Wiedemann-Beckwith syndrome: further prenatal characterization of the condition

Imprinting as Basis for Complex Evolutionary Novelties in Eutherians

The epigenetic phenomenon of genomic imprinting is puzzling. While epigenetic modifications in general are widely known in most species, genomic imprinting in the animal kingdom is restricted to autosomes of therian mammals, mainly eutherians, and to a lesser extent in marsupials. Imprinting causes monoallelic gene expression. It represents functional haploidy of certain alleles while bearing the evolutionary cost of diploidization, which is the need of a complex cellular architecture and the danger of producing aneuploid cells by mitotic and meiotic errors. The parent-of-origin gene expression has stressed many theories. Most prominent theories, such as the kinship (parental conflict) hypothesis for maternally versus paternally derived alleles, explain only partial aspects of imprinting. The implementation of single-cell transcriptome analyses and epigenetic research allowed detailed study of monoallelic expression in a spatial and temporal manner and demonstrated a broader but much more complex and differentiated picture of imprinting. In this review, we summarize all these aspects but argue that imprinting is a functional haploidy that not only allows a better gene dosage control of critical genes but also increased cellular diversity and plasticity. Furthermore, we propose that only the occurrence of allele-specific gene regulation mechanisms allows the appearance of evolutionary novelties such as the placenta and the evolutionary expansion of the eutherian brain.

Genomic imprinting in human placentation

Background

Genomic imprinting (GI) is a mammalian-specific epigenetic phenomenon that has been implicated in the evolution of the placenta in mammals.

Methods

Embryo transfer procedures and trophoblast stem (TS) cells were used to re-examine mouse placenta-specific GI genes. For the analysis of human GI genes, cytotrophoblast cells isolated from human placental tissues were used. Using human TS cells, the biological roles of human GI genes were examined.

Main findings

(1) Many previously identified mouse GI genes were likely to be falsely identified due to contaminating maternal cells. (2) Human placenta-specific GI genes were comprehensively determined, highlighting incomplete erasure of germline DNA methylation in the human placenta. (3) Human TS cells retained normal GI patterns. (4) Complete hydatidiform mole-derived TS cells were characterized by aberrant GI and enhanced trophoblastic proliferation. The maternally expressed imprinted gene p57KIP2 may be responsible for the enhanced proliferation. (5) The primate-specific microRNA cluster on chromosome 19, which is a placenta-specific GI gene, is essential for self-renewal and differentiation of human TS cells.

Conclusion

Genomic imprinting plays diverse and important roles in human placentation. Experimental analyses using TS cells suggest that the GI maintenance is necessary for normal placental development in humans.

Familial Beckwith-Wiedemann syndrome: Prenatal manifestation and a possible expansion of the phenotype

We describe a case of Beckwith-Wiedemann syndrome (BWS) demonstrating pre- and post-natal intra-familial variability. Our first encounter with the family occurred in the 1990s following the birth of 3 affected offspring. The first two pregnancies presented with exomphalos and elevated second trimester maternal serum alpha-fetoprotein (msAFP, 3.43 and 4.01 MOM, respectively) as well as elevated maternal human chorionic gonadotrophin (mhCG, 4.33 and 8.8 MOM, respectively). The diagnosis of BWS was confirmed postnatally in both cases. The third ongoing pregnancy presented only with elevated mhCG (7.09 MOM) and no malformation. Nonetheless BWS was suspected. The diagnosis was confirmed postnatally with clinical manifestations including macroglossia and cleft palate. Two affected female siblings were also diagnosed with Mullerian agenesis in adulthood. Suspecting a common genetic etiology, sequencing of the CDKN1C gene revealed a maternally inherited, likely pathogenic variant (NM_000076.2: c.367_385del; p.(Ala123Serfs*143)) causative of BWS. Chromosomal microarray and whole exome sequencing did not reveal any other pathogenic variant that would explain the Mullerian agenesis. One of the affected females underwent successful preimplantation genetic testing (PGT) with a surrogate and gave birth to a healthy female. To the best of our knowledge, this is the first report of Mullerian agenesis as a possible rare expansion of the BWS phenotype. In addition, this case highlights the potential role of abnormal second trimester biochemical markers (msAFP, mHCG) as possible indicators of BWS, especially in familial cases.

Prenatal features in Beckwith-Wiedemann syndrome and indications for prenatal testing

BACKGROUND

Most cases of Beckwith-Wiedemann spectrum (BWSp) are diagnosed after birth and few studies evaluated the prenatal phenotype; here, we investigate these aspects in a large series of patients with BWSp.

METHODS

Eighty-nine patients with BWSp recruited through the BWSp Internal Registry of the Pediatric Genetics Unit of the Regina Margherita Children's Hospital of Torino and through the Italian Association of Patients with BWSp. Data collection was conducted through administration of a personalised questionnaire, interview to patients' parents, review of the clinical records, including prenatal ultrasound (US) and biochemical screening tests, physical examination and review of clinical and molecular data of the patients.

RESULTS

Seventeen patients (19.1%) were conceived through assisted reproductive techniques (ART). Twinning occurred in nine pregnancies (three from ART). Pregnancy biochemical screening tests showed increased alpha-fetoprotein (1.52±0.79 multiples of median (MoM), p=0.001), uEstriol (1.37±0.38 MoM, p<0.001) and total human chorionic gonadotrophin (2.14±2.12 MoM, p=0.008) at 15-18 weeks (n=28). Morphology US scan revealed abdominal and head circumferences higher than normal (1.42±1.10 SD scores, p<0.001 and 0.54±0.88, p<0.001, respectively) with normal femur lengths. Sixty-four cases (71.9%%) had a various combination of US findings, including macrosomia (n=32), omphalocele (n=15), enlargement of abdominal organs (n=6), macroglossia (n=11), adrenal cysts/masses (n=2), nephroureteral anomalies (n=11), polyhydramnios (n=28), placental enlargement (n=2) or mesenchymal dysplasia (n=4).

CONCLUSION

We propose a clinical scoring system for prenatal molecular investigations defining major, minor and supportive criteria among the several features often observed prenatally in BWSp.

Prenatal imaging throughout gestation in Beckwith-Wiedemann syndrome

PURPOSE

Prenatal occurrence and timing of appearance of associated features in Beckwith-Wiedemann syndrome (BWS) are unknown. We reviewed our BWS patients with serial fetal imaging and correlated these with postnatal findings.

METHODS

All BWS patients with fetal ultrasound (US) or magnetic resonance imaging (MRI) from 2000 to 2016 were reviewed to determine the presence of polyhydramnios, placentamegaly, macrosomia, macroglossia, retrognathia, omphalocele, visceromegaly, and hemihypertrophy. These observations were correlated with postnatal findings. Data were analyzed by Mann-Whitney U test.

RESULTS

Nine BWS patients underwent 42 fetal imaging studies with median of five (range of two to six) studies per patient between 13 and 35 weeks gestation. All prenatal findings were confirmed postnatally with complete concordance. All patients with omphalocele were detected early in gestation but other postnatal findings less predictably so. All omphaloceles were small, and were found significantly earlier in gestation than macrosomia (P = 0.004) and macroglossia (P = 0.012). Visceromegaly and retrognathia were less frequent, with no significant differences in median gestational age from omphalocele when prenatally identified.

CONCLUSIONS

In BWS, omphalocele is the most common prenatal finding and routinely observed in early gestation with 100% accuracy. Associated findings of macrosomia, macroglossia, visceromegaly, and retrognathia, when present, are detected later in gestation. Imaging in later gestation may reveal additional abnormalities that support a BWS diagnosis.

Fetal programming and Wilms tumor

BACKGROUND

The "fetal programming" hypothesis has been evaluated in many adult diseases including cancer, but not for Wilms tumor. Wilms tumor has been related to high birthweight, but little is known about other growth metrics such as a baby's birth length, ponderal index, or placenta size, which can shed additional light on growth patterns.

METHODS

Cases of Wilms tumor (N = 217) were taken from the Danish Cancer Registry, and controls (N = 4340) were randomly selected from the Population Register and matched to cases by sex and age. Linkage to the Medical Births Registry provided information on gestational factors and fetal growth measurements, while linkage to the Patient Register provided information on maternal and child health conditions.

RESULTS

Despite having typically normal to higher birthweights, Wilms tumor cases had smaller placentas (≤540 g; odds ratio (OR) = 4.24; 95% confidence interval (CI), 1.84-9.78) and a lower placenta-to-birthweight ratio (OR = 1.81; 95% CI, 1.17-2.82, per 1 SD decrease). Small placentas were more common among Wilms cases without congenital anomalies (OR = 6.43; 95% CI, 1.95-21.21). Wilms tumor cases had a higher prevalence of high birthweight (>4000 g; OR = 1.57; 95% CI, 1.11-2.22), birth length 55 cm or longer (OR = 1.74; 95% CI, 1.09-2.78), and being large for gestational age (OR = 1.79; 95% CI, 1.08-2.96).

CONCLUSIONS

Our study corroborates earlier studies showing associations with high birthweight and suggests associations between Wilms tumor and decreased placental size and low placenta-to-birthweight ratio.

Beckwith Wiedemann syndrome: A population-based study on prevalence, prenatal diagnosis, associated anomalies and survival in Europe

Beckwith Wiedemann syndrome is a complex developmental disorder characterized by somatic overgrowth, macroglossia, abdominal wall defects, neonatal hypoglycemia, and predisposition to embryonal tumors. We present epidemiological and clinical aspects of patients with Beckwith Wiedemann syndrome diagnosed prenatally or in the early years of life, using data from EUROCAT (European Surveillance of Congenital Anomalies) registries. The study population consisted of 371 cases identified between January 1990 and December 2015 in 34 registries from 16 European countries. There were 15 (4.0%) terminations of pregnancy after prenatal detection of severe anomaly/anomalies, 10 fetal deaths (2.7%), and 346 (93.3%) live-births. Twelve (3.6%) of the 330 live-births with available information on survival died in the first week of life, of those eleven (91.6%) were preterm. First-year survival rate was 90.9%. Prematurity was present in 40.6% of males and 33.9% of females. Macrosomia was found in 49.2% and 43.3% of preterm males and females, respectively. Of term newborns, 41.1% of males and 24% of females were macrosomic. Out of 353 cases with known time of diagnosis, 39.9% were suspected prenatally, 36.3% at birth, 7.6% were diagnosed in the first week of life, and 16.2% in the first year of life. The mean gestational age at prenatal diagnosis by obstetric ultrasound was 19.8 ± 6.2 (11-39) gestational weeks. The mean prenatal diagnosis of cases where parents opted for termination of pregnancy was 15.3 ± 2.4 (11-22) gestational weeks, and the mean gestational age at termination was 19.3 ± 4.1 (13-26) gestational weeks. The prenatal detection rate was 64.1% (141/220) with no significant change over time. There were 12.7% of familial cases. The study confirmed the association of assisted reproductive technologies with Beckwith Wiedemann syndrome, as 7.2% (13/181) of patients were conceived by one of the methods of assisted reproductive technologies, which was three times higher compared to the general population of the countries included in the study. Twin pregnancies of undetermined zygosity were recorded in 5.7% (21/365) cases, and were on average three to four times more common than in European countries that participated in the study. The estimated mean prevalence of classical Beckwith Wiedemann syndrome in Europe was 3.8 per 100,000 births or 1:26,000 births.

Beckwith-Weidemann syndrome with IC2 (KvDMR1) hypomethylation defect: a novel mutation

The Beckwith-Wiedemann syndrome (BWS) is a rare genetic syndrome. However, this is one of the most common overgrowth syndromes. This is a genetically and clinically heterogeneous syndrome. Here, we report a case of Beckwith-Weidemann syndrome without macrosomia, visceromegaly and hemihyperplasia but having macroglossia, omphalocele and anterior linear ear lobe creases. The diagnosis was confirmed by gene analysis suggestive of imprinting centre 2 (KvDMR1) hypomethylation defect.

De novo paternal origin duplication of chromosome 11p15.5: report of two Chinese cases with Beckwith-Wiedemann syndrome

Background

The molecular etiology of Beckwith-Wiedemann syndrome (BWS) is complex and heterogeneous. Several subtypes of epigenetic-genetic alterations including aberrant methylation patterns, segmental uniparental disomy, single gene mutations, and copy number changes have been described. An integrated molecular approach to analyze the epigenetic-genetic alterations is required for accurate diagnosis of BWS.

Case presentation

We reported two Chinese cases with BWS detected by genome-wide copy number analysis and locus-specific methylation profiling. Prenatal analysis on cord blood of patient 1 showed a de novo paternal origin duplication spanning 896Kb at 11p15.5. Patient 2 was referred at 2-month old and the genetic analysis showed a de novo 228.8Kb deletion at 11p15.5 telomeric end and a de novo duplication of 2.5 Mb at 11p15.5–15.4. Both the duplications are of paternal origin with gain of methylation at the imprinting center 1 and thus belong to the subgroup of a low tumor risk.

Conclusion

Results from these two cases and other reported cases from literature indicated that paternally derived duplications at 11p15.5 region cause BWS. Combined chromosome microarray analysis and methylation profiling provided reliable diagnosis for this subtype of BWS. Characterization of genetic defects in BWS patients could lead to better understanding the genetic mechanisms of this clinically and genetically heterogeneous disorder.

Prenatal diagnosis of paternal duplication of 11p15.5→14.3: Its implication of Beckwith-Wiedemann syndrome

OBJECTIVE

To characterize a prenatally detected chromosomal aberration with molecular cytogenetic approaches and explore its relationship with Beckwith-Wiedemann syndrome (BWS).

CASE REPORT

A 33-year-old woman, gravida 2, para 0, was referred to our prenatal clinic at 20+ weeks due to an abnormal amniocentesis karyotyping finding, which showed 46,XY,add(11)(q24.2)dn. The mother conceived through in vitro fertilization-intracytoplasmic sperm injection (IVF-ICSI), then embryo transfer. Fetal ultrasound revealed a left-sided congenital diaphragmatic hernia, overgrowth of the fetus, and an enlarged placenta. After genetic counseling and careful deliberation by the family, the pregnancy was subsequently terminated at 22+ weeks of gestation, delivering a fetus weighing 810 g (85^th to 90^th centile) and a placenta of 325 g (85^th to 90^th centile). To further delineate the nature of the rearrangement involved in the defective chromosome 11, repeat chromosomal analyses, including array comparative genomic hybridization (aCGH) test and quantitative fluorescence-polymerase chain reaction (QF-PCR) using short tandem repeat (STR) markers, were performed by sampling fetal tissue. The final result confirmed a diagnosis of 46,XY,del(11)(q24.3q25),dup(11)(p14.3p15.5). The abnormal chromosome 11 was inherited from the father and the duplicated segment involved 11p15.5, a critical imprinting region for BWS.

CONCLUSION

We presented a prenatally detected chromosomal aberration characterized by paternal duplication of chromosome 11p15.5, which strongly related to the phenotypic manifestation of BWS.

Placental mesenchymal dysplasia without fetal development in a twin gestation: a case report and review of the spectrum of androgenetic biparental mosaicism

We report a dichorionic twin gestation with diffuse placental mesenchymal dysplasia (PMD) and androgenetic biparental mosaicism (ABM) involving one twin's placenta with complete absence of fetal development for that twin. To our knowledge, this is the 1st reported case of PMD without fetal development. We discuss the gross, histologic, and genetic hallmarks of PMD and the spectrum of variability depending on degree and distribution of ABM.

Beckwith-Wiedemann syndrome in sibs discordant for IC2 methylation

Genetically heterogeneous imprinting disorders include Beckwith-Wiedemann syndrome (BWS) and multiple maternal hypomethylation syndrome (MMHS). Using DNA sequencing, quantitative PCR, SNuPE, pyrosequencing, and hybridization to the Illumina GoldenGate Methylation Cancer Panel 1 array, we characterized the genomic DNA of two brothers with BWS who were discordant for loss of methylation at several differentially methylated regions (DMR), including imprinting center 2 (IC2) on chromosome band 11p15.5, which is often hypomethylated in BWS. In keeping with MMHS, the elder child had hypomethylation of SGCE and PLAGL1 as well as of IC2, whereas the younger brother demonstrated no loss of methylation at these DMRs. Although this discordance is consistent with the observation that 15-20% of individuals with BWS do not have detectable genetic or epigenetic alterations of 11p15.5, this is the first report of familial recurrence of BWS with discordance for chromosomal 11p15.5 alterations. We hypothesize that this apparent discordance arises either from mosaicism precluding identification of IC2 hypomethylation in blood or buccal mucosa DNA of the younger child, or from hypomethylation at a site not interrogated by our molecular studies.

Partial molar pregnancy with a chromosomically and phenotypically normal embryo: presentation of an extremely rare case and review of literature

We present an extremely rare case of partial molar pregnancy with a chromosomically and phenotypically normal embryo and review of the literature. A 31-year-old nulliparous was referred to us at 30 weeks of gestation due to absence of fetal movements and subsequent ultrasound examination revealed intrauterine demise. Prenatal amniocentesis due to raised maternal serum α-fetoprotein had shown a karyotypically normal female embryo and second trimester ultrasound demonstrated no anatomic abnormalities. Upon induction of labor with misoprostol, a phenotypically normal embryo was delivered and the placenta showed intermixed areas of marked hydatidiform villous change and normal parenchyma. Pathologic examination of the placenta confirmed the molar change of placenta. Two are the main theories discussed herein that explain the placental molar changes in singleton pregnancies: confined placental mosaicism (one case reported to date) and placental mesenchymal dysplasia (70 cases reported). Differential diagnosis is based on histopathologic features and genetic analysis of placenta.

Addition of H19 'loss of methylation testing' for Beckwith-Wiedemann syndrome (BWS) increases the diagnostic yield

Beckwith-Wiedemann syndrome (BWS) is a clinical diagnosis; however, molecular confirmation via abnormal methylation of DMR2(LIT1) and/or DMR1(H19) has clinical utility due to epigenotype-tumor association. Despite the strong link between H19 hypermethylation and tumor risk, several diagnostic laboratories only test for hypomethylation of LIT1. We assessed the added diagnostic value of combined LIT1 and H19 testing in a large series of referred samples from 1298 patients, including 53 well-characterized patients from the St. Louis Children's Hospital BWS-Registry (validation samples) and 1245 consecutive nationwide referrals (practice samples). Methylation-sensitive enzymatic digestion with Southern hybridization assessed loss of normal imprinting. In the validation group, abnormal LIT1 hypomethylation was detected in 60% (32/52) of patients but LIT1/H19-combined testing was abnormal in 68% (36/53); sensitivity in the practice setting demonstrated 27% (342/1245) abnormal LIT1 and 32% (404/1245) abnormal LIT1/H19-combined. In addition, H19 methylation was abnormal in 7% of LIT1-normal patients. We observed absence of uniparental disomy (UPD) in 27% of combined LIT1/H19-abnormal samples, diagnostic of multilocus methylation abnormalities; in contrast to studies implicating that combined LIT1/H19 abnormalities are diagnostic of UPD. The overall low detection rate, even in validated patient samples and despite characterization of both loci and UPD status, emphasizes the importance of clinical diagnosis in BWS.

Genetic considerations in the prenatal diagnosis of overgrowth syndromes

Large (>90%) for gestational age (LGA) fetuses are usually identified incidentally. Detection of the LGA fetus should first prompt the provider to rule out incorrect dates and maternal diabetes. Once this is done, consideration should be given to certain overgrowth syndromes, especially if anomalies are present. The overgrowth syndromes have significant clinical and molecular overlap, and are associated with developmental delay, tumors, and other anomalies. Although genetic causes of overgrowth are considered postnatally, they are infrequently diagnosed prenatally. Here, we review prenatal sonographic findings in fetal overgrowth syndromes, including Pallister-Killian, Beckwith-Wiedemann, Sotos, Perlman, and Simpson-Golabi-Behmel. We also discuss prenatal diagnosis options and recurrence risks.

Sonographic assessment of renal growth in patients with Beckwith-Wiedemann syndrome: the Beckwith-Wiedemann syndrome renal nomogram

BACKGROUND

Beckwith-Wiedemann syndrome is a disorder of somatic overgrowth. Evidence of kidney overgrowth is a diagnostic criterion that may be used to help identify those patients who are at the greatest risk of developing Wilms tumors. In such subjects, kidney size is typically larger than that of age-matched normal controls.

OBJECTIVE

The purpose of our study was to generate a nomogram that could be used to measure renal dimensions in children with Beckwith-Wiedemann syndrome in a clinical setting.

MATERIALS & METHODS

All of the Beckwith-Wiedemann syndrome patients followed at our institution from 1996 to 2004 were eligible for inclusion in our study. Renal length was measured with a curvilinear transducer and with the patient supine. Renal lengths were measured for both kidneys using real-time ultrasound for all patients. Their data were compared with those of age-matched controls reported in the 1984 study by Rosenbaum et al.

RESULTS

Ninety-six children with Beckwith-Wiedemann syndrome were followed from 1996 to 2004. Forty-three of these patients met our criteria for inclusion in the study: 28 girls (65%) and 15 boys (35%). We identified a linear relationship between kidney length and patient age. No statistically significant differences in renal length were found between boys and girls (p=0.2153) or between the kidneys on either side of the body (p=0.9613).

CONCLUSION

Our study provides a practical, simple renal growth chart that offers a reasonable, sensitive method for evaluating kidney size in children with Beckwith-Wiedemann syndrome.

Placental mesenchymal dysplasia associated with fetal overgrowth and mosaic deletion of the maternal copy of 11p15.5

Placentae with mesenchymal dysplasia (PMD) are typically larger than average and show cystic areas on ultrasonography. Fetal outcomes are variable and are often associated with growth restriction. However, enigmatically, some associated fetuses show signs of Beckwith-Wiedemann syndrome (BWS). PMD has recently been shown to result from androgenetic (complete paternal uniparental disomy) chimerism in the placenta in pregnancies that were associated with some fetal growth restriction. Cases of PMD associated with overgrowth have not previously been investigated molecularly. We present a case of focal PMD associated with a male fetus showing overgrowth with an enlarged heart, marked fetal ascites and intrauterine fetal death at 34 weeks, but no other BWS manifestations. Mosaicism for an unbalanced translocation leading to deletion of the maternal copy of the BWS region on 11p15.5 and partial duplication of 17q was observed in placenta, but not fetal samples. While the placental findings of PMD can be caused by an unbalanced dosage of genes in 11p15.5 alone, fetal growth parameters appear to depend on the underlying mechanism and likely also the level and distribution of abnormal cells.

Syndromes and Disorders Associated with Omphalocele (I): Beckwith–Wiedemann Syndrome

Beckwith-Wiedemann syndrome (BWS, OMIM 130650) is characterized by macrosomia, macroglossia, visceromegaly, hemihypertrophy, abdominal wall defects, ear creases/pits, neonatal hypoglycemia, polyhydramnios, placentomegaly, placental mesenchymal dysplasia, cardiac defects, nevus flammeus, hemangiomata, and an increased frequency of embryonal tumors. This article provides an overview of BWS including the genetics, genetic diagnosis, genotype/epigenotype-phenotype correlations, association with assisted reproductive technology, and prenatal diagnosis. Omphalocele is an important sonographic marker for BWS. Prenatal detection of omphalocele, fetal overgrowth, polyhydramnios, increased abdominal circumference, placentomegaly and/or placental mesenchymal dysplasia should alert one to the possibility of BWS and prompt a genetic investigation and counseling for BWS.

Chromosome 11 segmental paternal isodisomy in amniocytes from two fetuses with omphalocoele: new highlights on phenotype-genotype correlations in Beckwith-Wiedemann syndrome

BACKGROUND

The phenotypic variability in Beckwith-Wiedemann syndrome (BWS) reflects the genetic heterogeneity of the mechanism which by default leads to the deregulation of genes located at 11p15.5. Genotype-phenotype correlation studies have demonstrated an association between omphalocoele and CDKN1C/p57 mutations or hypermethylation. Paternal uniparental disomy 11 (pUPD11) has been described only in the mosaic condition with both uniparental and biparental cell lines, and no association with omphalocoele has been pointed out.

METHODS

Two cases are presented here, in which a paternal segmental UPD11 was detected by molecular investigation of amniotic fluid cell cultures after the presence of apparently isolated omphalocoele was revealed in the fetuses by ultrasound scan. Further studies were performed on additional autoptic feto-placental tissues to characterise the distribution of the uniparental cell line and to unmask any biparental lineage in order to document in more detail the as yet unreported association between omphalocoele and pUPD11.

RESULTS

Results on the UPD distribution profile showed that the abdominal organs have a predominant uniparental constitution. This condition could mimic the effect of CDKN1C/p57 inactivation, causing the omphalocoele.

CONCLUSION

New genotype-phenotype correlations emerge from the investigated cases, suggesting that molecular analysis be extended to all cases with fetal omphalocoele in order to establish the incidence of pUPD11 in complete BWS and in monosymptomatic/mild forms.

Molecular and genomic characterisation of cryptic chromosomal alterations leading to paternal duplication of the 11p15.5 Beckwith-Wiedemann region

BACKGROUND

Beckwith-Wiedemann syndrome (BWS) is an overgrowth disorder with increased risk of paediatric tumours. The aetiology involves epigenetic and genetic alterations affecting the 11p15 region, methylation of the differentially methylated DMR2 region being the most common defect, while less frequent aetiologies include mosaic paternal 11p uniparental disomy (11patUPD), maternally inherited mutations of the CDKN1C gene, and hypermethylation of DMR1. A few patients have cytogenetic abnormalities involving 11p15.5.

METHODS

Screening of 70 trios of BWS probands for 11p mosaic paternal UPD and for cryptic cytogenetic rearrangements using microsatellite segregation analysis identified a profile compatible with paternal 11p15 duplication in two patients.

RESULTS

Fluorescence in situ hybridisation analysis revealed in one case the unbalanced translocation der(21)t(11;21)(p15.4;q22.3) originated from missegregation of a cryptic paternal balanced translocation. The second patient, trisomic for D11S1318, carried a small de novo dup(11)(p15.5p15.5), resulting from unequal recombination at paternal meiosis I. The duplicated region involves only IC1 and spares IC2/LIT1, as shown by fluorescent in situ hybridisation (FISH) mapping of the proximal duplication breakpoint within the amino-terminal part of KvLQT1.

CONCLUSIONS

An additional patient with Wolf-Hirschorn syndrome was shown by FISH studies to carry a der(4)t(4;11)(p16.3;p15.4), contributed by a balanced translocation father. Interestingly, refined breakpoint mapping on 11p and the critical regions on the partner 21q and 4p chromosomal regions suggested that both translocations affecting 11p15.4 are mediated by segmental duplications. These findings of chromosomal rearrangements affecting 11p15.5-15.4 provide a tool to further dissect the genomics of the BWS region and the pathogenesis of this imprinting disorder.

Beckwith-Wiedemann Syndrome Presenting with an Elevated Triple Screen in the Second Trimester of Pregnancy

BACKGROUND

Beckwith-Wiedemann syndrome (BWS) is a distinct clinical syndrome with unique features, generally diagnosed postnatally.

CASE

A 26-year-old patient, gravida 4, para 3-0-0-3, was noted to have an abnormal maternal serum screen. Amniocentesis with imaging studies were remarkable only for a two-vessel umbilical cord and prominent maternal ovaries. The patient developed HELLP syndrome at 28 weeks and delivered a viable female infant with distinct clinical features. The diagnosis of BWS was confirmed by hypermethylation of the H19 gene on chromosome 11p15.5.

CONCLUSION

This case describes a novel presentation of BWS and underscores the diagnostic potential of routine prenatal screens.

Prenatal diagnosis of fetal bilateral adrenal carcinoma

Fetal malignancies that are capable of metastasizing to other fetal organs and the placenta are exceedingly rare. Fetal tumors are suspected on ultrasonography in the presence of structures of abnormal shape or size that are occasionally associated with polyhydramnios and hydrops. Most of the large abdominal masses detected antenatally are renal in origin, although adrenal tumors should also be kept in mind in their differential diagnosis. We report a case of a large-for-gestational-age fetus with abdominal distention secondary to bilateral adrenal carcinoma, polyhydramnios and placental enlargement. Postmortem histological findings included nesidioblastosis, (i.e. hyperplasia of the cells of the islets of Langerhans) and adrenocortical cytomegaly, suggestive of a form of Beckwith-Wiedemann syndrome.

Unbalanced placental expression of imprinted genes in human intrauterine growth restriction

Imprinted genes control fetal and placental growth in mice and in rare human syndromes, but the role of these genes in sporadic intrauterine growth restriction (IUGR) is less well-studied. We measured the ratio of mRNA from a maternally expressed imprinted gene, PHLDA2, to that from a paternally expressed imprinted gene, MEST, by Northern blotting in 38 IUGR-associated placentae and 75 non-IUGR placentae and found an increase in the PHLDA2/MEST mRNA ratio in IUGR (p=0.0001). Altered expression of PHLDA2 and MEST was not accompanied by changes in DNA methylation within their imprinting centers, and immunohistochemistry showed PHLDA2 protein appropriately restricted to villous and intermediate cytotrophoblast in the IUGR placentae. We next did a genome-wide survey of mRNA expression in 14 IUGR placentae with maternal vascular under-perfusion compared to 15 non-IUGR placentae using Affymetrix U133A microarrays. In this series six imprinted genes were differentially expressed by ANOVA with a Benjamini-Hochberg false discovery rate of 0.05, with increased expression of PHLDA2 and decreased expression of MEST, MEG3, GATM, GNAS and PLAGL1 in IUGR placentae. At lower significance, we found IGF2 mRNA decreased and CDKN1C mRNA increased in the IUGR cases. We confirmed the significant reduction in MEG3 non-translated RNA in IUGR placentae by Northern blotting. In addition to imprinted genes, the microarray data highlighted non-imprinted genes acting in endocrine signaling (LEP, CRH, HPGD, INHBA), tissue growth (IGF1), immune modulation (INDO, PSG-family genes), oxidative metabolism (GLRX), vascular function (AGTR1, DSCR1) and metabolite transport (SLC-family solute carriers) as differentially expressed in IUGR vs. non-IUGR placentae.

Inheritance pattern of Beckwith-Wiedemann syndrome is heterogeneous in 291 families with an affected proband

Beckwith-Wiedemann syndrome (BWS) is congenital disorder whose molecular etiology is related to genetic and epigenetic mutations on 11p15. The majority of cases of BWS are sporadic, but a substantial proportion are familial, with an unknown inheritance pattern, although autosomal dominant and sex-dependent inheritance have been proposed. We tested the hypothesis that in familial BWS, autosomal dominant inheritance is the primary mode of transmission underlying familial instances. Segregation analysis was performed in 291 families ascertained with an affected child. Individuals were considered to have BWS if they had two of five major features: macroglossia, macrosomia, hypoglycemia at birth, abdominal wall defect, and ear pits or creases. Models of inheritance were tested using pedigree analysis package (PAP) parameterized for a discrete trait. A total of 291 families of an affected proband were included in the study. The analysis was based on a revised general model that included a boundary solution. Sporadic and environmental models were rejected. Overall, the results suggested Mendelian inheritance but under recessive or additive mode of inheritance, which fit the data equally well rather than dominant inheritance. However, the presence of families in the cohort consistent with dominant and sex-dependent inheritance suggest familial BWS may be a heterogeneous group comprised of different inheritance patterns. Familial BWS does not appear to be consistent with autosomal dominant transmission, and is likely a complex mixture of different inheritance patterns.

Factors associated with preterm delivery in mothers of children with Beckwith-Wiedemann syndrome: a case cohort study from the BWS registry

Pregnancy that results in a child with Beckwith-Wiedemann syndrome (BWS) is associated with preterm delivery. Based on previous case series, we hypothesized that preterm delivery of a child with BWS was due to known risk factors for preterm delivery such as polyhydramnios and gestational hypertension. A case cohort study using the BWS Registry at Washington University School of Medicine was undertaken. Cases were pregnancies that resulted in the birth of a child with BWS, controls were pregnancies resulting in the birth of siblings without BWS. Univariate analyses of maternal complications and logistic regression to predict preterm delivery were used. Children with BWS (n = 304) were delivered preterm at a significantly higher rate than their siblings (n = 269) odds ratio 19.1 (95% CI 9.1-40.2). Polyhydramnios, gestational hypertension, and vaginal bleeding also occurred at high rates in the BWS group with odds ratios of 31.6 (95% CI 12.6-79.1), 2.4 (95% CI 1.4-4.1), and 3.9 (95% CI 2.3-6.4), respectively. In a multivariate logistic regression model within the BWS group, polyhydramnios, vaginal bleeding, and gestational hypertension were significant predictors of preterm delivery, odds ratios of 2.9 (95% CI 1.6-5.4), 2.6 (95% CI 1.3-5.0), and 5.3 (2.3-12.0), respectively. However, a significant proportion, 6.5% (18 of 277), of patients in the BWS group delivered preterm without known risk factors. Preterm delivery of a child with BWS is associated with an increased frequency of polyhydramnios, gestational hypertension, and vaginal bleeding in the mother. However, preterm delivery also occurs in the absence of these risk factors.

Prenatal diagnosis of Beckwith-Wiedemann syndrome

OBJECTIVES

The diagnosis of Beckwith-Wiedemann syndrome (BWS) typically is made after birth. To our knowledge, no established guidelines exist for the prenatal diagnosis of this condition. We present two new cases of prenatally diagnosed BWS and propose a diagnostic schema.

METHODS

Published reports obtained from Medline searches were reviewed and combined with our cases.

RESULTS

Our proposed schema of two major criteria (abdominal wall defect, macroglossia, macrosomia) or one major plus two minor criteria (nephromegaly/dysgenesis, adrenal cytomegaly, aneuploidy/abnormal loci, polyhydramnios) fits all published reports of prenatally diagnosed BWS.

CONCLUSION

The prenatal diagnosis of BWS can be reliably made by applying our proposed guidelines. This schema allows for uniform fetal diagnosis of the syndrome and helps prepare for prenatal counseling and peri- and post-natal management strategies.

Giant omphalocele and “prune belly” sequence as components of the Beckwith-Wiedemann syndrome

We report a case of severe Beckwith-Wiedemann syndrome (BWS) in a fetus at 16 weeks of gestation. This presentation, incompatible with life, included a giant omphalocele and absence of abdominal wall musculature with extremely dilated bladder, as in the "prune belly" sequence. Adrenal cytomegaly pointed to BWS. Molecular analysis confirmed the diagnosis of BWS and showed an isolated demethylation of the KCNQ1OT1 gene. This report demonstrates that lethal fetal abdominal wall defects associated with adrenal cytomegaly are linked to epigenetic change of the 11p15 imprinted region.

Imprinting and disease

Deregulation of imprinted genes has been observed in a number of human diseases such as Beckwith-Wiedemann syndrome, Prader-Willi/Angelman syndromes and cancer. Imprinting diseases are characterised by complex patterns of mutations and associated phenotypes affecting pre- and postnatal growth and neurological functions. Regulation of imprinted gene expression is mediated by allele-specific epigenetic modifications of DNA and chromatin. These modifications preferentially affect central regulatory elements that control in cis over long distances allele-specific expression of several neighbouring genes. Investigations of imprinting diseases have a strong impact on biomedical research and provide interesting models for function and mechanisms of epigenetic gene control.

Chorioangioma and its severe infantile sequelae: case report

OBJECTIVE

This case report describes a rare clinical presentation of chorioangioma diagnosed prenatally because of raised-maternal serum (MS) alpha-fetoprotein.

METHODS

A thirty-year-old woman gravida 2, para 1 was referred to the ultrasound unit at 18 weeks of gestation because of abnormal MS triple-test results. This included AFP level of 14.9 MoM; hCG of 3.42 MoM and uE3 of 1.01 MoM. A detailed anomaly scan revealed a singleton fetus with no sonographically detectable malformations and normal amniotic fluid. The placenta was posterior. A well-circumscribed, rounded, predominantly hypoechoic lesion near the chorionic surface measuring 5 x 5 cm and protruding into the amniotic cavity was detected. Color Doppler sonogram showed no blood flow within the mass, but clear fetal waveforms in its periphery were demonstrated, and the diagnosis of chorioangioma was made. The pregnancy was followed uneventfully until 35 weeks of gestation when polyhydramnios and severe fetal cardiomegaly developed. Labor was therefore induced.

RESULTS

A euploid female, who had multiple diffuse cutaneous and liver angiomatosis was born. She died at the age of one month because of cardiac failure and infection.

CONCLUSIONS

The present case alerts to the interrelationship between placental and fetal angiomas. This may lead to severe infantile sequelae because of similar lesions.