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Wu J, Lei M, Wang X, Liu N, Xu X, Gu C, Yu Y, Liu W. Prader-Willi syndrome patient with atypical phenotypes caused by mosaic deletion in the paternal 15q11-q13 region: a case report. Ital J Pediatr 2022; 48:204. [PMID: 36582000 PMCID: PMC9798715 DOI: 10.1186/s13052-022-01398-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 12/15/2022] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Prader-Willi syndrome (PWS) is a multisystemic complex genetic disorder caused by the loss of paternally expressed genes in the human chromosome region 15q11.2-q13. It is characterized by severe hypotonia and feeding difficulties in early infancy, followed in later infancy or early childhood by excessive eating and gradual development of morbid obesity. Motor milestones and language development are delayed and most patients have intellectual disability. CASE PRESENTATION Here we describe a rare PWS case caused by mosaic imprinting defect in the region 15q11.2-q13 of paternal origin. The proband was a male child with a clinical presentation of global developmental delay and hypotonia with specific facial features. Karyotype of the child was noted as mosaic: 45XY,der(15)?t(15;21),-21[26]/46,XY[24]. Whole-exome sequencing (WES) identified a deletion of 22.7 Mb in size at chr15q11.2q21.1 region and a deletion of 2.1 Mb in size at chr21q22.3 region. The Methylation-specific multiplex ligation-dependent probe amplification(MS-MLPA) of the 15q11.2-q13 region showed that the loading ratio of methylated alleles was 70% and that of unmethylated alleles was 30%(50% normal), which confirmed that the loss of mosaic imprinted defects in the paternal allele led to the diagnosis of PWS. CONCLUSIONS We propose that complete clinical criteria for PWS should not be considered sensitive in diagnosing partial atypical PWS due to mosaic imprinting defects. In contrast, clinical suspicion based on less restrictive criteria followed by multiple techniques is a more powerful approach.
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Affiliation(s)
- Jinying Wu
- Tianjin Pediatric Research Institute, Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China
- Tianjin Key Laboratory of Birth Defects for Prevention and Treatment, Tianjin, 300134, China
| | - Meifang Lei
- Department of Neurology, Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China
| | - Xuetao Wang
- Tianjin Pediatric Research Institute, Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China
- Tianjin Key Laboratory of Birth Defects for Prevention and Treatment, Tianjin, 300134, China
| | - Nan Liu
- Tianjin Pediatric Research Institute, Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China
- Tianjin Key Laboratory of Birth Defects for Prevention and Treatment, Tianjin, 300134, China
| | - Xiaowei Xu
- Tianjin Pediatric Research Institute, Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China
- Tianjin Key Laboratory of Birth Defects for Prevention and Treatment, Tianjin, 300134, China
| | - Chunyu Gu
- Tianjin Pediatric Research Institute, Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China
- Tianjin Key Laboratory of Birth Defects for Prevention and Treatment, Tianjin, 300134, China
| | - Yuping Yu
- Graduate College of Tianjin Medical University, Tianjin, 300070, China
| | - Wei Liu
- Tianjin Children's Hospital (Children's Hospital of Tianjin University), Tianjin, 300134, China.
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Anderlid BM, Lundin J, Malmgren H, Lehtihet M, Nordgren A. Small mosaic deletion encompassing the snoRNAs and SNURF-SNRPN results in an atypical Prader-Willi syndrome phenotype. Am J Med Genet A 2013; 164A:425-31. [PMID: 24311433 DOI: 10.1002/ajmg.a.36307] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 09/29/2013] [Indexed: 11/06/2022]
Abstract
Genetic analyses were performed in a male patient with suspected Prader-Willi syndrome who presented with hypogonadism, excessive eating, central obesity, small hands and feet and cognition within the low normal range. However, he had no neonatal hypotonia or feeding problems during infancy. Chromosome analysis showed a normal male karyotype. Further analysis with array-CGH identified a mosaic 847 kb deletion in 15q11-q13, including SNURF-SNRPN, the snoRNA gene clusters SNORD116 (HBII-85), SNORD115, (HBII-52), SNORD109 A and B (HBII-438A and B), SNORD64 (HBII-13), and NPAP1 (C15ORF2). MLPA confirmed the deletion and the results were compatible with a paternal origin. Metaphase-FISH verified the mosaicism with the deletion present in 58% of leukocytes analyzed. Three smaller deletions in this region have previously been reported in patients with Prader-Willi syndrome phenotype. All three deletions included SNORD116, but only two encompassed parts of SNURF-SNRPN, implicating SNORD116 as the major contributor to the Prader-Willi phenotype. Our case adds further information about genotype-phenotype correlation and supports the hypothesis that SNORD116 plays a major role in the pathogenesis of Prader-Willi syndrome. Furthermore, it examplifies diagnostic difficulties in atypical cases and illustrates the need for additional testing methods when Prader-Willi syndrome is suspected.
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Affiliation(s)
- Britt-Marie Anderlid
- Department of Molecular Medicine and Surgery, Clinal Genetic Unit, Centre of Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden
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Rossi E, Giorda R, Bonaglia MC, Candia SD, Grechi E, Franzese A, Soli F, Rivieri F, Patricelli MG, Saccilotto D, Bonfante A, Giglio S, Beri S, Rocchi M, Zuffardi O. De novo unbalanced translocations in Prader-Willi and Angelman syndrome might be the reciprocal product of inv dup(15)s. PLoS One 2012; 7:e39180. [PMID: 22720067 PMCID: PMC3375265 DOI: 10.1371/journal.pone.0039180] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 05/21/2012] [Indexed: 11/30/2022] Open
Abstract
The 15q11-q13 region is characterized by high instability, caused by the presence of several paralogous segmental duplications. Although most mechanisms dealing with cryptic deletions and amplifications have been at least partly characterized, little is known about the rare translocations involving this region. We characterized at the molecular level five unbalanced translocations, including a jumping one, having most of 15q transposed to the end of another chromosome, whereas the der(15)(pter->q11-q13) was missing. Imbalances were associated either with Prader-Willi or Angelman syndrome. Array-CGH demonstrated the absence of any copy number changes in the recipient chromosome in three cases, while one carried a cryptic terminal deletion and another a large terminal deletion, already diagnosed by classical cytogenetics. We cloned the breakpoint junctions in two cases, whereas cloning was impaired by complex regional genomic architecture and mosaicism in the others. Our results strongly indicate that some of our translocations originated through a prezygotic/postzygotic two-hit mechanism starting with the formation of an acentric 15qter->q1::q1->qter representing the reciprocal product of the inv dup(15) supernumerary marker chromosome. An embryo with such an acentric chromosome plus a normal chromosome 15 inherited from the other parent could survive only if partial trisomy 15 rescue would occur through elimination of part of the acentric chromosome, stabilization of the remaining portion with telomere capture, and formation of a derivative chromosome. All these events likely do not happen concurrently in a single cell but are rather the result of successive stabilization attempts occurring in different cells of which only the fittest will finally survive. Accordingly, jumping translocations might represent successful rescue attempts in different cells rather than transfer of the same 15q portion to different chromosomes. We also hypothesize that neocentromerization of the original acentric chromosome during early embryogenesis may be required to avoid its loss before cell survival is finally assured.
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Affiliation(s)
- Elena Rossi
- Medical Genetics, University of Pavia, Pavia, Italy
| | - Roberto Giorda
- Scientific Institute Eugenio Medea, Bosisio Parini, Lecco, Italy
| | | | - Stefania Di Candia
- Department of Pediatrics, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | - Elena Grechi
- Department of Pediatrics, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy
| | | | - Fiorenza Soli
- Medical Genetics Department, APSS Trento, Trento, Italy
| | | | - Maria Grazia Patricelli
- Biologia Molecolare Clinica e Citogenetica, Diagnostica e Ricerca, San Raffaele SPA, Milan, Italy
| | | | - Aldo Bonfante
- Genetica Medica, Ospedale Civile, Bassano del Grappa, Italy
| | - Sabrina Giglio
- Medical Genetics Unit, Meyer Children's Hospital, University of Firenze, Firenze, Italy
| | - Silvana Beri
- Scientific Institute Eugenio Medea, Bosisio Parini, Lecco, Italy
| | | | - Orsetta Zuffardi
- Medical Genetics, University of Pavia, Pavia, Italy
- IRCCS “C. Mondino National Neurological Institute” Foundation, Pavia, Italy
- * E-mail:
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