Molecular Analysis of an Extra inv dup(15)(q13) Chromosome in Two Patients with Angelman Syndrome

Angelman syndrome (AS) is caused by the loss of function of yet unidentified gene(s) which map within 15q 11-13 and show monoallelic expression from the maternal allele. Lack of the maternal allele(s), due to either a deletion on the maternal chromosome 15 (about 70% of AS patients) or a paternal uniparental disomy (UPD)15 (<5%), are the most common molecular defects in AS. Prader-Willi syndrome (PWS) also maps to proximal 15q, but is caused by the loss of function of paternally expressed gen(s) [1]. Here we describe clinical, cytogenetic and molecular data for two non-related patients with AS who carry a nonmosaic extra cromosome inv dup(15).

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Quantitative Analysis of SRNPN Gene Methylation by Pyrosequencing as a Diagnostic Test for Prader–Willi Syndrome and Angelman Syndrome

Clinical Chemistry ◽

10.1373/clinchem.2005.065086 ◽

2006 ◽

Vol 52 (6) ◽

pp. 1005-1013 ◽

Cited By ~ 49

Author(s):

Helen E White ◽

Victoria J Durston ◽

John F Harvey ◽

Nicholas CP Cross

Keyword(s):

Diagnostic Test ◽

Angelman Syndrome ◽

Uniparental Disomy ◽

Chromosome 15 ◽

Prader Willi Syndrome ◽

Maternal Uniparental Disomy ◽

Cpg Sites ◽

Specific Pcr ◽

Small Nuclear Ribonucleoprotein ◽

Maternal Contribution

Abstract Background: Angelman syndrome (AS) and Prader–Willi syndrome (PWS) are 2 distinct neurodevelopmental disorders caused primarily by deficiency of specific parental contributions at an imprinted domain within the chromosomal region 15q11.2-13. In most cases, lack of paternal contribution leads to PWS either by paternal deletion (∼70%) or maternal uniparental disomy (UPD; ∼30%). Most cases of AS result from the lack of a maternal contribution from this same region by maternal deletion (∼70%) or by paternal UPD (∼5%). Analysis of allelic methylation differences at the small nuclear ribonucleoprotein polypeptide N (SNRPN) locus can differentiate the maternally and paternally inherited chromosome 15 and can be used as a diagnostic test for AS and PWS. Methods: Sodium bisulfite–treated genomic DNA was PCR-amplified for the SNRPN gene. We used pyrosequencing to individually quantify the resulting artificial C/T sequence variation at CpG sites. Anonymized DNA samples from PWS patients (n = 40), AS patients (n = 31), and controls (n = 81) were analyzed in a blinded fashion with 2 PCR and 3 pyrosequencing reactions. We compared results from the pyrosequencing assays with those obtained with a commonly used methylation-specific PCR (MS-PCR) diagnostic protocol. Results: The pyrosequencing assays had a sensitivity and specificity of 100% and provided quantification of methylation at 12 CpG sites within the SNRPN locus. The resulting diagnoses were 100% concordant with those obtained from the MS-PCR protocol. Conclusions: Pyrosequencing is a rapid and robust method for quantitative methylation analysis of the SNRPN locus and can be used as a diagnostic test for PWS and AS.

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Prader-Willi syndrome: reflections on seminal studies and future therapies

Open Biology ◽

10.1098/rsob.200195 ◽

2020 ◽

Vol 10 (9) ◽

pp. 200195

Author(s):

Michael S. Chung ◽

Maéva Langouët ◽

Stormy J. Chamberlain ◽

Gordon G. Carmichael

Keyword(s):

Genomic Imprinting ◽

Angelman Syndrome ◽

Cpg Island ◽

Uniparental Disomy ◽

Large Deletion ◽

Paternal Allele ◽

Prader Willi Syndrome ◽

Loss Of Function ◽

Maternal Uniparental Disomy ◽

Parental Allele

Prader-Willi syndrome (PWS) is caused by the loss of function of the paternally inherited 15q11-q13 locus. This region is governed by genomic imprinting, a phenomenon in which genes are expressed exclusively from one parental allele. The genomic imprinting of the 15q11-q13 locus is established in the germline and is largely controlled by a bipartite imprinting centre. One part, termed the Prader-Willi syndrome imprinting center (PWS-IC), comprises a CpG island that is unmethylated on the paternal allele and methylated on the maternal allele. The second part, termed the Angelman syndrome imprinting centre, is required to silence the PWS_IC in the maternal germline. The loss of the paternal contribution of the imprinted 15q11-q13 locus most frequently occurs owing to a large deletion of the entire imprinted region but can also occur through maternal uniparental disomy or an imprinting defect. While PWS is considered a contiguous gene syndrome based on large-deletion and uniparental disomy patients, the lack of expression of only non-coding RNA transcripts from the SNURF-SNRPN/SNHG14 may be the primary cause of PWS. Patients with small atypical deletions of the paternal SNORD116 cluster alone appear to have most of the PWS related clinical phenotypes. The loss of the maternal contribution of the 15q11-q13 locus causes a separate and distinct condition called Angelman syndrome. Importantly, while much has been learned about the regulation and expression of genes and transcripts deriving from the 15q11-q13 locus, there remains much to be learned about how these genes and transcripts contribute at the molecular level to the clinical traits and developmental aspects of PWS that have been observed.

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Why is There No Diploid Overdose Effect in Prader-Willi Syndrome Due to Uniparental Disomy?

Acta geneticae medicae et gemellologiae twin research ◽

10.1017/s0001566000001288 ◽

1996 ◽

Vol 45 (1-2) ◽

pp. 179-189 ◽

Cited By ~ 3

Author(s):

A. Smith

Keyword(s):

Uniparental Disomy ◽

Good Evidence ◽

Monoallelic Expression ◽

Chromosome 15 ◽

Prader Willi Syndrome ◽

Phenotypic Effect ◽

Biallelic Expression ◽

Chromosome 11P15 ◽

Imprinted Gene ◽

Maternal Imprinting

AbstractDue to DNA technology, it is now apparent that the mechanisms of genetic disease are more complex than the model of a gene with biallelic expression in the diploid state. If a gene is imprinted, monoallelic expression is the norm when the chromosomes of a pair are inherited normally from each parent. Uniparental disomy (UPD) is the abnormal situation where both chromosomes of a pair come from the same parent. When the chromosome contains an imprinted gene, UPD may result in nullisomy or disomy for a functional copy of that gene. If there are two imprinted loci on the same chromosome, UPD for that chromosome results in nullisomy for one imprinted gene but functional disomy for the other a “diploid overdose” (DO). This situation has been well demonstrated in the Prader-Willi syndrome (PWS) which is the nullisomic phenotype for the PWS gene(s) on chromosome 15q 11-13. Chromosome 15q11-13 also contains the gene for Angelman syndrome (AS) which has a phenotype distinct from PWS. Both loci are subject to imprinting – in PWS, the imprint is on the maternal chromosome 15, in AS it is on the paternal chromosome 15. All individuals with PWS due to maternal UPD, while functionally nullisomic for the PWS locus, are functionally disomic for the AS locus – a DO situation. Assuming that biallelic expression of an imprinted gene is harmful, one would expect DO for an imprinted gene to produce a phenotypic effect. Cases of PWS due to UPD do not appear to differ from those due to deletion (hypopigmentation in deletional cases can be explained by loss of D15S12 downstream from the critical region). There is no good evidence of DO for the AS locus in PWS due to UPD. Why then was it ‘necessary’ in evolutionary terms to imprint the AS locus and maintain the imprint faithfully for life. A similar situation of two imprinted genes on the same chromosome occurs with IGF2 and H19 on chromosome 11p15. Maternal imprinting for IGF2 and paternal imprinting for H19 is the norm. Paternal UPD in this situation does lead to a DO effect, namely Beckwith-Wiedemann syndrome. The possibility of a DO effect needs to be considered when assessing the phenotypic spectrum of UPD for other chromosomes currently under investigation.

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Mosaic Segmental and Whole-Chromosome upd(11)mat in Silver-Russell Syndrome

Genes ◽

10.3390/genes12040581 ◽

2021 ◽

Vol 12 (4) ◽

pp. 581

Author(s):

Laura Pignata ◽

Angela Sparago ◽

Orazio Palumbo ◽

Elena Andreucci ◽

Elisabetta Lapi ◽

...

Keyword(s):

Molecular Level ◽

Opposite Sign ◽

Uniparental Disomy ◽

Differentially Methylated Region ◽

Imprinted Genes ◽

Loss Of Function ◽

Growth Disturbances ◽

Molecular Defects ◽

Entire Chromosome ◽

Silver Russell Syndrome

Molecular defects altering the expression of the imprinted genes of the 11p15.5 cluster are responsible for the etiology of two congenital disorders characterized by opposite growth disturbances, Silver–Russell syndrome (SRS), associated with growth restriction, and Beckwith–Wiedemann syndrome (BWS), associated with overgrowth. At the molecular level, SRS and BWS are characterized by defects of opposite sign, including loss (LoM) or gain (GoM) of methylation at the H19/IGF2:intergenic differentially methylated region (H19/IGF2:IG-DMR), maternal or paternal duplication (dup) of 11p15.5, maternal (mat) or paternal (pat) uniparental disomy (upd), and gain or loss of function mutations of CDKN1C. However, while upd(11)pat is found in 20% of BWS cases and in the majority of them it is segmental, upd(11)mat is extremely rare, being reported in only two SRS cases to date, and in both of them is extended to the whole chromosome. Here, we report on two novel cases of mosaic upd(11)mat with SRS phenotype. The upd is mosaic and isodisomic in both cases but covers the entire chromosome in one case and is restricted to 11p14.1-pter in the other case. The segmental upd(11)mat adds further to the list of molecular defects of opposite sign in SRS and BWS, making these two imprinting disorders even more specular than previously described.

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Safety and effectiveness of growth hormone therapy in infants with Prader-Willi syndrome younger than 2 years: a prospective study

Journal of Pediatric Endocrinology and Metabolism ◽

10.1515/jpem-2018-0539 ◽

2019 ◽

Vol 32 (8) ◽

pp. 879-884 ◽

Cited By ~ 3

Author(s):

Raquel Corripio ◽

Carla Tubau ◽

Laura Calvo ◽

Carme Brun ◽

Núria Capdevila ◽

...

Keyword(s):

Growth Hormone ◽

Prospective Study ◽

Mixed Model ◽

Standard Deviation Score ◽

Uniparental Disomy ◽

Chromosome 15 ◽

Prader Willi Syndrome ◽

Gh Treatment ◽

Maternal Uniparental Disomy ◽

A Prospective Study

Abstract Background There is little evidence of the effects of early treatment with growth hormone (GH) in infants with Prader-Willi syndrome (PWS). A prospective study was conducted to assess the safety of GH therapy in infants younger than 2 years of age with PWS. Methods A total of 14 patients with PWS started treatment with GH under the age of 2 years and were followed over a 2-year period. A deletion of chromosome 15 was present in nine infants (64.3%) and maternal uniparental disomy 15 in five infants (35.7%). The median age at start of GH treatment was 9.6 months (interquartile range [IQR] 9.0–18.3 months). Changes in height standard deviation score (SDS), body mass index (BMI) SDS and subcapsular and tricipital skinfolds in the follow-up period were evaluated with a mixed-model regression analysis using the Package R. Results There were no fatal adverse events. A significant decrease (p < 0.001) in tricipital and subcapsular skinfold thickness, with an upward trend of height SDS and a downward trend of BMI SDS, was observed. Infants who started GH before 15 months of age started walking at a median of 18.0 [17.0–19.5] months vs. 36.6 [36.3–37.8] months for those who began treatment with GH after 15 months of age (p = 0.024). Conclusions GH treatment in infants with PWS less than 2 years of age is safe and improved body composition. Infants who received GH before the age of 15 months started to walk earlier.

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Molecular and Clinical Studies of Polish Patients with Prader-Willi Syndrome

Acta geneticae medicae et gemellologiae twin research ◽

10.1017/s0001566000001446 ◽

1996 ◽

Vol 45 (1-2) ◽

pp. 273-276

Author(s):

A. Szpecht-Potocka ◽

E. Obersztyn ◽

M. Karwacki ◽

E. Bocian ◽

J. Bal ◽

...

Keyword(s):

Pattern Analysis ◽

Clinical Symptoms ◽

Uniparental Disomy ◽

Methylation Pattern ◽

Microsatellite Analysis ◽

Prader Willi Syndrome ◽

Methylation Analysis ◽

Molecular Defects ◽

Parent Of Origin ◽

Cytogenetic Methods

AbstractA group of 30 patients clinically described as having the Prader-Willi Syndrome (PWS) were studied using microsatellites from 15q11-13 and methylation analysis with probe PW71B (D15S63). The patients were categorized according to clinical symptoms. 80% of all patients were informative using molecular and cytogenetic methods. Among 8 patients with an atypical PWS phenotype, 2 showed uniparental disomy, and 2 had a mosaic deletion for 15q. The last 4 atypical and 2 typical patients had neither molecular defects confirmed by microsatellite analysis nor a parent-of-origin-specific methylation pattern for PWS. Our results confirm that methylation pattern analysis provides an additional and alternative microsatellite analysis to diagnose PWS.

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Non-chromosome 15 marker chromosome in a Prader-Willi syndrome patient with uniparental disomy

Pediatrics International ◽

10.1111/j.1442-200x.2006.02163.x ◽

2006 ◽

Vol 48 (1) ◽

pp. 97-99

Author(s):

MIZUHO ICHIKAWA ◽

MAKI OKAJIMA ◽

TAKAHITO WADA ◽

YUMI GOKAN ◽

HIROMI SHIMAKAGE ◽

...

Keyword(s):

Marker Chromosome ◽

Uniparental Disomy ◽

Chromosome 15 ◽

Prader Willi Syndrome ◽

Syndrome Patient

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BIOLOGICAL SCIENCES: Genetics

10.1101/404061 ◽

2018 ◽

Author(s):

Jack S. Hsiao ◽

Noelle D. Germain ◽

Andrea Wilderman ◽

Christopher Stoddard ◽

Luke A. Wojenski ◽

...

Keyword(s):

Boundary Element ◽

Angelman Syndrome ◽

Antisense Transcript ◽

Neurodevelopmental Disorder ◽

Boundary Function ◽

Paternal Allele ◽

Loss Of Function ◽

Maternal Allele ◽

Specific Expression ◽

Human Neurons

ABSTRACTAngelman syndrome (AS) is a severe neurodevelopmental disorder caused by the loss of function from the maternal allele of UBE3A, a gene encoding an E3 ubiquitin ligase. UBE3A is only expressed from the maternally-inherited allele in mature human neurons due to tissue-specific genomic imprinting. Imprinted expression of UBE3A is restricted to neurons by expression of UBE3A antisense transcript (UBE3A-ATS) from the paternally-inherited allele, which silences the paternal allele of UBE3A in cis. However, the mechanism restricting UBE3A-ATS expression and UBE3A imprinting to neurons is not understood. We used CRISPR/Cas9-mediated genome editing to functionally define a bipartite boundary element critical for neuron-specific expression of UBE3A-ATS in humans. Removal of this element led to upregulation of UBE3A-ATS without repressing paternal UBE3A. However, increasing expression of UBE3A-ATS in the absence of the boundary element resulted in full repression of paternal UBE3A, demonstrating that UBE3A imprinting requires both the loss of function from the boundary element as well as upregulation of UBE3A-ATS. These results suggest that manipulation of the competition between UBE3A-ATS and UBE3A may provide a potential therapeutic approach for AS.SIGNIFICANCE STATEMENTAngelman syndrome is a neurodevelopmental disorder caused by loss of function from the maternal allele of UBE3A, an imprinted gene. The paternal allele of UBE3A is silenced by a long, non-coding antisense transcript in mature neurons. We have identified a boundary element that stops the transcription of the antisense transcript in human pluripotent stem cells, and thus restricts UBE3A imprinted expression to neurons. We further determined that UBE3A imprinting requires both the loss of the boundary function and sufficient expression of the antisense transcript to silence paternal UBE3A. These findings provide essential details about the mechanisms of UBE3A imprinting that may suggest additional therapeutic approaches for Angelman syndrome.

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The phenomenology and diagnosis of psychiatric illness in people with Prader–Willi syndrome

Psychological Medicine ◽

10.1017/s0033291707002504 ◽

2008 ◽

Vol 38 (10) ◽

pp. 1505-1514 ◽

Cited By ~ 80

Author(s):

S. Soni ◽

J. Whittington ◽

A. J. Holland ◽

T. Webb ◽

E. N. Maina ◽

...

Keyword(s):

Family History ◽

Affective Disorder ◽

Psychiatric Illness ◽

Uniparental Disomy ◽

Psychotic Symptoms ◽

Chromosome 15 ◽

Prader Willi Syndrome ◽

Psychotic Illness ◽

Genetic Subtype ◽

History Of

BackgroundPsychotic illness is strongly associated with the maternal uniparental disomy (mUPD) genetic subtype of Prader–Willi syndrome (PWS), but not the deletion subtype (delPWS). This study investigates the clinical features of psychiatric illness associated with PWS. We consider possible genetic and other mechanisms that may be responsible for the development of psychotic illness, predominantly in those with mUPD.MethodThe study sample comprised 119 individuals with genetically confirmed PWS, of whom 46 had a history of psychiatric illness. A detailed clinical and family psychiatric history was obtained from these 46 using the PAS-ADD, OPCRIT, Family History and Life Events Questionnaires.ResultsIndividuals with mUPD had a higher rate of psychiatric illness than those with delPWS (22/34 v. 24/85, p<0.001). The profile of psychiatric illness in both genetic subtypes resembled an atypical affective disorder with or without psychotic symptoms. Those with delPWS were more likely to have developed a non-psychotic depressive illness (p=0.005) and those with mUPD a bipolar disorder with psychotic symptoms (p=0.00005). Individuals with delPWS and psychotic illness had an increased family history of affective disorder. This was confined exclusively to their mothers.ConclusionsPsychiatric illness in PWS is predominately affective with atypical features. The prevalence and possibly the severity of illness are greater in those with mUPD. We present a ‘two-hit’ hypothesis, involving imprinted genes on chromosome 15, for the development of affective psychosis in people with PWS, regardless of genetic subtype.

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