Congenital diaphragmatic hernia (CDH) is a common and well-studied birth defect. The etiology of most cases remains unknown but increasing evidence points to genetic causation. The data supporting genetic etiologies which are detailed below include the association of CDH with recurring chromosome abnormalities, the existence of CDH-multiplex families, and the co-occurrence of CDH with additional congenital malformations.
congenital diaphragmatic hernia; Bochdalek hernia; Morgagni hernia; classification; mortality; epidemiology; isolated CDH; syndromic CDH; genetic syndromes; multiplex families; chromosome abnormalities
Cytogenetic and molecular cytogenetic studies demonstrate association between congenital diaphragmatic hernia (CDH) and chromosome 1q41q42 deletions. In this study, we screened a large CDH cohort (N=179) for microdeletions in this interval by the multiplex ligation-dependent probe amplification (MLPA) technique, and also sequenced two candidate genes located therein, dispatched 1 (DISP1) and homo sapiens H2.0-like homeobox (HLX). MLPA analysis verified deletions of this region in two cases, an unreported patient with a 46,XY,del(1)(q41q42.13) karyotype and a previously reported patient with a Fryns syndrome phenotype [Kantarci et al., 2006]. HLX sequencing showed a novel but maternally inherited single nucleotide variant (c.27C>G) in a patient with isolated CDH, while DISP1 sequencing revealed a mosaic de novo heterozygous substitution (c.4412C>G; p.Ala1471Gly) in a male with a left-sided Bochdalek hernia plus multiple other anomalies. Pyrosequencing demonstrated the mutant allele was present in 43%, 12%, and 4.5% of the patient’s lymphoblastoid, peripheral blood lymphocytes, and saliva cells, respectively. We examined Disp1 expression at day E11.5 of mouse diaphragm formation and confirmed its presence in the pleuroperitoneal fold, as well as the nearby lung which also expresses Sonic hedgehog (Shh).
Our report describes the first de novo DISP1 point mutation in a patient with complex CDH. Combining this finding with Disp1 embryonic mouse diaphragm and lung tissue expression, as well as previously reported human chromosome 1q41q42 aberrations in patients with CDH, suggests that DISP1 may warrant further consideration as a CDH candidate gene.
congenital diaphragmatic hernia (CDH); chromosome 1q41q42 deletion; microdeletion; MLPA; pyrosequencing; Sonic Hedgehog (SHH) pathway; pleuroperitoneal fold (PPF)
Congenital diaphragmatic defects (CDDs) are a common group of birth defects, yet we presently know little about their pathogenesis. No systematic study documenting the detailed morphology of CDD has been performed, and current classification schemata of diaphragm phenotypes incompletely capture the location and extent of diaphragmatic involvement. To define the range of CDD anatomy, diaphragmatic pathology was reviewed from an examination of 181 autopsy records of children with CDDs at Children’s Hospital Boston between 1927 and 2006. Defects were classified according to several parameters, including type (communicating versus noncommunicating) and location (anterior, posterior, etc.). The information permitted development of a phenotyping worksheet for prospective use on patients undergoing diaphragmatic repair at Children’s Hospital Boston or MassGeneral Hospital for Children. Fifty-three patients who died between 1990 and 2006 had a total of 63 defects. Thirty-nine had a “classic” CDD phenotype (64% posterolateral, 18% hemidiaphragmatic aplasia, and 18% anterior). The remaining 19 defects, not fitting classical descriptions, were located in the posteromedial, anterolateral, or lateral regions of the diaphragm. Prospective data collected during surgical repair revealed posterolateral defects in 34 of 41 cases that demonstrated wide phenotypic variability in size, location, shape, type, and extent of organ displacement. Congenital diaphragmatic defects display significant phenotypic variation. Because rigorous anatomic evaluation and documentation are important steps towards elucidating the developmental biology of these disorders, we suggest establishment of a new and more precise classification using the model presented herein.
Bochdalek; CDH; diaphragm; hernia; pulmonary hypoplasia; sac hernia
Mutations in the gene LRP2 have recently been identified as the cause of Donnai-Barrow and Facio-oculo-acoustico-renal (DB/FOAR) syndrome. More than two dozen cases, the first reported more than 30 years ago by Holmes, have been published. Summarizing available information, we highlight the cardinal features of the disorder found in ≥90% of published cases. These features include: agenesis of the corpus callosum, developmental delay, enlarged anterior fontanelle, high myopia, hypertelorism, proteinuria, and sensorineural hearing loss. Congenital diaphragmatic hernia and omphalocele are reported in only half of the patients. There is no evidence for genotype-phenotype correlation, though the sample size is too small to preclude this with certainty. Although several conditions to consider in the differential diagnosis are highlighted, the diagnosis of DB/FOAR syndrome should not be difficult to establish as its constellation of findings is strikingly characteristic.
Donnai-Barrow (DB) syndrome; facio-oculo-acoustico-renal (FOAR); syndrome; LRP2; megalin; congenital diaphragmatic hernia; agenesis of corpus callosum
Williams-Beuren syndrome (WBS) is a microdeletion disorder caused by heterozygous loss of approximately 1.5-Mb pairs of DNA from chromosome 7. Patients with WBS have a characteristic constellation of medical and cognitive findings, with a hallmark feature of generalized arteriopathy presenting as stenoses of elastic arteries and hypertension. Human and mouse studies establish that defects in the elastin gene, leading to elastin haploinsufficiency, underlie the arteriopathy. In this review we describe potential links between elastin expression and arteriopathy, possible explanations for disease variability, and current treatment options and their limitations, and we propose several new directions for the development of nonsurgical preventative therapies based on insights from elastin biology.
Williams-Beuren Syndrome (WBS) is caused by a submicroscopic deletion on chromosome 7q11.23 that encompasses the entire elastin (ELN) gene. Elastin, a key component of elastic fibers within the lung, is progressively destroyed in emphysema. Defects in the elastin gene have been associated with increased susceptibility towards developing chronic obstructive pulmonary disease (COPD) and emphysema in both humans and mice. We postulate that hemizygosity at the elastin gene locus may increase susceptibility towards the development of COPD and emphysema in subjects with WBS. We describe an adult subject with WBS who was a lifelong non-smoker and was found to have moderate emphysema. We also examined the pulmonary function of a separate cohort of adolescents and young adults with WBS. Although no significant spirometric abnormalities were identified, a significant proportion of subjects reported respiratory symptoms. Thus while significant obstructive disease does not appear to be common in relatively young adults with WBS, subclinical emphysema and lung disease may exist which possibly could worsen with advancing age. Further investigation may elucidate the pathogenesis of non-smoking related emphysema.
Elastin; emphysema; pulmonary function tests; Williams Syndrome
Interferon regulatory factor 6 (IRF6) belongs to a family of nine transcription factors that share a highly conserved helix–turn–helix DNA-binding domain and a less conserved protein-binding domain. Most IRFs regulate the expression of interferon-α and -β after viral infection1, but the function of IRF6 is unknown. The gene encoding IRF6 is located in the critical region for the Van der Woude syndrome (VWS; OMIM 119300) locus at chromosome 1q32–q41 (refs 2,3). The disorder is an autosomal dominant form of cleft lip and palate with lip pits4, and is the most common syndromic form of cleft lip or palate. Popliteal pterygium syndrome (PPS; OMIM 119500) is a disorder with a similar orofacial phenotype that also includes skin and genital anomalies5. Phenotypic overlap6 and linkage data7 suggest that these two disorders are allelic. We found a nonsense mutation in IRF6 in the affected twin of a pair of monozygotic twins who were discordant for VWS. Subsequently, we identified mutations in IRF6 in 45 additional unrelated families affected with VWS and distinct mutations in 13 families affected with PPS. Expression analyses showed high levels of Irf6 mRNA along the medial edge of the fusing palate, tooth buds, hair follicles, genitalia and skin. Our observations demonstrate that haploinsufficiency of IRF6 disrupts orofacial development and are consistent with dominant-negative mutations disturbing development of the skin and genitalia.
Congenital diaphragmatic hernia (CDH) is a common and often devastating birth defect. In order to learn more about possible genetic causes, we reviewed and classified 203 cases of the Bochdalek hernia type identified through the Brigham and Women’s Hospital (BWH) Active Malformation Surveillance Program over a 28-year period. Phenotypically, 55% of the cases had isolated CDH, and 45% had complex CDH defined as CDH in association with additional major malformations or as part of a syndrome. When classified according to likely etiology, 17% had a Recognized Genetic etiology for their CDH, while the remaining 83% had No Apparent Genetic etiology. Detailed analysis using this largest cohort of consecutively collected cases of CDH showed low precurrence among siblings. Additionally, there was no concordance for CDH among five monozygotic twin pairs. These findings, in conjunction with previous reports of de novo dominant mutations in patients with CDH, suggest that new mutations may be an important mechanism responsible for CDH. The twin data also raise the possibility that epigenetic abnormalities contribute to the development of CDH.
congenital diaphragmatic hernia; discordant monozygotic twins; precurrence risk; review
The co-occurrence of congenital diaphragmatic hernia (CDH) and cardiovascular malformations (CVMs) has important clinical, genetic, and developmental implications. Previous examinations of this topic often included patients with genetic syndromes. To correct this potential bias, we undertook an extensive review of the literature and obtained new data. The frequency of CVMs associated with isolated CDH was 11–15%. A careful analysis of CVMs indicates that atrial and ventricular septal defects, conotruncal defects, and left ventricular outflow tract obstructive defects were the most common type of CVMs, but proportional to the frequency of occurrence in the general population. The combination of CVM and CDH results in a poorer prognosis than would be expected with either malformation alone. However, the impact on survival from patients with a genetic syndrome has not been consistently evaluated. We encourage researchers to re-analyze existing series and recommend that future studies distinguish isolated CDH from that which is associated with other malformations, especially as part of genetic syndromes. Therapies should be tailored to maximize cardiac output and systemic oxygen delivery rather than systemic oxygen saturation alone. Although there is speculation about the frequency with which isolated left ventricular “hypoplasia” occurs in patients with CDH, we suggest it results from compression of a pre-load deficient left ventricle by the hypertensive right ventricle, and unlike true hypoplasia, is reversible. Irrespective of the type of severity of CVMs in patients with CDH, the degree of pulmonary hypoplasia and pulmonary vascular disease predicts outcome.
cardiovascular malformations; congenital diaphragmatic hernia; congenital heart defects; hypoplastic left heart
Donnai–Barrow syndrome [Faciooculoacousticorenal (FOAR) syndrome; DBS/FOAR] is a rare autosomal recessive disorder resulting from mutations in the LRP2 gene located on chromosome 2q31.1. We report a unique DBS/FOAR patient homozygous for a 4-bp LRP2 deletion secondary to paternal uniparental isodisomy for chromosome 2. The propositus inherited the mutation from his heterozygous carrier father, whereas the mother carried only wild-type LRP2 alleles. This is the first case of DBS/FOAR resulting from uniparental disomy (UPD) and the fourth published case of any paternal UPD 2 ascertained through unmasking of an autosomal recessive disorder. The absence of clinical symptoms above and beyond the classical phenotype in this and the other disorders suggests that paternal chromosome 2 is unlikely to contain imprinted genes notably affecting either growth or development. This report highlights the importance of parental genotyping in order to give accurate genetic counseling for autosomal recessive disorders.
Donnai–Barrow (DBS/FOAR) syndrome; uniparental isodisomy (UPD); paternal chromosome 2; reduction to homoallelism
A standard oral glucose tolerance test (OGTT) was administered to 28 adults with Williams syndrome (WS). Three quarters of the WS subjects showed abnormal glucose curves, meeting diagnostic criteria for either diabetes or the pre-diabetic state of impaired glucose tolerance. Fasting mean glucose and median insulin levels did not differ significantly in the total WS cohort versus age–gender–BMI matched controls, though the glucose area under the curve was greater in the WS subjects. HbA1c levels were not as reliable as the OGTT in diagnosing the presence of diabetes. Given the high prevalence of impaired glucose regulation, adults with WS should be screened for diabetes, and when present should be treated in accordance with standard medical practice. Hemizygosity for a gene mapping to the Williams syndrome chromosome region (WSCR) is likely the major factor responsible for the high frequency of diabetes in WS. Syntaxin-1A is a prime candidate gene based on its location in the WSCR, its role in insulin release, and the presence of abnormal glucose metabolism in mouse models with aberrantly expressed Stx-1a.
PMID: 20425788 CAMSID: cams394
diabetes mellitus; impaired glucose tolerance; Williams syndrome chromosome region (WSCR); syntaxin-1A (STX-1A); oral glucose tolerance test
Myokymia is characterized by spontaneous, involuntary muscle fiber group contraction visible as vermiform movement of the overlying skin. Myokymia with episodic ataxia is a rare, autosomal dominant trait caused by mutations in KCNA1, encoding a voltage-gated potassium channel. In the present study, we report a family with four members affected with myokymia. Additional clinical features included motor delay initially diagnosed as cerebral palsy, worsening with febrile illness, persistent extensor plantar reflex, and absence of epilepsy or episodic ataxia. Mutation analysis revealed a novel c.676C>A substitution in the potassium channel gene KCNA1, resulting in a T226K nonconservative missense mutation in the Kv1.1 subunit in all affected individuals. Electrophysiological studies of the mutant channel expressed in Xenopus oocytes indicated a loss of function. Co-expression of WT and mutant cRNAs significantly reduced whole-oocyte current compared to expression of WT Kv1.1 alone.
Myokymia; Potassium channel; Mutation
Congenital diaphragmatic hernia and other congenital diaphragmatic defects are associated with significant mortality and morbidity in neonates; however, the molecular basis of these developmental anomalies is unknown. In an analysis of E18.5 embryos derived from mice treated with N-ethyl-N-nitrosourea, we identified a mutation that causes pulmonary hypoplasia and abnormal diaphragmatic development. Fog2 (Zfpm2) maps within the recombinant interval carrying the N-ethyl-N-nitrosourea-induced mutation, and DNA sequencing of Fog2 identified a mutation in a splice donor site that generates an abnormal transcript encoding a truncated protein. Human autopsy cases with diaphragmatic defect and pulmonary hypoplasia were evaluated for mutations in FOG2. Sequence analysis revealed a de novo mutation resulting in a premature stop codon in a child who died on the first day of life secondary to severe bilateral pulmonary hypoplasia and an abnormally muscularized diaphragm. Using a phenotype-driven approach, we have established that Fog2 is required for normal diaphragm and lung development, a role that has not been previously appreciated. FOG2 is the first gene implicated in the pathogenesis of nonsyndromic human congenital diaphragmatic defects, and its necessity for pulmonary development validates the hypothesis that neonates with congenital diaphragmatic hernia may also have primary pulmonary developmental abnormalities.
Birth defects involving the diaphragm are as common and as serious as genetic disorders such as cystic fibrosis, yet the underlying causes of these defects are unknown. Most babies born with diaphragmatic defects have very small lungs, and many die in the newborn period with severe breathing difficulties. It is unknown whether the small lungs occur because these children have a diaphragmatic defect, or whether some patients might have a genetic abnormality that affects the development of both the lung and the diaphragm simultaneously.
In a screen of fetal mice carrying chemically induced genetic mutations, the authors found that a mutation in the gene Fog2 (Friend of gata 2), causes abnormal diaphragm development and small lungs. The lungs have a primary developmental abnormality that includes the specific loss of one lung lobe. Based on this result, the authors studied children affected with diaphragmatic abnormalities, and identified one human baby with a serious mutation in the human gene FOG2 who died at five hours of life with severe breathing difficulties, a diaphragmatic defect, and small lungs.
The authors have established that Fog2 is necessary for both diaphragm and lung development in mice and in humans. This is the first known cause of a nonsyndromic congenital diaphragmatic defect and establishes that some patients may have a primary developmental abnormality of both the lung and the diaphragm.
Advances in genetic epidemiology have increased understanding of common, polygenic preventable diseases such as type 2 diabetes. As genetic risk testing based on this knowledge moves into clinical practice, we propose that genetic counselors will need to expand their roles and adapt traditional counseling techniques for this new patient set. In this paper, we present a genetic counseling intervention developed for a clinical trial [Genetic Counseling/Lifestyle Change for Diabetes Prevention, ClinicalTrials.gov identifier: NCT01034319] designed to motivate behavioral changes for diabetes prevention. Seventy-two phenotypically high-risk participants received counseling that included their diabetes genetic risk score, general education about diabetes risk factors, and encouragement to participate in a diabetes prevention program. Using two validated genetic counseling scales, participants reported favorable perceived control and satisfaction with the counseling session. Our intervention represents one model for applying traditional genetic counseling principles to risk testing for polygenetic, preventable diseases, such as type 2 diabetes.
Genetic counseling; Type 2 diabetes; Polygenic risk counseling; Diabetes prevention
Chromosome 8p23.1 is a common hotspot associated with major congenital malformations, including congenital diaphragmatic hernia (CDH) and cardiac defects. We present findings from high-resolution arrays in patients who carry a loss (n =18) or a gain (n =1) of sub-band 8p23.1. We confirm a region involved in both diaphragmatic and heart malformations. Results from a novel CNVConnect algorithm, prioritizing protein–protein interactions between products of genes in the 8p23.1 hotspot and products of previously known CDH causing genes, implicated GATA4, NEIL2, and SOX7 in diaphragmatic defects. Sequence analysis of these genes in 226 chromosomally normal CDH patients, as well as in a small number of deletion 8p23.1 patients, showed rare unreported variants in the coding region; these may be contributing to the diaphragmatic phenotype. We also demonstrated that two of these three genes were expressed in the E11.5–12.5 primordial mouse diaphragm, the developmental stage at which CDH is thought to occur. This combination of bioinformatics and expression studies can be applied to other chromosomal hotspots, as well as private microdeletions or microduplications, to identify causative genes and their interaction networks.
congenital diaphragmatic hernia; congenital heart defect; DNA copy number variants; deletion 8p23 1; duplication 8p23 1; CNVConnect; GATA4; SOX7; NEIL2
Craniofrontonasal syndrome (CFNS), an X-linked disorder caused by loss-of-function mutations of EFNB1, exhibits a paradoxical sex reversal in phenotypic severity: females characteristically have frontonasal dysplasia, craniosynostosis and additional minor malformations, but males are usually more mildly affected with hypertelorism as the only feature. X-inactivation is proposed to explain the more severe outcome in heterozygous females, as this leads to functional mosaicism for cells with differing expression of EPHRIN-B1, generating abnormal tissue boundaries—a process that cannot occur in hemizygous males. Apparently challenging this model, males occasionally present with a more severe female-like CFNS phenotype. We hypothesized that such individuals might be mosaic for EFNB1 mutations and investigated this possibility in multiple tissue samples from six sporadically presenting males. Using denaturing high performance liquid chromatography, massively parallel sequencing and multiplex-ligation-dependent probe amplification (MLPA) to increase sensitivity above standard dideoxy sequencing, we identified mosaic mutations of EFNB1 in all cases, comprising three missense changes, two gene deletions and a novel point mutation within the 5′ untranslated region (UTR). Quantification by Pyrosequencing and MLPA demonstrated levels of mutant cells between 15 and 69%. The 5′ UTR variant mutates the stop codon of a small upstream open reading frame that, using a dual-luciferase reporter construct, was demonstrated to exacerbate interference with translation of the wild-type protein. These results demonstrate a more severe outcome in mosaic than in constitutionally deficient males in an X-linked dominant disorder and provide further support for the cellular interference mechanism, normally related to X-inactivation in females.
Donnai-Barrow syndrome is associated with agenesis of the corpus callosum, congenital diaphragmatic hernia, facial dysmorphology, ocular anomalies, sensorineural hearing loss and developmental delay. By studying multiplex families, we mapped this disorder to chromosome 2q23.3–31.1 and identified LRP2 mutations in six families with Donnai-Barrow syndrome and one family with facio-oculo-acoustico-renal syndrome. LRP2 encodes megalin, a multiligand uptake receptor that regulates levels of diverse circulating compounds. This work implicates a pathway with potential pharmacological therapeutic targets.
Cardiovascular abnormalities, especially structural congenital heart defects (CHDs), commonly occur in malformation syndromes and genetic disorders. Individuals with syndromes comprise a significant proportion of those affected with selected CHDs such as complete atrioventricular canal, interrupted arch type B, supravalvar aortic stenosis and pulmonary stenosis. As these individuals age, they contribute to the growing population of adults with special health care needs. Although most will require longterm cardiology followup, primary care providers, geneticists and other specialists should be aware of (1) the type and frequency of cardiovascular abnormalities, (2) the range of clinical outcomes, and (3) guidelines for prospective management and treatment of potential complications. This article reviews fundamental genetic, cardiac, medical and reproductive issues associated with common genetic syndromes which are frequently associated with a cardiovascular abnormality. New data are also provided about the cardiac status of adults with a 22q11.2 deletion and with Down syndrome.
congenital heart defect; deletion 22q11; Down syndrome; Marfan syndrome; Noonan syndrome; Turner syndrome; Williams-Beuren syndrome