Semaphorin 3d signaling defects are associated with anomalous pulmonary venous connections

Total anomalous pulmonary venous connection (TAPVC) is a potentially lethal congenital disorder that occurs when the pulmonary veins do not connect normally to the left atrium, allowing mixing of pulmonary and systemic blood. In contrast to the extensive knowledge of arterial vascular patterning, little is known about the patterning of veins. Here we show that the secreted guidance molecule semaphorin 3d (Sema3d) is crucial for the normal patterning of pulmonary veins. Prevailing models suggest that TAPVC occurs when the midpharyngeal endothelial strand (MES), the precursor of the common pulmonary vein, does not form at the proper location on the dorsal surface of the embryonic common atrium. However, we found that TAPVC occurs in Sema3d mutant mice despite normal formation of the MES. In these embryos, the maturing pulmonary venous plexus does not anastomose uniquely with the properly formed MES. In the absence of Sema3d, endothelial tubes form in a region that is normally avascular, resulting in aberrant connections. Normally, Sema3d provides a repulsive cue to endothelial cells in this area, establishing a boundary. Sequencing of SEMA3D in individuals with anomalous pulmonary veins identified a phenylalanine-to-leucine substitution that adversely affects SEMA3D function. These results identify Sema3d as a crucial pulmonary venous patterning cue and provide experimental evidence for an alternate developmental model to explain abnormal pulmonary venous connections.

Novel COCH mutation in a family with autosomal dominant late onset sensorineural hearing impairment and tinnitus

This report describes a three generation family with late onset bilateral sensorineural hearing impairment (BLSNHI) and tinnitus in which a novel mutation in the COCH gene was identified after a genome-wide linkage approach. The COCH gene is one of the few genes clinically examined when investigating the etiology of autosomal dominant late onset hearing impairment. Initially mutations in the COCH gene were only reported in exons 4 and 5, coding for the LCCL protein domain. More recently, additional mutations have been identified in exon 12, the only mutations identified outside of the LCCL domain. Currently clinical genetic testing for the COCH gene primarily focuses on identifying mutations in these three exons. In this study, we identify a novel mutation in the COCH gene in exon 11, which, like the exon 12 mutations, falls within the vWFA2 protein domain. This finding reinforces the need for clinical genetic screening of the COCH gene to be expanded beyond the current limited exon screening, as there is now more evidence to support that mutations in other areas of this gene are also causative of a similar form of late onset BLSNHI.

Developmental and behavioral characteristics of individuals with Pallister-Killian syndrome

Pallister-Killian syndrome is a sporadic disorder caused by the presence of mosaic tetrasomy of the short arms of chromosome 12. Case reports of children with Pallister-Killian syndrome have described a range of developmental and behavioral outcomes, but no systematic studies of these outcomes exist. The objective of this study was to describe developmental and behavioral characteristics of individuals with Pallister-Killian syndrome participating in a national meeting of families and their affected children. Sixteen individuals with Pallister-Killian syndrome, ages 16 months to 19 years, were studied using questionnaires and direct interview. Among the 16 patients enrolled in the study, 3 probands were between 16 and 19 months, and had severe developmental delay. Among the rest of the 13 probands older than 24 months, 11 children had a developmental level of less than 8 months age equivalent. They were non-ambulatory, non-verbal, and passive, requiring extensive assistance in daily living. There were two higher functioning children who were ambulatory, and verbal. One of these children met criteria for Autism on the Autism Diagnostic Interview-Revised. Thus, although most individuals with Pallister-Killian syndrome studied showed profound intellectual disability and sensory impairments, individuals with Pallister-Killian syndrome can have mild to moderate intellectual disability. Therefore, in individuals with physical examination findings of Pallister-Killian syndrome, formal diagnostic testing should be considered, even in individuals with mild to moderate intellectual disability. Further studies will be needed to determine if these higher functioning children with Pallister-Killian syndrome are at increased risk for autism.

Novel clinical manifestations in Pallister-Killian syndrome: comprehensive evaluation of 59 affected individuals and review of previously reported cases

Pallister-Killian syndrome is a rare, multi-system developmental diagnosis typically caused by tetrasomy of chromosome 12p that exhibits tissue-limited mosaicism. The spectrum of clinical manifestations in Pallister-Killian syndrome is wide and includes craniofacial anomalies, clefts, ophthalmologic, audiologic, cardiac, musculoskeletal, diaphragmatic, gastrointestinal, genitourinary, and cutaneous anomalies in association with intellectual disability and seizures. Growth parameters are often normal to elevated at birth with deceleration of growth postnatally. No formal estimate of the prevalence of Pallister-Killian syndrome has been made. Here, we report the clinical findings in 59 individuals with Pallister-Killian syndrome who were ascertained at Pallister-Killian syndrome Foundation family meetings held in the summers of 2006, 2008, 2009, and 2010. In addition, the clinical findings of 152 cases reported in the medical literature were reviewed and compared to the cohort examined here. Several novel clinical characteristics were identified through detailed dysmorphology examinations of this cohort and reassertion of a mild developmental variant is described. This report expands the clinical manifestations of Pallister-Killian syndrome and highlights the variable expressivity of this diagnosis with important implications for diagnosis and counseling.

Seizure characteristics in Pallister-Killian syndrome

Pallister-Killian syndrome (PKS) is a congenital disorder attributed to supernumerary isochromosome 12p mosaicism. Craniofacial dysmorphism, learning impairment and seizures are considered cardinal features. However, little is known regarding the seizure and epilepsy patterns in PKS. To better define the prevalence and spectrum of seizures in PKS, we studied 51 patients (39 male, 12 female; median age 4 years and 9 months; age range 7 months to 31 years) with confirmed 12p tetrasomy. Using a parent-based structured questionnaire, we collected data regarding seizure onset, frequency, timing, semiology, and medication therapy. Patients were recruited through our practice, at PKS Kids family events, and via the PKS Kids website. Epilepsy occurred in 27 (53%) with 23 (85%) of those with seizures having seizure onset prior to 3.5 years of age. Mean age at seizure onset was 2 years and 4 months. The most common seizure types were myoclonic (15/27, 56%), generalized convulsions (13/27, 48%), and clustered tonic spasms (similar to infantile spasms; 8/27, 30%). Thirteen of 27 patients with seizures (48%) had more than one seizure type with 26 out of 27 (96%) ever having taken antiepileptic medications. Nineteen of 27 (70%) continued to have seizures and 17/27 (63%) remained on antiepileptic medication. The most commonly used medications were: levetiracetam (10/27, 37%), valproic acid (10/27, 37%), and topiramate (9/27, 33%) with levetiracetam felt to be "most helpful" by parents (6/27, 22%). Further exploration of seizure timing, in-depth analysis of EEG recordings, and collection of MRI data to rule out confounding factors is warranted.

Proteomic profile identifies dysregulated pathways in Cornelia de Lange syndrome cells with distinct mutations in SMC1A and SMC3 genes

Mutations in cohesin genes have been identified in Cornelia de Lange syndrome (CdLS), but its etiopathogenetic mechanisms are still poorly understood. To define biochemical pathways that are affected in CdLS, we analyzed the proteomic profile of CdLS cell lines carrying mutations in the core cohesin genes, SMC1A and SMC3. Dysregulated protein expression was found in CdLS probands compared to controls. The proteomics analysis was able to discriminate between probands harboring mutations in the different domains of the SMC proteins. In particular, proteins involved in the response to oxidative stress were specifically down-regulated in hinge mutated probands. In addition, the finding that CdLS cell lines show an increase in global oxidative stress argues that it could contribute to some CdLS phenotypic features such as premature physiological aging and genome instability. Finally, the c-MYC gene represents a convergent hub lying at the center of dysregulated pathways, and is down-regulated in CdLS. This study allowed us to highlight, for the first time, specific biochemical pathways that are affected in CdLS, providing plausible causal evidence for some of the phenotypic features seen in CdLS.

HDAC8 mutations in Cornelia de Lange syndrome affect the cohesin acetylation cycle

Cornelia de Lange syndrome (CdLS) is a dominantly inherited congenital malformation disorder, caused by mutations in the cohesin-loading protein NIPBL for nearly 60% of individuals with classical CdLS, and by mutations in the core cohesin components SMC1A (~5%) and SMC3 (<1%) for a smaller fraction of probands. In humans, the multisubunit complex cohesin is made up of SMC1, SMC3, RAD21 and a STAG protein. These form a ring structure that is proposed to encircle sister chromatids to mediate sister chromatid cohesion and also has key roles in gene regulation. SMC3 is acetylated during S-phase to establish cohesiveness of chromatin-loaded cohesin, and in yeast, the class I histone deacetylase Hos1 deacetylates SMC3 during anaphase. Here we identify HDAC8 as the vertebrate SMC3 deacetylase, as well as loss-of-function HDAC8 mutations in six CdLS probands. Loss of HDAC8 activity results in increased SMC3 acetylation and inefficient dissolution of the ‘used’ cohesin complex released from chromatin in both prophase and anaphase. SMC3 with retained acetylation is loaded onto chromatin, and chromatin immunoprecipitation sequencing analysis demonstrates decreased occupancy of cohesin localization sites that results in a consistent pattern of altered transcription seen in CdLS cell lines with either NIPBL or HDAC8 mutations.

Congenital heart disease in Cornelia de Lange syndrome: phenotype and genotype analysis

Congenital heart disease (CHD) has been reported to occur in 14-70% of individuals with Cornelia de Lange syndrome (CdLS, OMIM 122470) and accounts for significant morbidity and mortality when present. Charts from a cohort of 479 patients with CdLS were reviewed for cardiac evaluations, gene testing and information to determine phenotypic severity. Two hundred fifty-nine individuals had either documented structural defects or minor cardiac findings. The presence of CHD was then quantified as a function of mutation status and severity of CdLS: mild, moderate, or severe. Different types of CHD were also evaluated by mutation status to assess for any genotype-phenotype correlation. NIPBL, SMC1A, and SMC3 mutation-positive patients were equally likely to have CHD, although the number of SMC1A and SMC3 mutation-positive patients were small in comparison. Structural CHDs were more likely to be present in individuals with moderate and severe CdLS than in the mild phenotype. This study evaluates the trends of CHD seen in the CdLS population and correlates these findings with genotype.

Subtelomeric deletion of chromosome 10p15.3: clinical findings and molecular cytogenetic characterization

We describe 19 unrelated individuals with submicroscopic deletions involving 10p15.3 characterized by chromosomal microarray (CMA). Interestingly, to our knowledge, only two individuals with isolated, submicroscopic 10p15.3 deletion have been reported to date; however, only limited clinical information is available for these probands and the deleted region has not been molecularly mapped. Comprehensive clinical history was obtained for 12 of the 19 individuals described in this study. Common features among these 12 individuals include: cognitive/behavioral/developmental differences (11/11), speech delay/language disorder (10/10), motor delay (10/10), craniofacial dysmorphism (9/12), hypotonia (7/11), brain anomalies (4/6) and seizures (3/7). Parental studies were performed for nine of the 19 individuals; the 10p15.3 deletion was de novo in seven of the probands, not maternally inherited in one proband and inherited from an apparently affected mother in one proband. Molecular mapping of the 19 individuals reported in this study has identified two genes, ZMYND11 (OMIM 608668) and DIP2C (OMIM 611380; UCSC Genome Browser), mapping within 10p15.3 which are most commonly deleted. Although no single gene has been identified which is deleted in all 19 individuals studied, the deleted region in all but one individual includes ZMYND11 and the deleted region in all but one other individual includes DIP2C. There is not a clearly identifiable phenotypic difference between these two individuals and the size of the deleted region does not generally predict clinical features. Little is currently known about these genes complicating a direct genotype/phenotype correlation at this time. These data however, suggest that ZMYND11 and/or DIP2C haploinsufficiency contributes to the clinical features associated with 10p15 deletions in probands described in this study.

Identification of a prenatal profile of Cornelia de Lange syndrome (CdLS): a review of 53 CdLS pregnancies

Cornelia de Lange Syndrome (CdLS) is a multisystem developmental disorder characterized by growth retardation, cognitive impairment, external and internal structural malformations, and characteristic facial features. Currently, there are no definitive prenatal screening measures that lead to the diagnosis of CdLS. In this study, documented prenatal findings in CdLS syndrome were analyzed towards the development of a prenatal profile predictive of CdLS. We reviewed 53 cases of CdLS (29 previously reported and 24 unreported) in which prenatal observations/findings were available. The review of these cases revealed a pattern of sonographic findings, including obvious associated structural defects, growth restriction, as well as a more subtle, but strikingly characteristic, facial profile, and suggestive of a recognizable prenatal ultrasonographic profile for CdLS. In addition, the maternal serum marker, PAPP-A, may be reduced and fetal nuchal translucency (NT) may be increased in some pregnancies when measured at an appropriate gestational age. In conclusion, CdLS can be prenatally diagnosed or readily ruled out in a family with a known mutation in a CdLS gene. The characteristic ultrasonographic profile may allow for prenatal diagnosis of CdLS in (1) subsequent pregnancies to a couple with a prior child with CdLS in whom a mutation has not been identified or (2) when there are unexplained pregnancy signs of fetal abnormality, such as oligo- or polyhydramnios, a low maternal serum PAPP-A level and/or increased NT, fetal growth retardation, or structural anomalies consistent with CdLS.

Evaluating the quality of care provided by graduates of international medical schools

One-quarter of practicing physicians in the United States are graduates of international medical schools. The quality of care provided by doctors educated abroad has been the subject of ongoing concern. Our analysis of 244,153 hospitalizations in Pennsylvania found that patients of doctors who graduated from international medical schools and were not U.S. citizens at the time they entered medical school had significantly lower mortality rates than patients cared for by doctors who graduated from U.S. medical schools or who were U.S. citizens and received their degrees abroad. The patient population consisted of those with congestive heart failure or acute myocardial infarction. We found no significant mortality difference when comparing all international medical graduates with all U.S. medical school graduates.

Germline mosaicism in Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) is a genetic disorder associated with delayed growth, intellectual disability, limb reduction defects, and characteristic facial features. Germline mosaicism has been a described mechanism for CdLS when there are several affected offspring of apparently unaffected parents. Presently, the recurrence risk for CdLS has been estimated to be as high as 1.5%; however, this figure may be an underrepresentation. We report on the molecularly defined germline mosaicism cases from a large CdLS database, representing the first large case series on germline mosaicism in CdLS. Of the 12 families, eight have been previously described; however, four have not. No one specific gene mutation, either in the NIPBL or the SMC1A gene, was associated with an increased risk for germline mosaicism. Suspected or confirmed cases of germline mosaicism in our database range from a conservative 3.4% up to 5.4% of our total cohort. In conclusion, the potential reproductive recurrence risk due to germline mosiacism should be addressed in prenatal counseling for all families who have had a previously affected pregnancy or child with CdLS.

Occurrence and clinical features of epileptic and non-epileptic paroxysmal events in five children with Pallister-Killian syndrome

Pallister-Killian syndrome (PKS) is a rare, sporadic genetic disorder caused by tetrasomy 12p mosaicism associated with a supernumerary isochromosome. Craniofacial dysmorphism, learning impairment and seizures are considered characteristic. However, little is known of the seizure and epilepsy patterns seen in PKS. To better define the occurrence and nature of epileptic and non-epileptic paroxysmal events in PKS, we describe our experience with 5 patients and compare their features with data from a larger cohort of PKS patients ascertained via a web-based parental questionnaire. Three of the 5 patients have had definite epileptic seizures, and one other has had paroxysmal events as yet not clarified. Four of the 5 have also had either non-epileptic paroxysmal events or episodes of uncertain nature. In those with epilepsy, all have had some period of relatively refractory seizures, all have required more than one antiepileptic drug, but none experienced status epilepticus. Only one of the patients with epilepsy (the oldest) has gone into remission. In two of the four with non-epileptic events, video-electroencephalographic monitoring has been valuable in clarifying the nature of the events. EEG characteristics include a slow dominant frequency as well as generalized and focal epileptiform features. Brain MRI findings can be normal but are variable. These specific findings correspond well to information reported by parents in a larger cohort of 51 individuals with PKS. Better understanding of the nature of epileptic and non-epileptic events in PKS will result from a more detailed analysis of objective data obtained from this larger cohort, and from deeper understanding of the molecular impact of 12p tetrasomy in selected cell lines.

Characterization of DNA methylation and its association with other biological systems in lymphoblastoid cell lines

Lymphoblastoid cell line (LCL) is a common tool to study genetic disorders. However, it has not been fully characterized to what degree LCLs preserve the in vivo status of non-genetic biological systems, such as DNA methylation and gene transcription. We previously reported that DNA methylation in LCLs is highly variable in a data set of ~27,000 CpG dinucleotide sites around transcription start site (TSS) and 63 human subjects including healthy controls and probands of genetic disorders. Disease-causing mutations are linked to differential methylation at some CpG sites, but account for a small proportion of the total variance. In this study, we repeated the experiments to ensure that the high variance is not due to technical error and scrutinized the characteristics of DNA methylation and its association with other biological systems. Using sequence information and ChIP-seq data, we conclude that local CpG density and histone modifications not only correlate to baseline methylation level, but also affect the direction of methylation change in LCLs. Integrative analysis of gene transcription and DNA methylation data of the same subjects shows that medium or high methylation around TSS blocks the transcription while low methylation is a necessary, but not sufficient condition of downstream gene transcription. We utilized epigenetic information around TSS to predict active gene transcription via logistic regression models. The multivariate model using DNA methylation, eight histone modifications, and two regulatory protein complexes (CTCF and cohesin) as predictors has better performance (accuracy=95.1%) than any univariate models of single predictors. Linear regression analysis further shows that the transcriptional levels predicted by epigenetic markers have significant correlation to microarray measurements (p=2.2e-10). This study provides new insights into the epigenetic systems of LCLs and suggests that more specifically designed experiments are needed to improve our understanding on this topic.

NIPBL rearrangements in Cornelia de Lange syndrome: evidence for replicative mechanism and genotype-phenotype correlation

PURPOSE

Cornelia de Lange syndrome (CdLS) is a multisystem congenital anomaly disorder characterized by mental retardation, limb abnormalities, distinctive facial features, and hirsutism. Mutations in three genes involved in sister chromatid cohesion, NIPBL, SMC1A, and SMC3, account for ~55% of CdLS cases. The molecular etiology of a significant fraction of CdLS cases remains unknown. We hypothesized that large genomic rearrangements of cohesin complex subunit genes may play a role in the molecular etiology of this disorder.

METHODS

Custom high-resolution oligonucleotide array comparative genomic hybridization analyses interrogating candidate cohesin genes and breakpoint junction sequencing of identified genomic variants were performed.

RESULTS

Of the 162 patients with CdLS, for whom mutations in known CdLS genes were previously negative by sequencing, deletions containing NIPBL exons were observed in 7 subjects (~5%). Breakpoint sequences in five patients implicated microhomology-mediated replicative mechanisms-such as serial replication slippage and fork stalling and template switching/microhomology-mediated break-induced replication-as a potential predominant contributor to these copy number variations. Most deletions are predicted to result in haploinsufficiency due to heterozygous loss-of-function mutations; such mutations may result in a more severe CdLS phenotype.

CONCLUSION

Our findings suggest a potential clinical utility to testing for copy number variations involving NIPBL when clinically diagnosed CdLS cases are mutation-negative by DNA-sequencing studies.

NOTCH2 mutations in Alagille syndrome

BACKGROUND

Alagille syndrome (ALGS) is a dominant, multisystem disorder caused by mutations in the Jagged1 (JAG1) ligand in 94% of patients, and in the NOTCH2 receptor in <1%. There are only two NOTCH2 families reported to date. This study hypothesised that additional NOTCH2 mutations would be present in patients with clinical features of ALGS without a JAG1 mutation.

METHODS

The study screened a cohort of JAG1-negative individuals with clinical features suggestive or diagnostic of ALGS for NOTCH2 mutations.

RESULTS

Eight individuals with novel NOTCH2 mutations (six missense, one splicing, and one non-sense mutation) were identified. Three of these patients met classic criteria for ALGS and five patients only had a subset of features. The mutations were distributed across the extracellular (N=5) and intracellular domains (N=3) of the protein. Functional analysis of four missense, one nonsense, and one splicing mutation demonstrated decreased Notch signalling of these proteins. Subjects with NOTCH2 mutations demonstrated highly variable expressivity of the affected systems, as with JAG1 individuals. Liver involvement was universal in NOTCH2 probands and they had a similar prevalence of ophthalmologic and renal anomalies to JAG1 patients. There was a trend towards less cardiac involvement in the NOTCH2 group (60% vs 100% in JAG1). NOTCH2 (+) probands exhibited a significantly decreased penetrance of vertebral abnormalities (10%) and facial features (20%) when compared to the JAG1 (+) cohort.

CONCLUSIONS

This work confirms the importance of NOTCH2 as a second disease gene in ALGS and expands the repertoire of the NOTCH2 related disease phenotype.

Genome-wide SNP genotyping identifies the Stereocilin (STRC) gene as a major contributor to pediatric bilateral sensorineural hearing impairment

Hearing loss is the most prevalent sensory perception deficit in humans, affecting 1/500 newborns, can be syndromic or nonsyndromic and is genetically heterogeneous. Nearly 80% of inherited nonsyndromic bilateral sensorineural hearing loss (NBSNHI) is autosomal recessive. Although many causal genes have been identified, most are minor contributors, except for GJB2, which accounts for nearly 50% of all recessive cases of severe to profound congenital NBSNHI in some populations. More than 60% of children with a NBSNHI do not have an identifiable genetic cause. To identify genetic contributors, we genotyped 659 GJB2 mutation negative pediatric probands with NBSNHI and assayed for copy number variants (CNVs). After identifying 8 mild-moderate NBSNHI probands with a Chr15q15.3 deletion encompassing the Stereocilin (STRC) gene amongst this cohort, sequencing of STRC was undertaken in these probands as well as 50 probands and 14 siblings with mild-moderate NBSNHI and 40 probands with moderately severe-profound NBSNHI who were GJB2 mutation negative. The existence of a STRC pseudogene that is 99.6% homologous to the STRC coding region has made the sequencing interpretation complicated. We identified 7/50 probands in the mild-moderate cohort to have biallelic alterations in STRC, not including the 8 previously identified deletions. We also identified 2/40 probands to have biallelic alterations in the moderately severe-profound NBSNHI cohort, notably no large deletions in combination with another variant were found in this cohort. The data suggest that STRC may be a common contributor to NBSNHI among GJB2 mutation negative probands, especially in those with mild to moderate hearing impairment.

Renal anomalies in Alagille syndrome: a disease-defining feature

Alagille syndrome (ALGS) is an autosomal dominant condition, primarily caused by mutations in JAGGED1. ALGS is defined by cholestatic liver disease, cardiac disease and involvement of the face, skeleton, and eyes with variable expression of these features. Renal involvement has been reported though not formally described. The objective of this study was to systematically characterize the renal involvement in ALGS. We performed a retrospective review of 466 JAGGED1 mutation-positive ALGS patients. Charts were reviewed for serum biochemistries, renal ultrasounds or other imaging, urinalysis, and clinical reports from pediatric nephrologists. The clinical data were reviewed by two pediatric hepatologists and a pediatric nephrologist. Of 466 charts reviewed we found 187 yielded evaluable renal information. Of these, 73/187 were shown to have renal involvement, representing 39% of the study cohort. Renal dysplasia was the most common anomaly seen. Genotype analysis of the JAGGED1 mutations in the patients with and without renal involvement did not reveal an association with mutation type. From the study we concluded that renal involvement has a prevalence of 39% in ALGS in our evaluable patients. Renal dysplasia is the most common renal anomaly. This finding correlates with the known role of the Notch pathway in glomerular development. Since renal disease of the type seen in ALGS can impair growth and impact liver transplantation, there is a clear need for a prospective study of renal involvement in ALGS and the development of guidelines for evaluation and management. These data also suggest that renal involvement be considered the sixth defining criterion for ALGS.

Causes of death and autopsy findings in a large study cohort of individuals with Cornelia de Lange syndrome and review of the literature

To identify causes of death (COD) in propositi with Cornelia de Lange syndrome (CdLS) at various ages, and to develop guidelines to improve management and avoid morbidity and mortality, we retrospectively reviewed a total of 426 propositi with confirmed clinical diagnoses of CdLS in our database who died in a 41-year period between 1966 and 2007. Of these, 295 had an identifiable COD reported to us. Clinical, laboratory, and complete autopsy data were completed on 41, of which 38 were obtainable, an additional 19 had autopsies that only documented the COD, and 45 propositi had surgical, imaging, or terminal event clinical documentation of their COD. Proband ages ranged from fetuses (21-40 weeks gestation) to 61 years. A literature review was undertaken to identify all reported causes of death in CdLS individuals. In our cohort of 295 propositi with a known COD, respiratory causes including aspiration/reflux and pneumonias were the most common primary causes (31%), followed by gastrointestinal disease, including obstruction/volvulus (19%). Congenital anomalies accounted for 15% of deaths and included congenital diaphragmatic hernia and congenital heart defects. Acquired cardiac disease accounted for 3% of deaths. Neurological causes and accidents each accounted for 8%, sepsis for 4%, cancer for 2%, renal disease for 1.7%, and other causes, 9% of deaths. We also present 21 representative clinical cases for illustration. This comprehensive review has identified important etiologies contributing to the morbidity and mortality in this population that will provide for an improved understanding of clinical complications, and management for children and adults with CdLS.

The incidence of thrombocytopenia in children with Cornelia de Lange syndrome

Thrombocytopenia was first reported in Cornelia de Lange syndrome (CdLS) by Froster in 1993. Despite early reports, thrombocytopenia has been rarely reported in this disorder. We performed a retrospective analysis of a large cohort of patients with CdLS. We calculated prevalence of thrombocytopenia in three subsets of this cohort: the entire cohort (n = 1,740), a subset of subjects with substantial clinical records (n = 695) and a subset of subjects with clinical information regarding platelet counts (n = 85). This analysis revealed that 15 have had thrombocytopenia (18% of those with available blood counts); seven had immune thrombocytopenia (ITP). The reported prevalence of pediatric ITP is between 5 and 13 per 100,000 persons. The prevalence of ITP in this cohort is between 7/1,740 and 7/85, giving a relative risk of ITP of between 30 (CI 12-77) and 633 (CI 259-1,549). Contrary to the reported cases in the literature, none of our patients have had progression of the thrombocytopenia nor have they developed other cytopenias. All 15 patients with thromobocytopenia had CdLS based on clinical criteria. Of the 10 patients tested for mutations in NIBPL, 8 had mutations identified. These data support an increased incidence of thrombocytopenia and ITP in CdLS. Subsequently, patients are at risk for spontaneous hemorrhage, and likely increased risk secondary to the high frequency of self-injurious behavior. Although further studies are needed to better define the scope of the problem and to define the mechanisms of thrombocytopenia in CdLS, we would recommend screening for thrombocytopenia upon diagnosis and at 5-year intervals thereafter.

Facial diagnosis of mild and variant CdLS: Insights from a dysmorphologist survey

Cornelia de Lange syndrome (CdLS) is a dominant disorder with classic severe forms and milder atypical variants. Central to making the diagnosis is identification of diagnostic facial features. With the recognition that patients with SMC1A and SMC3 mutations have milder, atypical features, we surveyed 65 dysmorphologists using facial photographs from 32 CdLS patients with the goals of (1) Illustrating examples of milder patients with SMC1A mutations and (2) Obtaining objective data to determine which facial features were useful and misleading in making a diagnosis of CdLS. Clinicians were surveyed whether the patient had CdLS or another diagnosis, the certainty of response and the clinical features used to support each response. Using only facial photographs, an average of 24 cases (75%) were accurately diagnosed per clinician. Correct diagnoses were made in 90% of classic CdLS and 87% of non-CdLS cases, however, only 54% of mild or variant CdLS were correctly diagnosed by respondents. We confirmed that CdLS is most accurately diagnosed in childhood and the diagnosis becomes increasingly difficult with age. This survey demonstrated that emphasis is placed on the eyebrows, nasal features, prominent upper lip and micrognathia. In addition, the presence of fuller, atypical eyebrows, a prominent nasal bridge and significant prognathism with age dissuaded survey takers from arriving at a diagnosis of CdLS in individuals with mild NIPBL and SMC1A mutations. This work underscores the difficulty in diagnosing patients with mild and variant CdLS and serves to objectively classify both useful and misleading features in the diagnosis of CdLS.

Genome-wide DNA methylation analysis in cohesin mutant human cell lines

The cohesin complex has recently been shown to be a key regulator of eukaryotic gene expression, although the mechanisms by which it exerts its effects are poorly understood. We have undertaken a genome-wide analysis of DNA methylation in cohesin-deficient cell lines from probands with Cornelia de Lange syndrome (CdLS). Heterozygous mutations in NIPBL, SMC1A and SMC3 genes account for ∼65% of individuals with CdLS. SMC1A and SMC3 are subunits of the cohesin complex that controls sister chromatid cohesion, whereas NIPBL facilitates cohesin loading and unloading. We have examined the methylation status of 27 578 CpG dinucleotides in 72 CdLS and control samples. We have documented the DNA methylation pattern in human lymphoblastoid cell lines (LCLs) as well as identified specific differential DNA methylation in CdLS. Subgroups of CdLS probands and controls can be classified using selected CpG loci. The X chromosome was also found to have a unique DNA methylation pattern in CdLS. Cohesin preferentially binds to hypo-methylated DNA in control LCLs, whereas the differential DNA methylation alters cohesin binding in CdLS. Our results suggest that in addition to DNA methylation multiple mechanisms may be involved in transcriptional regulation in human cells and in the resultant gene misexpression in CdLS.

Jagged1 (JAG1) mutations in patients with tetralogy of Fallot or pulmonic stenosis

Mutations in the Notch pathway ligand Jagged1 (JAG1) cause Alagille syndrome (AGS), as well as cardiac defects in seemingly nonsyndromic individuals. To estimate the frequency of JAG1 mutations in cases with right-sided cardiac defects not otherwise diagnosed with AGS, we screened 94 cases with tetralogy of Fallot (TOF) and 50 with pulmonic stenosis/peripheral pulmonary stenosis (PS/PPS) or pulmonary valve atresia with intact ventricular septum (PA) for mutations. Sequence changes were identified in three TOF and three PS/PPS/PA patients, that were not present in 100 controls. We identified one frameshift and two missense mutations in the TOF cases, and one frameshift and two missense mutations in cases with PS/PPS/PA. The four missense mutations were assayed for their effect on protein localization, posttranslational modification, and ability to activate Notch signaling. The missense mutants displayed heterogeneous behavior in these assays, some with complete haploinsufficiency, suggesting that there are additional modifiers leading to organ specific features. We identified functionally significant mutations in 2% (2/94) of TOF patients and 4% (2/50) of PS/PPS/PA patients. Patients with right-sided cardiac defects should be carefully screened for features of AGS or a family history of cardiac defects that might suggest the presence of a JAG1 mutation.

Mutations and variants in the cohesion factor genes NIPBL, SMC1A, and SMC3 in a cohort of 30 unrelated patients with Cornelia de Lange syndrome

Cornelia de Lange syndrome (CdLS) manifests facial dysmorphic features, growth and cognitive impairment, and limb malformations. Mutations in three genes (NIPBL, SMC1A, and SMC3) of the cohesin complex and its regulators have been found in affected patients. Here, we present clinical and molecular characterization of 30 unrelated patients with CdLS. Eleven patients had mutations in NIPBL (37%) and three patients had mutations in SMC1A (10%), giving an overall rate of mutations of 47%. Several patients shared the same mutation in NIPBL (p.R827GfsX2) but had variable phenotypes, indicating the influence of modifiers in CdLS. Patients with NIPBL mutations had a more severe phenotype than those with mutations in SMC1A or those without identified mutations. However, a high incidence of palate defects was noted in patients with SMC1A mutations. In addition, we observed a similar phenotype in both male and female patients with SMC1A mutations. Finally, we report the first patient with an SMC1A mutation and the Sandifer complex.