Congenital heart defects in molecularly proven Kabuki syndrome patients

Biallelic OTUD6B variants associated with a Kabuki syndrome-like disorder in three siblings: A clinical report and literature review

Biallelic variants in the OTUD6B gene have been reported in the literature in association with an intellectual developmental disorder featuring dysmorphic facies, seizures, and distal limb abnormalities. Physical differences described for affected individuals suggest that the disorder may be clinically recognizable, but previous publications have reported an initial clinical suspicion for Kabuki syndrome (KS) in some affected individuals. Here, we report on three siblings with biallelic variants in OTUD6B co-segregating with neurodevelopmental delay, shared physical differences, and other clinical findings similar to those of previously reported individuals. However, clinical manifestations such as long palpebral fissures, prominent and cupped ears, developmental delay, growth deficiency, persistent fetal fingertip pads, vertebral anomaly, and seizures in the proband were initially suggestive of KS. In addition, previously unreported clinical manifestations such as delayed eruption of primary dentition, soft doughy skin with reduced sweating, and mirror movements present in our patients suggest an expansion of the phenotype, and we perform a literature review to update on current information related to OTUD6B and human gene-disease association.

Systemic and oral abnormalities in Kabuki syndrome: a case series

OBJECTIVE

This study analyzed the systemic and oral abnormalities in individuals with Kabuki syndrome (KS) that might be investigated to enhance the early diagnosis and treatment by a multidisciplinary team, minimizing the consequences to the individual's health.

STUDY DESIGN

Clinical examination was conducted on 15 individuals to investigate orodental alterations such as tooth abnormalities and cleft lip and/or palate, and the patient records were also reviewed to investigate systemic diseases such as cardiopathies, infectious and immunologic diseases, nephropathies, and delayed neuropsychomotor development.

RESULTS

All individuals with KS presented cleft lip and/or palate, 11 (73.34%) tooth abnormalities, 5 (33.34%) congenital cardiopathies, 12 (80%) infectious or immunologic diseases, 1 (6.67%) nephropathy, and 14 (93.34%) had an intellectual disability.

CONCLUSION

Individuals with KS often have dental anomalies such as hypodontia, cleft or palate, and systemic disorders such as congenital heart disease and infectious diseases. Intellectual disability is present in most cases. These alterations should be investigated as early as possible to prevent the increase in morbidity in these individuals.

Chromatinopathies: insight in clinical aspects and underlying epigenetic changes

Chromatinopathies (CPs), a group of rare inborn defects characterized by chromatin state imbalance, have evolved from initially resembling Cornelia de Lange syndrome to encompass a wide array of genetic diseases with diverse clinical presentations. The CPs classification now includes human developmental disorders caused by germline mutations in epigenes, genes that regulate the epigenome. Recent advances in next-generation sequencing have enabled the association of 154 epigenes with CPs, revealing distinctive DNA methylation patterns known as episignatures.It has been shown that episignatures are unique for a particular CP or share similarities among specific CP subgroup. Consequently, these episignatures have emerged as promising biomarkers for diagnosing and treating CPs, differentiating subtypes, evaluating variants of unknown significance, and facilitating targeted therapies tailored to the underlying epigenetic dysregulation.The following review was conducted to collect, summarize, and analyze data regarding CPs in such aspects as clinical evaluation encompassing long-term patient care, underlying epigenetic changes, and innovative molecular and bioinformatic methodologies that have been devised for the assessment of CPs. We have also shed light on promising novel treatment options that have surfaced in recent research and presented a synthesis of ongoing clinical trials, contributing to the current understanding of the dynamic and evolving nature of CPs investigation.

Illuminating the Genetic Basis of Congenital Heart Disease in Patients with Kabuki Syndrome

Congenital heart defects (CHDs) affect a substantial proportion of patients with Kabuki syndrome. However, the prevalence and type of CHD and the genotype-phenotype correlations in Asian populations are not fully elucidated. This study performed a retrospective analysis of 23 Taiwanese patients with molecularly confirmed Kabuki syndrome. Twenty-two patients presented with pathogenic variants in the KMT2D gene. Comprehensive clinical assessments were performed. A literature review was conducted to summarize the spectrum of CHDs in patients with Kabuki syndrome. In total, 16 (73.9%) of 22 patients with pathogenic KMT2D variants had CHDs. The most common types of CHD were atrial septal defects (37.5%), ventricular septal defects (18.8%), coarctation of the aorta (18.8%), bicuspid aortic valve (12.5%), persistent left superior vena cava (12.5%), mitral valve prolapse (12.5%), mitral regurgitation (12.5%), and patent ductus arteriosus (12.5%). Other cardiac abnormalities were less common. Further, there were no clear genotype-phenotype correlations found. A literature review revealed similar patterns of CHDs, with a predominance of left-sided obstructive lesions and septal defects. In conclusion, the most common types of CHDs in Taiwanese patients with Kabuki syndrome who presented with KMT2D mutations are left-sided obstructive lesions and septal defects.

Sex-specific difference in phenotype of Kabuki syndrome type 2 patients: a matched case-control study

BACKGROUND

Kabuki syndrome (KS) is a monogenic disorder leading to special facial features, mental retardation, and multiple system malformations. Lysine demethylase 6A, (KDM6A, MIM*300128) is the pathogenic gene of Kabuki syndrome type 2 (KS2, MIM#300867), which accounts for only 5%-8% of KS. Previous studies suggested that female patients with KS2 may have a milder phenotype.

METHOD

We summarized the phenotype and genotype of KS2 patients who were diagnosed in Shanghai Children's Medical Center since July 2017 and conducted a 1:3 matched case-control study according to age and sex to investigate sex-specific differences between patients with and without KS2.

RESULTS

There were 12 KS2 cases in this study, and 8 of them matched with 24 controls. The intelligence quotient (IQ) score of the case group was significantly lower than that of the control group (P < 0.001). In addition, both the incidence of intellectual disability (ID) (IQ < 70) and moderate-to-severe ID (IQ < 55) were significantly higher in the case group than those in the control group. No sex-specific difference was found in the incidence of ID or moderate-to-severe ID between the female cases and female controls, whereas there was a significant difference between male cases and male controls. Furthermore, the rate of moderate-to-severe ID and congenital heart disease (CHD) was significantly higher in the male group than that in the female group.

CONCLUSIONS

Our results showed that a sex-specific difference was exhibited in the clinical phenotypes of KS2 patients. The incidence of CHD was higher in male patients, and mental retardation was significantly impaired. However, the female patients' phenotype was mild.

Next generation phenotyping for diagnosis and phenotype-genotype correlations in Kabuki syndrome

The field of dysmorphology has been changed by the use Artificial Intelligence (AI) and the development of Next Generation Phenotyping (NGP). The aim of this study was to propose a new NGP model for predicting KS (Kabuki Syndrome) on 2D facial photographs and distinguish KS1 (KS type 1, KMT2D-related) from KS2 (KS type 2, KDM6A-related). We included retrospectively and prospectively, from 1998 to 2023, all frontal and lateral pictures of patients with a molecular confirmation of KS. After automatic preprocessing, we extracted geometric and textural features. After incorporation of age, gender, and ethnicity, we used XGboost (eXtreme Gradient Boosting), a supervised machine learning classifier. The model was tested on an independent validation set. Finally, we compared the performances of our model with DeepGestalt (Face2Gene). The study included 1448 frontal and lateral facial photographs from 6 centers, corresponding to 634 patients (527 controls, 107 KS); 82 (78%) of KS patients had a variation in the KMT2D gene (KS1) and 23 (22%) in the KDM6A gene (KS2). We were able to distinguish KS from controls in the independent validation group with an accuracy of 95.8% (78.9-99.9%, p < 0.001) and distinguish KS1 from KS2 with an empirical Area Under the Curve (AUC) of 0.805 (0.729-0.880, p < 0.001). We report an automatic detection model for KS with high performances (AUC 0.993 and accuracy 95.8%). We were able to distinguish patients with KS1 from KS2, with an AUC of 0.805. These results outperform the current commercial AI-based solutions and expert clinicians.

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.

Human Genetics of Semilunar Valve and Aortic Arch Anomalies

Lesions of the semilunar valve and the aortic arch can occur either in isolation or as part of well-described clinical syndromes. The polygenic cause of calcific aortic valve disease will be discussed including the key role of NOTCH1 mutations. In addition, the complex trait of bicuspid aortic valve disease will be outlined, both in sporadic/familial cases and in the context of associated syndromes, such as Alagille, Williams, and Kabuki syndromes. Aortic arch abnormalities particularly coarctation of the aorta and interrupted aortic arch, including their association with syndromes such as Turner and 22q11 deletion, respectively, are also discussed. Finally, the genetic basis of congenital pulmonary valve stenosis is summarized, with particular note to Ras-/mitogen-activated protein kinase (Ras/MAPK) pathway syndromes and other less common associations, such as Holt-Oram syndrome.

Neonatal Kabuki syndrome caused by KMT2D mutation: A case report

BACKGROUND

Kabuki syndrome (KS) is an autosomal dominant inherited syndrome that involves multiple organs and systems. Gene mutation is the main cause of KS. The reported mutations in X-linked histone H3 lysine 4 methylase (KMT2D) and KDM6A genes are 2 relatively clear pathogenic pathways. In this paper, we report a case of KS with neonatal hypoglycemia and special features caused by KMT2D gene mutation confirmed by whole exome sequencing, it enriched the clinical phenotype spectrum and gene mutation spectrum of KS, which helps to improve the understanding of the disease.

CASE REPORT

Through whole exome sequencing, we performed gene diagnosis of a newborn child with special facial features and multiple malformations, which revealed heterozygous mutation of NM_003482.3:c.755dupA(p.His252Glnfs*21) in KMT2D gene. It is consistent with the pathogenesis of KS, an autosomal dominat genetic disease caused by KMT2D gene mutation. This pathogenic mutation has not been prebiously reported.

DISCUSSION

KS has strong clinical characteristics and biological heterogeneity. Genetic diagnosis can help identify mutant gene types. However, the relationship between genotype and phenotype has not been fully clarified. The molecular etiological mechanism still needs to be further explored and elucidated.

Distinct Roles for COMPASS Core Subunits Set1, Trx, and Trr in the Epigenetic Regulation of Drosophila Heart Development

Highly evolutionarily conserved multiprotein complexes termed Complex of Proteins Associated with Set1 (COMPASS) are required for histone 3 lysine 4 (H3K4) methylation. Drosophila Set1, Trx, and Trr form the core subunits of these complexes. We show that flies deficient in any of these three subunits demonstrated high lethality at eclosion (emergence of adult flies from their pupal cases) and significantly shortened lifespans for the adults that did emerge. Silencing Set1, trx, or trr in the heart led to a reduction in H3K4 monomethylation (H3K4me1) and dimethylation (H3K4me2), reflecting their distinct roles in H3K4 methylation. Furthermore, we studied the gene expression patterns regulated by Set1, Trx, and Trr. Each of the COMPASS core subunits controls the methylation of different sets of genes, with many metabolic pathways active early in development and throughout, while muscle and heart differentiation processes were methylated during later stages of development. Taken together, our findings demonstrate the roles of COMPASS series complex core subunits Set1, Trx, and Trr in regulating histone methylation during heart development and, given their implication in congenital heart diseases, inform research on heart disease.

Clinical and molecular analysis of Guangxi patients with Kabuki syndrome and KMT2D mutations

Kabuki syndrome (KS) is a multiple congenital anomaly syndrome that is characterized by postnatal growth deficiency, hypotonia, short stature, mild-to-moderate intellectual disability, skeletal abnormalities, persistence of fetal fingertip pads, and distinct facial appearance. It is mainly caused by pathogenic/likely pathogenic variants in the KMT2D or KDM6A genes. Here, we described the clinical features of nine sporadic KS patients with considerable phenotypic heterogeneity. In addition to intellectual disability and short stature, our patients presented with a high prevalence of motor retardation and recurrent otitis media. We recommended that KS should be strongly considered in patients with motor delay, short stature, intellectual disability, language disorder and facial deformities. Nine KMT2D variants, four of which were novel, were identified by whole-exome sequencing. The variants included five nonsense variants, two frameshift variants, one missense variant, and one non-canonical splice site variant. In addition, we reviewed the mutation types of the pathogenic KMT2D variants in the ClinVar database. We also indicated that effective mRNA analysis, using biological materials from patients, is helpful in classifying the pathogenicity of atypical splice site variants. Pedigree segregation analysis may also provide valuable information for pathogenicity classification of novel missense variants. These findings extended the mutation spectrum of KMT2D and provided new insights into the understanding of genotype-phenotype correlations, which are helpful for accurate genetic counseling and treatment optimization.

A Comprehensive Review of Management Strategies for Bicuspid Aortic Valve (BAV): Exploring Epidemiology, Aetiology, Aortopathy, and Interventions in Light of Recent Guidelines

OBJECTIVE

bicuspid aortic valve (BAV) stands as the most prevalent congenital heart condition intricately linked to aortic pathologies encompassing aortic regurgitation (AR), aortic stenosis, aortic root dilation, and aortic dissection. The aetiology of BAV is notably intricate, involving a spectrum of genes and polymorphisms. Moreover, BAV lays the groundwork for an array of structural heart and aortic disorders, presenting varying degrees of severity. Establishing a tailored clinical approach amid this diverse range of BAV-related conditions is of utmost significance. In this comprehensive review, we delve into the epidemiology, aetiology, associated ailments, and clinical management of BAV, encompassing imaging to aortic surgery. Our exploration is guided by the perspectives of the aortic team, spanning six distinct guidelines.

METHODS

We conducted an exhaustive search across databases like PubMed, Ovid, Scopus, and Embase to extract relevant studies. Our review incorporates 84 references and integrates insights from six different guidelines to create a comprehensive clinical management section.

RESULTS

BAV presents complexities in its aetiology, with specific polymorphisms and gene disorders observed in groups with elevated BAV prevalence, contributing to increased susceptibility to other cardiovascular conditions. The altered hemodynamics inherent to BAV instigate adverse remodelling of the aorta and heart, thus fostering the development of epigenetically linked aortic and heart diseases. Employing TTE screening for first-degree relatives of BAV patients might be beneficial for disease tracking and enhancing clinical outcomes. While SAVR is the primary recommendation for indicated AVR in BAV, TAVR might be an option for certain patients endorsed by adept aortic teams. In addition, proficient teams can perform aortic valve repair for AR cases. Aortic surgery necessitates personalized evaluation, accounting for genetic makeup and risk factors. While the standard aortic replacement threshold stands at 55 mm, it may be tailored to 50 mm or even 45 mm based on patient-specific considerations.

CONCLUSION

This review reiterates the significance of considering the multifactorial nature of BAV as well as the need for further research to be carried out in the field.

Chromatin regulators in the TBX1 network confer risk for conotruncal heart defects in 22q11.2DS

Congenital heart disease (CHD) affecting the conotruncal region of the heart, occurs in 40-50% of patients with 22q11.2 deletion syndrome (22q11.2DS). This syndrome is a rare disorder with relative genetic homogeneity that can facilitate identification of genetic modifiers. Haploinsufficiency of TBX1, encoding a T-box transcription factor, is one of the main genes responsible for the etiology of the syndrome. We suggest that genetic modifiers of conotruncal defects in patients with 22q11.2DS may be in the TBX1 gene network. To identify genetic modifiers, we analyzed rare, predicted damaging variants in whole genome sequence of 456 cases with conotruncal defects and 537 controls, with 22q11.2DS. We then performed gene set approaches and identified chromatin regulatory genes as modifiers. Chromatin genes with recurrent damaging variants include EP400, KAT6A, KMT2C, KMT2D, NSD1, CHD7 and PHF21A. In total, we identified 37 chromatin regulatory genes, that may increase risk for conotruncal heart defects in 8.5% of 22q11.2DS cases. Many of these genes were identified as risk factors for sporadic CHD in the general population. These genes are co-expressed in cardiac progenitor cells with TBX1, suggesting that they may be in the same genetic network. The genes KAT6A, KMT2C, CHD7 and EZH2, have been previously shown to genetically interact with TBX1 in mouse models. Our findings indicate that disturbance of chromatin regulatory genes impact the TBX1 gene network serving as genetic modifiers of 22q11.2DS and sporadic CHD, suggesting that there are some shared mechanisms involving the TBX1 gene network in the etiology of CHD.

The Roles of Histone Lysine Methyltransferases in Heart Development and Disease

Epigenetic marks regulate the transcriptomic landscape by facilitating the structural packing and unwinding of the genome, which is tightly folded inside the nucleus. Lysine-specific histone methylation is one such mark. It plays crucial roles during development, including in cell fate decisions, in tissue patterning, and in regulating cellular metabolic processes. It has also been associated with varying human developmental disorders. Heart disease has been linked to deregulated histone lysine methylation, and lysine-specific methyltransferases (KMTs) are overrepresented, i.e., more numerous than expected by chance, among the genes with variants associated with congenital heart disease. This review outlines the available evidence to support a role for individual KMTs in heart development and/or disease, including genetic associations in patients and supporting cell culture and animal model studies. It concludes with new advances in the field and new opportunities for treatment.

Insights into the perinatal phenotype of Kabuki syndrome in infants identified by genome-wide sequencing

Increasing use of unbiased genomic sequencing in critically ill infants can expand understanding of rare diseases such as Kabuki syndrome (KS). Infants diagnosed with KS through genome-wide sequencing performed during the initial hospitalization underwent retrospective review of medical records. Human phenotype ontology terms used in genomic analysis were aggregated and analyzed. Clinicians were surveyed regarding changes in management and other care changes. Fifteen infants met inclusion criteria. KS was not suspected prior to genomic sequencing. Variants were classified as Pathogenic (n = 10) or Likely Pathogenic (n = 5) by American College of Medical Genetics and Genomics Guidelines. Fourteen variants were de novo (KMT2D, n = 12, KDM6A, n = 2). One infant inherited a likely pathogenic variant in KMT2D from an affected father. Frequent findings involved cardiovascular (14/15) and renal (7/15) systems, with palatal defects also identified (6/15). Three infants had non-immune hydrops. No minor anomalies were universally documented; ear anomalies, micrognathia, redundant nuchal skin, and hypoplastic nails were common. Changes in management were reported in 14 infants. Early use of unbiased genome-wide sequencing enabled a molecular diagnosis prior to clinical recognition including infants with atypical or rarely reported features of KS while also expanding the phenotypic spectrum of this rare disorder.

Insights into the genotype-phenotype relationship of ocular manifestations in Kabuki syndrome

We aim to assess if genotype-phenotype correlations are present within ocular manifestations of Kabuki syndrome (KS) among a large multicenter cohort. We conducted a retrospective, medical record review including clinical history and comprehensive ophthalmological examinations of a total of 47 individuals with molecularly confirmed KS and ocular manifestations at Boston Children's Hospital and Cincinnati Children's Hospital Medical Center. We assessed information regarding ocular structural, functional, and adnexal elements as well as pertinent associated phenotypic features associated with KS. For both type 1 KS (KS1) and type 2 KS (KS2), we observed more severe eye pathology in nonsense variants towards the C-terminus of each gene, KMT2D and KDM6A, respectively. Furthermore, frameshift variants appeared to be not associated with structural ocular elements. Between both types of KS, ocular structural elements were more frequently identified in KS1 compared with KS2, which only involved the optic disc in our cohort. These results reinforce the need for a comprehensive ophthalmologic exam upon diagnosis of KS and regular follow-up exams. The specific genotype may allow risk stratification of the severity of the ophthalmologic manifestation. However, additional studies involving larger cohorts are needed to replicate our observations and conduct powered analyses to more formally risk-stratify based on genotype, highlighting the importance of multicenter collaborations in rare disease research.

Congenital aortic valve stenosis: from pathophysiology to molecular genetics and the need for novel therapeutics

Congenital aortic valve stenosis (AVS) is one of the most common valve anomalies and accounts for 3%-6% of cardiac malformations. As congenital AVS is often progressive, many patients, both children and adults, require transcatheter or surgical intervention throughout their lives. While the mechanisms of degenerative aortic valve disease in the adult population are partially described, the pathophysiology of adult AVS is different from congenital AVS in children as epigenetic and environmental risk factors play a significant role in manifestations of aortic valve disease in adults. Despite increased understanding of genetic basis of congenital aortic valve disease such as bicuspid aortic valve, the etiology and underlying mechanisms of congenital AVS in infants and children remain unknown. Herein, we review the pathophysiology of congenitally stenotic aortic valves and their natural history and disease course along with current management strategies. With the rapid expansion of knowledge of genetic origins of congenital heart defects, we also summarize the literature on the genetic contributors to congenital AVS. Further, this increased molecular understanding has led to the expansion of animal models with congenital aortic valve anomalies. Finally, we discuss the potential to develop novel therapeutics for congenital AVS that expand on integration of these molecular and genetic advances.

KMT2A‐D pathogenicity, prevalence, and variation according to a population database

INTRODUCTION

The KMT2 family of genes is essential epigenetic regulators promoting gene expression. The gene family contains three subgroups, each with two paralogues: KMT2A and KMT2B; KMT2C and KMT2D; KMT2F and KMT2G. KMT2A-D are among the most frequent somatically altered genes in several different cancer types. Somatic KMT2A rearrangements are well-characterized in infant leukemia (IL), and growing evidence supports the role of additional family members (KMT2B, KMT2C, and KMT2D) in leukemogenesis. Enrichment of rare heterozygous frameshift variants in KMT2A and C has been reported in acute myeloid leukemia (AML), IL, and solid tumors. Currently, the non-synonymous variation, prevalence, and penetrance of these four genes are unknown.

METHODS

This study determined the prevalence of pathogenic/likely pathogenic (P/LP) germline KMT2A-D variants in a cancer-free adult population from the Genome Aggregation Database (gnomAD). Two methods of variant interpretation were utilized: a manual genomic variant interpretation and an automated ACMG pipeline.

RESULTS

The ACMG pipeline identified considerably fewer P/LP variants (n = 89) compared to the manual method (n = 660) in all 4 genes. Consequently, the total P/LP prevalence and allele frequency (AF) were higher in the manual method (1:112, AF = 4.46E-03) than in ACMG (1:832, AF = 6.01E-04). Multiple ancestry-exclusive P/LP variants were identified along with an increased frequency in males compared to females. Many of these variants identified in this population database are also associated with severe juvenile conditions.

CONCLUSION

These data demonstrate that putatively functional germline variation in these developmentally important genes is more common than previously appreciated and identification in cancer-free adults may indicate incomplete penetrance for many of these variants. Future research should examine a genetic predisposing role in IL and other pediatric cancers.

Systems analysis of de novo mutations in congenital heart diseases identified a protein network in the hypoplastic left heart syndrome

Despite a strong genetic component, only a few genes have been identified in congenital heart diseases (CHDs). We introduced systems analyses to uncover the hidden organization on biological networks of mutations in CHDs and leveraged network analysis to integrate the protein interactome, patient exomes, and single-cell transcriptomes of the developing heart. We identified a CHD network regulating heart development and observed that a sub-network also regulates fetal brain development, thereby providing mechanistic insights into the clinical comorbidities between CHDs and neurodevelopmental conditions. At a small scale, we experimentally verified uncharacterized cardiac functions of several proteins. At a global scale, our study revealed developmental dynamics of the network and observed its association with the hypoplastic left heart syndrome (HLHS), which was further supported by the dysregulation of the network in HLHS endothelial cells. Overall, our work identified previously uncharacterized CHD factors and provided a generalizable framework applicable to studying many other complex diseases. A record of this paper's Transparent Peer Review process is included in the supplemental information.

From Genotype to Phenotype-A Review of Kabuki Syndrome

Kabuki syndrome (KS) is a rare neuro-developmental disorder caused by variants in genes of histone modification, including KMT2D and KDM6A. This review assesses our current understanding of KS, which was originally named Niikawa-Kuroki syndrome, and aims to guide surveillance and medical care of affected individuals as well as identify gaps in knowledge and unmet patient needs. Ovid MEDLINE and EMBASE databases were searched from 1981 to 2021 to identify reports related to genotype and systems-based phenotype characterization of KS. A total of 2418 articles were retrieved, and 152 were included in this review, representing a total of 1369 individuals with KS. Genotype, phenotype, and the developmental and behavioral profile of KS are reviewed. There is a continuous clinical phenotype spectrum associated with KS with notable variability between affected individuals and an emerging genotype-phenotype correlation. The observed clinical variability may be attributable to differences in genotypes and/or unknown genetic and epigenetic factors. Clinical management is symptom oriented, fragmented, and lacks established clinical care standards. Additional research should focus on enhancing understanding of the burden of illness, the impact on quality of life, the adult phenotype, life expectancy and development of standard-of-care guidelines.

Histone methyltransferase KMT2D contributes to the protection of myocardial ischemic injury

Histone H3 lysine 4 (H3K4) methyltransferase 2D (KMT2D) plays an important role in cell development in early life. However, the function of KMT2D in adult cells such as cardiomyocytes or neurons has not been reported. In this study, cardiomyocyte-specific KMT2D knockout (KMT2D-cKO) and control (KMT2D-Ctl) mice were exposed to sham or myocardial ischemia (MI) surgery. Depletion of KMT2D aggravated the ischemic area, led to the increased mortality (26.5% in KMT2D-cKO vs 12.5% in KMT2D-Ctl) of the mice, and weakened the left ventricular systolic function. RNA-seq analysis in cardiac tissues identified genes whose expression was changed by MI and KMT2D deletion. Combined with the genome-wide association study (GWAS) analysis, cardiac disease-associated genes Rasd1, Thsd7a, Ednra, and Tns1 were identified. The expression of the Rasd1 was significantly decreased by MI or the loss of KMT2D in vivo. Meanwhile, ChIP assays demonstrated that either MI or loss of KMT2D attenuated monomethylated H3K4 (H3K4me1) enrichment on the enhancer of Rasd1. By generating a KMT2D knockout (H9C2-KO) H9C2 monoclone, we verified that the expression of Rasd1 was controlled by KMT2D, and the expression of Rasd1 was decreased by serum starvation but not low-(O₂) treatment in H9C2 cells. KMT2D has a protective effect on ischemic myocardium by regulating cardiac disease-associated genes including Rasd1. KMT2D is required for the H3K4me1 deposition on the enhancer of Rasd1. Our data for the first time suggest that KMT2D-mediated Rasd1 expression may play an important protective effect on adult cells during nutritional deficiency caused by ischemic injury.

Genome-wide DNA methylation profiling confirms a case of low-level mosaic Kabuki syndrome 1

Kabuki syndrome is a Mendelian disorder of the epigenetic machinery characterized by typical dysmorphic features, intellectual disability, and postnatal growth deficiency. Pathogenic variants in the genes encoding the chromatin modifiers KMT2D and KDM6A are responsible for Kabuki syndrome 1 (KS1) and Kabuki syndrome 2 (KS2), respectively. In addition, 11 cases of KS1 caused by mosaic variants in KMT2D have been reported in the literature. Some of these individuals display milder craniofacial and growth phenotypes, and most do not have congenital heart defects. We report the case of an infant with severe hypoplastic left heart syndrome with mitral atresia and aortic atresia (HLHS MA-AA), pulmonary vein stenosis, and atypical facies with a somatic mosaic de novo nonsense variant in KMT2D (c.8200C>T, p.R2734*) identified on trio exome sequencing of peripheral blood and present in 11.2% of sequencing reads. KS was confirmed with EpiSign, a diagnostic genome-wide DNA methylation platform used to identify epigenetic signatures. This case suggests that use of this newly available clinical test can guide the interpretation of low-level mosaic variants identified through sequencing and suggests a new lower limit of mosaicism in whole blood required for a diagnosis of KS.

Epigenetics in Congenital Heart Disease

Embryonic heart development is an intricate process that mainly involves morphogens, transcription factors, and cardiac genes. The precise spatiotemporal expression of these genes during different developmental stages underlies normal heart development. Thus, mutation or aberrant expression of these genes may lead to congenital heart disease (CHD). However, evidence demonstrates that the mutation of genes accounts for only a small portion of CHD cases, whereas the aberrant expression regulated by epigenetic modification plays a predominant role in the pathogenesis of CHD. In this review, we provide essential knowledge on the aberrant epigenetic modification involved in the pathogenesis of CHD. Then, we discuss recent advances in the identification of novel epigenetic biomarkers. Last, we highlight the epigenetic roles in some adverse intrauterine environment‐related CHD, which may help the prevention, diagnosis, and treatment of these kinds of CHD.

Case Report: An Infant With Kabuki Syndrome, Alobar Holoprosencephaly and Truncus Arteriosus: A Case for Whole Exome Sequencing in Neonates With Congenital Anomalies

Kabuki syndrome is a rare multiple anomalies syndrome associated with mutations in KMT2D or KDM6A. It is characterized by infantile hypotonia, developmental delay and/or intellectual disability, long palpebral fissures with everted lateral third of the lower eyelids and typical facial features. Intracranial anomalies occur infrequently in patients with KS and holoprosencephaly has only been recently described. Additionally, though congenital heart diseases are common in patients with KS, to our knowledge truncus arteriosus has never been reported in a patient with KS. We present an unusual case of KS in an infant with holoprosencephaly and truncus arteriosus with partial anomalous pulmonary venous return. Duo whole exome sequencing in our patient identified a pathogenic nonsense variant in exon 10 of KMT2D (c.2782C > T; p. Gln928*) establishing the diagnosis. This report further expands the phenotypic spectrum of patients with Kabuki syndrome and emphasizes the utility of performing large scale sequencing in neonates with multiple congenital anomalies.

Aortic coarctation with cardiac fibroma in a young patient: a case report

Background

Cardiac fibroma and aortic coarctation are rarely observed concomitantly in the same patient. We report a case of cardiac fibroma with aortic coarctation treated with a hybrid surgical procedure. To the best of our knowledge, this is the first case of these two abnormalities existing in one patient.

Case summary

A 22-year-old female patient visited the clinic with a 10-year history of hypertension. Physical examination revealed blood pressure of the upper extremities 50 mmHg higher than that of the lower extremities. Computed tomography angiography revealed a post-ductal-type aortic coarctation at the beginning segment of the descending aorta along with a 7.7 cm × 5.1 cm left ventricular mass. Transthoracic echocardiogram showed a mass at the middle segments of the lateral wall and apex and posterior wall of the left ventricle. Cardiac magnetic resonance imaging also showed the mass with hypointense signal on T1, hyperintense signal on T2, and intense signal on late gadolinium enhancement. No evidences of metastatic lesions were observed on ¹⁸F-fluorodeoxyglucose positron emission tomography. The patient underwent a hybrid surgery involving aortic stent implantation and complete left ventricular mass removal. The gradient between stenosis returned to <10 mmHg after the procedure. Pathologic findings revealed cardiac fibroma.

Discussion

It is rare to encounter a patient suffering from both cardiac fibroma and aortic coarctation. No evidences indicated a single cause or syndrome resulting in the coexistence of these two abnormalities. A hybrid surgery involving aortic stent implantation and complete cardiac mass resection could optimize the treatment in such cases.

Integrative analysis of genomic variants reveals new associations of candidate haploinsufficient genes with congenital heart disease

Numerous genetic studies have established a role for rare genomic variants in Congenital Heart Disease (CHD) at the copy number variation (CNV) and de novo variant (DNV) level. To identify novel haploinsufficient CHD disease genes, we performed an integrative analysis of CNVs and DNVs identified in probands with CHD including cases with sporadic thoracic aortic aneurysm. We assembled CNV data from 7,958 cases and 14,082 controls and performed a gene-wise analysis of the burden of rare genomic deletions in cases versus controls. In addition, we performed variation rate testing for DNVs identified in 2,489 parent-offspring trios. Our analysis revealed 21 genes which were significantly affected by rare CNVs and/or DNVs in probands. Fourteen of these genes have previously been associated with CHD while the remaining genes (FEZ1, MYO16, ARID1B, NALCN, WAC, KDM5B and WHSC1) have only been associated in small cases series or show new associations with CHD. In addition, a systems level analysis revealed affected protein-protein interaction networks involved in Notch signaling pathway, heart morphogenesis, DNA repair and cilia/centrosome function. Taken together, this approach highlights the importance of re-analyzing existing datasets to strengthen disease association and identify novel disease genes and pathways.

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.

Short Stature Syndromes: Case Series from India

Syndromes causing short stature include Noonan syndrome (NS), Williams syndrome, and Silver–Russell syndrome (SRS). SRS is a primordial dwarfism with genetic heterogeneity. The SRS children present with prenatal growth retardation, neonatal hypoglycemia, feeding difficulties, physical asymmetry, with scoliosis and cardiac defect in some cases. The incidence is up to 1 in 100,000. Uniparental disomy, methylation abnormalities, and variants in some genes have been found underlying such phenotype. Growth hormone therapy has been used to improve the height gain in these patients. NS has genetic heterogeneity and most patients present with short stature with or without cardiac defect. Multiple genetic variants, mostly autosomal dominant, contribute to the phenotype. With the availability of next-generation sequencing, more and more genetic disorders causing short stature are being identified in different ethnic populations like Kabuki syndrome and Nance–Horan syndrome. Here, we present some cases of SRS and other additional syndromes with dysmorphism seen in past 5 years.

Kabuki Syndrome-Clinical Review with Molecular Aspects

Kabuki syndrome (KS) is a rare developmental disorder principally comprised of developmental delay, hypotonia and a clearly defined dysmorphism: elongation of the structures surrounding the eyes, a shortened and depressed nose, thinning of the upper lip and thickening of the lower lip, large and prominent ears, hypertrichosis and scoliosis. Other characteristics include poor physical growth, cardiac, gastrointestinal and renal anomalies as well as variable behavioral issues, including autistic features. De novo or inherited pathogenic/likely pathogenic variants in the KMT2D gene are the most common cause of KS and account for up to 75% of patients. Variants in KDM6A cause up to 5% of cases (X-linked dominant inheritance), while the etiology of about 20% of cases remains unknown. Current KS diagnostic criteria include hypotonia during infancy, developmental delay and/or intellectual disability, typical dysmorphism and confirmed pathogenic/likely pathogenic variant in KMT2D or KDM6A. Care for KS patients includes the control of physical and psychomotor development during childhood, rehabilitation and multi-specialist care. This paper reviews the current clinical knowledge, provides molecular and scientific links and sheds light on the treatment of Kabuki syndrome individuals.

COngenital heart disease and the Diagnostic yield with Exome sequencing (CODE) study: prospective cohort study and systematic review

OBJECTIVE

To determine the incremental yield of antenatal exome sequencing (ES) over chromosomal microarray analysis (CMA) or conventional karyotyping in prenatally diagnosed congenital heart disease (CHD).

METHODS

A prospective cohort study of 197 trios undergoing ES following CMA or karyotyping owing to CHD identified prenatally and a systematic review of the literature were performed. MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov (January 2000 to October 2019) databases were searched electronically for studies reporting on the diagnostic yield of ES in prenatally diagnosed CHD. Selected studies included those with more than three cases, with initiation of testing based upon prenatal phenotype only and that included cases in which CMA or karyotyping was negative. The incremental diagnostic yield of ES was assessed in: (1) all cases of CHD; (2) isolated CHD; (3) CHD associated with extracardiac anomaly (ECA); and (4) CHD according to phenotypic subgroup.

RESULTS

In our cohort, ES had an additional diagnostic yield in all CHD, isolated CHD and CHD associated with ECA of 12.7% (25/197), 11.5% (14/122) and 14.7% (11/75), respectively (P = 0.81). The corresponding pooled incremental yields from 18 studies (encompassing 636 CHD cases) included in the systematic review were 21% (95% CI, 15-27%), 11% (95% CI, 7-15%) and 37% (95% CI, 18-56%), respectively. The results did not differ significantly when subanalysis was limited to studies including more than 20 cases, except for CHD associated with ECA, in which the incremental yield was greater (49% (95% CI, 17-80%)). In cases of CHD associated with ECA in the primary analysis, the most common extracardiac anomalies associated with a pathogenic variant were those affecting the genitourinary system (23/52 (44.2%)). The greatest incremental yield was in cardiac shunt lesions (41% (95% CI, 19-63%)), followed by right-sided lesions (26% (95% CI, 9-43%)). In the majority (68/96 (70.8%)) of instances, pathogenic variants occurred de novo and in autosomal dominant (monoallelic) disease genes. The most common (19/96 (19.8%)) monogenic syndrome identified was Kabuki syndrome.

CONCLUSIONS

There is an apparent incremental yield of prenatal ES in CHD. While the greatest yield is in CHD associated with ECA, consideration could also be given to performing ES in the presence of an isolated cardiac abnormality. A policy of routine application of ES would require the adoption of robust bioinformatic, clinical and ethical pathways. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Using Xenopus to analyze neurocristopathies like Kabuki syndrome

Neurocristopathies are human congenital syndromes that arise from defects in neural crest (NC) development and are typically associated with malformations of the craniofacial skeleton. Genetic analyses have been very successful in identifying pathogenic mutations, however, model organisms are required to characterize how these mutations affect embryonic development thereby leading to complex clinical conditions. The African clawed frog Xenopus laevis provides a broad range of in vivo and in vitro tools allowing for a detailed characterization of NC development. Due to the conserved nature of craniofacial morphogenesis in vertebrates, Xenopus is an efficient and versatile system to dissect the morphological and cellular phenotypes as well as the signaling events leading to NC defects. Here, we review a set of techniques and resources how Xenopus can be used as a disease model to investigate the pathogenesis of Kabuki syndrome and neurocristopathies in a wider sense.

Transcriptome Analysis Reveals High Similarities between Adult Human Cardiac Stem Cells and Neural Crest-Derived Stem Cells

For the identification of a stem cell population, the comparison of transcriptome data enables the simultaneous analysis of tens of thousands of molecular markers and thus enables the precise distinction of even closely related populations. Here, we utilized global gene expression profiling to compare two adult human stem cell populations, namely neural crest-derived inferior turbinate stem cells (ITSCs) of the nasal cavity and human cardiac stem cells (hCSCs) from the heart auricle. We detected high similarities between the transcriptomes of both stem cell populations, particularly including a range of neural crest-associated genes. However, global gene expression likewise reflected differences between the stem cell populations with regard to their niches of origin. In a broader analysis, we further identified clear similarities between ITSCs, hCSCs and other adherent stem cell populations compared to non-adherent hematopoietic progenitor cells. In summary, our observations reveal high similarities between adult human cardiac stem cells and neural crest-derived stem cells from the nasal cavity, which include a shared relation to the neural crest. The analyses provided here may help to understand underlying molecular regulators determining differences between adult human stem cell populations.

The entangled relationship between cilia and actin

Primary cilia are microtubule-based sensory cell organelles that are vital for tissue and organ development. They act as an antenna, receiving and transducing signals, enabling communication between cells. Defects in ciliogenesis result in severe genetic disorders collectively termed ciliopathies. In recent years, the importance of the direct and indirect involvement of actin regulators in ciliogenesis came into focus as it was shown that F-actin polymerisation impacts ciliation. The ciliary basal body was further identified as both a microtubule and actin organising centre. In the current review, we summarize recent studies on F-actin in and around primary cilia, focusing on different actin regulators and their effect on ciliogenesis, from the initial steps of basal body positioning and regulation of ciliary assembly and disassembly. Since primary cilia are also involved in several intracellular signalling pathways such as planar cell polarity (PCP), subsequently affecting actin rearrangements, the multiple effectors of this pathway are highlighted in more detail with a focus on the feedback loops connecting actin networks and cilia proteins. Finally, we elucidate the role of actin regulators in the development of ciliopathy symptoms and cancer.

Neonatal hyperinsulinemic hypoglycemia: case report of kabuki syndrome due to a novel KMT2D splicing-site mutation

Background

Persistent neonatal hypoglycemia, owing to the possibility of severe neurodevelopmental consequences, is a leading cause of neonatal care admission. Hyperinsulinemic hypoglycemia is often resistant to dextrose infusion and needs rapid diagnosis and treatment. Several congenital conditions, from single gene defects to genetic syndromes should be considered in the diagnostic approach. Kabuki syndrome type 1 (MIM# 147920) and Kabuki syndrome type 2 (MIM# 300867), can be associated with neonatal hyperinsulinemic hypoglycemia.

Patient presentation

We report a female Italian (Sicilian) child, born preterm at 35 weeks gestation, with persistent hypoglycemia. Peculiar facial dysmorphisms, neonatal hypotonia, and cerebellar vermis hypoplasia raised suspicion of Kabuki syndrome. Hyperinsulinemic hypoglycemia was confirmed with glucagon test and whole-exome sequencing (WES) found a novel heterozygous splicing-site mutation (c.674-1G > A) in KMT2D gene. Hyperinsulinemic hypoglycemia was successfully treated with diazoxide. At 3 months corrected age for prematurity, a mild global neurodevelopmental delay, postnatal weight and occipitofrontal circumference growth failure were reported.

Conclusions

Kabuki syndrome should be considered when facing neonatal persistent hypoglycemia. Diazoxide may help to improve hyperinsulinemic hypoglycemia. A multidisciplinary and individualized follow-up should be carried out for early diagnosis and treatment of severe pathological associated conditions.

De Novo KMT2D Heterozygous Frameshift Deletion in a Newborn with a Congenital Heart Anomaly

Kabuki syndrome (KS) is characterized by typical facial features and patients are also affected by multiple congenital anomalies, of which congenital heart anomalies (CHAs) are present in 28.0 to 80.0%. In approximately 75.0% of patients, the genetic causes of KS are caused by mutation in the KMT2D gene. Although KS is a well-characterized syndrome, reaching the diagnosis in neonates is still challenging. Namely, newborns usually display mild facial features; therefore the diagnosis is mainly based on congenital malformations. In our case, a newborn was referred for next generation sequencing (NGS) testing due to the prenatally observed CHA. After birth, a ventricular septal defect (VSD), vesicoureteral reflux, muscular hypotonia, cleft palate, mild microcephaly, and some dysmorphic features, were noted. The NGS analysis was performed on the proband’s genomic DNA using the TruSight One Sequencing Panel, which enriches exons of 4813 genes with clinical relevance to the disease. After variant calling, NGS data analysis was predominantly focused on rare variants in genes involved in VSD, microcephaly, and muscular hypotonia; features observed predominantly in our proband. With the aforementioned protocol, we were able to determine the previously unreported de novo frameshift deletion in the KMT2D gene resulting in translation termination. Although our proband is a typical representative of KS, his diagnosis was reached only after NGS analysis. Our proband thus represents the importance of genotypephenotype driven NGS analysis in diagnosis of patients with congenital anomalies.

Update of the genotype and phenotype of KMT2D and KDM6A by genetic screening of 100 patients with clinically suspected Kabuki syndrome

Kabuki syndrome is characterized by a variable degree of intellectual disability, characteristic facial features, and complications in various organs. Many variants have been identified in two causative genes, that is, lysine methyltransferase 2D (KMT2D) and lysine demethylase 6A (KDM6A). In this study, we present the results of genetic screening of 100 patients with a suspected diagnosis of Kabuki syndrome in our center from July 2010 to June 2018. We identified 76 variants (43 novel) in KMT2D and 4 variants (3 novel) in KDM6A as pathogenic or likely pathogenic. Rare variants included a deep splicing variant (c.14000-8C>G) confirmed by RNA sequencing and an 18% mosaicism level for a KMT2D mutation. We also characterized a case with a blended phenotype consisting of Kabuki syndrome, osteogenesis imperfecta, and 16p13.11 microdeletion. We summarized the clinical phenotypes of 44 patients including a patient who developed cervical cancer of unknown origin at 16 years of age. This study presents important details of patients with Kabuki syndrome including rare clinical cases and expands our genetic understanding of this syndrome, which will help clinicians and researchers better manage and understand patients with Kabuki syndrome they may encounter.

Contribution of single-gene defects to congenital cardiac left-sided lesions in the prenatal setting

OBJECTIVES

To explore the contribution of single-gene defects to the genetic cause of cardiac left-sided lesions (LSLs), and to evaluate the incremental diagnostic yield of whole-exome sequencing (WES) for single-gene defects in fetuses with LSLs without aneuploidy or a pathogenic copy-number variant (pCNV).

METHODS

Between 10 April 2015 and 30 October 2018, we recruited 80 pregnant women diagnosed with a LSL who had termination of pregnancy and genetic testing. Eligible LSLs were aortic valve atresia or stenosis, coarctation of the aorta, mitral atresia or stenosis and hypoplastic left heart syndrome (HLHS). CNV sequencing (CNV-seq) and WES were performed sequentially on specimens from these fetuses and their parents. CNV-seq was used to identify aneuploidies and pCNVs, while WES was used to identify diagnostic genetic variants in cases without aneuploidy or pCNV.

RESULTS

Of 80 pregnancies included in the study, 27 (33.8%) had a genetic diagnosis. CNV-seq analysis identified six (7.5%) fetuses with aneuploidy and eight (10.0%) with pCNVs. WES analysis of the remaining 66 cases revealed diagnostic genetic variants in 13 (19.7%) cases, indicating that the diagnostic yield of WES for the entire cohort was 16.3% (13/80). KMT2D was the most frequently mutated gene (7/66 (10.6%)) in fetuses with LSL without aneuploidy or pCNVs, followed by NOTCH1 (4/66 (6.1%)). HLHS was the most prevalent cardiac phenotype (4/7) in cases with a KMT2D mutation in this cohort. An additional six (9.1%) cases were found to have potentially deleterious variants in candidate genes.

CONCLUSIONS

Single-gene defects contribute substantially to the genetic etiology of fetal LSLs. KMT2D mutations accounted for approximately 10% of LSLs in our fetal cohort. WES has the potential to provide genetic diagnoses in fetuses with LSLs without aneuploidy or pCNVs. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Genetics in bicuspid aortic valve disease: Where are we?

Bicuspid aortic valve (BAV) is the most common congenital heart defect, found in up to 2% of the population and associated with a 30% lifetime risk of complications. BAV is inherited as an autosomal dominant trait with incomplete penetrance and variable expressivity due to a complex genetic architecture that involves many interacting genes. In this review, we highlight the current state of knowledge about BAV genetics, principles and methods for BAV gene discovery, clinical applications of BAV genetics, and important future directions.

Comorbidity of congenital heart defects and holoprosencephaly is likely genetically driven and gene-specific

Comorbidity of holoprosencephaly (HPE) and congenital heart disease (CHD) in individuals with genetic variants in known HPE-related genes has been recurrently observed. Morphogenesis of the brain and heart from very early stages are regulated by several biological pathways, some of them involved in both heart and brain development as evidenced by genetic studies on model organisms. For instance, downregulation of Hedgehog or Nodal signaling pathways, both known as major triggers of HPE, has been shown to play a role in the pathogenesis of CHD, including structural defects and left-right asymmetry defects. In this study, individuals with various types of HPE were investigated clinically and by genomic sequencing. Cardiac phenotypes were assessed in 434 individuals with HPE who underwent targeted sequencing. CHDs were identified in 8% (n = 33) of individuals, including 10 (30%) cases of complex heart disease. Only four individuals (4/33) had damaging variants in the known HPE genes STAG2, SIX3, and SHH. Interestingly, no CHD was identified in the 37 individuals of our cohort with pathogenic variants in ZIC2. These findings suggest that CHD occurs more frequently in HPE-affected individuals with or without identifiable genetic variants, and this co-occurrence may be genetically driven and gene-specific.

Next-generation sequencing in prenatal setting: Some examples of unexpected variant association

The application of next-generation sequencing to fetal pathology has proved to increase the diagnostic yield in fetuses with abnormal ultrasounds. We retrospectively reviewed genetic data of 30 selected cases studied through targeted resequencing of OMIM genes. In our experience, clinical data proved to be essential to support diagnostic reasoning and enhance variants' assessment. The molecular diagnosis was reached in 19/30 (63%) cases. Only in 7/19 cases the molecular diagnosis confirmed the initial diagnostic hypothesis, showing the relevance of the genotype-first approach. According to the genotype-phenotype correlation, we were able to divide the solved cases into three groups: i) the correlation is well established but it was missed due to lack of specificity, unusual presentation or recent description; ii) the clinical presentation is much more severe than currently known for the underlying condition; iii) the correlation does not recapitulate the entire phenotype, possibly due to the fetal presentation or multiple coexisting conditions. Moreover, we found a higher proportion of recessive diagnosis in abnormal fetuses compared to cohorts of individuals with developmental delay. Our findings suggest that fetal pathology may be enriched in rare alleles and/or in unusual combinations, counter-selected in postnatal genomes and thus contributing to both phenotypic extremeness and atypical presentation.

Tumor-infiltrating lymphocyte-derived MLL2 independently predicts disease-free survival for patients with early-stage oral squamous cell carcinoma

BACKGROUND

MLL2 (mixed-lineage leukemia 2) is recognized as an essential role in regulating histone 3 lysine 4 tri-methylation (H3K4me3) in mammalian cells. It is frequently mutated to promote developmental diseases and tumor initiation. However, the expression pattern of MLL2 and its clinical significance for patients with early-stage oral squamous cell carcinoma (OSCC) remain totally unknown.

METHODS

Eighty-five samples of primary early-stage OSCC were enrolled in this retrospective study, and immunohistochemistry (IHC) was performed to detect the spatial pattern of MLL2. The diagnostic and prognostic value of MLL2 were assessed.

RESULTS

MLL2 was widely expressed in tumor cells (TCs), fibroblast-like cells (FLCs), and tumor-infiltrating lymphocytes (TILs), both in tumor center and invasive tumor front, and showed no distributive heterogeneity. Moreover, regardless of cell types and microlocalization, patients with high expressed MLL2 had increased depth invasion of tumor (DOI). Besides, upregulation of MLL2^TC and MLL2^TIL in tumor center were both associated with poor differentiation, but showed no correlation with tumor growth with comparable Ki-67 levels. Prognostic analysis indicated that early-stage OSCC patients with enhanced MLL2^TIL in invasive tumor front were susceptible to occur postoperative metastasis and recurrence. Indeed, patients with higher expressed MLL2^TIL showed shorter overall survival (OS) and disease-free survival (DFS), and MLL2^TIL in invasive tumor front was an independent risk factor of DFS.

CONCLUSION

TIL-derived MLL2 in invasive tumor front was an independent prognostic factor of DFS for early-stage OSCC patients.

Kabuki syndrome: novel pathogenic variants, new phenotypes and review of literature

Objective

This study describes 5 novel variants of 7 KMT2D/KDM6A gene and summarizes the clinical manifestations and the mutational spectrum of 47 Chinese Kabuki syndrome (KS) patients.

Methods

Blood samples were collected for whole-exome sequencing (WES) for 7 patients and their parents if available. Phenotypic and genotypic spectra of 40 previously published unrelated Chinese KS patients were summarized.

Result

Genetic sequencing identified six KMT2D variants (c.3926delC, c.5845delC, c.6595delT, c.12630delG, c.16294C > T, and c.16442delG) and one KDM6A variant (c.2668-2671del). Of them, 4 variants (c.3926delC, c.5845delC, c.12630delG, and c.16442delG) in KMT2D gene and the variant (c.2668-2671del) in KDM6A gene were novel. Combining with previously published Chinese KS cases, the patients presented with five cardinal manifestations including facial dysmorphism, intellectual disability, growth retardation, fingertip pads and skeletal abnormalities. In addition, 29.5% (5/17) patients had brain abnormalities, such as hydrocephalus, cerebellar vermis dysplasia, thin pituitary and white matter myelination delay, corpus callosum hypoplasia and Dandy-Walker malformation.

Conclusion

In this report, five novel variants in KMT2D/KDM6A genes are described. A subset of Chinese KS patients presented with brain abnormalities that were not previously reported. Our study expands the mutational and phenotypic spectra of KS.

Prenatal and perinatal history in Kabuki Syndrome

Kabuki syndrome (KS) is a disorder of epigenetic dysregulation due to heterozygous mutations in KMT2D or KDM6A, genes encoding a lysine-specific methyltransferase or demethylase, respectively. The phenotype is highly variable, including congenital cardiac and renal anomalies, developmental delay, hypotonia, failure to thrive, short stature, and immune dysfunction. All affected individuals have characteristic facial features. As KS natural history has not been fully delineated, limited information exists on its prenatal and perinatal history. Two tertiary centers collected retrospective data from individuals with KS (N = 49) using a questionnaire followed by review of medical records. Data from 49 individuals (age range: 7 months-33 years; 37% male; 36 with KMT2D mutations, 2 with KDM6A mutations, and 11 diagnosed clinically) were examined. Polyhydramnios affected 16 of 39 (41%) pregnancies. Abnormal quad screens in four out of nine (44%) pregnancies and reduced placental weights also complicated KS pregnancies. These data comprise the first large dataset on prenatal and perinatal history in individuals with confirmed (genetically or clinically) KS. Over a third of pregnancies were complicated by polyhydramnios, possibly secondary to abnormal craniofacial structures and functional impairment of swallowing. The differential diagnosis for polyhydramnios in the absence of intrauterine growth retardation should include KS.

Genetic Basis for Congenital Heart Disease: Revisited: A Scientific Statement From the American Heart Association

This review provides an updated summary of the state of our knowledge of the genetic contributions to the pathogenesis of congenital heart disease. Since 2007, when the initial American Heart Association scientific statement on the genetic basis of congenital heart disease was published, new genomic techniques have become widely available that have dramatically changed our understanding of the causes of congenital heart disease and, clinically, have allowed more accurate definition of the pathogeneses of congenital heart disease in patients of all ages and even prenatally. Information is presented on new molecular testing techniques and their application to congenital heart disease, both isolated and associated with other congenital anomalies or syndromes. Recent advances in the understanding of copy number variants, syndromes, RASopathies, and heterotaxy/ciliopathies are provided. Insights into new research with congenital heart disease models, including genetically manipulated animals such as mice, chicks, and zebrafish, as well as human induced pluripotent stem cell-based approaches are provided to allow an understanding of how future research breakthroughs for congenital heart disease are likely to happen. It is anticipated that this review will provide a large range of health care-related personnel, including pediatric cardiologists, pediatricians, adult cardiologists, thoracic surgeons, obstetricians, geneticists, genetic counselors, and other related clinicians, timely information on the genetic aspects of congenital heart disease. The objective is to provide a comprehensive basis for interdisciplinary care for those with congenital heart disease.

Inhibition of Notch signaling rescues cardiovascular development in Kabuki Syndrome

Kabuki Syndrome patients have a spectrum of congenital disorders, including congenital heart defects, the primary determinant of mortality. Seventy percent of Kabuki Syndrome patients have mutations in the histone methyl-transferase KMT2D. However, the underlying mechanisms that drive these congenital disorders are unknown. Here, we generated and characterized zebrafish kmt2d null mutants that recapitulate the cardinal phenotypic features of Kabuki Syndrome, including microcephaly, palate defects, abnormal ear development, and cardiac defects. The cardiac phenotype consists of a previously unknown vasculogenesis defect that affects endocardium patterning and, consequently, heart ventricle lumen formation. Additionally, zebrafish kmt2d null mutants have angiogenesis defects depicted by abnormal aortic arch development, hyperactive ectopic blood vessel sprouting, and aberrant patterning of the brain vascular plexus. We demonstrate that zebrafish kmt2d null mutants have robust Notch signaling hyperactivation in endocardial and endothelial cells, including increased protein levels of the Notch transcription factor Rbpj. Our zebrafish Kabuki Syndrome model reveals a regulatory link between the Notch pathway and Kmt2d during endothelium and endocardium patterning and shows that pharmacological inhibition of Notch signaling rebalances Rbpj protein levels and rescues the cardiovascular phenotype by enhancing endothelial and endocardial cell proliferation and stabilizing endocardial patterning. Taken together, these findings demonstrate that Kmt2d regulates vasculogenesis and angiogenesis, provide evidence for interactions between Kmt2d and Notch signaling in Kabuki Syndrome, and suggest future directions for clinical research.

Novel heterozygous variants in KMT2D associated with holoprosencephaly

Lysine methyltransferase 2D (KMT2D; OMIM 602113) encodes a histone methyltransferase involved in transcriptional regulation of the beta-globin and estrogen receptor as part of a large protein complex known as activating signal cointegrator-2-containing complex (ASCOM). Heterozygous germline mutations in the KMT2D gene are known to cause Kabuki syndrome (OMIM 147920), a developmental multisystem disorder. Neither holoprosencephaly nor other defects in human forebrain development have been previously associated with Kabuki syndrome. Here we report two patients diagnosed with alobar holoprosencephaly in their antenatal period with de novo monoallelic KMT2D variants identified by trio-based exome sequencing. The first patient was found to have a stop-gain variant c.12565G>T (p.Gly4189*), while the second patient had a missense variant c.5A>G (p.Asp2Gly). Phenotyping of each patient did not reveal any age-related feature of Kabuki syndrome. These two cases represent the first report on association between KMT2D and holoprosencephaly.

Mixed-lineage leukemia protein 2 suppresses ciliary assembly by the modulation of actin dynamics and vesicle transport

Primary cilia are critically involved in the coordination of diverse signaling pathways and ciliary defects are associated with a variety of human diseases. The past decades have witnessed great progress in the core machinery orchestrating ciliary assembly. However, the upstream epigenetic cues that direct ciliogenesis remain elusive. Herein, we demonstrate that mixed-lineage leukemia protein 2 (MLL2), a histone methyltransferase, plays a negative role in ciliogenesis. RNA-sequencing analysis reveals that the expression of five actin-associated proteins is significantly downregulated in MLL2-depleted cells. Overexpression of these proteins partially rescues ciliary abnormality elicited by MLL2 depletion. Our data also show that actin dynamics is remarkably changed in MLL2-depleted cells, resulting in the impairment of cell adhesion, spreading, and motility. In addition, MLL2 depletion promotes ciliary vesicle trafficking to the basal body in an actin-related manner. Together, these results reveal that MLL2 inhibits ciliogenesis by modulating actin dynamics and vesicle transport, and suggest that alteration of MLL2 may contribute to the pathogenesis of cilium-associated diseases.

Development and evolution of the metazoan heart

The mechanisms of the evolution and development of the heart in metazoans are highlighted, starting with the evolutionary origin of the contractile cell, supposedly the precursor of cardiomyocytes. The last eukaryotic common ancestor is likely a combination of several cellular organisms containing their specific metabolic pathways and genetic signaling networks. During evolution, these tool kits diversified. Shared parts of these conserved tool kits act in the development and functioning of pumping hearts and open or closed circulations in such diverse species as arthropods, mollusks, and chordates. The genetic tool kits became more complex by gene duplications, addition of epigenetic modifications, influence of environmental factors, incorporation of viral genomes, cardiac changes necessitated by air‐breathing, and many others. We evaluate mechanisms involved in mollusks in the formation of three separate hearts and in arthropods in the formation of a tubular heart. A tubular heart is also present in embryonic stages of chordates, providing the septated four‐chambered heart, in birds and mammals passing through stages with first and second heart fields. The four‐chambered heart permits the formation of high‐pressure systemic and low‐pressure pulmonary circulation in birds and mammals, allowing for high metabolic rates and maintenance of body temperature. Crocodiles also have a (nearly) separated circulation, but their resting temperature conforms with the environment. We argue that endothermic ancestors lost the capacity to elevate their body temperature during evolution, resulting in ectothermic modern crocodilians. Finally, a clinically relevant paragraph reviews the occurrence of congenital cardiac malformations in humans as derailments of signaling pathways during embryonic development.

The cardiac regulatory toolkit contains many factors including epigenetic, genetic, viral, hemodynamic, and environmental factors, but also transcriptional activators, repressors, duplicated genes, redundancies and dose‐dependancies.

Numerous toolkits regulate mechanisms including cell‐cell interactions, EMT, mitosis patterns, cell migration and differentiation and left/right sidedness involved in the development of endocardial cushions, looping, septum complexes, pharyngeal arch arteries, chamber and valve formation and conduction system.

Evolutionary development of the yolk sac circulation likely preceded the advent of endothermy in amniotes.

Parallel evolutionary traits regulate the development of contractile pumps in various taxa often in conjunction with the gut, lungs and excretory organs.

Loss of function of Kmt2d, a gene mutated in Kabuki syndrome, affects heart development in Xenopus laevis

BACKGROUND

Kabuki syndrome is a haploinsufficient congenital multi-organ malformation syndrome, which frequently includes severe heart defects. Mutations in the histone H3K4 methyltransferase KMT2D have been identified as the main cause of Kabuki syndrome, however, the role of KMT2D in heart development remains to be characterized.

RESULTS

Here we analyze the function of Kmt2d at different stages of Xenopus heart development. Xenopus Kmt2d is ubiquitously expressed at early stages of cardiogenesis, with enrichment in the anterior region including the cardiac precursor cells. Morpholino-mediated knockdown of Kmt2d led to hypoplastic hearts lacking the three-chambered structure. Analyzing different stages of cardiogenesis revealed that development of the first and second heart fields as well as cardiac differentiation were severely affected by loss of Kmt2d function.

CONCLUSION

Kmt2d loss of function in Xenopus recapitulates the hypoplastic heart defects observed in Kabuki syndrome patients and shows that Kmt2d function is required for the establishment of the primary and secondary heart fields. Thus, Xenopus Kmt2d morphants can be a valuable tool to elucidate the etiology of the congenital heart defects associated with Kabuki syndrome.

Kabuki syndrome: international consensus diagnostic criteria

BACKGROUND

Kabuki syndrome (KS) is a clinically recognisable syndrome in which 70% of patients have a pathogenic variant in KMT2D or KDM6A. Understanding the function of these genes opens the door to targeted therapies. The purpose of this report is to propose diagnostic criteria for KS, particularly when molecular genetic testing is equivocal.

METHODS

An international group of experts created consensus diagnostic criteria for KS. Systematic PubMed searches returned 70 peer-reviewed publications in which at least one individual with molecularly confirmed KS was reported. The clinical features of individuals with known mutations were reviewed.

RESULTS

The authors propose that a definitive diagnosis can be made in an individual of any age with a history of infantile hypotonia, developmental delay and/or intellectual disability, and one or both of the following major criteria: (1) a pathogenic or likely pathogenic variant in KMT2D or KDM6A; and (2) typical dysmorphic features (defined below) at some point of life. Typical dysmorphic features include long palpebral fissures with eversion of the lateral third of the lower eyelid and two or more of the following: (1) arched and broad eyebrows with the lateral third displaying notching or sparseness; (2) short columella with depressed nasal tip; (3) large, prominent or cupped ears; and (4) persistent fingertip pads. Further criteria for a probable and possible diagnosis, including a table of suggestive clinical features, are presented.

CONCLUSION

As targeted therapies for KS are being developed, it is important to be able to make the correct diagnosis, either with or without molecular genetic confirmation.