Cardio-facio-cutaneous syndrome (CFC) is one of the RASopathies that bears many clinical features in common with the other syndromes in this group, most notably Noonan syndrome and Costello syndrome. ...CFC is genetically heterogeneous and caused by gene mutations in the Ras/mitogen-activated protein kinase pathway. The major features of CFC include characteristic craniofacial dysmorphology, congenital heart disease, dermatologic abnormalities, growth retardation, and intellectual disability. It is essential that this condition be differentiated from other RASopathies, as a correct diagnosis is important for appropriate medical management and determining recurrence risk. Children and adults with CFC require multidisciplinary care from specialists, and the need for comprehensive management has been apparent to families and health care professionals caring for affected individuals. To address this need, CFC International, a nonprofit family support organization that provides a forum for information, support, and facilitation of research in basic medical and social issues affecting individuals with CFC, organized a consensus conference. Experts in multiple medical specialties provided clinical management guidelines for pediatricians and other care providers. These guidelines will assist in an accurate diagnosis of individuals with CFC, provide best practice recommendations, and facilitate long-term medical care.
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.
Noonan syndrome (NS) is a common, clinically and genetically heterogeneous condition characterized by distinctive facial features, short stature, chest deformity, congenital heart disease, and other ...comorbidities. Gene mutations identified in individuals with the NS phenotype are involved in the Ras/MAPK (mitogen-activated protein kinase) signal transduction pathway and currently explain ∼61% of NS cases. Thus, NS frequently remains a clinical diagnosis. Because of the variability in presentation and the need for multidisciplinary care, it is essential that the condition be identified and managed comprehensively. The Noonan Syndrome Support Group (NSSG) is a nonprofit organization committed to providing support, current information, and understanding to those affected by NS. The NSSG convened a conference of health care providers, all involved in various aspects of NS, to develop these guidelines for use by pediatricians in the diagnosis and management of individuals with NS and to provide updated genetic findings.
Exome sequencing has markedly enhanced the discovery of genes implicated in Mendelian disorders, particularly for individuals in whom a known clinical entity could not be assigned. This has led to ...the recognition that phenotypic heterogeneity resulting from allelic mutations occurs more commonly than previously appreciated. Here, we report that missense variants in CDC42, a gene encoding a small GTPase functioning as an intracellular signaling node, underlie a clinically heterogeneous group of phenotypes characterized by variable growth dysregulation, facial dysmorphism, and neurodevelopmental, immunological, and hematological anomalies, including a phenotype resembling Noonan syndrome, a developmental disorder caused by dysregulated RAS signaling. In silico, in vitro, and in vivo analyses demonstrate that mutations variably perturb CDC42 function by altering the switch between the active and inactive states of the GTPase and/or affecting CDC42 interaction with effectors, and differentially disturb cellular and developmental processes. These findings reveal the remarkably variable impact that dominantly acting CDC42 mutations have on cell function and development, creating challenges in syndrome definition, and exemplify the importance of functional profiling for syndrome recognition and delineation.
Congenital disorders of glycosylation are rare conditions caused by genetic defects in glycan synthesis, processing or transport. Most congenital disorders of glycosylation involve defects in the ...formation or transfer of the lipid-linked oligosaccharide precursor of N-linked glycans. SLC35A2-CDG (previously CDG-IIm) is caused by hemizygous or heterozygous mutations in the X-linked gene SLC35A2 that encodes a UDP-galactose transporter. To date there have only been 10 reported patients with SLC35A2 mutations. Importantly, the patient presented here was not identified in infancy by transferrin isoform analysis, the most common testing to identify patients with a congenital disorder of glycosylation.
A 27 month old girl with developmental delay, central hypotonia, cerebral atrophy, and failure to thrive with growth retardation was identified by whole exome sequencing to have a mosaic missense variant in SLC35A2 (c.991G > A). This particular variant has been previously reported in a male as a mutation. Comparison of all clinical findings and new information on growth pattern, growth hormone testing and neurodevelopmental evaluation are detailed on the patient presented.
This patient report increases the clinical and scientific knowledge of SLC35A2-CDG, a rare condition. New information on reduced growth, growth hormone sufficiency, lack of seizures, and neurodevelopmental status are presented. This new information will be helpful to clinicians caring for individuals with SLC35A2-CDG. This report also alerts clinicians that transferrin isoform measurements do not identify all patients with congenital disorders of glycosylation.
Gene mutations within the RAS-MAPK signaling cascade result in Noonan syndrome (NS), neurofibromatosis type 1 (NF1), and related disorders. Recent research has documented an increased risk for social ...difficulties and features of autism spectrum disorder (ASD) among children with these conditions. Despite this emerging evidence, the neuropsychological characteristics associated with social skills deficits are not well understood, particularly for children with NS.
Parents of children with NS (n = 39), NF1 (n = 39), and unaffected siblings (n = 32) between the ages of 8 and 16 years were administered well-validated caregiver questionnaires assessing their child's social skills, language abilities, attention-deficit hyperactivity disorder (ADHD) symptoms and anxiety.
With respect to overall social skills, average ratings of children in both clinical groups were similar, and indicated weaker social skills compared to unaffected siblings. Although ratings of social skills were outside of normal limits for more than four in ten children within the clinical groups, most of the deficits were mild/moderate. Fifteen percent of the children with NS and 5% of the children with NF1 were rated as having severe social skills impairment (< - 2SD). Independent of diagnosis, having fewer ADHD symptoms or better social-pragmatic language skills was predictive of stronger social skills.
Amidst efforts to support social skill development among children and adolescents with RASopathies, neuropsychological correlates such as social language competence, attention, and behavioral self-regulation could be important targets of intervention.
Char syndrome is an autosomal dominant trait characterized by patent ductus arteriosus, facial dysmorphism and hand anomalies. Using a positional candidacy strategy, we mapped TFAP2B, encoding a ...transcription factor expressed in neural crest cells, to the Char syndrome critical region and identified missense mutations altering conserved residues in two affected families. Mutant TFAP2B proteins dimerized properly in vitro, but showed abnormal binding to TFAP2 target sequence. Dimerization of both mutants with normal TFAP2B adversely affected transactivation, demonstrating a dominant-negative mechanism. Our work shows that TFAP2B has a role in ductal, facial and limb development and suggests that Char syndrome results from derangement of neural-crest-cell derivatives.
Pathogenic variants in the chromatin organizer CTCF were previously reported in seven individuals with a neurodevelopmental disorder (NDD).
Through international collaboration we collected data from ...39 subjects with variants in CTCF. We performed transcriptome analysis on RNA from blood samples and utilized Drosophila melanogaster to investigate the impact of Ctcf dosage alteration on nervous system development and function.
The individuals in our cohort carried 2 deletions, 8 likely gene-disruptive, 2 splice-site, and 20 different missense variants, most of them de novo. Two cases were familial. The associated phenotype was of variable severity extending from mild developmental delay or normal IQ to severe intellectual disability. Feeding difficulties and behavioral abnormalities were common, and variable other findings including growth restriction and cardiac defects were observed. RNA-sequencing in five individuals identified 3828 deregulated genes enriched for known NDD genes and biological processes such as transcriptional regulation. Ctcf dosage alteration in Drosophila resulted in impaired gross neurological functioning and learning and memory deficits.
We significantly broaden the mutational and clinical spectrum ofCTCF-associated NDDs. Our data shed light onto the functional role of CTCF by identifying deregulated genes and show that Ctcf alterations result in nervous system defects in Drosophila.
Genomic disorders contribute significantly to genetic disease and, as detection methods improve, greater numbers are being defined. Paralogous low copy repeats (LCRs) mediate many of the chromosomal ...rearrangements that underlie these disorders, predisposing chromosomes to recombination errors. Deletions of proximal 22q11.2 comprise the most frequently occurring microdeletion syndrome, DiGeorge/Velocardiofacial syndrome (DGS/VCFS), in which most breakpoints have been localized to a 3 Mb region containing four large LCRs. Immediately distal to this region, there are another four related but smaller LCRs that have not been characterized extensively. We used paralog-specific primers and long-range PCR to clone, sequence, and examine the distal deletion breakpoints from two patients with de novo deletions mapping to these distal LCRs. Our results present definitive evidence of the direct involvement of LCRs in 22q11 deletions and map both breakpoints to the BCRL module, common to most 22q11 LCRs, suggesting a potential region for LCR-mediated rearrangement both in the distal LCRs and in the DGS interval. These are the first reported cases of distal 22q11 deletions in which breakpoints have been characterized at the nucleotide level within LCRs, confirming that distal 22q11 LCRs can and do mediate rearrangements leading to genomic disorders.
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