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Ortega V, Louie RJ, Jones MA, Chaubey A, DuPont BR, Britt A, Ray J, McLean SD, Littlejohn RO, Velagaleti G. Copy neutral absence of heterozygosity on chromosome 15 distal long arm: A surrogate marker for Prader-Willi/Angelman syndromes? Mol Cytogenet 2021; 14:37. [PMID: 34261519 PMCID: PMC8278679 DOI: 10.1186/s13039-021-00558-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 07/06/2021] [Indexed: 11/25/2022] Open
Abstract
Background Copy-neutral absence of heterozygosity (CN-AOH) observed on a single chromosome or part of a chromosome may be indicative of uniparental disomy (UPD) and may require additional testing when such chromosomes or chromosome regions are known to harbor imprinted genes. Case presentation Here we report 2 cases of neonates that presented to clinic with hypotonia, poor oral skills including inability to feed by mouth, weak cry, no response to noxious stimulation and vertical plantar creases (case 1) and hypotonia and respiratory distress (case 2). A preliminary chromosome analysis showed normal karyotypes in both cases while the high-resolution single nucleotide polymorphism (SNP) microarray showed copy neutral absence of heterozygosity involving chromosome 15 distal long arm. In case 1, the CN-AOH involved a 28.7 Mb block from genomic coordinates 73703619_102429049. In case 2, the CN-AOH involved a 15.3 Mb block from genomic coordinates 54729197_70057534. In both cases, methylation-specific PCR did not detect an unmethylated allele for the SNRPN gene suggesting either a deletion of paternal allele or maternal UPD for chromosome 15. Since microarray analysis did not show any copy number alterations on chromosome 15, a microdeletion was ruled out. Conclusions Based on our cases, we suggest that CN-AOH on chromosome 15, even if it does not involve the critical region of 15q12q13, should warrant additional studies for diagnosis of Prader–Willi/Angelman syndromes.
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Affiliation(s)
- Veronica Ortega
- Department of Pathology, University of Texas Health, San Antonio, TX, USA
| | | | | | | | | | - Allison Britt
- Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA
| | - Joseph Ray
- Department of Pediatrics, University of Texas Medical Branch, Galveston, TX, USA
| | - Scott D McLean
- Department of Pediatrics, Baylor College of Medicine, San Antonio, TX, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Rebecca O Littlejohn
- Department of Pediatrics, Baylor College of Medicine, San Antonio, TX, USA.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Gopalrao Velagaleti
- Department of Pathology, University of Texas Health, San Antonio, TX, USA. .,Department of Pathology and Laboratory Medicine, University of Texas Health Science Center Mail Code, Mail Code 7750, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA.
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