Analysis of Ellis van Creveld syndrome gene products: implications for cardiovascular development and disease

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

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

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

Although cardiac abnormalities have been observed in a growing class of human disorders caused by defective primary cilia, the function of cilia in the heart remains an underexplored area. The primary function of cilia in the heart was long thought to be restricted to left-right axis patterning during embryogenesis. However, new findings have revealed broad roles for cilia in congenital heart disease, valvulogenesis, myocardial fibrosis and regeneration, and mechanosensation. In this Review, we describe advances in our understanding of the mechanisms by which cilia function contributes to cardiac left-right axis development and discuss the latest findings that highlight a broader role for cilia in cardiac development. Specifically, we examine the growing line of evidence connecting cilia function to the pathogenesis of congenital heart disease. Furthermore, we also highlight research from the past 10 years demonstrating the role of cilia function in common cardiac valve disorders, including mitral valve prolapse and aortic valve disease, and describe findings that implicate cardiac cilia in mechanosensation potentially linking haemodynamic and contractile forces with genetic regulation of cardiac development and function. Finally, given the presence of cilia on cardiac fibroblasts, we also explore the potential role of cilia in fibrotic growth and summarize the evidence implicating cardiac cilia in heart regeneration.

Cardiac Defects and Genetic Syndromes: Old Uncertainties and New Insights

Recent advances in understanding the genetic causes and anatomic subtypes of cardiac defects have revealed new links between genetic etiology, pathogenetic mechanisms and cardiac phenotypes. Although the same genetic background can result in different cardiac phenotypes, and similar phenotypes can be caused by different genetic causes, researchers’ effort to identify specific genotype–phenotype correlations remains crucial. In this review, we report on recent advances in the cardiac pathogenesis of three genetic diseases: Down syndrome, del22q11.2 deletion syndrome and Ellis–Van Creveld syndrome. In these conditions, the frequent and specific association with congenital heart defects and the recent characterization of the underlying molecular events contributing to pathogenesis provide significant examples of genotype–phenotype correlations. Defining these correlations is expected to improve diagnosis and patient stratification, and it has relevant implications for patient management and potential therapeutic options.

Genetic and epigenetic mechanisms in the development of congenital heart diseases

Congenital heart disease (CHD) is the most common of congenital cardiovascular malformations associated with birth defects, and it results in significant morbidity and mortality worldwide. The classification of CHD is still elusive owing to the complex pathogenesis of CHD. Advances in molecular medicine have revealed the genetic basis of some heart anomalies. Genes associated with CHD might be modulated by various epigenetic factors. Thus, the genetic and epigenetic factors are gradually accepted as important triggers in the pathogenesis of CHD. However, few literatures have comprehensively elaborated the genetic and epigenetic mechanisms of CHD. This review focuses on the etiology of CHD from genetics and epigenetics to discuss the role of these factors in the development of CHD. The interactions between genetic and epigenetic in the pathogenesis of CHD are also elaborated. Chromosome abnormalities and gene mutations in genetics, and DNA methylations, histone modifications and on-coding RNAs in epigenetics are summarized in detail. We hope the summative knowledge of these etiologies may be useful for improved diagnosis and further elucidation of CHD so that morbidity and mortality of children with CHD can be reduced in the near future.

Isolated hexadactylia: A rare case of central polydactyly of the foot

BACKGROUND

Central polydactyly of foot is uncommon form of polydactyly but it usually causes intermetatarsal widening because of metatarsal bifurcation. Central polydactyly associated with T shaped bifurcation of metatarsal in vertical plane has not been reported yet.

CASE

We present a 4 year male child with extra toe on the dorsal aspect of right foot with complains of difficulty in wearing footwear and poor cosmesis. The extra digit was fully developed with bifurcation of 2^nd metatarsal bone proximal to the head without any intermetatarsal widening. The angular deviation was 45° to the longitudinal axis of foot and in a plane vertical to the transverse arch of foot. The child was operated with excision of extra toe without any residual bony deformity.

CONCLUSION

The central polydactyly is rare type of polydactyly of foot. Central polydactyly with metatarsal extension causing intermetatarsal widening has been well described entity. But the previous classifications need to be modified to include central polydactyly with vertical oriented T bifurcation of metatarsal bone without intermetatarsal widening.

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.

Molecular mechanisms of Ellis‑van Creveld gene variations in ventricular septal defect

The Ellis-van Creveld (EVC) gene is associated with various congenital heart diseases. However, studies on EVC gene variations in ventricular septal defect (VSD) and the underlying molecular mechanisms are sparse. The present study detected 11 single-nucleotide polymorphisms (SNPs) in 65 patients with VSD and 210 control patients from the Chinese Han population. Of the identified SNPs only the c.1727G>A SNP site was positively associated with the development of VSD (P<0.007). A known mutation, c.343C>G, was also identified, which causes a leucine to valine substitution at amino acid 115 of the EVC protein (p.L115V). The results of functional prediction indicated that c.343C>G may be a pathogenic mutation. In addition, in NIH3T3 mouse embryonic fibroblast cells, the EVC c.343C>G mutation significantly decreased cell proliferation and increased apoptosis. Further investigation demonstrated that in NIH3T3 cells, overexpression of EVC c.343C>G mutation reduced the binding between EVC and smoothened, which further downregulated the activity of the hedgehog (Hh) signaling pathway and the expression of downstream cyclin D1 and B-cell lymphoma 2 proteins with SAG. The c.1727G>A SNP of the EVC gene increased VSD susceptibility in patients from the Chinese Han population. The molecular mechanism underlying the development of VSD induced by the EVC c.343C>G mutation may be due to a reduction in the anti-apoptotic and proliferative abilities of cardiomyocytes via downregulation of Hh pathway activity. The results of the present study may provide novel targets for the diagnosis and treatment of patients with VSD.

The Role of Hedgehog Signalling in the Formation of the Ventricular Septum

An incomplete septation of the ventricles in the vertebrate heart that disturbes the strict separation between the contents of the two ventricles is termed a ventricular septal defect (VSD). Together with bicuspid aortic valves, it is the most frequent congenital heart disease in humans. Until now, life-threatening VSDs are usually treated surgically. To avoid surgery and to develop an alternative therapy (e.g., a small molecule therapy), it is necessary to understand the molecular mechanisms underlying ventricular septum (VS) development. Consequently, various studies focus on the investigation of signalling pathways, which play essential roles in the formation of the VS. In the past decade, several reports found evidence for an involvement of Hedgehog (HH) signalling in VS development. In this review article, we will summarise the current knowledge about the association between HH signalling and VS formation and discuss the use of such knowledge to design treatment strategies against the development of VSDs.

Management of Congenital Heart Disease Associated with Ellis-van Creveld Short-rib Thoracic Dysplasia

OBJECTIVE

To evaluate clinical outcome of patients with Ellis-van Creveld syndrome (EVC) in whom congenital heart disease (CHD) repair was delayed intentionally to reduce the risk of postoperative respiratory morbidity and mortality.

STUDY DESIGN

This retrospective review of 51 EVC c.1886+5G>T homozygotes born between 2005 and 2014 focused on 18 subjects who underwent surgery for CHD, subdivided into early (mean, 1.3 months) vs delayed (mean, 50.1 months) repair.

RESULTS

Growth trajectories differed between control subjects and patients with EVC, and CHD was associated with slower weight gain. Relative to controls, infants with EVC had a 40%-75% higher respiratory rates (independent of CHD) accompanied by signs of compensated respiratory acidosis. Blood gases and respiratory rates approached normal values by age 4 years. Hemodynamically significant CHD was present in 23 children, 18 (78%) of whom underwent surgical repair. Surgery was performed at 1.3 ± 1.3 months for children born between 2005 and 2009 (n = 9) and 50.1 ± 40.2 months (P = .009) for children born between 2010 and 2014 (n = 9). The latter had shorter postoperative mechanical ventilation (1.1 ± 2.4 days vs 49.6 ± 57.1 days; P = .075), shorter intensive care duration of stay (16 ± 24 days vs 48.6 ± 44.2 days; P = .155), and no postoperative tracheostomies (vs 60%; P = .028) or deaths (vs 44%; P = .082).

CONCLUSION

Among children with EVC and possibly other short-rib thoracic dysplasias, delayed surgical repair of CHD reduces postoperative morbidity and improves survival. Respiratory rate serves as a simple indicator for optimal timing of surgical repair.

Truncation and microdeletion of EVC/EVC2 with missense mutation of EFCAB7 in Ellis-van Creveld syndrome

Ellis-van Creveld syndrome (EvC) is a ciliopathy with cardiac anomalies, disproportionate short stature, polydactyly, dystrophic nails and oral defects. To obtain further insight into the genetics of EvC, we screened EVC/EVC2 mutations in eight Vietnamese EvC patients. All the patients had a congenital heart defect with atypical oral and/or skeletal abnormalities. One had compound heterozygous EVC2 mutations: a novel mutation c.769G > T-p.E177X in exon 6 inherited from father and another previously reported c.2476C > T-p.R826X mutation in exon 14 inherited from mother. The EVC2 mRNA expression level was significantly lower in the patient and her parents compared to controls. Another case had a novel heterozygous EVC mutation (c.1717C > G-p.S572X) in exon 12, inherited from his father. Of note, the mother without any EVC mutation on Sanger sequencing showed a lower expression level of EVC mRNA compared with controls. SNP array analysis revealed that the patient and mother had a heterozygous 16.4 kb deletion in EVC. This patient also had a heterozygous novel variant in exon 9 of EFCAB7 (c.1171 T > C-p.Y391H), inherited from his father. The atypical cardiac phenotype of this patient and the father suggested that EFCAB7 may modify the phenotype by interacting with EVC. In conclusion, we detected two novel nonsense mutations and a partial deletion of EVC/EVC2 in two Vietnamese families with EvC. Moreover, we found in one family a missense mutation of EFCAB7, a possible modifier gene in EvC and its related disorders.

Cilia gene mutations cause atrioventricular septal defects by multiple mechanisms

Atrioventricular septal defects (AVSDs) are a common severe form of congenital heart disease (CHD). In this study we identified deleterious non-synonymous mutations in two cilia genes, Dnah11 and Mks1, in independent N-ethyl-N-nitrosourea-induced mouse mutant lines with heritable recessive AVSDs by whole-exome sequencing. Cilia are required for left/right body axis determination and second heart field (SHF) Hedgehog (Hh) signaling, and we find that cilia mutations affect these requirements differentially. Dnah11^avc4 did not disrupt SHF Hh signaling and caused AVSDs only concurrently with heterotaxy, a left/right axis abnormality. In contrast, Mks1^avc6 disrupted SHF Hh signaling and caused AVSDs without heterotaxy. We performed unbiased whole-genome SHF transcriptional profiling and found that cilia motility genes were not expressed in the SHF whereas cilia structural and signaling genes were highly expressed. SHF cilia gene expression predicted the phenotypic concordance between AVSDs and heterotaxy in mice and humans with cilia gene mutations. A two-step model of cilia action accurately predicted the AVSD/heterotaxyu phenotypic expression pattern caused by cilia gene mutations. We speculate that cilia gene mutations contribute to both syndromic and non-syndromic AVSDs in humans and provide a model that predicts the phenotypic consequences of specific cilia gene mutations.

Meiotic and pedigree segregation analyses in carriers of t(4;8)(p16;p23.1) differing in localization of breakpoint positions at 4p subband 4p16.3 and 4p16.1

PURPOSE

The purpose of this study was to compare meiotic segregation in sperm cells from two carriers with t(4;8)(p16;p23.1) reciprocal chromosome translocations (RCTs), differing in localization of the breakpoint positions at the 4p subband-namely, 4p16.3 (carrier 1) and 4p16.1 (carrier 2)-and to compare data of the pedigree analyses performed by direct method.

METHODS

Three-color fluorescent in situ hybridization (FISH) on sperm cells and FISH mapping for the evaluation of the breakpoint positions, data from pedigrees, and direct segregation analysis of the pedigrees were performed.

RESULTS

Similar proportions of normal/balanced and unbalanced sperm cells were found in both carriers. The most common was an alternate type of segregation (about 52 % and about 48 %, respectively). Unbalanced adjacent I and adjacent II karyotypes were found in similar proportions about 15 %. The direct segregation analysis (following Stengel-Rutkowski) of the pedigree of carriers of t(4;8)(p16.1;p23.1) was performed and results were compared with the data of the pedigree segregation analysis obtained earlier through the indirect method. The probability of live-born progeny with unbalanced karyotype for carriers of t(4;8)(p16.1;p23.1) was moderately high at 18.8 %-comparable to the value obtained using the indirect method for the same carriership, which was 12 %. This was, however, markedly lower than the value of 41.2 % obtained through the pedigree segregation indirect analysis estimated for carriers of t(4;8)(p16.3;p23.1), perhaps due to the unique composition of genes present within the 4p16.1-4p 16.3 region.

CONCLUSIONS

Revealed differences in pedigree segregation analysis did not correspond to the very similar profile of meiotic segregation patterns presented by carrier 1 and carrier 2. Most probably, such discordances may be due to differences in embryo survival rates arising from different genetic backgrounds.

Novel mutations in EVC cause aberrant splicing in Ellis-van Creveld syndrome

Ellis-van Creveld syndrome (EvC) is a rare autosomal recessive disorder characterized by disproportionate chondrodysplasia, postaxial polydactyly, nail dystrophy, dental abnormalities and in a proportion of patients, congenital cardiac malformations. Weyers acrofacial dysostosis (Weyers) is another dominantly inherited disorder allelic to EvC syndrome but with milder phenotypes. Both disorders can result from loss-of-function mutations in either EVC or EVC2 gene, and phenotypes associated with the two gene mutations are clinically indistinguishable. We present here a clinical and molecular analysis of a Chinese family manifested specific features of EvC syndrome. Sequencing of both EVC and EVC2 identified two novel heterozygous splice site mutations c.384+5G>C in intron 3 and c.1465-1G>A in intron 10 in EVC, which were inherited from mother and father, respectively. In vitro minigene expression assay, RT-PCR and sequencing analysis demonstrated that c.384+5G>C mutation abolished normal splice site and created a new cryptic acceptor site within exon 4, whereas c.1465-1G>A mutation affected consensus splice junction site and resulted in full exon 11 skipping. These two aberrant pre-mRNA splicing processes both produced in-frame abnormal transcripts that possibly led to abolishment of important functional domains. To our knowledge, this is the first report of EVC mutations that cause EvC syndrome in Chinese population. Our data revealed that EVC splice site mutations altered splicing pattern and helped elucidate the pathogenesis of EvC syndrome.

Ellis van Creveld syndrome in a Tunisian child revealed by an Eisenmenger syndrome

Ellis-van Creveld syndrome (EvC) is an autosomal recessive inherited disease resulting from mutations in EVC1 or EVC2. Patients with this condition normally have chondrodysplasia, postaxial polydactyly, ectodermal dysplasia and congenital heart defects. We report the case of a 13-year-old Tunisian child who was admitted for cyanosis and acute heart failure. On clinical examination, he presented with typical features of EvC, cyanosis and dyspnea. EvC was confirmed by genetic tests, and echocardiography showed a partial atrioventricular canal defect with supra-systemic pulmonary artery pressure. The patient was treated; however, the evolution was fatal.

Ellis–van Creveld Syndrome in Grey Alpine Cattle

Ellis–van Creveld (EvC) syndrome is a human autosomal recessive disorder caused by a mutation in either the EVC or EVC2 gene, and presents with short limbs, polydactyly, and ectodermal and heart defects. The aim of this study was to understand the pathologic basis by which deletions in the EVC2 gene lead to chondrodysplastic dwarfism and to describe the morphologic, immunohistochemical, and molecular hallmarks of EvC syndrome in cattle. Five Grey Alpine calves, with a known mutation in the EVC2 gene, were autopsied. Immunohistochemistry was performed on bone using antibodies to collagen II, collagen X, sonic hedgehog, fibroblast growth factor 2, and Ki67. Reverse transcription polymerase chain reaction was performed to analyze EVC1 and EVC2 gene expression. Autopsy revealed long bones that were severely reduced in length, as well as genital and heart defects. Collagen II was detected in control calves in the resting, proliferative, and hypertrophic zones and in the primary and secondary spongiosa, with a loss of labeling in the resting zone of 2 dwarfs. Collagen X was expressed in hypertrophic zone in the controls but was absent in the EvC cases. In affected calves and controls, sonic hedgehog labeled hypertrophic chondrocytes and primary and secondary spongiosa similarly. FGF2 was expressed in chondrocytes of all growth plate zones in the control calves but was lost in most EvC cases. The Ki67 index was lower in cases compared with controls. EVC and EVC2 transcripts were detected. Our data suggest that EvC syndrome of Grey Alpine cattle is a disorder of chondrocyte differentiation, with accelerated differentiation and premature hypertrophy of chondrocytes, and could be a spontaneous model for the equivalent human disease.

Morphogenesis and molecular considerations on congenital cardiac septal defects

The primary unseptated heart tube undergoes extensive remodeling including septation at the atrial, atrioventricular, ventricular, and ventriculo-arterial level. Alignment and fusion of the septal components is required to ensure full septation of the heart. Deficiencies lead to septal defects at various levels. Addition of myocardium and mesenchymal tissues from the second heart field (SHF) to the primary heart tube, as well as a population of neural crest cells, provides the necessary cellular players. Surprisingly, the study of the molecular background of these defects does not show a great diversity of responsible transcription factors and downstream gene pathways. Epigenetic modulation and mutations high up in several transcription factor pathways (e.g. NODAL and GATA4) may lead to defects at all levels. Disturbance of modulating pathways, involving primarily the SHF-derived cell populations and the genes expressed therein, results at the arterial pole (e.g. TBX1) in a spectrum of ventricular septal defects located at the level of the outflow tract. At the venous pole (e.g. TBX5), it can explain a variety of atrial septal defects. The various defects can occur as isolated anomalies or within families. In this review developmental, morphological, genetic, as well as epigenetic aspects of septal defects are discussed.

Rare autosomal copy number variations in early-onset familial Alzheimer's disease

Over 200 rare and fully penetrant pathogenic mutations in amyloid precursor protein (APP), presenilin 1 and 2 (PSEN1 and PSEN2) cause a subset of early-onset familial Alzheimer's disease (EO-FAD). Of these, 21 cases of EO-FAD families carrying unique APP locus duplications remain the only pathogenic copy number variations (CNVs) identified to date in Alzheimer's disease (AD). Using high-density DNA microarrays, we performed a comprehensive genome-wide analysis for the presence of rare CNVs in 261 EO-FAD and early/mixed-onset pedigrees. Our analysis revealed 10 novel private CNVs in 10 EO-FAD families overlapping a set of genes that includes: A2BP1, ABAT, CDH2, CRMP1, DMRT1, EPHA5, EPHA6, ERMP1, EVC, EVC2, FLJ35024 and VLDLR. In addition, CNVs encompassing two known frontotemporal dementia genes, CHMP2B and MAPT were found. To our knowledge, this is the first study reporting rare gene-rich CNVs in EO-FAD and early/mixed-onset AD that are likely to underlie pathogenicity in familial AD and perhaps related dementias.

Deletion in the EVC2 gene causes chondrodysplastic dwarfism in Tyrolean Grey cattle

During the summer of 2013 seven Italian Tyrolean Grey calves were born with abnormally short limbs. Detailed clinical and pathological examination revealed similarities to chondrodysplastic dwarfism. Pedigree analysis showed a common founder, assuming autosomal monogenic recessive transmission of the defective allele. A positional cloning approach combining genome wide association and homozygosity mapping identified a single 1.6 Mb genomic region on BTA 6 that was associated with the disease. Whole genome re-sequencing of an affected calf revealed a single candidate causal mutation in the Ellis van Creveld syndrome 2 (EVC2) gene. This gene is known to be associated with chondrodysplastic dwarfism in Japanese Brown cattle, and dwarfism, abnormal nails and teeth, and dysostosis in humans with Ellis-van Creveld syndrome. Sanger sequencing confirmed the presence of a 2 bp deletion in exon 19 (c.2993_2994ACdel) that led to a premature stop codon in the coding sequence of bovine EVC2, and was concordant with the recessive pattern of inheritance in affected and carrier animals. This loss of function mutation confirms the important role of EVC2 in bone development. Genetic testing can now be used to eliminate this form of chondrodysplastic dwarfism from Tyrolean Grey cattle.

Cilia and coordination of signaling networks during heart development

Primary cilia are unique sensory organelles that coordinate a wide variety of different signaling pathways to control cellular processes during development and in tissue homeostasis. Defects in function or assembly of these antenna-like structures are therefore associated with a broad range of developmental disorders and diseases called ciliopathies. Recent studies have indicated a major role of different populations of cilia, including nodal and cardiac primary cilia, in coordinating heart development, and defects in these cilia are associated with congenital heart disease. Here, we present an overview of the role of nodal and cardiac primary cilia in heart development.

First-trimester prenatal diagnosis of Ellis-van Creveld syndrome

OBJECTIVE

To present the perinatal findings and first-trimester molecular and transabdominal ultrasound diagnosis of a fetus with Ellis-van Creveld (EvC) syndrome.

CASE REPORT

A 35-year-old woman was referred for genetic counseling at 13 weeks of gestation because of a family history of skeletal dysplasia. She had experienced one spontaneous abortion, and delivered one male fetus and one female fetus with EvC syndrome. During this pregnancy, a prenatal transabdominal ultrasound at 13(+4) weeks of gestation revealed a nuchal translucency (NT) thickness of 2.0 mm, an endocardial cushion defect, postaxial polydactyly of bilateral hands, and mesomelic dysplasia of the long bones. Amniocentesis was performed at 13(+5) weeks of gestation. Results of a cytogenetic analysis revealed a karyotype of 46,XX and that of a molecular analysis revealed compound heterozygous mutations of c.1195C>T and c.871-2_894del26 in the EVC2 gene. Prenatal ultrasound at 16 weeks of gestation showed a fetus with short limbs, an endocardial cushion defect, and postaxial polydactyly of bilateral hands. The parents decided to terminate the pregnancy, and a 116-g female fetus was delivered with a narrow thorax, shortening limbs, and postaxial polydactyly of the hands.

CONCLUSION

Prenatal diagnosis of an endocardial cushion defect with postaxial polydactyly should include a differential diagnosis of EvC syndrome in addition to short rib-polydactyly syndrome, Bardet-Biedl syndrome, orofaciodigital syndrome, Smith-Lemli-Opitz syndrome, and hydrolethalus syndrome.

Identification of one novel mutation in the EVC2 gene in a Chinese family with Ellis-van Creveld syndrome

Ellis-van Creveld syndrome (EvC) is a rare autosomal recessive skeletal dysplasia characterized by short limbs, short ribs, postaxial polydactyly, and dysplastic nails and teeth. It is caused by biallelic mutations in the EVC or EVC2 gene. Here, we identified a novel nonsense mutation p.W828X (c.2484G>A) in exon 14 and a recurrent nonsense mutation p. R399X (c.1195C>T) in exon 10 of EVC2 gene in a Chinese boy with EvC. Identification of a novel genotype in EvC will provide clues to the phenotype-genotype relations and may assist not only in the clinical diagnosis of EvC but also in the interpretation of genetic information used for prenatal diagnosis and genetic counseling.

Ellis van Creveld syndrome--a report of two siblings

Chondro-ectodermal dysplasia is a rare autosomal recessive disorder which affects the ectodermal, mesodermal and endodermal derivatives. There are numerous conditions reported under this title which include Ellis van Creveld syndrome. The oral findings include multiple gingivolabial frena, dental abnormality, malocclusion and hypodontia. The diagnosis of Ellis van Creveld syndrome is based on the presence of oral mucosal changes like notching of the lower alveolus, fusion of the upper lip and gingival mucosa; dental changes like oligodontia, conical shape of anterior teeth and occasional presence of neonatal teeth. The authors report a rare case of Ellis van Creveld syndrome occurring among two siblings with oral mucosal, dental and skeletal abnormalities.

Ellis-van Creveld syndrome and congenital heart defects: presentation of an additional 32 cases

Ellis-van Creveld (EVC) syndrome is a rare genetic abnormality that has been linked to a mutation in the EVC or EVC2 genes. Common atrium (CA) is an uncommon cardiac malformation, and yet it is commonly found in patients with EVC. We performed a retrospective review of the cases submitted to the Pediatric Cardiac Care Consortium (PCCC) between 1982 and 2007. A review of the English-language literature for previously published cases, as well as current genetic research findings, was also performed. Thirty-two pediatric patients with congenital heart disease (CHD) and EVC syndrome were identified in the PCCC database. Twenty-eight (88%) had an endocardial cushion defect, with 15 of these having primary failure of atrial septation resulting in CA. Persistent left superior vena cava (LSVC) and pulmonary venous connection abnormalities were common. The incidence of persistent LSVC and pulmonary venous abnormalities were greater than previously reported for patients with EVC. Our study reviews the reported literature and adds 32 additional cases from the PCCC database. Review of the cardiac phenotype in patients with EVC syndrome reveals a characteristic pattern of atrioventricular canal defects with systemic and pulmonary venous abnormalities. The frequent association of these abnormalities is strongly reminiscent of the cardiac phenotype found in patients with heterotaxy syndromes. Emerging molecular and developmental studies suggest that EVC and EVC2 proteins may be important for cilia function, which is implicated in the pathogenesis of heterotaxy syndromes. It is speculated that coordinate function between the EVC proteins is required for a cilia-dependent cardiac morphogenesis.

Two novel heterozygous mutations of EVC2 cause a mild phenotype of Ellis-van Creveld syndrome in a Chinese family

Ellis-van Creveld syndrome (EvC, chondroectodermal dysplasia; OMIM 225500) is an autosomal recessive skeletal dysplasia with associated multisystem involvement. The syndrome is characterized by short limbs, short ribs, postaxial polydactyly, dysplastic nails, and abnormal teeth. Congenital heart defects occur in 50-60% of cases. In this study, we report EvC in a 6-year-old Chinese girl with hypodontia and polydactyly, mild short stature, and abnormalities of the knee joints. No signs of short ribs, narrow thorax, or congenital heart defects were found in this patient. The EvC phenotype shares some similarity with Weyers acrofacial dysostosis (Weyer; OMIM 193530), an autosomal dominant disorder clinically characterized by mild short stature, postaxial polydactyly, nail dystrophy, and dysplastic teeth. Mutations in EVC or EVC2 are associated with both EvC syndrome and Weyers acrodental dysostosis, but the two conditions differ in the severity of the phenotype and their pattern of inheritance. In this study, two novel heterozygous EVC2 mutations, IVS5-2A > G and c.2653C > T (Arg885X), were identified in the patient. The IVS5-2A > G mutation was inherited from the patient's mother and the c.2653C > T from her father. Her parents have no phenotypic symptoms similar to those of the patient. These findings extend the mutation spectrum of this malformation syndrome and provide the possibility of prenatal diagnosis for future offspring in this family.

Ellis-van Creveld syndrome: prenatal diagnosis, molecular analysis and genetic counseling

OBJECTIVE

To present the perinatal findings and molecular genetic analysis of two siblings with Ellis-van Creveld (EvC) syndrome.

MATERIALS, METHODS AND RESULTS

A 33-year-old woman, gravida 3, para 1, was referred for genetic counseling at 18 gestational weeks because of recurrent fetal skeletal dysplasia. Two years previously, she had delivered a 1,316-g dead male baby at 28 gestational weeks with a karyotype of 46,XY, postaxial polydactyly of the hands, thoracic narrowness, endocardial cushion defects, transposition of the great arteries, shortening of the long bones, malposition of the toes, and hypoplastic nails. During this pregnancy, prenatal ultrasound at 18 gestational weeks revealed shortening of the long bones (equivalent to 15 weeks), postaxial polydactyly of both hands, thoracic narrowness, and endocardial cushion defects. The pregnancy was subsequently terminated, and a 236-g female fetus was delivered with a karyotype of 46,XX, postaxial polydactyly of the hands, thoracic dysplasia, endocardial cushion defects, shortening of the long bones, and malposition of the toes and hypoplastic nails. The phenotype of each of the two siblings was consistent with EVC syndrome. Molecular analysis of the EVC and EVC2 genes revealed heterozygous mutations in the EVC2 gene. A heterozygous deletion mutation of a 26-bp deletion of c.871-2_894del26 encompassing the junction between intron 7 and exon 8 of the EVC2 gene was found in the mother and two siblings, and a heterozygous nonsense mutation of c.1195C >T, p.R399X in exon 10 of the EVC2 gene was found in the father and two siblings.

CONCLUSION

Prenatal sonographic identification of endocardial cushion defects in association with shortening of the long bones should alert clinicians to the possibility of EvC syndrome and prompt a careful search of hexadactyly of the hands. Molecular analysis of the EVC and EVC2 genes is helpful in genetic counseling in cases with prenatally detected postaxial polydactyly, thoracic narrowness, short limbs and endocardial cushion defects.

Ellis-van Creveld syndrome and Weyers acrodental dysostosis are caused by cilia-mediated diminished response to hedgehog ligands

Ellis-van Creveld syndrome (EvC; OMIM 225500) is a recessive disorder comprising chondrodysplasia, polydactyly, nail dysplasia, orofacial abnormalities and, in a proportion of patients, cardiovascular malformations. Weyers acrodental dysostosis (Weyers; OMIM 193530) is an allelic dominant disorder comprising polydactyly, nail dysplasia, and orofacial abnormalities. EvC results from loss-of-function mutations in EVC or EVC2, the phenotype associated with the mutations in these two genes being indistinguishable. Three convincing causative mutations have been identified in patients with Weyers acrodental dysostosis, which are clustered in the last coding exon of EVC2 and lead to production of a truncated protein lacking the final 43 amino acids. Localization and function of EVC and EVC2 are inferred from studying the murine orthologs. Both Evc and Evc2 proteins localize to the basal bodies of primary cilia and analysis of an Ellis-van Creveld mouse model, which includes the limb shortening and tooth abnormalities of EvC patients, has demonstrated Hedgehog signaling defects in the absence of Evc. The loss of Evc2 has not been studied directly, but Hedgehog signaling is impaired when a mutant murine Evc2 Weyer variant is expressed in vitro. We conclude that the phenotypic abnormalities in EvC and Weyers syndrome result from tissue specific disruption of the response to Hh ligands.