhanced in the maternal zygotic mutant background. In the chd7 mutant fish, we found shortened craniofacial cartilages and extra cartilage formation. Furthermore, the length of the ventral aorta is altered in chd7 mutants. Many CHARGE patients have aortic arch anomalies. It should be noted that the aberrant branching of the first branchial arch artery is observed for the first time in chd7 fish mutants. To understand the cellular mechanism of CHARGE syndrome, neural crest cells (NCCs), that contribute to craniofacial and cardiovascular tissues, are examined using sox10:Cre lineage tracing. In contrast to its function in cranial NCCs, we found that the cardiac NCC-derived mural cells along the ventral aorta and aortic arch arteries are not affected in chd7 mutant fish. The chd7 fish mutants we generated recapitulate some of the craniofacial and cardiovascular phenotypes found in CHARGE patients and can be used to further determine the roles of CHD7.

CHD7 regulates otic lineage specification and hair cell differentiation in human inner ear organoids

Mutations in CHD7 cause CHARGE syndrome, affecting multiple organs including the inner ear in humans. We investigate how CHD7 mutations affect inner ear development using human pluripotent stem cell-derived organoids as a model system. We find that loss of CHD7 or its chromatin remodeling activity leads to complete absence of hair cells and supporting cells, which can be explained by dysregulation of key otic development-associated genes in mutant otic progenitors. Further analysis of the mutant otic progenitors suggests that CHD7 can regulate otic genes through a chromatin remodeling-independent mechanism. Results from transcriptome profiling of hair cells reveal disruption of deafness gene expression as a potential underlying mechanism of CHARGE-associated sensorineural hearing loss. Notably, co-differentiating CHD7 knockout and wild-type cells in chimeric organoids partially rescues mutant phenotypes by restoring otherwise severely dysregulated otic genes. Taken together, our results suggest that CHD7 plays a critical role in regulating human otic lineage specification and hair cell differentiation.

Eyes on CHARGE syndrome: Roles of CHD7 in ocular development

The development of the vertebrate visual system involves complex morphogenetic interactions of cells derived from multiple embryonic lineages. Disruptions in this process are associated with structural birth defects such as microphthalmia, anophthalmia, and coloboma (collectively referred to as MAC), and inherited retinal degenerative diseases such as retinitis pigmentosa and allied dystrophies. MAC and retinal degeneration are also observed in systemic congenital malformation syndromes. One important example is CHARGE syndrome, a genetic disorder characterized by coloboma, heart defects, choanal atresia, growth retardation, genital abnormalities, and ear abnormalities. Mutations in the gene encoding Chromodomain helicase DNA binding protein 7 (CHD7) cause the majority of CHARGE syndrome cases. However, the pathogenetic mechanisms that connect loss of CHD7 to the ocular complications observed in CHARGE syndrome have not been identified. In this review, we provide a general overview of ocular development and congenital disorders affecting the eye. This is followed by a comprehensive description of CHARGE syndrome, including discussion of the spectrum of ocular defects that have been described in this disorder. In addition, we discuss the current knowledge of CHD7 function and focus on its contributions to the development of ocular structures. Finally, we discuss outstanding gaps in our knowledge of the role of CHD7 in eye formation, and propose avenues of investigation to further our understanding of how CHD7 activity regulates ocular and retinal development.

Differential requirement for DICER1 activity during the development of mitral and tricuspid valves

Mitral and tricuspid valves are essential for unidirectional blood flow in the heart. They are derived from similar cell sources, and yet congenital dysplasia affecting both valves is clinically rare, suggesting the presence of differential regulatory mechanisms underlying their development. Here, we specifically inactivated Dicer1 in the endocardium during cardiogenesis and found that Dicer1 deletion caused congenital mitral valve stenosis and regurgitation, whereas it had no impact on other valves. We showed that hyperplastic mitral valves were caused by abnormal condensation and extracellular matrix (ECM) remodeling. Our single-cell RNA sequencing analysis revealed impaired maturation of mesenchymal cells and abnormal expression of ECM genes in mutant mitral valves. Furthermore, expression of a set of miRNAs that target ECM genes was significantly lower in tricuspid valves compared to mitral valves, consistent with the idea that the miRNAs are differentially required for mitral and tricuspid valve development. We thus reveal miRNA-mediated gene regulation as a novel molecular mechanism that differentially regulates mitral and tricuspid valve development, thereby enhancing our understanding of the non-association of inborn mitral and tricuspid dysplasia observed clinically.

Drp1 regulates transcription of ribosomal protein genes in embryonic hearts

Mitochondrial dysfunction causes severe congenital cardiac abnormalities and prenatal/neonatal lethality. The lack of sufficient knowledge regarding how mitochondrial abnormalities affect cardiogenesis poses a major barrier for the development of clinical applications that target mitochondrial deficiency-induced inborn cardiomyopathies. Mitochondrial morphology, which is regulated by fission and fusion, plays a key role in determining mitochondrial activity. Dnm1l encodes a dynamin-related GTPase, Drp1, which is required for mitochondrial fission. To investigate the role of Drp1 in cardiogenesis during the embryonic metabolic shift period, we specifically inactivated Dnm1l in second heart field-derived structures. Mutant cardiomyocytes in the right ventricle (RV) displayed severe defects in mitochondrial morphology, ultrastructure and activity. These defects caused increased cell death, decreased cell survival, disorganized cardiomyocytes and embryonic lethality. By characterizing this model, we reveal an AMPK-SIRT7-GABPB axis that relays the reduced cellular energy level to decrease transcription of ribosomal protein genes in cardiomyocytes. We therefore provide the first genetic evidence in mouse that Drp1 is essential for RV development. Our research provides further mechanistic insight into how mitochondrial dysfunction causes pathological molecular and cellular alterations during cardiogenesis.

Sentinels of chromatin: chromodomain helicase DNA-binding proteins in development and disease

Chromatin is highly dynamic, undergoing continuous global changes in its structure and type of histone and DNA modifications governed by processes such as transcription, repair, replication, and recombination. Members of the chromodomain helicase DNA-binding (CHD) family of enzymes are ATP-dependent chromatin remodelers that are intimately involved in the regulation of chromatin dynamics, altering nucleosomal structure and DNA accessibility. Genetic studies in yeast, fruit flies, zebrafish, and mice underscore essential roles of CHD enzymes in regulating cellular fate and identity, as well as proper embryonic development. With the advent of next-generation sequencing, evidence is emerging that these enzymes are subjected to frequent DNA copy number alterations or mutations and show aberrant expression in malignancies and other human diseases. As such, they might prove to be valuable biomarkers or targets for therapeutic intervention.

Advances in Chromodomain Helicase DNA-Binding (CHD) Proteins Regulating Stem Cell Differentiation and Human Diseases

Background: Regulation of gene expression is critical for stem cell differentiation, tissue development, and human health maintenance. Recently, epigenetic modifications of histone and chromatin remodeling have been verified as key controllers of gene expression and human diseases.

Objective: In this study, we review the role of chromodomain helicase DNA-binding (CHD) proteins in stem cell differentiation, cell fate decision, and several known human developmental disorders and cancers.

Conclusion: CHD proteins play a crucial role in stem cell differentiation and human diseases.

The Cardiac Neural Crest Cells in Heart Development and Congenital Heart Defects

The neural crest (NC) is a multipotent and temporarily migratory cell population stemming from the dorsal neural tube during vertebrate embryogenesis. Cardiac neural crest cells (NCCs), a specified subpopulation of the NC, are vital for normal cardiovascular development, as they significantly contribute to the pharyngeal arch arteries, the developing cardiac outflow tract (OFT), cardiac valves, and interventricular septum. Various signaling pathways are shown to orchestrate the proper migration, compaction, and differentiation of cardiac NCCs during cardiovascular development. Any loss or dysregulation of signaling pathways in cardiac NCCs can lead to abnormal cardiovascular development during embryogenesis, resulting in abnormalities categorized as congenital heart defects (CHDs). This review focuses on the contributions of cardiac NCCs to cardiovascular formation, discusses cardiac defects caused by a disruption of various regulatory factors, and summarizes the role of multiple signaling pathways during embryonic development. A better understanding of the cardiac NC and its vast regulatory network will provide a deeper insight into the mechanisms of the associated abnormalities, leading to potential therapeutic advancements.

CHARGE syndrome and related disorders: A mechanistic link

CHARGE syndrome is an autosomal dominant malformation disorder caused by pathogenic variants in the chromatin remodeler CHD7. Affected are craniofacial structures, cranial nerves and multiple organ systems. Depending on the combination of malformations present, its distinction from other congenital disorders can be challenging. To gain a better insight into the regulatory disturbances in CHARGE syndrome, we performed RNA-Seq analysis on blood samples of 19 children with CHARGE syndrome and a confirmed disease-causing CHD7 variant in comparison to healthy control children. Our analysis revealed a distinct CHARGE syndrome pattern with downregulation of genes that are linked to disorders described to mimic the CHARGE phenotype, i.e. KMT2D and KDM6A (Kabuki syndrome), EP300 and CREBBP (Rubinstein-Taybi syndrome) and ARID1A and ARID1B (Coffin-Siris syndrome). Furthermore, by performing protein-protein interaction studies using co-immunoprecipitation, direct yeast-two hybrid and in situ proximity ligation assays, we could demonstrate an interplay between CHD7, KMT2D, KDM6A and EP300. In summary, our data demonstrate a mechanistic and regulatory link between the developmental disorders CHARGE-, Kabuki- and Rubinstein Taybi-syndrome providing an explanation for the overlapping phenotypes.

Epigenetic Regulation of Cardiac Neural Crest Cells

The cardiac neural crest cells (cNCCs) is a transient, migratory cell population that contribute to the formation of major arteries and the septa and valves of the heart. Abnormal development of cNCCs leads to a spectrum of congenital heart defects that mainly affect the outflow region of the hearts. Signaling molecules and transcription factors are the best studied regulatory events controlling cNCC development. In recent years, however, accumulated evidence supports that epigenetic regulation also plays an important role in cNCC development. Here, we summarize the functions of epigenetic regulators during cNCC development as well as cNCC related cardiovascular defects. These factors include ATP-dependent chromatin remodeling factors, histone modifiers and DNA methylation modulators. In many cases, mutations in the genes encoding these factors are known to cause inborn heart diseases. A better understanding of epigenetic regulators, their activities and their roles during heart development will ultimately contribute to the development of new clinical applications for patients with congenital heart disease.

Semaphorin Regulation by the Chromatin Remodeler CHD7: An Emerging Genetic Interaction Shaping Neural Cells and Neural Crest in Development and Cancer

CHD7 is a chromatin remodeler protein that controls gene expression via the formation of multi-protein complexes with specific transcription factors. During development, CHD7 controls several differentiation programs, mainly by acting on neural progenitors and neural crest (NC) cells. Thus, its roles range from the central nervous system to the peripheral nervous system and the organs colonized by NC cells, including the heart. Accordingly, mutated CHD7 is linked to CHARGE syndrome, which is characterized by several neuronal dysfunctions and by malformations of NC-derived/populated organs. Altered CHD7 has also been associated with different neoplastic transformations. Interestingly, recent evidence revealed that semaphorins, a class of molecules involved in developmental and pathological processes similar to those controlled by CHD7, are regulated by CHD7 in a context-specific manner. In this article, we will review the recent insights that support the existence of genetic interactions between these pathways, both during developmental processes and cancer progression.