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Gene variants that dysregulate signaling through the RAS-MAPK pathway cause cardiofaciocutaneous syndrome (CFCS), a rare multi-system disorder. Infantile epileptic spasms syndrome (IESS) and other forms of epilepsy are among the most serious complications. To investigate clinical presentation, treatment outcomes, and genotype-phenotype associations in CFCS patients with IESS, molecular genetics and clinical neurological history were reviewed across two large clinical research cohorts (n = 180). IESS presented in 18/180 (10%) cases, including 16 patients with BRAF variants and 2 with MAP2K1 variants. Among IESS patients with BRAF variants, 16/16 (100%) had sequence changes affecting the protein kinase domain (exons 11-16), although only 57% of total BRAF variants occurred in this domain. Clinical onset of spasms occurred at a median age of 5.4 months (range: 1-24 months). Among 13/18 patients whose IESS resolved with anti-seizure medications, 10 were treated with ACTH and/or vigabatrin. A substantial majority of CFCS patients with IESS subsequently developed other epilepsy types (16/18; 89%). In terms of neurodevelopmental outcomes, gross motor function and verbal communication were more limited in patients with a history of IESS compared to those without IESS. These findings can inform clinical neurological care guidelines for CFCS and development of relevant pre-clinical models for severe epilepsy phenotypes.

RASopathies are a group of genetic disorders that are caused by genes that affect the canonical Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Despite tremendous progress in understanding the molecular consequences of these genetic anomalies, little movement has been made in translating these findings to the clinic. This year, the seventh International RASopathies Symposium focused on expanding the research knowledge that we have gained over the years to enhance new discoveries in the field, ones that we hope can lead to effective therapeutic treatments. Indeed, for the first time, research efforts are finally being translated to the clinic, with compassionate use of Ras/MAPK pathway inhibitors for the treatment of RASopathies. This biannual meeting, organized by the RASopathies Network, brought together basic scientists, clinicians, clinician scientists, patients, advocates, and their families, as well as representatives from pharmaceutical companies and the National Institutes of Health. A history of RASopathy gene discovery, identification of new disease genes, and the latest research, both at the bench and in the clinic, were discussed.

Background:HeterozygousTTNtruncating variants cause 10% to 20% of idiopathic dilated cardiomyopathy (DCM). Although variants which disrupt canonical splice signals (ie, invariant dinucleotide of the splice donor site, invariant dinucleotide of the splice acceptor site) at exon-intron junctions are readily recognized asTTNtruncating variants, the effects of other nearby sequence variations on splicing and their contribution to disease is uncertain.Methods:Rare variants of unknown significance located in the splice regions of highly expressedTTNexons from 203 DCM cases, 3329 normal subjects, and clinical variant databases were identified. The effects of these variants on splicing were assessed using an in vitro splice assay.Results:Splice-altering variants of unknown significance were enriched in DCM cases over controls and present in 2% of DCM patients (P=0.002). Application of this method to clinical variant databases demonstrated 20% of similar variants of unknown significance inTTNsplice regions affect splicing. Noncanonical splice-altering variants were most frequently located at position +5 of the donor site (P=4.4×107) and position -3 of the acceptor site (P=0.002). SpliceAI, an emerging in silico prediction tool, had a high positive predictive value (86%–95%) but poor sensitivity (15%–50%) for the detection of splice-altering variants. Alternate exons spliced out of mostTTNtranscripts frequently lacked the consensus base at +5 donor and −3 acceptor positions.Conclusions:Noncanonical splice-altering variants inTTNexplain 1-2% of DCM and offer a 10-20% increase in the diagnostic power ofTTNsequencing in this disease. These data suggest rules that may improve efforts to detect splice-altering variants in other genes and may explain the low percent splicing observed for many alternateTTNexons.

Pulmonary vein stenosis (PVS) is a rare, frequently lethal disease with heterogeneous phenotypes and an unclear etiology. Limited studies have reported associations between PVS and congenital heart disease (CHD), chronic lung disease (CLD), and/or prematurity, however, to date, there have been no studies that report detailed clinical syndromic phenotypes and the potential role of genetics in PVS. An existing registry of multivessel PVS patients seen at Boston Children’s Hospital (BCH) was queried between August 2006 and January 2017 for all existing genetic testing data on these patients. PVS was defined as an intraluminal pulmonary venous obstruction in ≥2 vessels with mean pressure gradients &gt, 4 mmHg. One-hundred-and-fifty-seven patients (46% female, with a median age at PVS diagnosis of 3 months) formed the cohort. Seventy-one (45%) patients had available genetic testing information. Of the 71 patients, a likely genetic diagnosis was found in 23 (32%) patients: 13 (57%) were diagnosed with Trisomy 21 (T21), five (22%) with Smith–Lemli–Opitz Syndrome, five (22%) had other pathologic genetic disease, and 24 (33%) had variants of unknown significance. The majority of 13 patients with T21 and PVS had common atrioventricular canal (CAVC) (10, 77%) and all had severe pulmonary hypertension (PHTN), which led to their PVS diagnosis. In our study, PVS was associated with T21, the majority of whom also had CAVC and PHTN. Therefore, complete assessment of the pulmonary veins should be considered for all T21 patients, especially those with CAVC presenting with PHTN. Furthermore, prospective standardized genetic testing with detailed clinical phenotyping may prove informative about potential genetic etiologies of PVS.

Background Genetic testing in pediatric primary dilated cardiomyopathy (DCM) patients has identified numerous disease‐causing variants, but few studies have evaluated genetic testing outcomes in this population in the context of patient and familial clinical data or assessed the clinical implications of temporal changes in genetic testing results. Methods and Results We performed a retrospective analysis of all patients with primary DCM who presented to our institution between 2008 and 2018. Variants identified by genetic testing were reevaluated for pathogenicity on the basis of current guidelines for variant classification. A total of 73 patients with primary DCM presented to our institution and 63 (86%) were probands that underwent cardiomyopathy‐specific gene testing. A disease‐causing variant was identified in 19 of 63 (30%) of cases, with at least 9/19 (47%) variants occurring de novo. Positive family history was not associated with identification of a causal variant. Reclassification of variants resulted in the downgrading of a large proportion of variants of uncertain significance and did not identify any new disease‐causing variants. Conclusions Clinical genetic testing identifies a causal variant in one third of pediatric patients with primary DCM. Variant reevaluation significantly decreased the number of variants of uncertain significance, but a large burden of variants of uncertain significance remain. These results highlight the need for periodic reanalysis of genetic testing results, additional investigation of genotype‐phenotype correlations in DCM through large, multicenter genetic studies, and development of improved tools for functional characterization of variants of uncertain significance.

PCGF2 encodes the polycomb group ring finger 2 protein, a transcriptional repressor involved in cell proliferation, differentiation, and embryogenesis. PCGF2 is a component of the polycomb repressive complex 1 (PRC1), a multiprotein complex which controls gene silencing through histone modification and chromatin remodelling. We report the phenotypic characterization of 13 patients (11 unrelated individuals and a pair of monozygotic twins) with missense mutations in PCGF2. All the mutations affected the same highly conserved proline in PCGF2 and were de novo, excepting maternal mosaicism in one. The patients demonstrated a recognizable facial gestalt, intellectual disability, feeding problems, impaired growth, and a range of brain, cardiovascular, and skeletal abnormalities. Computer structural modeling suggests the substitutions alter an N-terminal loop of PCGF2 critical for histone biding. Mutant PCGF2 may have dominant-negative effects, sequestering PRC1 components into complexes that lack the ability to interact efficiently with histones. These findings demonstrate the important role of PCGF2 in human development and confirm that heterozygous substitutions of the Pro65 residue of PCGF2 cause a recognizable syndrome characterized by distinctive craniofacial, neurological, cardiovascular, and skeletal features.

Congenital heart disease (CHD) is the leading cause of mortality from birth defects. Here, exome sequencing of a single cohort of 2,871 CHD probands, including 2,645 parent-offspring trios, implicated rare inherited mutations in 1.8%, including a recessive founder mutation in GDF1 accounting for ∼5% of severe CHD in Ashkenazim, recessive genotypes in MYH6 accounting for ∼11% of Shone complex, and dominant FLT4 mutations accounting for 2.3% of Tetralogy of Fallot. De novo mutations (DNMs) accounted for 8% of cases, including ∼3% of isolated CHD patients and ∼28% with both neurodevelopmental and extra-cardiac congenital anomalies. Seven genes surpassed thresholds for genome-wide significance, and 12 genes not previously implicated in CHD had >70% probability of being disease related. DNMs in ∼440 genes were inferred to contribute to CHD. Striking overlap between genes with damaging DNMs in probands with CHD and autism was also found.

The mechanisms underlying de novo insertion/deletion (indel) genesis, such as polymerase slippage, have been hypothesized but not well characterized in the human genome. We implemented two methodological improvements, which were leveraged to dissect indel mutagenesis. We assigned de novo variants to parent-of-origin (i.e., phasing) with low-coverage long-read whole-genome sequencing, achieving better phasing compared to short-read sequencing (medians of 84% and 23%, respectively). We then wrote an application programming interface to classify indels into three subtypes according to sequence context. Across three cohorts with different phasing methods (Ntrios = 540, all cohorts), we observed that one de novo indel subtype, change in copy count (CCC), was significantly correlated with father's (p = 7.1 × 10-4 ) but not mother's (p = .45) age at conception. We replicated this effect in three cohorts without de novo phasing (ppaternal = 1.9 × 10-9 , pmaternal = .61; Ntrios = 3,391, all cohorts). Although this is consistent with polymerase slippage during spermatogenesis, the percentage of variance explained by paternal age was low, and we did not observe an association with replication timing. These results suggest that spermatogenesis-specific events have a minor role in CCC indel mutagenesis, one not observed for other indel subtypes nor for maternal age in general. These results have implications for indel modeling in evolution and disease.

The RASopathies are a group of disorders due to variations of genes associated with the Ras/MAPK pathway. Some of the RASopathies include neurofibromatosis type 1 (NF1), Noonan syndrome, Noonan syndrome with multiple lentigines, cardiofaciocutaneous (CFC) syndrome, Costello syndrome, Legius syndrome, and capillary malformation-arteriovenous malformation (CM-AVM) syndrome. In combination, the RASopathies are a frequent group of genetic disorders. This report summarizes the proceedings of the 4th International Symposium on Genetic Disorders of the Ras/MAPK pathway and highlights gaps in the field. (c) 2016 Wiley Periodicals, Inc.

Truncating mutations in the TTN gene are the most common genetic cause of dilated cardiomyopathy in adults but their role in young patients is unknown. We studied 82 young dilated cardiomyopathy subjects and found that the prevalence of truncating TTN mutations in adolescents was similar to adults, but surprisingly few truncating TTN mutations were identified in affected children, including one confirmed de novo variant. In several cases, truncating TTN mutations in children with dilated cardiomyopathy had evidence of additional clinical or genetic risk factors. These findings have implications for genetic testing and suggest that single truncating TTN mutations are insufficient alone to cause pediatric-onset dilated cardiomyopathy.

Congenital heart disease (CHD) patients have an increased prevalence of extracardiac congenital anomalies (CAs) and risk of neurodevelopmental disabilities (NDDs). Exome sequencing of 1213 CHD parent-offspring trios identified an excess of protein-damaging de novo mutations, especially in genes highly expressed in the developing heart and brain. These mutations accounted for 20% of patients with CHD, NDD, and CA but only 2% of patients with isolated CHD. Mutations altered genes involved in morphogenesis, chromatin modification, and transcriptional regulation, including multiple mutations in RBFOX2, a regulator of mRNA splicing. Genes mutated in other cohorts examined for NDD were enriched in CHD cases, particularly those with coexisting NDD. These findings reveal shared genetic contributions to CHD, NDD, and CA and provide opportunities for improved prognostic assessment and early therapeutic intervention in CHD patients.

The RASopathies are a group of genetic disorders that result from germline pathogenic variants affecting RAS-mitogen activated protein kinase (MAPK) pathway genes. RASopathies share RAS/MAPK pathway dysregulation and share phenotypic manifestations affecting numerous organ systems, causing lifelong and at times life-limiting medical complications. RASopathies may benefit from precision medicine approaches. For this reason, the Sixth International RASopathies Symposium focused on exploring precision medicine. This meeting brought together basic science researchers, clinicians, clinician scientists, patient advocates, and representatives from pharmaceutical companies and the National Institutes of Health. Novel RASopathy genes, variants, and animal models were discussed in the context of medication trials and drug development. Attempts to define and measure meaningful endpoints for treatment trials were discussed, as was drug availability to patients after trial completion. ispartof: AMERICAN JOURNAL OF MEDICAL GENETICS PART A vol:182 issue:3 pages:597-606 ispartof: location:United States status: published

© 2018, American College of Medical Genetics and Genomics. Purpose: We evaluated strategies for identifying disease-causing variants in genetic testing for dilated cardiomyopathy (DCM). Methods: Cardiomyopathy gene panel testing was performed in 532 DCM patients and 527 healthy control subjects. Rare variants in 41 genes were stratified using variant-level and gene-level characteristics. Results: A majority of DCM cases and controls carried rare protein-altering cardiomyopathy gene variants. Variant-level characteristics alone had limited discriminative value. Differentiation between groups was substantially improved by addition of gene-level information that incorporated ranking of genes based on literature evidence for disease association. The odds of DCM were increased to nearly 9-fold for truncating variants or high-impact missense variants in the subset of 14 genes that had the strongest biological links to DCM (P

Cardiomyopathy (CM) in children shares some features with cardiomyopathy in adults but also has many important unique features. Heretofore, genetic testing panels, testing strategies, and treatment recommendations have largely been based on studies in adult populations. In general, CMs in children are much more likely to be genetic and to have extracardiac manifestations that should be medically addressed. Therefore, genetic testing in children with CM is an essential part of their initial evaluation and the ongoing care of the child and family. CMs in children are more genetically heterogeneous, and many of the genes that are rare causes of CM in children are not currently included in testing panels, and future genetic testing is likely to increasingly utilize more comprehensive approaches such as whole exome/whole genome sequencing with focused analysis of all the genes that can cause CM in children.

Aortopathy can be defined as aortic dilation, aneurysm, dissection, and tortuosity. Familial aortopathy may occur secondary to fibrillin-1 (FBN1) mutations in the setting of Marfan syndrome, or may occur as a result of other genetic defects with different, but occasionally overlapping, phenotypes. Because of the phenotypic overlap and genetic heterogeneity of disorders featuring aortopathy, we developed a next generation sequencing (NGS) assay and comparative genomic hybridization (CGH) array to detect mutations in 10 genes that cause thoracic aortic aneurysms (TAAs). Here, we report on the clinical and molecular findings in 175 individuals submitted for aortopathy panel testing at ARUP laboratories. Ten genes associated with heritable aortopathies were targeted using hybridization capture prior to sequencing. NGS results were analyzed, and variants were confirmed using Sanger sequencing. Array CGH was used to detect copy-number variation. Of 175 individuals, 18 had a pathogenic mutation and 32 had a variant of uncertain significance (VUS). Most pathogenic mutations (72%) were identified in FBN1. A novel large SMAD3 duplication and FBN1 deletion were identified. Over half who had TAAs or other aortic involvement tested negative for a mutation, suggesting that additional aortopathy genes exist. We anticipate that the clinical sensitivity of at least 10.3% will rise with VUS reclassification and as additional genes are identified and included in the panel. The aortopathy NGS panel aids in the timely molecular diagnosis of individuals with disorders featuring aortopathy and guides proper treatment.

Noonan syndrome (NS) is a relatively common genetic disorder, characterized by typical facies, short stature, developmental delay, and cardiac abnormalities. Known causative genes account for 70-80% of clinically diagnosed NS patients, but the genetic basis for the remaining 20-30% of cases is unknown. We performed next-generation sequencing on germ-line DNA from 27 NS patients lacking a mutation in the known NS genes. We identified gain-of-function alleles in Ras-like without CAAX 1 (RIT1) and mitogen-activated protein kinase kinase 1 (MAP2K1) and previously unseen loss-of-function variants in RAS p21 protein activator 2 (RASA2) that are likely to cause NS in these patients. Expression of the mutant RASA2, MAP2K1, or RIT1 alleles in heterologous cells increased RAS-ERK pathway activation, supporting a causative role in NS pathogenesis. Two patients had more than one disease-associated variant. Moreover, the diagnosis of an individual initially thought to have NS was revised to neurofibromatosis type 1 based on an NF1 nonsense mutation detected in this patient. Another patient harbored a missense mutation in NF1 that resulted in decreased protein stability and impaired ability to suppress RAS-ERK activation; however, this patient continues to exhibit a NS-like phenotype. In addition, a nonsense mutation in RPS6KA3 was found in one patient initially diagnosed with NS whose diagnosis was later revised to Coffin-Lowry syndrome. Finally, we identified other potential candidates for new NS genes, as well as potential carrier alleles for unrelated syndromes. Taken together, our data suggest that next-generation sequencing can provide a useful adjunct to RASopathy diagnosis and emphasize that the standard clinical categories for RASopathies might not be adequate to describe all patients.

Study of monogenic mitochondrial cardiomyopathies may yield insights into mitochondrial roles in cardiac development and disease. Here, we combined patient-derived and genetically engineered induced pluripotent stem cells (iPSCs) with tissue engineering to elucidate the pathophysiology underlying the cardiomyopathy of Barth syndrome (BTHS), a mitochondrial disorder caused by mutation of the gene encoding tafazzin (TAZ ). Using BTHS iPSC-derived cardiomyocytes (iPSC-CMs), we defined metabolic, structural and functional abnormalities associated with TAZ mutation. BTHS iPSC-CMs assembled sparse and irregular sarcomeres, and engineered BTHS 'heart-on-chip' tissues contracted weakly. Gene replacement and genome editing demonstrated that TAZ mutation is necessary and sufficient for these phenotypes. Sarcomere assembly and myocardial contraction abnormalities occurred in the context of normal whole-cell ATP levels. Excess levels of reactive oxygen species mechanistically linked TAZ mutation to impaired cardiomyocyte function. Our study provides new insights into the pathogenesis of Barth syndrome, suggests new treatment strategies and advances iPSC-based in vitro modeling of cardiomyopathy.

Genetic syndromes resulting from molecular alterations of the RAS-MAPK signaling cascade have become the focus of heightened interest among behavioral scientists due to discoveries that proteins within this pathway play an important role in memory formation and consolidation. Individuals with Noonan syndrome (NS), caused by germline mutations in the RAS-MAPK pathway, exhibit wide variability in cognitive and memory skills. The current study aimed to characterize memory deficits that occur in some affected individuals as a key step toward understanding the neurocognitive effects of dysregulated Ras signaling. Learning and memory skills were assessed among twenty-nine children and adolescents with NS using the Wide Range Assessment of Memory and Learning, Second Edition. Performance across subdomains (verbal memory, visual memory and working memory) was compared, as well as the effect of response type (free recall vs. recognition). For immediate memory, children with NS performed significantly better on verbal memory tasks than on visual memory or working memory tasks. For delayed memory, verbal free recall tasks that depend heavily on prefrontal-hippocampal networks were more challenging than recognition tasks that rely on more distributed temporal cortical regions. Additionally, verbal information presented in context was more easily retained than that presented in a rote format. The current study contributes to our knowledge of the effects of dysregulated RAS-MAPK signaling on the brain and behavior. Continued research on neurocognitive skills in NS has the potential to generate a novel conceptualization of how learning disabilities can arise from altered molecular processes within a specific biological pathway.

© 2016, Springer-Verlag Berlin Heidelberg. The 22q11.2 deletion syndrome (22q11DS; velocardiofacial/DiGeorge syndrome; VCFS/DGS; MIM #192430; 188400) is the most common microdeletion syndrome. The phenotypic presentation of 22q11DS is highly variable; approximately 60–75 % of 22q11DS patients have been reported to have a congenital heart defect (CHD), mostly of the conotruncal type, and/or aortic arch defect. The etiology of the cardiac phenotypic variability is not currently known for the majority of patients. We hypothesized that rare copy number variants (CNVs) outside the 22q11.2 deleted region may modify the risk of being born with a CHD in this sensitized population. Rare CNV analysis was performed using Affymetrix SNP Array 6.0 data from 946 22q11DS subjects with CHDs (n = 607) or with normal cardiac anatomy (n = 339). Although there was no significant difference in the overall burden of rare CNVs, an overabundance of CNVs affecting cardiac-related genes was detected in 22q11DS individuals with CHDs. When the rare CNVs were examined with regard to gene interactions, specific cardiac networks, such as Wnt signaling, appear to be overrepresented in 22q11DS CHD cases but not 22q11DS controls with a normal heart. Collectively, these data suggest that CNVs outside the 22q11.2 region may contain genes that modify risk for CHDs in some 22q11DS patients.

Congenital heart disease (CHD) occurs in ∼1% of newborns. CHD arises from many distinct etiologies, ranging from genetic or genomic variation to exposure to teratogens, which elicit diverse cell and molecular responses during cardiac development. To systematically explore the relationships between CHD risk factors and responses, we compiled and integrated comprehensive datasets from studies of CHD in humans and model organisms. We examined two alternative models of potential functional relationships between genes in these datasets: direct convergence, in which CHD risk factors significantly and directly impact the same genes and molecules and functional convergence, in which risk factors significantly impact different molecules that participate in a discrete heart development network. We observed no evidence for direct convergence. In contrast, we show that CHD risk factors functionally converge in protein networks driving the development of specific anatomical structures (e.g., outflow tract, ventricular septum, and atrial septum) that are malformed by CHD. This integrative analysis of CHD risk factors and responses suggests a complex pattern of functional interactions between genomic variation and environmental exposures that modulate critical biological systems during heart development.

Low copy repeat (LCR) sequences in 17p11.2 predispose this region to genomic deletions and duplications. Duplication of 17p11.2, also known as Potocki-Lupski syndrome (PTLS), is a well-described microduplication syndrome featuring cognitive and language deficits, developmental delay, autistic behavior, structural cardiovascular anomalies, hypotonia, failure to thrive, apnea, and dysmorphism. We present a mother and her two children who share both dysmorphic features and the dup(17)(p11.2p11.2); the first child was born with hypoplastic left heart (HLH). The dup(17)(p11.2p11.2) was identified by GTG-banding analysis of peripheral blood specimens from all three individuals and confirmed by fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH). Here we provide a thorough description of the phenotypes of the affected individuals, as well as describe physical features not reported previously for PTLS.

Cardiofaciocutaneous syndrome (CFC) and Noonan syndrome (NS) are two phenotypically overlapping genetic disorders whose underlying molecular etiologies affect a common signaling pathway. Mutations in the BRAF, MEK1, and MEK2 genes cause most cases of CFC and mutations in PTPN11, SOS1, KRAS, and RAF1 typically cause NS. Although both syndromes are associated with developmental delays of varying severity, the extent to which the behavioral profiles differ may shed light on the different roles these respective genes play in development of skills necessary for everyday functioning. In this study, profiles of adaptive behavior of individuals with CFC and NS who had confirmed pathogenic mutations in Ras/mitogen-activated protein kinase (MAPK) pathway genes were investigated. Patterns of strengths and weaknesses, age-related differences, and risk factors for difficulties in adaptive skills were assessed. Although genes acting more downstream in the Ras/MAPK pathway were associated with more difficulties in adaptive functioning than genes more upstream in the pathway, several inconsistencies highlight the wide spectrum of possible developmental courses in CFC and NS. Along with clinical and genetic factors, variables such as chronological age, gestational age at birth, and parental education levels accounted for significant variance in adaptive skills. Results indicate that there is wide heterogeneity in adaptive functioning in CFC and NS, but that these abilities are correlated to some extent with the specific disease-causing genes.

The Pediatric Cardiac Genomics Consortium (PCGC) designed the Congenital Heart Disease Genetic Network Study to provide phenotype and genotype data for a large congenital heart defects (CHDs) cohort. This article describes the PCGC cohort, overall and by major types of CHDs (e.g., conotruncal defects) and subtypes of conotrucal heart defects (e.g., tetralogy of Fallot) and left ventricular outflow tract obstructions (e.g., hypoplastic left heart syndrome). Cases with CHDs were recruited through ten sites, 2010–2014. Information on cases (N = 9,727) and their parents was collected through interviews and medical record abstraction. Four case characteristics, eleven parental characteristics, and thirteen parent-reported neurodevelopment outcomes were summarized using counts and frequencies and compared across CHD types and subtypes. Eleven percent of cases had a genetic diagnosis. Among cases without a genetic diagnosis, the majority had conotruncal heart defects (40%) or left ventricular outflow tract obstruction (21%). Across CHD types, there were significant differences (p

The RASopathies are a group of genetic syndromes caused by germline mutations in genes that encode components of the Ras/mitogen-activated protein kinase (MAPK) pathway. Some of these syndromes are neurofibromatosis type 1, Noonan syndrome, Costello syndrome, cardio-facio-cutaneous syndrome, LEOPARD syndrome and Legius syndrome. Their common underlying pathogenetic mechanism brings about significant overlap in phenotypic features and includes craniofacial dysmorphology, cardiac, cutaneous, musculoskeletal, GI and ocular abnormalities, and a predisposition to cancer. The proceedings from the symposium “Genetic Syndromes of the Ras/MAPK Pathway: From Bedside to Bench and Back” chronicle the timely and typical research symposium which brought together clinicians, basic scientists, physician-scientists, advocate leaders, trainees, students and individuals with Ras syndromes and their families. The goals, to discuss basic science and clinical issues, to set forth a solid framework for future research, to direct translational applications towards therapy and to set forth best practices for individuals with RASopathies was successfully meet with a commitment to begin to move towards clinical trials.

Noonan syndrome (NS) is an autosomal dominant genetic disorder associated with highly variable features, including heart disease, short stature, minor facial anomalies and learning disabilities. Recent gene discoveries have laid the groundwork for exploring whether variability in the NS phenotype is related to differences at the genetic level. Here we examine the influence of both genotype and non-genotypic factors on cognitive functioning. Data are presented from 65 individuals with Noonan syndrome (ages 4 to 18) who were evaluated using standardized measures of intellectual functioning. The cohort included 33 individuals with PTPN11 mutations, 6 individuals with SOS1 mutations, 1 individual with a BRAF mutation, and 25 participants with negative, incomplete or no genetic testing. Results indicate that genotype differences may account for some of the variation in cognitive ability in NS. Whereas cognitive impairments were common among individuals with PTPN11 mutations and those with unknown mutations, all of the individuals with SOS1 mutations exhibited verbal and nonverbal cognitive skills in the average range or higher. Participants with N308D and N308S mutations in PTPN11 also demonstrated no (or mild) cognitive delays. Additional influences such as hearing loss, motor dexterity and parental education levels accounted for significant variability in cognitive outcomes. Severity of cardiac disease was not related to cognitive functioning. Our results suggest that some NS-causing mutations have a more marked impact on cognitive skills than others.

Background: Hypertrophic cardiomyopathy (HCM) is a major cause of death in infants and children. Noonan Syndrome (NS), an autosomal dominant RASopathy disorder, is characterized by multiple defects, including short stature, facial dysmorphia, and congenital heart defects that include HCM. RASopathies are caused by germ-line mutations that affect the canonical RAS-MAPK pathway. Indeed, 95% of NS patients with a mutation in Raf1 , a gene that plays an integral role in this signaling cascade, exhibit HCM. However, the molecular mechanisms that elicit HCM in these patients remain poorly understood. Objective: To generate human NS Raf1 induced-pluripotent stem cells (iPSCs), correct the mutation by genome editing and subsequently differentiate isogenic iPSC lines into cardiomyocytes to characterize the molecular and genetic basis of HCM in NS patients. Results: We generated iPSCs from skin fibroblasts obtained from a NS pediatric patient with a single point mutation in the Raf1 gene. Using electroporation of four episomal vectors containing the Yamanaka factors, we obtained several iPSC clones with normal karyotypes and strong expression of pluripotent markers (Nanog, Oct4, Lin28, Sox2) as detected by RT-qPCR and immunofluorescence. We next corrected the mutation in the NS Raf1 iPSCs using genome editing CRISPR-Cas9 nickase technology. Correction of the Raf1 mutation was determined at the clonal level by PCR followed by Restriction Fragment Length Polymorphism and confirmed by Sanger sequencing. In addition, by inducing a Cas9 nickase-dependent frame shift mutation we also generated an isogenic iPSC line where Raf1 gene was knockout (KO), as demonstrated at the RNA level by RT-qPCR and at the protein level by Western Blot. We next differentiated these multiple iPSC lines (mutant, corrected and KO) into isogenic beating cardiomyocytes, with more >98% of the cells positive for specific cardiomyocyte markers (α-actinin and cardiac TroponinT). Conclusion: We have successfully generated human NS Raf1 isogenic iPSC lines and corresponding cardiomyocytes. Currently, we are in progress of characterizing these cardiac cells to determine the molecular basis of NS-dependent HCM. Ultimately, our work should reveal new targets to treat HCM in NS patients.

© 2015 by The American Society of Human Genetics. All rights reserved. The 22q11.2 deletion syndrome (22q11DS; velocardiofacial/DiGeorge syndrome; VCFS/DGS) is the most common microdeletion syndrome and the phenotypic presentation is highly variable. Approximately 65% of individuals with 22q11DS have a congenital heart defect (CHD), mostly of the conotruncal type, and/or an aortic arch defect. The etiology of this phenotypic variability is not currently known. We hypothesized that copy-number variants (CNVs) outside the 22q11.2 deleted region might increase the risk of being born with a CHD in this sensitized population. Genotyping with Affymetrix SNP Array 6.0 was performed on two groups of subjects with 22q11DS separated by time of ascertainment and processing. CNV analysis was completed on a total of 949 subjects (cohort 1, n = 562; cohort 2, n = 387), 603 with CHDs (cohort 1, n = 363; cohort 2, n = 240) and 346 with normal cardiac anatomy (cohort 1, n = 199; cohort 2, n = 147). Our analysis revealed that a duplication of SLC2A3 was the most frequent CNV identified in the first cohort. It was present in 18 subjects with CHDs and 1 subject without (p = 3.12 × 10-3, two-tailed Fisher's exact test). In the second cohort, the SLC2A3 duplication was also significantly enriched in subjects with CHDs (p = 3.30 × 10-2, two-tailed Fisher's exact test). The SLC2A3 duplication was the most frequent CNV detected and the only significant finding in our combined analysis (p = 2.68 × 10-4, two-tailed Fisher's exact test), indicating that the SLC2A3 duplication might serve as a genetic modifier of CHDs and/or aortic arch anomalies in individuals with 22q11DS.

Cardiac left ventricular outflow tract (LVOT) defects represent a common but heterogeneous subset of congenital heart disease for which gene identification has been difficult. We describe a 46,XY,t(1;5)(p36.11;q31.2)dn translocation carrier with pervasive developmental delay who also exhibited LVOT defects, including bicuspid aortic valve (BAV), coarctation of the aorta (CoA) and patent ductus arteriosus (PDA). The 1p breakpoint disrupts the 5' UTR of AHDC1, which encodes AT-hook DNA-binding motif containing-1 protein, and AHDC1-truncating mutations have recently been described in a syndrome that includes developmental delay, but not congenital heart disease [Xia, F., Bainbridge, M.N., Tan, T.Y., Wangler, M.F., Scheuerle, A.E., Zackai, E.H., Harr, M.H., Sutton, V.R., Nalam, R.L., Zhu, W. et al. (2014) De Novo truncating mutations in AHDC1 in individuals with syndromic expressive language delay, hypotonia, and sleep apnea. Am. J. Hum. Genet., 94, 784-789]. On the other hand, the 5q translocation breakpoint disrupts the 3' UTR of MATR3, which encodes the nuclear matrix protein Matrin 3, and mouse Matr3 is strongly expressed in neural crest, developing heart and great vessels, whereas Ahdc1 is not. To further establish MATR3 3' UTR disruption as the cause of the proband's LVOT defects, we prepared a mouse Matr3(Gt-ex13) gene trap allele that disrupted the 3' portion of the gene. Matr3(Gt-ex13) homozygotes are early embryo lethal, but Matr3(Gt-ex13) heterozygotes exhibit incompletely penetrant BAV, CoA and PDA phenotypes similar to those in the human proband, as well as ventricular septal defect (VSD) and double-outlet right ventricle (DORV). Both the human MATR3 translocation breakpoint and the mouse Matr3(Gt-ex13) gene trap insertion disturb the polyadenylation of MATR3 transcripts and alter Matrin 3 protein expression, quantitatively or qualitatively. Thus, subtle perturbations in Matrin 3 expression appear to cause similar LVOT defects in human and mouse.

International audience; The RASopathies constitute a family of autosomal-dominant disorders whose major features include facial dysmorphism, cardiac defects, reduced postnatal growth, variable cognitive deficits, ectodermal and skeletal anomalies, and susceptibility to certain malignancies. Noonan syndrome (NS), the commonest RASopathy, is genetically heterogeneous and caused by functional dysregulation of signal transducers and regulatory proteins with roles in the RAS/extracellular signal-regulated kinase (ERK) signal transduction pathway. Mutations in known disease genes account for approximately 80% of affected individuals. Here, we report that missense mutations altering Son of Sevenless, Drosophila, homolog 2 (SOS2), which encodes a RAS guanine nucleotide exchange factor, occur in a small percentage of subjects with NS. Four missense mutations were identified in five unrelated sporadic cases and families transmitting NS. Disease-causing mutations affected three conserved residues located in the Dbl homology (DH) domain, of which two are directly involved in the intramolecular binding network maintaining SOS2 in its autoinhibited conformation. All mutations were found to promote enhanced signaling from RAS to ERK. Similar to NS-causing SOS1 mutations, the phenotype associated with SOS2 defects is characterized by normal development and growth, as well as marked ectodermal involvement. Unlike SOS1 mutations, however, those in SOS2 are restricted to the DH domain

The Noonan syndrome and its related disorders, now collectively called RASopathies, are autosomal dominant traits with pleiomorphic features, including cardiovascular involvement at high prevalence. The cardiovascular abnormalities include congenital heart defects, with valve stenosis and atrial septal defects being commonest, and an early-onset form of hypertrophic cardiomyopathy. The mutations underlying the RASopathies alter genes encoding proteins with roles in signal transduction through the RAS/MAPK pathway. Nearly all lesions are missense variants and generally have gain-of-function effects. Mutations in several genes underlie the Noonan syndrome, the commonest of these disorders, with well-established genotype-phenotype correlations. Disease pathogenesis for the RASopathies is being elucidated using mouse models, which generally recapitulate the associated cardiovascular defects. It appears that certain phenotypes may be amenable to drug therapies, but gene/mutation-specific approaches may be necessary.

Noonan syndrome, the most common single-gene cause of congenital heart disease, is characterized by short stature, characteristic facies, learning problems and leukemia predisposition. Gain-of-function mutations in PTPN11, encoding the tyrosine phosphatase SHP2, cause approximately 50% of Noonan syndrome cases. SHP2 is required for RAS-ERK MAP kinase (MAPK) cascade activation, and Noonan syndrome mutants enhance ERK activation ex vivo and in mice. KRAS mutations account for

We report on a patient with Noonan syndrome due to SHOC2 missense mutation predicting p.Ser2Gly, recently described in association with Noonan syndrome. The male infant presented with fetal distress requiring premature delivery at 32 weeks and was noted to have dysmorphic features, edema, hepatosplenomegaly, leukocytosis, thrombocytopenia, and respiratory distress following birth. An echocardiogram revealed hypertrophic cardiomyopathy with left ventricular outflow tract obstruction. The infant's cardiac lesion rapidly progressed, and he was discharged home for palliative care. Clinical testing of genes causative of Noonan syndrome and related disorders detected the previously reported, pathogenic, de novo SHOC2 missense mutation predicting p.Ser2Gly. The patient's cardiac findings and features were not typical for those individuals previously reported with this SHOC2 mutation and thus expand the clinical phenotype.

Supplemental Digital Content is available in the text., Background— The 22q11.2 deletion syndrome (22q11.2DS; DiGeorge syndrome/velocardiofacial syndrome) occurs in 1 of 4000 live births, and 60% to 70% of affected individuals have congenital heart disease, ranging from mild to severe. In our cohort of 1472 subjects with 22q11.2DS, a total of 62% (n=906) have congenital heart disease and 36% (n=326) of these have tetralogy of Fallot (TOF), comprising the largest subset of severe congenital heart disease in the cohort. Methods and Results— To identify common genetic variants associated with TOF in individuals with 22q11.2DS, we performed a genome-wide association study using Affymetrix 6.0 array and imputed genotype data. In our cohort, TOF was significantly associated with a genotyped single-nucleotide polymorphism (rs12519770, P=2.98×10−8) in an intron of the adhesion GPR98 (G-protein–coupled receptor V1) gene on chromosome 5q14.3. There was also suggestive evidence of association between TOF and several additional single-nucleotide polymorphisms in this region. Some genome-wide significant loci in introns or noncoding regions could affect regulation of genes nearby or at a distance. On the basis of this possibility, we examined existing Hi-C chromatin conformation data to identify genes that might be under shared transcriptional regulation within the region on 5q14.3. There are 6 genes in a topologically associated domain of chromatin with GPR98, including MEF2C (Myocyte-specific enhancer factor 2C). MEF2C is the only gene that is known to affect heart development in mammals and might be of interest with respect to 22q11.2DS. Conclusions— In conclusion, common variants may contribute to TOF in 22q11.2DS and may function in cardiac outflow tract development.

Item does not contain fulltext RASopathies, a family of disorders characterized by cardiac defects, defective growth, facial dysmorphism, variable cognitive deficits and predisposition to certain malignancies, are caused by constitutional dysregulation of RAS signalling predominantly through the RAF/MEK/ERK (MAPK) cascade. We report on two germline mutations (p.Gly39dup and p.Val55Met) in RRAS, a gene encoding a small monomeric GTPase controlling cell adhesion, spreading and migration, underlying a rare (2 subjects among 504 individuals analysed) and variable phenotype with features partially overlapping Noonan syndrome, the most common RASopathy. We also identified somatic RRAS mutations (p.Gly39dup and p.Gln87Leu) in 2 of 110 cases of non-syndromic juvenile myelomonocytic leukaemia, a childhood myeloproliferative/myelodysplastic disease caused by upregulated RAS signalling, defining an atypical form of this haematological disorder rapidly progressing to acute myeloid leukaemia. Two of the three identified mutations affected known oncogenic hotspots of RAS genes and conferred variably enhanced RRAS function and stimulus-dependent MAPK activation. Expression of an RRAS mutant homolog in Caenorhabditis elegans enhanced RAS signalling and engendered protruding vulva, a phenotype previously linked to the RASopathy-causing SHOC2(S2G) mutant. Overall, these findings provide evidence of a functional link between RRAS and MAPK signalling and reveal an unpredicted role of enhanced RRAS function in human disease.

Noonan syndrome, a developmental disorder characterized by congenital heart defects, reduced growth, facial dysmorphism and variable cognitive deficits, is caused by constitutional dysregulation of the RAS-MAPK signaling pathway. Here we report that germline NRAS mutations conferring enhanced stimulus-dependent MAPK activation account for some cases of this disorder. These findings provide evidence for an obligate dependency on proper NRAS function in human development and growth.

Exome sequencing of patients with congenital heart disease (CHD) and their unaffected parents reveals an excess of strong-effect, protein-altering de novo mutations in genes expressed in the developing heart, many of which regulate chromatin modification in key developmental genes; collectively, these mutations are predicted to account for approximately 10% of severe CHD cases. This paper demonstrates that de novo mutations with large effect have a role in the pathogenesis of at least 10% of cases of congenital heart disease (CHD). Using exome sequence analysis in parent–offspring trios Richard Lifton and colleagues compared the frequency of de novo mutations, identified by exome sequencing, in 362 CHD parent–offspring trios and 264 control trios. Gene ontology analysis demonstrated significant enrichment of de novo protein-altering mutation of genes involved in chromatin modification, notably a marked enrichment of genes involved in the production, removal and reading of methylation of histone H3K4 and H3K27. Congenital heart disease (CHD) is the most frequent birth defect, affecting 0.8% of live births1. Many cases occur sporadically and impair reproductive fitness, suggesting a role for de novo mutations. Here we compare the incidence of de novo mutations in 362 severe CHD cases and 264 controls by analysing exome sequencing of parent–offspring trios. CHD cases show a significant excess of protein-altering de novo mutations in genes expressed in the developing heart, with an odds ratio of 7.5 for damaging (premature termination, frameshift, splice site) mutations. Similar odds ratios are seen across the main classes of severe CHD. We find a marked excess of de novo mutations in genes involved in the production, removal or reading of histone 3 lysine 4 (H3K4) methylation, or ubiquitination of H2BK120, which is required for H3K4 methylation2,3,4. There are also two de novo mutations in SMAD2, which regulates H3K27 methylation in the embryonic left–right organizer5. The combination of both activating (H3K4 methylation) and inactivating (H3K27 methylation) chromatin marks characterizes ‘poised’ promoters and enhancers, which regulate expression of key developmental genes6. These findings implicate de novo point mutations in several hundreds of genes that collectively contribute to approximately 10% of severe CHD.

Noonan syndrome (NS) is a heterogeneous developmental disorder caused by missense mutations in genes involved in the Ras/MAPK signaling pathway, a major mediator of early and late developmental processes. The diagnosis of NS is made on clinical grounds with molecular confirmation of a mutation found in 63% of cases. Key clinical features include short stature, cardiac defects, developmental delay, lymphatic dysplasias, bleeding tendency, and a constellation of distinctive facial features and physical exam findings. The prevalence of medical issues or the development of new ones in adults with NS is not well-studied. This cross-sectional study reports on the prevalence of clinical conditions and their ages of onset in a cohort of 35 adolescents and adults with NS aged 16-68 years old (mean age 28 years). In this cohort, 34 of 35 subjects (97%) had had full PTPN11 sequencing; 37% were PTPN11 positive, 23% were SOS1 positive, and 3% were BRAF positive. Mean adult height in both men and women was at the 3rd-10th centile. The most prevalent clinical findings in this cohort included pulmonary valve stenosis (71%), easy bruising (63%), GERD (60%), constipation (51%), scoliosis (54%), chronic joint pain (54%), lymphedema (49%), depression (49%), anxiety (49%), Chiari malformation (20%), and osteopenia/osteoporosis (14%). In summary, adults with NS are affected by multi-organ morbidity and require special medical management aimed towards the most prevalent and serious known medical complications. Larger studies characterizing the clinical conditions found in NS adults are needed to provide potential genotype-phenotype correlations that may aid in clinical management.

Dilated cardiomyopathy (DCM) is an important cause of heart failure and the leading indication for cardiac transplantation worldwide.1 With careful evaluation of relatives, familial disease can be identified in ~30% of patients with seemingly idiopathic DCM.2 This connection indicates that genetic etiologies play an important role in disease pathogenesis. It also has important implications for families, because relatives are at risk for developing disease. Indeed, consensus guidelines for idiopathic DCM recommend that first-degree relatives of patients begin longitudinal echocardiography-based screening early in life.3 Therefore, greater understanding of the genetic basis of DCM will not only advance knowledge of fundamental disease biology, but will also improve clinical management of families by definitively identifying at-risk relatives, thereby allowing longitudinal screening to be focused only on mutation carriers. Characterizing the genetics of DCM has been a challenging task owing to incomplete knowledge of the genes involved in disease as well as difficulties determining if DNA variants identified in patients are clinically significant. More than 40 different genes have been implicated in causing DCM. Unlike hypertrophic cardiomyopathy (HCM), which is largely a disease of the sarcomere, the pathways leading to DCM are considerably more diverse, involving genes encoding components of the sarcomere, Z-disk, nuclear lamina proteins, intermediate filaments, and the dystrophin-associated glycoprotein complex.4 Individually, each of these genes provides a very modest contribution to the overall incidence of disease, and efforts to identify other DCM-associated genes are ongoing. As a result, current genetic testing strategies are relatively insensitive in DCM. For example, the Familial Dilated Cardiomyopathy Project analyzed 14 genes in >300 index patients and identified disease-associated variants in only 20%–30% of cases.5∓9 Furthermore, even if genetic testing identifies a variant that differs from the expected/reference genetic sequence in a patient with DCM, it can be very difficult to determine whether the variant is a true pathogenic mutation capable of causing disease, is disease modifying, or merely represents benign genetic variation.10,11 This difficulty reflects the remarkable complexity in human genomic variation.12 Correctly classifying DNA variants is obviously important to avoid false positive and negative genetic testing results, but there are no universal standards for interpretation. Interpretations are often based on only a small number of criteria, such as evolutionary conservation and absence of the DNA variant in a relatively small cohort of healthy control subjects. In addition to a more complete compendium of genes that cause DCM, rigorous standardized metrics to classify DNA variants, and greater experience genotyping broader populations with disease are needed. Unlike earlier studies in which genetic testing was performed in carefully cultivated research cohorts, in the present study we assess genetic testing in real-life clinical practice. Using structured criteria to classify the significance of DNA variants, we describe the prevalence of gene mutations in a diverse population of DCM patients referred to a single laboratory for clinical genetic testing. We also examine factors that may influence the likelihood of identifying a mutation, to better characterize the sensitivity, or yield, of genetic testing in the clinical setting. This information helps to shape the role of genetic testing in practice and to guide patient selection to maximize yield.

C16orf35 is a conserved and widely expressed gene lying adjacent to the human α-globin cluster in all vertebrate species. In-depth sequence analysis shows that C16orf35 (now called NPRL3) is an orthologue of the yeast gene Npr3 (nitrogen permease regulator 3) and, furthermore, is a paralogue of its protein partner Npr2. The yeast Npr2/3 dimeric protein complex senses amino acid starvation and appropriately adjusts cell metabolism via the TOR pathway. Here we have analysed a mouse model in which expression of Nprl3 has been abolished using homologous recombination. The predominant effect on RNA expression appears to involve genes that regulate protein synthesis and cell cycle, consistent with perturbation of the mTOR pathway. Embryos homozygous for this mutation die towards the end of gestation with a range of cardiovascular defects, including outflow tract abnormalities and ventriculoseptal defects consistent with previous observations, showing that perturbation of the mTOR pathway may affect development of the myocardium. NPRL3 is a candidate gene for harbouring mutations in individuals with developmental abnormalities of the cardiovascular system. © 2012 Springer Science+Business Media, LLC.

Barth syndrome (BTHS); MIM accession # 302060) is a rare X-linked recessive cardioskeletal mitochondrial myopathy with features of cardiomyopathy, neutropenia, and growth abnormalities. The objectives of this study were to further elucidate the natural history, clinical disease presentation, and course, and describe growth characteristics for males with BTHS. Patients with a confirmed genetic diagnosis of BTHS are referred to the BTHS Registry through the Barth Syndrome Foundation, self-referral, or physician referral. This study is based on data obtained from 73 subjects alive at the time of enrollment that provided self-reported and/or medical record abstracted data. The mean age at diagnosis of BTHS was 4.04 ± 5.45 years. While the vast majority of subjects reported a history of cardiac dysfunction, nearly 6% denied any history of cardiomyopathy. Although most subjects had only mildly abnormal cardiac function by echocardiography reports, 70% were recognized as having cardiomyopathy in the first year of life and 12% have required cardiac transplantation. Of the 73 enrolled subjects, there have been five deaths. Growth curves were generated demonstrating a shift down for weight, length, and height versus the normative population with late catch up in height for a significant percentage of cases. This data also confirms a significant number of patients with low birth weight, complications in the newborn period, failure to thrive, neutropenia, developmental delay of motor milestones, and mild learning difficulties. However, it is apparent that the disease manifestations are variable, both over time for an individual patient and across the BTHS population.

Aberrant organ development is associated with a wide spectrum of disorders, from schizophrenia to congenital heart disease, but systems-level insight into the underlying processes is very limited. Using heart morphogenesis as general model for dissecting the functional architecture of organ development, we combined detailed phenotype information from deleterious mutations in 255 genes with high-confidence experimental interactome data, and coupled the results to thorough experimental validation. Hereby, we made the first systematic analysis of spatio-temporal protein networks driving many stages of a developing organ identifying several novel signaling modules. Our results show that organ development relies on surprisingly few, extensively recycled, protein modules that integrate into complex higher-order networks. This design allows the formation of a complicated organ using simple building blocks, and suggests how mutations in the same genes can lead to diverse phenotypes. We observe a striking temporal correlation between organ complexity and the number of discrete functional modules coordinating morphogenesis. Our analysis elucidates the organization and composition of spatio-temporal protein networks that drive the formation of organs, which in the future may lay the foundation of novel approaches in treatments, diagnostics, and regenerative medicine., Eunice Kennedy Shriver National Institute of Child Health and Human Development (U.S.) (RO1 grant HD055150-03)

Branchio-oculo-facial syndrome (BOFS) is a rare autosomal-dominant cleft palate-craniofacial disorder with variable expressivity. The major features include cutaneous anomalies (cervical, infra- and/or supra-auricular defects, often with dermal thymus), ocular anomalies, characteristic facial appearance (malformed pinnae, oral clefts), and, less commonly, renal and ectodermal (dental and hair) anomalies. The molecular basis for this disorder is heretofore unknown. We detected a 3.2 Mb deletion by 500K SNP microarray in an affected mother and son with BOFS at chromosome 6p24.3. Candidate genes in this region were selected for sequencing on the basis of their expression patterns and involvement in developmental pathways associated with the clinical findings of BOFS. Four additional BOFS patients were found to have de novo missense mutations in the highly conserved exons 4 and 5 (basic region of the DNA binding domain) of the TFAP2A gene in the candidate deleted region. We conclude BOFS is caused by mutations involving TFAP2A. More patients need to be studied to determine possible genetic heterogeneity and to establish whether there are genotype-phenotype correlations.

Udgivelsesdato: 2007-May

The cardiofaciocutaneous (CFC) syndrome is a condition of sporadic occurrence, with patients showing multiple congenital anomalies and mental retardation. It is characterised by failure to thrive, relative macrocephaly, a distinctive face with prominent forehead, bitemporal constriction, absence of eyebrows, hypertelorism, downward‐slanting palpebral fissures often with epicanthic folds, depressed nasal root and a bulbous tip of the nose. The cutaneous involvement consists of dry, hyperkeratotic, scaly skin, sparse and curly hair, and cavernous haemangiomata. Most patients have a congenital heart defect, most commonly pulmonic stenosis and hypertrophic cardiomyopathy. The developmental delay usually is moderate to severe. The syndrome is caused by gain‐of‐function mutations in four different genes BRAF, KRAS, mitogen‐activated protein/extracellular signal‐regulated kinase MEK1 and MEK2, all belonging to the same RAS–extracellular signal‐regulated kinase (ERK) pathway that regulates cell differentiation, proliferation and apoptosis. The CFC syndrome is a member of a family of syndromes that includes the Noonan and Costello syndromes, presenting with phenotypic similarities. Noonan syndrome is caused by mutations in the protein tyrosine phosphatase SHP‐2 gene (PTPN11), with a few people having a mutation in KRAS. Costello syndrome is caused by mutations in HRAS. The protein products of these genes also belong to the RAS–ERK pathway. Thus, the clinical overlap of these three conditions, which often poses a problem of differential diagnosis, is explained by their pathogenetic relatedness.