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20p12.3 microdeletion predisposes to Wolff–Parkinson–White syndrome with variable neurocognitive deficits
  1. S R Lalani1,
  2. J V Thakuria2,
  3. G F Cox2,
  4. X Wang1,
  5. W Bi1,
  6. M S Bray1,
  7. C Shaw1,
  8. S W Cheung1,
  9. A C Chinault1,
  10. B A Boggs1,
  11. Z Ou1,
  12. E K Brundage1,
  13. J R Lupski1,
  14. J Gentile2,
  15. S Waisbren2,
  16. A Pursley1,
  17. L Ma3,
  18. M Khajavi1,
  19. G Zapata1,
  20. R Friedman4,
  21. J J Kim4,
  22. J A Towbin4,
  23. P Stankiewicz1,
  24. S Schnittger5,
  25. I Hansmann6,
  26. T Ai7,
  27. S Sood7,
  28. X H Wehrens7,
  29. J F Martin3,
  30. J W Belmont1,
  31. L Potocki1
  1. 1
    Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
  2. 2
    Division of Genetics, Children’s Hospital Boston, Boston, Massachusetts, USA
  3. 3
    Institute of Biosciences and Technology, Texas A&M System Health Science Center, Houston, Texas, USA
  4. 4
    Department of Cardiology, Baylor College of Medicine, Houston, Texas, USA
  5. 5
    MLL Munich Leukemia Laboratory, Munich, Germany
  6. 6
    Institut für Humangenetik und Medizinische Biologie, Halle/Saale, Germany
  7. 7
    Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, USA
  1. Dr S R Lalani, Department of Molecular and Human Genetics, One Baylor Plaza, BCM225, MARB, R713, Houston, Texas 77030, USA; seemal{at}bcm.tmc.edu

Abstract

Background: Wolff–Parkinson–White syndrome (WPW) is a bypass re-entrant tachycardia that results from an abnormal connection between the atria and ventricles. Mutations in PRKAG2 have been described in patients with familial WPW syndrome and hypertrophic cardiomyopathy. Based on the role of bone morphogenetic protein (BMP) signalling in the development of annulus fibrosus in mice, it has been proposed that BMP signalling through the type 1a receptor and other downstream components may play a role in pre-excitation.

Methods and results: Using the array comparative genomic hybridisation (CGH), we identified five individuals with non-recurrent deletions of 20p12.3. Four of these individuals had WPW syndrome with variable dysmorphisms and neurocognitive delay. With the exception of one maternally inherited deletion, all occurred de novo, and the smallest of these harboured a single gene, BMP2. In two individuals with additional features of Alagille syndrome, deletion of both JAG1 and BMP2 were identified. Deletion of this region has not been described as a copy number variant in the Database of Genomic Variants and has not been identified in 13 321 individuals from other cohort examined by array CGH in our laboratory.

Conclusions: Our findings demonstrate a novel genomic disorder characterised by deletion of BMP2 with variable cognitive deficits and dysmorphic features and show that individuals bearing microdeletions in 20p12.3 often present with WPW syndrome.

https://doi.org/10.1136/jmg.2008.061002

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    Wolff–Parkinson–White syndrome (WPW) is a pre-excitation disorder that is associated with specific electrocardiography (ECG) findings, including a shortened for age PR interval and a slurred upstroke to the QRS complex (that is, delta wave). While some individuals may remain asymptomatic throughout their lives, others are prone to tachyarrhythmias that may be life threatening. The prevalence of this condition based on the ECG criteria is estimated to be 1–3/1000 individuals.1 A genetic basis for this condition was initially inferred by Vidaillet et al2 who found familial occurrence of accessory atrioventricular (AV) pathways in 3.4% of WPW probands. Typically, WPW syndrome occurs sporadically; however, in a minority of cases it is inherited either as an autosomal dominant simple pre-excitation trait,3 or as part of a more complex phenotype, such as Ebstein’s anomaly,4 mitochondrial disease,5 or hypertrophic cardiomyopathy (HCM).6 The first description of a molecular basis of WPW syndrome was provided by Blair et al7 and Gollob et al8 who reported mutations in the γ-2 regulatory subunit of AMP activated protein kinase (PRKAG2) in patients with familial HCM and WPW syndrome.

    Here we describe four patients with electrocardiographic features of WPW syndrome, cognitive delay and dysmorphic features, who were found to have variable chromosomal deletions involving BMP2.

    PATIENTS AND METHODS

    Written informed consents were obtained from the patients and the study was performed in accordance with the institutional guidelines for human research with approval by the institutional review board at Baylor College of Medicine. Our patients consisted of two groups: group 1 included five individuals with variable 20p12 deletions; and group 2 comprised 20 individuals with either isolated WPW syndrome or WPW with associated HCM. Ventricular pre-excitation was diagnosed in four out of five individuals in group 1 and all patients in group 2, based on standard 12 lead ECG, on the basis of a short PR interval (<120 ms), with a prolonged QRS complex (>110 ms) and an abnormal initial QRS vector (a delta wave).

    Patient 1

    In the first group, patient 1 was ascertained when array comparative genomic hybridisation (CGH) was performed at age 2.5 months because of dysmorphisms, mild hypotonia, and WPW syndrome. He was born after a full term pregnancy; his birth weight was 3140 g (25th centile), his length was 47 cm (10th centile), and his head circumference was 34 cm (25th centile). He was incidentally found to have WPW during the evaluation for suspected seizures and mild respiratory difficulties in the newborn period. Echocardiogram showed an atrial septal defect. Brain imaging studies, electroencephalography (EEG), and brainstem auditory evoked response (BAER) testing were normal. He began walking at 14 months of age. Language delay was suspected and formal testing at 20 months using the Preschool Language Scales, 4th edition (PLS-4), determined a score of 79, below the average range of abilities for comprehension and use of spoken language. Using Stark Assessment of Early Vocal Development (SAEVD), he was placed at level 5, the “Canonical Syllables” stage of vocal development, typically mastered between 6–10 months of age. His physical examination at 20 months of age showed both weight and height 2 SD below the mean and head circumference at 25th centile. Dysmorphic features included downslanting palpebral fissures, bilateral epicanthal folds, broad nasal root and bridge, malar hypoplasia, full cheeks with microstomia, pectus deformity with a carinatum appearance superiorly and excavatum appearance inferiorly, and persistent fetal pads (fig 1A, B). He continues to have asymptomatic WPW.

    Figure 1
    Figure 1 Photographs of individuals with submicroscopic BMP2 deletion (submitted with written consents from the patient or his/her legal guardian for publication in print and online). Patient 1 (A, B) at the age of 12 months, with downslanting palpebral fissures, malar hypoplasia, long philtrum, microstomia, and pectus deformity. Patient 2 (C, D) at the age of 5 years, with macrocephaly, a frontal upsweep, downslanting palpebral fissures, hypertelorism, long philtrum, microstomia, and small ears with thickened helices. Patient 3 (E, F) at the age of 37 years, with hypertelorism, malar hypoplasia and macrocephaly.

    Patients 2 and 3

    Patient 2 in group 1 was born full term with birth weight of 8 lb (3.6 kg) (75th centile) and length of 19 inches (48 cm) (25th centile) to a mother with a history of learning difficulties. Four hours after birth, he developed supraventricular tachycardia and was diagnosed with WPW syndrome. On echocardiogram, there was no evidence of a structural heart defect. Brain magnetic resonance imaging (MRI) showed ventriculomegaly with a prominent subarachnoid space consistent with benign external hydrocephalus. BAER testing was normal. He had moderate cognitive, speech and gross motor delays. He started walking independently at 17 months of age. Using the Bayley Scales of Infant Development at 5 years of age, he tested at 34 month, 42 month and 39 month levels for cognition, receptive communication, and expressive communication, respectively. His physical examination at the age of 5 years showed weight at 75th centile, height at 25th centile and head circumference 2.5 SD above the mean. His dysmorphic features included macrocephaly, a frontal upsweep, downslanting palpebral fissures, epicanthal folds, hypertelorism, long philtrum, microstomia, small ears with thickened helices, and broad thumbs and toes with persistent fetal pads (fig 1C, D). Supraventricular tachycardia (SVT) in this patient was controlled with sotalol.

    Patient 3, the mother of patient 2, exhibited mild cognitive delay and required special education from elementary through high school years. On Wechsler Adult Intelligence Scale, 3rd edition (WAIS-III), her overall IQ was determined to be 90, with below average score of 84 (14th centile) for working memory and processing speed. Using the Behavior Rating Inventory of Executive Function, Parent Form, she scored in the clinically significant range with metacognition index T score of 67 (93%), indicating difficulty to initiate, plan, organise, and sustain future oriented problem solving. Using Conners’ ADHD (attention deficit hyperactivity disorder) Index, she scored in the clinically significant range for inattention and memory problems. Her dysmorphisms, when evaluated at 37 years of age, included macrocephaly, with head circumference 2.25 SD above the mean, hypertelorism, malar hypoplasia and persistent fetal pads (fig 1E, F). Although she had a previous history of palpitations and suspected SVT, she did not have features consistent with WPW by ECG and Holter monitoring at the time of evaluation.

    Patients 4 and 5

    The clinical features and cytogenetic findings of patients 4 and 5 in group 1 have been described previously9 10 and are summarised in table 1.

    View this table:
    Table 1 Clinical features of five patients with variable deletions involving BMP2

    Array CGH

    Peripheral blood samples from patients 1, 2, and 3 in group 1 were submitted for clinical testing to the Baylor Medical Genetics Laboratories (http://www.bcm.edu/cma/) for bacterial artificial chromosome (BAC) array CGH analyses. Reciprocal dye reversal experiments were performed as previously described.11 Hybridised arrays were scanned into 16-bit TIFF image files using an Axon two-colour microarray scanner 4000B and quantified by using GenePix Pro 6.0 software (GenePix 4000B from Axon Instruments, Union City, California, USA). Data analysis was performed by a web-based software platform with the capability of displaying the raw, normalised, and integrated data of all clones to detect genomic copy number changes for each patient relative to a gender matched control as described.12 A copy number loss was determined by a combined log2 ratio of test/control <−0.2 and a p value <0.05. Fluorescence in situ hybridisation (FISH) experiments on metaphase were performed to confirm deletion of the region corresponding to BAC clone, RP11-116E13 in three patients identified by the clinical array CGH. Miniprep BAC DNA (100 ng) was labelled with Spectrum Orange-dUTP or Spectrum Green-dUTP (Vysis, Downers Grove, Illinois, USA), according to the manufacturer’s instructions, and used as probes for FISH analysis using standard protocols.13 To map precisely the deletion breakpoints, genome-wide analysis for DNA copy number alterations was performed in patient 1 using Illumina HumanHap300 genotyping BeadChip array (317K, Illumina, San Diego, California, USA) and in patients 2, 3 and 5 using the Agilent Human Genome Microarray Kit 244A (Agilent Technologies, Santa Clara, California, USA) according to the manufacturer’s specifications, as described previously.14 15

    Southern analysis

    Deletion mapping of patient 4 was performed by semiquantitative Southern blotting using nine genic and restriction fragment length polymorphism (RFLP) probes, spanning loci from 20p11.23 to 20p13. Measurements were performed with most probes on three independent Southern blots. DNA probes used were pBMP for BMP, lambdaHDGI for PDYN, HuPrPcDNA for PRNP, hSGI for SCGI, pR12.21 for D20S5, pD3H12 for D20S6, pFMS76 for D20S23 and Mfd25 for D20S27.

    BMP2 gene copy number analysis and sequencing

    Group 2 patients were studied with a customised high definition CGH microarray (Agilent Technologies) in a 44 K format that included 45 predesigned, in silico validated oligonucleotide probes (∼60 bp) spanning exonic, intronic, and 5′ and 3′ regions of BMP2. Agilent data were analysed using Feature Extraction and CGH Analytics softwares from the manufacturer. Mutation analysis of BMP2 was also performed in this group after amplifying the protein encoding sequences of BMP2 through the polymerase chain reaction (PCR) from genomic DNA (sequence of primers and amplification conditions available on request). The PCR products were purified using ExoSAP-IT (USB Corporation, Cleveland, Ohio, USA) and sequenced with a dye terminator cycle sequencing system (Applied Biosystems 3730xl).

    Generating Bmp2 null allele

    To generate the Bmp2LacZ knock-in allele, a targeting vector was constructed that introduced SalI and Xho sites into exon3 that encodes the Bmp2 mature ligand. A LacZ-cassette followed by a loxp-flanked PGKneomycin resistance gene was cloned into the SalI and Xho sites resulting in removal of the majority of the coding sequence in exon3 to generate a Bmp2 null allele. The mice for this study were on a mixed genetic background B6/129/ICR.

    Cardiac electrophysiology

    Fourteen Bmp2+/− mice of different age groups (9: 3 weeks old; 3: 9 weeks old; and 2: 18 months old) were analysed for pre-excitation. The Bmp2+/− mice and 4 WT were anesthetised with isoflurane (1.5% with 100% O2). In vivo cardiac electrophysiology was performed using a computer based data acquisition system. An eight electrode lumen catheter (1.1F, model EPR-800, Millar Instruments, Houston, Texas, USA) was inserted through the jugular vein and advanced into the right atrium and ventricle for pacing and recording. Surface and intracardiac electrophysiology parameters were assessed at baseline, as described.16 Right atrial pacing was performed using 2 ms current pulses delivered by an external stimulator (STG-3008, MultiChannel Systems, Reutlingen, Germany). After a period of baseline rhythm, decremental atrial pacing was applied whereby the cycle length was repeatedly shortened by 2 ms, starting from a pacing cycle length of 20 ms less than the intrinsic sinus cycle length, until continuous atrial capture could not be maintained. Sinus node recovery time (SNRT), measured after a 15 s pacing train with a basic cycle length (BCL) of 100 ms, was defined as the interval between the last stimulus in the pacing train and the onset of first sinus return beat. Atrial effective refractory period (AERP), measured at a BCL of 100 ms, was defined as the longest S1–S2 coupling interval for atria that failed to capture. Atrioventricular nodal ERP (AVERP) was defined as the maximal S1S2 coupling interval that failed to propagate to the ventricle. To assess the presence of accessory pathway, adenosine (2 mg/kg intravenously) was administered and the recordings were evaluated for AV block. Inducibility of atrial fibrillation was tested twice, according to the protocol described by Verheule et al.17

    RESULTS

    Array CGH

    The diagnostic array CGH analysis in patient 1 identified genomic loss of copy number involving 20p12.3, detected by one BAC clone RP11-116E13 (fig 2A). In patients 2 and 3, in addition to this genomic region, a loss of the genomic region corresponding to the BAC clone RP11-973N22 and located ∼1 Mb centromeric to RP11-116E13 was found (fig 2D). These findings were subsequently verified by FISH analyses (fig 2C, E). Using genome-wide CGH array, patient 1 was found to have a de novo copy number loss of 1.1 Mb, involving only one gene, BMP2 (fig 2B). Patients 2 and 3, the proband and his mother were both found to have a larger 2.3 Mb deletion involving BMP2 and seven other genes (fig 2F, G). This deletion was not identified in the unaffected parents of patient 3 (supplemental fig 1). To address whether the identified deletion was a benign copy number variant (CNV), we analysed the hybridisation data from these two clones in 13 321 individuals subjected to the clinical array CGH at Baylor Medical Genetics Laboratory. None of the other individuals analysed demonstrated loss of copy number detected by these clones with combined log2 ratio of test/control <−0.2 as seen in patients 1, 2 and 3. In addition, no CNVs in the deleted region were identified in the Database of Genomic Variants (http://projects.tcag.ca/variation/), indicating that there are no large common copy number polymorphisms in this genomic region.

    Figure 2
    Figure 2 Summary of the results using targeted array comparative genomic hybridisation (CGH), fluorescence in situ hybridisation (FISH) and genome wide array CGH analyses in patients 1, 2, and 3. Note the genomic loss of copy number detected by RP11-116E13 in patients 1, 2, 3 with additional loss of copy number detected by RP11-973N22 in patients 2, 3 (A, D, circled), identified on the clinical array CGH. FISH confirmed the deletion detected by RP11-116E13 in these patients by the loss of hybridisation signal on one copy of chromosome 20 (C, E, deletion represented by the highlighted arrow). Fine mapping of the breakpoints using Illumina HumanHap300 genotyping BeadChip array (317K) in patient 1 (B), showed a de novo 1.1 Mb deletion involving a single gene, BMP2. The 244k Human Genome Agilent microarray showed 2.3 Mb deletion involving multiple genes, including BMP2 in patients 2 and 3 (F and G, respectively).

    Since haploinsufficiency for JAG1, located in close proximity to BMP2 on 20p12.2, causes Alagille syndrome (MIM 118450),18 we investigated whether WPW syndrome was reported in previously described patients with Alagille syndrome having larger deletions involving 20p12. We identified two such cases, patient 4 with del(20)(p11.23)9 and patient 5 with del(20)(p12p13).10 Genotyping of patient 4 by semiquantitative Southern blotting mapped the distal breakpoint between CHGB and PRNP and the proximal breakpoint between D20S6 and D20S23. Thus the deletion of this patient spanned a segment of at least 4.2 Mb harbouring the BMP2 gene (fig 3). Using genome-wide CGH array analysis, patient 5 was found to have a genomic copy number loss of 10.7 Mb, including BMP2 (fig 3). We then assessed whether point mutations in BMP2 account for WPW, both in the isolated cases as well as in those with WPW associated with hypertrophic cardiomyopathy. Analysis of 20 such individuals did not reveal mutations in the coding region of this gene. Additionally, a customised high resolution array CGH analysis did not detect significant copy number alterations involving the BMP2 gene in these patients.

    Figure 3
    Figure 3 Schematic illustration of the identified deletions of distal chromosome 20p in patients 1–5, with contiguous genes represented between the 4.7–10.6 Mb interval.

    Phenotype characterisation of Bmp2+/− mice by electrophysiology

    There was no significant difference in the mean (SD) PR interval (46 (3.3) vs 43 (2.9) ms; ns) or QRS duration (9.8 (3.9) vs 8.8 (0.6) ms; ns) comparing WT and Bmp2+/− mice. The AV refractory period, atrial effective refractory period and the sinus node recovery times were not altered in the WT and Bmp2+/− mice (data not shown). There was no evidence of delta wave in any of the 14 Bmp2+/− mice studied. Evidence of accessory pathway in Bmp2+/− was evaluated using atrial programmed electrical stimulation. Decremental atrial pacing resulted in prolonged AV conduction in both WT and Bmp2+/− mice. Intravenous adenosine injection during atrial pacing resulted in AV block in all the mice (4 WT and 14 Bmp2+/−) studied, indicating the absence of an accessory pathway. None of the mice showed evidence of atrial arrhythmias.

    DISCUSSION

    Over the last decade, it has become increasingly evident that the genetic mechanisms for many disease traits involve genomic rearrangements rather than point mutations in single genes.19 Locus specific mutation rates for genomic rearrangements have been found to be 2–4 orders of magnitude greater than nucleotide specific rates for base substitutions.20 Here, we report the first clinical description of a genomic disorder causing ventricular pre-excitation and cognitive delay associated with heterozygous deletion within 20p12.3. The description of the smallest de novo deletion involving only the BMP2 gene in patient 1 and others with variable 20p12 deletions, all including BMP2, suggests that the clinical phenotype of WPW in these patients may be a consequence of hemizygosity of BMP2. JAG1, the gene responsible for Alagille syndrome, maps approximately 3.8 Mb centromeric to BMP2. Alagille syndrome is a complex multisystem disorder with clinical manifestations including intrahepatic bile duct paucity and right ventricular outflow tract defects.21 While WPW is not a feature of Alagille syndrome, we hypothesised that rare individuals with deletions involving both JAG1 and BMP2 would have WPW syndrome. This was indeed demonstrated in both patients 4 and 5, who were described previously with cytogenetically visible deletions of chromosome 20p. Furthermore, we studied an additional patient with Alagille syndrome with a large (∼6 Mb) 20p deletion who did not manifest WPW and found that while the deletion encompassed JAG1, the distal breakpoint of the deletion mapped approximately 400 kb centromeric to BMP2, involving the most adjacent proximal gene, HAO1 and leaving the BMP2 gene intact (supplemental fig 2).

    The role of bone morphogenic proteins has been extensively studied in heart, neural, bone, and cartilage development. The signalling of these proteins belonging to the class of transforming growth factor, TGF-β superfamily of proteins is known to be mediated through specific type I and II serine/threonine kinase receptors. BMP2 binds to the type II receptors, BMPRII and ActRIIA, and the type I receptors, ALK3 and ALK6.22 The interaction of intracellular Smad signalling molecules with these receptor complexes and other transcription factors defines the range of biological responses associated with the BMPs. Although homozygous null mutation of BMP2 in mouse results in embryonic lethality,23 conditional ablation of Bmp2 has shown that Bmp2 deficient endothelium is unable to undergo epithelial to mesenchymal transformation (EMT), thus impairing the development of endocardial cushion.24 Gaussin et al25 showed that Alk3/Bmpr1a receptor is required for development of the AV canal (AVC) into valves as well as the formation of annulus fibrosus, which insulates the ventricles from inappropriate excitation by the atria. By selectively deleting Alk3 in cardiac myocytes of the AVC in mice, conduction defects compatible with pre-excitation were observed. In these mice, the disruption of the posterior annulus fibrosus created a myocytic connection between the left atrium and ventricle connected by gap junctions, Cx43 to conduct the electrical impulse. In WPW syndrome, it is well recognised that the muscular connections outside of the specialised conduction system are composed of myocardial fibres expressing Cx43.26 27 Indeed, disruption of annulus fibrosus by glycogen filled myocytes has been shown to be caused by mutations in PRKAG2.28 These functional analyses facilitate our understanding of the disease pathogenesis as it relates to BMP2 signalling.

    There are about six genes telomeric to BMP2, that are deleted in patients 2, 3, 4 and 5 including KIND1 (associated with autosomal recessive Kindler disease), LRRN4, CRLS1, MCM8, TRMT6, and CHGB. While it is possible that the expression of any of these genes could potentially be affected by the smallest deletion seen in patient 1, BMP2 remains an important candidate gene for WPW based on the common deletion in all affected cases and the phenotype observed in Alk3 conditional knockout mice. Since Bmp2−/− mice are embryonic lethal, we wanted to assess if the WPW phenotype could be recapitulated in Bmp2+/− mice. Detailed electrophysiology study of 14 Bmp2+/− mice did not reveal any evidence of pre-excitation. Apart from the physiological differences between mice and humans, and incomplete penetrance of the cardiac phenotype in Bmp2 heterozygous mice, these findings possibly reflect redundancy among multiple BMP ligands, as promiscuity in the interaction of vertebrate TGFβ ligands and receptors is well characterised and is also evident among protosomal organisms.29

    Key points

    • We describe a novel genomic disorder characterised by Wolff-Parkinson-White (WPW) syndrome, dysmorphic features, and variable cognitive deficits associated with microdeletion of the BMP2 region within 20p12.3.

    • Although WPW is frequently observed with the deletion of 20p12.3, there is some evidence of incomplete penetrance of this phenotype, in contrast to the musculoskeletal and neurocognitive characteristics, which appear to be fully penetrant in this disorder.

    • A contiguous gene deletion syndrome characterised by deletion of both BMP2 and JAG1 can result in pre-excitation with features of Alagille syndrome.

    In this study, we have shown the presence of WPW by ECG in four out of five individuals with deletion of this genomic region. It is important to realise that while anterograde conduction through an accessory pathway produces full pre-excitation resulting in the formation of a typical delta wave, in individuals with concealed accessory pathways, pre-excitation may not be readily visible on a standard 12 lead ECG, as conduction through the pathway is primarily retrograde (ventriculo-atrial). This can be true even in patients who have documented typical episodes of AV tachycardia.30 This is indeed a consideration in patient 3 with history of palpitations and a normal ECG. It is also possible that this individual did at one time have more prominent antegrade conduction through an accessory pathway and the conduction characteristics have since changed such that pre-excitation is currently not easily detected. It is well described that antegrade conduction through an accessory pathway can be variable or intermittent. Without prior ECGs or documentation of arrhythmias in this patient, the only definitive recourse would be an invasive electrophysiologic evaluation. While concealed accessory pathway is one explanation for the lack of WPW phenotype on ECG in patient 3, incomplete penetrance of the cardiac phenotype is also possible. Although the penetrance of pre-excitation in patients with deletion of this region on 20p12.3 will be better evaluated when more individuals are ascertained, the neurocognitive deficits and dysmorphisms appear to be fully penetrant in this disorder.

    Based on its embryonic pattern of expression, it is likely that disruption of BMP2 signalling causes diverse phenotypes in humans. Whether the BMP2 deletion alone is causally related to dysmorphisms and developmental problems seen in patients 1, 2, and 3 is not yet certain; however, this may reflect pleiotropic effects of BMP2 on musculoskeletal and language development.

    Our findings demonstrate a novel genomic disorder characterised by WPW syndrome and cognitive deficits and associated with microdeletion of the BMP2 region within 20p12.3. Additionally, we describe a new contiguous gene deletion syndrome with BMP2 and JAG1 deletions resulting in both WPW and features of Alagille syndrome. We have shown that patients bearing microdeletions in 20p12.3 often present with WPW. These individuals also exhibit variable cognitive deficits and dysmorphic features. If haploinsufficiency of BMP2 is indeed the mechanism involved in the conduction abnormalities seen in these patients, other defects of TGFβ signalling may be important in causing this relatively common developmental defect.

    Acknowledgments

    We are indebted to the families who participated in the study.

    REFERENCES

    1. ↵
      1. Packard JM,
      2. Graettinger JS,
      3. Graybiel A
      . Analysis of the electrocardiograms obtained from 1000 young healthy aviators; ten year follow-up. Circulation 1954;10:384–400.
      OpenUrlAbstract/FREE Full Text
    2. ↵
      1. Vidaillet HJ, Jr,
      2. Pressley JC,
      3. Henke E,
      4. Harrell FE, Jr,
      5. German LD
      . Familial occurrence of accessory atrioventricular pathways (preexcitation syndrome). N Engl J Med 1987;317:65–9.
      OpenUrlCrossRefPubMedWeb of Science
    3. ↵
      1. Chia BL,
      2. Yew FC,
      3. Chay SO,
      4. Tan AT
      . Familial Wolff-Parkinson-White syndrome. J Electrocardiol 1982;15:195–8.
      OpenUrlCrossRefPubMedWeb of Science
    4. ↵
      1. Deal BJ,
      2. Keane JF,
      3. Gillette PC,
      4. Garson A, Jr
      . Wolff-Parkinson-White syndrome and supraventricular tachycardia during infancy: management and follow-up. J Am Coll Cardiol 1985;5:130–5.
      OpenUrlCrossRefPubMedWeb of Science
    5. ↵
      1. Mashima Y,
      2. Kigasawa K,
      3. Hasegawa H,
      4. Tani M,
      5. Oguchi Y
      . High incidence of pre-excitation syndrome in Japanese families with Leber’s hereditary optic neuropathy. Clin Genet 1996;50:535–7.
      OpenUrlPubMed
    6. ↵
      1. Braunwald E,
      2. Morrow AG
      . Ventriculo-right atrial communication; diagnosis by clinical, hemodynamic and angiographic methods. Am J Med 1960;28:913–20.
      OpenUrlCrossRefPubMed
    7. ↵
      1. Blair E,
      2. Redwood C,
      3. Ashrafian H,
      4. Oliveira M,
      5. Broxholme J,
      6. Kerr B,
      7. Salmon A,
      8. Ostman-Smith I,
      9. Watkins H
      . Mutations in the gamma(2) subunit of AMP-activated protein kinase cause familial hypertrophic cardiomyopathy: evidence for the central role of energy compromise in disease pathogenesis. Hum Mol Genet 2001;10:1215–20.
      OpenUrlAbstract/FREE Full Text
    8. ↵
      1. Gollob MH,
      2. Green MS,
      3. Tang AS,
      4. Gollob T,
      5. Karibe A,
      6. Ali Hassan AS,
      7. Ahmad F,
      8. Lozado R,
      9. Shah G,
      10. Fananapazir L,
      11. Bachinski LL,
      12. Roberts R
      . Identification of a gene responsible for familial Wolff-Parkinson-White syndrome. [erratum appears in N Engl J Med 2001;345:552. Note: Hassan AS] N Engl J Med 2001;344:1823–31.
    9. ↵
      1. Shohat M,
      2. Herman V,
      3. Melmed S,
      4. Neufeld N,
      5. Schreck R,
      6. Pulst S,
      7. Graham JM, Jr,
      8. Rimoin DL,
      9. Korenberg JR
      . Deletion of 20p 11.23−pter with normal growth hormone-releasing hormone genes. Am J Med Genet 1991;39:56–63.
      OpenUrlCrossRefPubMed
    10. ↵
      1. Anad F,
      2. Burn J,
      3. Matthews D,
      4. Cross I,
      5. Davison BC,
      6. Mueller R,
      7. Sands M,
      8. Lillington DM,
      9. Eastham E
      . Alagille syndrome and deletion of 20p. J Med Genet 1990;27:729–37.
      OpenUrlAbstract/FREE Full Text
    11. ↵
      1. Lu XSC,
      2. Patel A,
      3. Li J,
      4. Cooper ML,
      5. Wells WR,
      6. Sullivan CM,
      7. Sahoo T,
      8. Yatsenki SA,
      9. Bacino CA,
      10. Stankiewicz P,
      11. Ou Z,
      12. Chinault AC,
      13. Beaudet AL,
      14. Lupski JR,
      15. Cheung SW,
      16. Ward PA
      . Clinical implementation of chromosomal microarray analysis: summary of 2513 postnatal cases. PLoS One 2007;1:e327–38.
      OpenUrl
    12. ↵
      1. Cheung SW,
      2. Shaw CA,
      3. Yu W,
      4. Li J,
      5. Ou Z,
      6. Patel A,
      7. Yatsenko SA,
      8. Cooper ML,
      9. Furman P,
      10. Stankiewicz P,
      11. Lupski JR,
      12. Chinault AC
      , Beaudet AL. Development and validation of a CGH microarray for clinical cytogenetic diagnosis.[erratum appears in Genet Med 2005;7:478] Genet Med 2005;7:422–32.
    13. ↵
      1. Trask BJ
      . Fluorescence in situ hybridization: applications in cytogenetics and gene mapping. Trends Genet 1991;7(5):149–54.
      OpenUrlPubMedWeb of Science
    14. ↵
      1. Steemers FJ,
      2. Gunderson KL
      . Whole genome genotyping technologies on the BeadArray platform. Biotechnology Journal 2007;2:41–9.
      OpenUrlCrossRefPubMed
    15. ↵
      1. Kristensen TD,
      2. Wesenberg F,
      3. Jonsson OG,
      4. Carlsen NT,
      5. Forestier E,
      6. Kirchhoff M,
      7. Lundsteen C,
      8. Schmiegelow K
      . High-resolution comparative genomic hybridisation yields a high detection rate of chromosomal aberrations in childhood acute lymphoblastic leukaemia. Eur J Haematol 2003;70:363–72.
      OpenUrlCrossRefPubMed
    16. ↵
      1. Sood S,
      2. Chelu MC,
      3. Van Oort RJ,
      4. Skapura D,
      5. Santonastasi M,
      6. Dobrev D,
      7. Wehrens XH
      . Intracellular calcium leak due to FKBP12.6 deficiency in mice facilitates the inducibility of atrial fibrillation. Heart Rhythm 2008;5:1047–54.
      OpenUrlCrossRefPubMedWeb of Science
    17. ↵
      1. Verheule S,
      2. Sato T,
      3. Everett Tt,
      4. Engle SK,
      5. Otten D,
      6. Rubart-von der Lohe M,
      7. Nakajima HO,
      8. Nakajima H,
      9. Field LJ,
      10. Olgin JE
      . Increased vulnerability to atrial fibrillation in transgenic mice with selective atrial fibrosis caused by overexpression of TGF-beta1. Circ Res 2004;94:1458–65.
      OpenUrlAbstract/FREE Full Text
    18. ↵
      1. Oda T,
      2. Elkahloun AG,
      3. Pike BL,
      4. Okajima K,
      5. Krantz ID,
      6. Genin A,
      7. Piccoli DA,
      8. Meltzer PS,
      9. Spinner NB,
      10. Collins FS,
      11. Chandrasekharappa SC
      . Mutations in the human Jagged1 gene are responsible for Alagille syndrome. Nat Genet 1997;16:235–42.
      OpenUrlCrossRefPubMedWeb of Science
    19. ↵
      1. Lupski JR
      . Genomic disorders: structural features of the genome can lead to DNA rearrangements and human disease traits. Trends Genet 1998;14:417–22.
      OpenUrlCrossRefPubMedWeb of Science
    20. ↵
      1. Lupski JR
      . Genomic rearrangements and sporadic disease. Nat Genet 2007;39(7 Suppl):S43–7.
      OpenUrlCrossRefPubMed
    21. ↵
      1. Alagille D
      . Alagille syndrome today. Clinical & Investigative Medicine - Medecine Clinique et Experimentale 1996;19:325–30.
      OpenUrl
    22. ↵
      1. Koenig BB,
      2. Cook JS,
      3. Wolsing DH,
      4. Ting J,
      5. Tiesman JP,
      6. Correa PE,
      7. Olson CA,
      8. Pecquet AL,
      9. Ventura F,
      10. Grant RA
      . Characterization and cloning of a receptor for BMP-2 and BMP-4 from NIH 3T3 cells. Mol Cell Biol 1994;14:5961–74.
      OpenUrlAbstract/FREE Full Text
    23. ↵
      1. Zhang H,
      2. Bradley A
      . Mice deficient for BMP2 are nonviable and have defects in amnion/chorion and cardiac development. Development 1996;122:2977–86.
      OpenUrlAbstract
    24. ↵
      1. Ma L,
      2. Lu MF,
      3. Schwartz RJ,
      4. Martin JF
      . Bmp2 is essential for cardiac cushion epithelial-mesenchymal transition and myocardial patterning. Development 2005;132:5601–11.
      OpenUrlAbstract/FREE Full Text
    25. ↵
      1. Gaussin V,
      2. Morley GE,
      3. Cox L,
      4. Zwijsen A,
      5. Vance KM,
      6. Emile L,
      7. Tian Y,
      8. Liu J,
      9. Hong C,
      10. Myers D,
      11. Conway SJ,
      12. Depre C,
      13. Mishina Y,
      14. Behringer RR,
      15. Hanks MC,
      16. Schneider MD,
      17. Huylebroeck D,
      18. Fishman GI,
      19. Burch JB,
      20. Vatner SF
      . Alk3/Bmpr1a receptor is required for development of the atrioventricular canal into valves and annulus fibrosus. Circ Res 2005;97:219–26.
      OpenUrlAbstract/FREE Full Text
    26. ↵
      1. Becker AE,
      2. Anderson RH
      . The Wolff-Parkinson-White syndrome and its anatomical substrates. Anat Rec 1981;201:169–77.
      OpenUrlCrossRefPubMed
    27. ↵
      1. Peters NS,
      2. Rowland E,
      3. Bennett JG,
      4. Green CR,
      5. Anderson RH,
      6. Severs NJ
      . The Wolff-Parkinson-White syndrome: the cellular substrate for conduction in the accessory atrioventricular pathway. Eur Heart J 1994;15:981–7.
      OpenUrlAbstract/FREE Full Text
    28. ↵
      1. Arad M,
      2. Moskowitz IP,
      3. Patel VV,
      4. Ahmad F,
      5. Perez-Atayde AR,
      6. Sawyer DB,
      7. Walter M,
      8. Li GH,
      9. Burgon PG,
      10. Maguire CT,
      11. Stapleton D,
      12. Schmitt JP,
      13. Guo XX,
      14. Pizard A,
      15. Kupershmidt S,
      16. Roden DM,
      17. Berul CI,
      18. Seidman CE,
      19. Seidman JG
      . Transgenic mice overexpressing mutant PRKAG2 define the cause of Wolff-Parkinson-White syndrome in glycogen storage cardiomyopathy. Circulation 2003;107:2850–6.
      OpenUrlAbstract/FREE Full Text
    29. ↵
      1. Krishna S,
      2. Maduzia LL,
      3. Padgett RW
      . Specificity of TGFbeta signaling is conferred by distinct type I receptors and their associated SMAD proteins in Caenorhabditis elegans. Development 1999;126:251–60.
      OpenUrlAbstract
    30. ↵
      1. Neuss H,
      2. Schlepper M,
      3. Thormann J
      . Analysis of re-entry mechanisms in the three patients with concealed Wolff-Parkinson-White syndrome. Circulation 1975;51:75–81.
      OpenUrlAbstract/FREE Full Text

    Supplementary materials

    • web only statement

      Seema R Lalani and Joseph V Thakuria are the co-first authors of this paper.

    • web only appendices 46/3/168

    Footnotes

    • Competing interests: None.

    • Funding: This work was supported by the Doris Duke Charitable Foundation and the Gillson Longenbaugh Foundation to SRL and by R01 DE/HD 12324-12 to JFM.

    • Patient consent: Obtained

    • ▸ Additional figures are published online only at http://jmg.bmj.com/content/vol46/issue3