Paternal Uniparental Disomy Research Articles

Restoration of Dlk1 and Rtl1 Is Necessary but Insufficient to Rescue Lethality in Intergenic Differentially Methylated Region (IG-DMR)-deficient Mice

In the Dlk1-Dio3 imprinted domain, an intergenic differentially methylated region (IG-DMR) regulates the parental allele-specific expression of imprinted genes. The maternally inherited deletion of IG-DMR (IG-DMR((-/+))) results in perinatal lethality because of the overexpression of paternally expressed genes and repression of maternally expressed noncoding RNAs (ncRNAs), including Gtl2. To better understand the possible contribution of paternally expressed genes to the lethality, we attempted to rescue the lethality of IG-DMR((-/+)) mutants by restoring the paternally expressed genes. Because the paternally inherited Gtl2 deletion (Gtl2((+/-))) induced a decrease in the expression of paternally expressed genes, we crossed female IG-DMR heterozygous mice and male Gtl2 heterozygous mutant mice. The resultant IG-DMR((-/+))/Gtl2((+/-)) double mutant mice had normal expression levels of paternally expressed genes, and none of them showed perinatal lethality; however, most mice showed postnatal lethality with decreased expression of the maternally expressed ncRNAs. Thus, we inferred that paternally expressed genes are necessary for perinatal survivability and that maternally expressed ncRNAs are involved in postnatal lethality.

Segmental paternal uniparental disomy (patUPD) of 14q32 with abnormal methylation elicits the characteristic features of complete patUPD14

Uniparental disomy (UPD) for chromosome 14 is associated with well-recognized phenotypes, depending on the parent of origin. Studies in mouse models and human patients have implicated the involvement of the distal region of the long arm of chromosome 14 in the distinctive phenotypes. This involvement is supported by the identification of an imprinting cluster at chromosome 14q32, encompassing the differentially methylated regions (DMRs), IG-DMR and MEG3-DMR, as well as the maternally expressed genes GTL2, DIO3, and RTL1 and the paternally expressed genes DLK1, RTL1as, and MEG8. Here we report on a preterm female infant with distal segmental paternal UPD14 (upd(14)pat) of 14q32-14q32.33, which resulted in thoracic deformity secondary to rib abnormalities ("coat-hanger" rib sign), polyhydramnios, and other congenital abnormalities characteristically described in cases of complete upd(14)pat. Microsatellite investigation demonstrated UPD of markers D14S250 and D14S1010, encompassing a approximately 3.5 Mb region of distal 14q and involving the imprinting cluster. This case provided insight into the etiology of the phenotypic effects of upd(14)pat, prompting methylation analysis of the GTL2 promoter and the DMR between GTL2 and DLK1. We compare the physical findings seen in this case with those of patients with other causes of abnormal methylation of 14q32, which consistently result in certain distinct clinical features, regardless of the cytogenetic and molecular etiology.

A Case Report of A 2.5-Year-Old Girl with Angelman Syndrome (AS)

Objective Syndrome (AS) is a genetically determined syndrome that has a unique behavioral phenotype. This syndrome is described as jerky ataxia and an unusual happy facial expression with pathological laughter. Severe mental retardation is a unique feature of the syndrome, together with microbrachycephaly and abnormal electroencephalographic findings with or without clinical seizures. The patients cannot speak or at most, they have a vocabulary consisting only of a few words. The genetic abnormality of AS has been located on chromosome 15q11-q13. Patients with AS mostly have deletions on the maternally derived allele (75–80%) while some of them show paternal uniparental disomy (~2%) or a rare imprinting mutation developmental disorder caused by deletion of the maternally-inherited chromosome 15q11–13. A 2.5-year-old girl is presented. Clinical suspicion of AS was raised at the age of 27 months when she presented with mental retardation and epilepsy, absence of speech, inability to gait and paroxysmal episodes of laughter. Moreover, she had facial dysmorphic features such as microbrachycephaly, mid-facial hypoplasia, macrostomia and a prominent mandible. Chromosomal analysis revealed 46 xx with the deletion of 15q chromosome (15q11q13-snrpn/ic) Our patient met the classical phenotype and genotype of AS.

Prenatal findings of paternal uniparental disomy 14: Report of four patients

Prenatal findings of paternal uniparental disomy 14: Report of four patients

Paternal uniparental isodisomy of chromosome 6 causing a complex syndrome including complete IFN‐γ receptor 1 deficiency

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare primary immunodeficiency associated with clinical disease caused by weakly virulent mycobacterial species. Interferon gamma receptor 1 (IFN-gammaR1) deficiency is a genetic etiology of MSMD. We describe the clinical and genetic features of a 7-year-old Italian boy suffering from MSMD associated with a complex phenotype, including neonatal hyperglycemia, neuromuscular disease, and dysmorphic features. The child also developed necrotizing pneumonia caused by Rhodococcus equi. The child is homozygous for a nonsense mutation in exon 3 of IFNGR1 as a result of paternal uniparental disomy (UPD) of the entire chromosome 6. This is the first reported case of uniparental disomy resulting in a complex phenotype including MSMD.

Cytogenetic contribution to uniparental disomy (UPD).

Uniparental disomy (UPD) is often considered as an event to be characterized exclusively by molecular genetic or epigenetic approaches. This review shows that at least one third of UPD cases emerge in connection with or due to a chromosomal rearrangement. Thus, additional (molecular) cytogenetic characterization of UPD cases is essential. Up to now > 1,100 UPD cases detected in clinical, non-tumor cases are reported in the literature. Recently, these cases were summarized in a regularly updated, freely available online database http://www.med.uni-jena.de/fish/sSMC/00START-UPD.htm. Based of this, here the presently known imprinting syndromes, the chromosomal contribution to UPD phenomenon, and the cytogenetic subgroups of UPD, including cases with normal, abnormal balanced or unbalanced karyotype (like e.g. small supernumerary marker chromosomes and Robertsonian translocations) and segmental UPD are reviewed. Furthermore, chromosome fragmentation as a possible mechanism of trisomic rescue is discussed, which might help to explain the observed 1:9 rate of maternal versus paternal UPD present in cases with original trisomic karyotypes. Overall, as UPD is more but an interesting rarity, the genetic background of each "UPD-patient" needs to be characterized besides by molecular methods, also by molecular cytogenetics in detail.

Non‐pathological paternal isodisomy of chromosome 2 detected from a genome‐wide SNP scan

Uniparental disomy (UPD) occurs when both homologs of achromosomal pair come from the father (paternal UPD) or themother(maternalUPD).Dependingonthemechanismbywhichitarises [Engel, 2006; Robinson, 2000], it can lead to heterodisomy(where both homologous chromosomes from the same parent arepresent), isodisomy (where two copies of the same homologouschromosomefromthesameparentarepresent),oramixofthetwo.UPD has been detected much more frequently for certain chro-mosomes(6,7,14,15,16)thanforothers(1,2,3,4,5,8,9,10,11,12,13,20,21,22,X),andithasyettobeobservedforchromosomes18or19[Engel,2006;Kotzot andUtermann,2005].Whiletheremaybe real differences in the frequencies of UPD across the chromo-somes,muchofthefrequencydifferencesreportedintheliteratureprobably reflect differential ascertainment: UPD in certain chro-mosomes causes syndromes that are easily diagnosed.Paternalisodisomyofchromosome2iscomparativelyrareintheliterature[KotzotandUtermann,2005],andallpreviouscasesofithave been found via genetic analyses of patients with diseases orphenotypes that suggested genetic abnormalities. Thompson et al.[2002]identifieduniparentalisodisomyina34-year-oldotherwisehealthypatientwithretinitispigmentosawhowashomozygousfortheMERTKmutationat2q14.1.ThispatientwassuspectedofUPDbecause the father was heterozygous for the mutation but themother was not a carrier [Thompson et al., 2002]. Similarly,Kantarci et al. [2008], Petit et al. [2005], and Chavez et al.[2000] discovered paternal isodisomy of chromosome 2 infollow-ups of cases of abnormal inheritance of Donnai–Barrowsyndrome, Crigler–Najjar type I syndrome, and steroid 5-alpha-reductase 2 deficiency, respectively.In the current report, we describe the first case of full paternalisodisomy of chromosome 2 from a population-based sample forwhich no clinical phenotype was apparent. The focal individual(Twin 1) was a dizygotic twin male. Phenotypic and genomic datafor Twin 1, his co-twin sister, and both parents were collected as apart of a genome-wide association study (n¼461 twins plussiblingsand215parents)ontheBrisbaneAdolescentTwinSample(for details, see Wright and Martin, 2004). Genomic DNA wasextracted from whole blood and genotyped on the AffymetrixHumanMapping50KArrayXbaGeneChip.Informedconsentwascollected from participants and their parents, and all proceduresand protocols were reviewed and approved by the QIMR HumanResearch Ethics Committee.Both parents of Twin 1 self-reported their ethnicity as Samoan,which was supported by principal components analysis of theidentity-by-state matrix from 50K autosomal SNPs. Despite re-peatedattempts,themotherofTwin1couldnotbecontacted,andso information on pregnancy, birth, and childhood are not avail-able. Twin 1 was 22 years of age at the time of a follow-upexaminationbyaclinicalgeneticist.Otherthana2/3toesyndactylyon one foot, Twin 1 was of normal appearance and had no otherapparent physical abnormalities. His head circumference was60.5cm, and his height of 171cm was normal for his family. Hisfull-scaleIQassessedpreviouslyatage16bytheMulti-dimensionalAptitudeBatterywas95(verbalIQ¼96andperformanceIQ¼94),comparable to the IQ of his co-twin sister (88) but lower than thesample average of 112. He reported needing tutoring in juniorschool, but he successfully completed high school. He has basic

The ontogeny of delta-like protein 1 messenger ribonucleic acid expression during muscle development and regeneration: Comparison of broiler and Leghorn chickens

Delta-like protein 1 (DLK1) has been implicated in the muscle hypertrophy observed in DLK1 transgenic mice, callipyge sheep, and mouse paternal uniparental disomy 12 and human paternal uniparental disomy 14 syndromes. The current study was aimed to determine chicken DLK1 (gDLK1) mRNA expression during primary muscle cell differentiation and during muscle regeneration after cold injury and to compare gDLK1 mRNA expression during skeletal muscle development in layers and broilers. In chicken primary muscle cell culture, gDLK1 mRNA expression was significantly increased from 12 to 48 h (P < or = 0.05) when the nascent myotubes were actively formed at d 2 to 3. Myogenin, a late myogenic marker gene, mRNA expression peaked at 36 to 48 h. Myogenic differentiation 1 (MyoD) and paired box gene 7 (Pax7), early myogenic marker genes, mRNA expression gradually decreased during myogenic differentiation. During muscle regeneration, the expression of MyoD and Pax7 peaked at d 2 (P < or = 0.05), and myogenin mRNA expression peaked at d 4 (P < or = 0.05). The induction of gDLK1 gene appeared between d 7 to 10 postinjury (P < or = 0.05) when myotubes were actively formed as also demonstrated in histological sections. The expression of gDLK1 was slowly downregulated to the control levels at d 14 when the damaged muscle appeared nearly healed. These data suggest that gDLK1 may be involved in the late myogenic stages of primary muscle cell differentiation and muscle regeneration. The gDLK1 mRNA in the muscle tissues was very abundant at embryonic ages but decreased after hatching in both broiler and layer chickens. Compared with layers, broiler muscle at embryonic d 13 had a 3-fold greater expression of DLK1 (P < or = 0.01). In addition, the gDLK1 mRNA expression at d 1, 11, and 33 post-hatch was significantly higher in broilers than layers (P < or = 0.05). Therefore, the relatively greater expression of the gDLK1 gene in muscles of broilers compared with layers suggests that gDLK1 may serve as a new selection marker for high muscle growth in chickens. These findings may provide new insight into chicken muscle development and regeneration.

A multiplex molecular assay for the detection of uniparental disomy for human chromosome 7

Uniparental disomy (UPD) describes the inheritance of both homologues of a pair of chromosomes from only one parent. This condition is often caused by nondisjunction events during meiosis. UPD has been reported as a rare cause of the autosomal recessive disorder and aberrant expression of imprinted genes that are expressed from only one parental allele, either maternal or paternal. Maternal and/or paternal UPD for chromosome 7 is the most frequently observed UPD after UPD15. Here we developed and validated, for the first time, an effective, CE-based method for a rapid and economic detection based on two-fluorescent STR multiplexes.

Mutation in the SLC9A6 gene is not a frequent cause of sporadic Angelman-like syndrome

Angelman syndrome (AS) (MIM #105530) is a neurodevelopmental disorder characterized by a broad range of clinical features, such as profound mental retardation, impairment of verbal language, usually ataxia, subtle dysmorphic facial features, a peculiar behavioral profile, with a happy disposition and outbursts of laughter, and a seizure disorder associated with a characteristic electroencephalographic pattern.1 It affects between 1:15 000 and 1:40 000 newborn children depending on ethnical and geographical areas.2, 3, 4, 5 Most cases of AS are sporadic, although several familial cases have been reported. A variety of different genetic mechanisms involving chromosome 15q11.2-13 (deletion, paternal uniparental disomy, imprinting center abnormality, and UBE3A (MIM #601623; 15q11.2) mutations) have been described in association with AS, all resulting in a deficiency of the ubiquitin-protein ligase E3A, which is involved in the process of ubiquitination.6 In some cases, patients with AS share common features with patients affected by Rett syndrome (MIM #312750).7 After extensive cytogenetic and molecular analysis of chromosome 15q11-13, there remains a small group of about 10–15% of AS patients, in whom no abnormality can be identified.

Angelman syndrome (AS, MIM 105830)

Angelman syndrome (AS) is a distinct neurogenetic syndrome, first described in 1965. The phenotype is well known in infancy and adulthood, but the clinical features may change with age. The main clinical characteristics include severe mental retardation, epileptic seizures and EEG abnormalilties, neurological problems and distinct facial dysmorphic features. Behavioural problems such as hyperactivity and sleeping problems are reported, although these patients present mostly a happy personality with periods of inappropriate laughter. Different underlying genetic mechanisms may cause AS, with deletion of chromosome 15 as the most frequent cause. Other genetic mechanisms such as paternal uniparental disomy, imprinting defect and mutation in the UBE3A gene are present in smaller groups of patients with AS. As the recurrence risk can be up to 50%, the clinical diagnosis of AS should be confirmed by laboratory tesing, and genetic counselling should be provided. Treatment of seizures, physical therapy or other intervention strategies are helpful to ameliorate the symptoms.

Reproductive consequences of genome-wide paternal uniparental disomy mosaicism: description of two cases with different mechanisms of origin and pregnancy outcomes

To describe the molecular and cytogenetic characterization of two different prenatal cases of androgenetic/biparental mosaicism and review the different possible mechanisms of origin in each case. Case study and literature review. Tertiary medical center (prenatal diagnosis unit). A 26-year-old pregnant woman referred for suspected partial mole placenta and a 33-year-old pregnant woman referred for polyhydramnios and fetal malformations. Ultrasound examination, prenatal invasive procedures, molecular and cytogenetic analysis, physical and pathologic evaluation, and genetic counseling. Cytogenetic analysis, fluorescent in situ hybridization, and quantitative fluorescence polymerase chain reaction (QF-PCR) analysis. The finding of a normal karyotype together with a triploidy-like QF-PCR profile led to the diagnosis of two cases of androgenetic (genome-wide paternal uniparental disomy)/biparental mosaicism. The first case showed placental mesenchymal dysplasia and a normal fetus, and the second one presented a fetus showing Beckwith-Wiedemann syndrome features and an apparently normal placenta. These cases highlight the wide range of possible clinical presentations of androgenetic/biparental mosaicism, the variety of mechanisms of their origin, and the importance of the combination of molecular and cytogenetic analysis to achieve an accurate diagnosis and provide reproductive counseling.

Two novel gap junction protein alpha 12 gene mutations in two Chinese patients with Pelizaeus–Merzbacher-like disease

Pelizaeus–Merzbacher-like disease (PMLD) is a hypomyelinating disorder of the central nervous system caused by mutation in the gap junction protein alpha 12 ( GJA12) gene. Uniparental disomy (UPD) is defined as the presence of a chromosome pair, in a diploid individual, that derives from only one parent. Here, we analyzed GJA12 gene mutations in two Chinese PMLD patients and two novel mutations of GJA12 c.216delGinsAA (c.P73fsX106) caused by paternal UPD for chromosome 1 and c.138C>G (p.I46M) were identified. The patient 1 harbored a homozygous frameshift mutation at c.216delGinsAA (p.P73fsX106) in the GJA12. Haplotype analysis of the entire chromosome 1 of the patient revealed that this chromosome was exclusively derived from her father. The GJA12 gene is located on chromosome 1q41-42 and falls within the region of paternal isodisomy on the q arm. Thus, a novel homozygous frameshift mutation p.P73fsX106, caused by paternal UPD for chromosome 1, was identified in patient 1 with PMLD. Patient 2 was found a homozygous missense mutation at c.138C>G (p.I46M). This is the first GJA12 gene mutations reported from two Chinese PMLD patients and one mutation was associated with UPD for chromosome 1.

Screening for Genomic Rearrangements and Methylation Abnormalities of the 15q11-q13 Region in Autism Spectrum Disorders

Maternally derived duplications of the 15q11-q13 region are the most frequently reported chromosomal aberrations in autism spectrum disorders (ASD). Prader-Willi and Angelman syndromes, caused by 15q11-q13 deletions or abnormal methylation of imprinted genes, are also associated with ASD. However, the prevalence of these disorders in ASD is unknown. The aim of this study was to assess the frequency of 15q11-q13 rearrangements in a large sample of patients ascertained for ASD. A total of 522 patients belonging to 430 families were screened for deletions, duplications, and methylation abnormalities involving 15q11-q13 with multiplex ligation-dependent probe amplification (MLPA). We identified four patients with 15q11-q13 abnormalities: a supernumerary chromosome 15, a paternal interstitial duplication, and two subjects with Angelman syndrome, one with a maternal deletion and the other with a paternal uniparental disomy. Our results show that abnormalities of the 15q11-q13 region are a significant cause of ASD, accounting for approximately 1% of cases. Maternal interstitial 15q11-q13 duplications, previously reported to be present in 1% of patients with ASD, were not detected in our sample. Although paternal duplications of chromosome 15 remain phenotypically silent in the majority of patients, they can give rise to developmental delay and ASD in some subjects, suggesting that paternally expressed genes in this region can contribute to ASD, albeit with reduced penetrance compared with maternal duplications. These findings indicate that patients with ASD should be routinely screened for 15q genomic imbalances and methylation abnormalities and that MLPA is a reliable, rapid, and cost-effective method to perform this screening.

Methylation-specific multiplex ligation-dependent probe amplification in diagnosis of Prader-Willi syndrome and Angelman syndrome

To verify the sensitivity and reliability of methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and to develop a simple, accurate, reliability method of genetic diagnosis for AS and PWS. Peripheral blood samples were collected from 4 suspected AS patients, 2 suspected PWS patients, 2 normal persons, and 2 molecular biologically proven positive controls (1 AS patient and 1 PWS patient). DNA was extracted and purified. MS-MLPA was used to detect the methylation of the CpG dinucleotide and the copy number in the 15q-q13 region. The results of MS-MLPA were confirmed by MSP. Three cases with maternal deletion on 15q11-q13 region and one case with paternal uniparental disomy (UPD) or imprinting center defect in 15q11-q13 region were found in the 4 suspected AS patients. One PWS case was found to be with paternal deletion in 15q11-q13 region and the other with paternal deletion in 15q11-q13 region or UPD or imprinting center defect in 15q11-q13 region. MS-MLPA is a simple, rapid, accurate, and reliable method of genetic test.

Androgenetic/Biparental Mosaicism in an Infant with Hepatic Mesenchymal Hamartoma and Placental Mesenchymal Dysplasia

Androgenetic/biparental mosaicism, in which a subset of cells has complete paternal uniparental disomy, is associated with placental mesenchymal dysplasia (PMD), which is compatible with fetal development, indicating that fetal organs could also have androgenetic/biparental mosaicism, but few cases of somatic mosaicism have been described. A hepatic mesenchymal hamartoma (HMH) was resected from an otherwise healthy, nondysmorphic, 11-month-old girl, whose prenatal development was complicated by PMD. Placenta, HMH, histologically normal liver, and other tissues were examined for androgenetic/biparental mosaicism by analysis of (1) polymorphic DNA microsatellite markers, (2) the methylation status of an imprinted gene, SNRPN, and (3) immunohistochemically detectable protein products of the imprinted genes p57KIP2 and PHLDA2. The patient's liver, HMH, and 1 placental sample demonstrated an increased ratio of paternal to maternal alleles, indicating androgenetic/biparental mosaicism. The androgenetic component comprised 26% to 60% of the cells. Other tissues, including a 2nd placental sample, white blood cells, umbilical cord, and abdominal fascia, had no detectable androgenetic component. Methylation analysis confirmed a relative excess of the paternally imprinted SNRPN homolog in the normal liver, HMH, and placenta. Placental p57KIP2 immunoreactivity was consistent with androgenetic/biparental mosaicism, but neither p57KIP2 nor PHLDA2 immunohistochemistry were informative for HMH, because neither antigen was detected in control liver samples. We report androgenetic/biparental mosaicism in nonplacental tissues of an infant with PMD and provide the 1st description of genome-wide paternal uniparental disomy in HMH. Androgenetic/biparental mosaicism appears to play a role in the pathogenesis of HMH and other somatic lesions, particularly those associated with PMD.

A review of known imprinting syndromes and their association with assisted reproduction technologies

An association between assisted reproduction technologies (ART) and abnormal genomic imprinting in humans has been recognized for several years; however, the magnitude of this risk and the spectrum of imprinting syndromes to which the risk applies remains unknown. Nine human imprinting syndromes have been identified but current evidence links ART with only three: Beckwith-Wiedemann syndrome, Angelman syndrome and the newly described maternal hypomethylation syndrome. There is currently a lack of evidence linking ART with the remaining six imprinting syndromes: Prader-Willi syndrome, Russell-Silver syndrome, maternal and paternal uniparental disomy of chromosome 14, pseudohypoparathyroidism type 1b and transient neonatal diabetes. Evidence from clinical reports suggests that the association between imprinting syndromes and ART may be restricted to syndromes where the imprinting change takes the form of hypomethylation on the maternal allele. In contrast, studies of gametes and early embryos suggest that ART can be associated with hypermethylation as well as hypomethylation, with imprinting changes occurring on paternal as well as maternal alleles. The health effects of ART-associated imprinting changes may also extend beyond the nine recognized imprinting syndromes.

Angelman Syndrome Due to a Novel Splicing Mutation of theUBE3AGene

Angelman syndrome is a neurodevelopmental disorder characterized by mental retardation, absence of speech, seizures, abnormal electroencephalography (EEG), and happy disposition. The syndrome results from lack of function of the maternal copy of the UBE3A gene on the imprinted Prader-Willi/Angelman syndrome critical region; it is caused by large deletions, paternal uniparental disomy, imprinting center defects or UBE3A deletions, and point mutations. We found a novel splice-site mutation of the UBE3A gene in a child with clinical and EEG features of Angelman syndrome. This case further points out the fact that individuals with Angelman syndrome and mutations of the UBE3A gene have a phenotype that tends to be rather mild, however, undistinguishable, both from the clinical and the electrophysiological points of view, from the Angelman syndrome phenotype due to other known molecular mechanisms.

Donnai–Barrow syndrome (DBS/FOAR) in a child with a homozygous LRP2 mutation due to complete chromosome 2 paternal isodisomy

Donnai-Barrow syndrome [Faciooculoacousticorenal (FOAR) syndrome; DBS/FOAR] is a rare autosomal recessive disorder resulting from mutations in the LRP2 gene located on chromosome 2q31.1. We report a unique DBS/FOAR patient homozygous for a 4-bp LRP2 deletion secondary to paternal uniparental isodisomy for chromosome 2. The propositus inherited the mutation from his heterozygous carrier father, whereas the mother carried only wild-type LRP2 alleles. This is the first case of DBS/FOAR resulting from uniparental disomy (UPD) and the fourth published case of any paternal UPD 2 ascertained through unmasking of an autosomal recessive disorder. The absence of clinical symptoms above and beyond the classical phenotype in this and the other disorders suggests that paternal chromosome 2 is unlikely to contain imprinted genes notably affecting either growth or development. This report highlights the importance of parental genotyping in order to give accurate genetic counseling for autosomal recessive disorders.

Rapid detection of methylation change at H19 in human imprinting disorders using methylation-sensitive high-resolution melting

Beckwith Wiedemann syndrome (BWS) and Russell Silver syndrome (RS) are growth disorders with opposing epimutations affecting the H19/IGF2 imprinting center at 11p15.5. Overgrowth and tumor risk in BWS is caused by aberrant expression of the paternally expressed, imprinted IGF2 gene, occurring as a consequence of mosaic hypermethylation within the imprinting center, or to mosaic paternal uniparental disomy (UPD). RS is characterized by severe intrauterine growth retardation (IUGR). A subset of RS cases were recently shown to have mosaic hypomethylation within the H19/IGF2 imprinting center, predicted to silence paternally expressed IGF2 in early development. Molecular diagnosis for BWS and RS involves methylation analysis of the H19 locus, enabling discrimination of allelic methylation patterns. In this study, methylation-sensitive high-resolution melting analysis (MS-HRM) was used to analyze methylation within the intergenic region of the H19 locus. A total of 36 samples comprising normal control (11), BWS (19), and RS (six) DNA were analyzed in a blinded study and scored as hypermethylated, normal, or hypomethylated. Results were compared with those derived by methylation-sensitive Southern blotting using the restriction enzymes Rsa I and Hpa II. A total of 100% concordance was obtained for the Southern blotting and MS-HRM scores. A total of three samples with paternal duplication affecting the H19/IGF2 region were scored as equivocal by both methods; however, 33 out of 36 (92%) the samples were unambiguously scored as being hypermethylated, hypomethylated, or normally methylated using MS-HRM. We conclude that MS-HRM is a rapid, cost-effective, and sensitive method for screening mosaic methylation changes at the H19 locus in BWS and RS.