Exonic duplication of the OTC gene by a complex rearrangement that likely occurred via a replication-based mechanism: A case report

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Abstract

Background: Ornithine transcarbamylase deficiency (OTCD) is an X-linked recessive disorder involving a defect in the urea cycle caused by OTC gene mutations. Although a total of 417 disease-causing mutations in OTC have been reported, structural abnormalities in this gene are rare. We here describe a female OTCD case caused by an exonic duplication of the OTC gene (exons 1-6). Case presentation: A 23-year-old woman with late-onset OTCD diagnosed by biochemical testing was subjected to subsequent genetic testing. Sanger sequencing revealed no pathogenic mutation throughout the coding exons of the OTC gene, but multiplex ligation-dependent probe amplification (MLPA) revealed duplication of exons 1-6. Further genetic analyses revealed an inversion of duplicated exon 1 and a tandem duplication of exons 2-6. Each of the junctions of the inversion harbored a microhomology and non-templated microinsertion, respectively, suggesting a replication-based mechanism. The duplication was also of de novo origin but segregation analysis indicated that it took place in the paternal chromosome. Conclusion: We report the first OTCD case harboring an exonic duplication in the OTC gene. The functional defects caused by this anomaly were determined via structural analysis of its complex rearrangements.

Original languageEnglish
Article number210
JournalBMC Medical Genetics
Volume19
Issue number1
DOIs
Publication statusPublished - 12-12-2018

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Ornithine Carbamoyltransferase Deficiency Disease
Gene Duplication
Exons
Mutation
Genes
Multiplex Polymerase Chain Reaction
Genetic Testing
Urea
Chromosomes

All Science Journal Classification (ASJC) codes

  • Genetics
  • Genetics(clinical)

Cite this

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title = "Exonic duplication of the OTC gene by a complex rearrangement that likely occurred via a replication-based mechanism: A case report",
abstract = "Background: Ornithine transcarbamylase deficiency (OTCD) is an X-linked recessive disorder involving a defect in the urea cycle caused by OTC gene mutations. Although a total of 417 disease-causing mutations in OTC have been reported, structural abnormalities in this gene are rare. We here describe a female OTCD case caused by an exonic duplication of the OTC gene (exons 1-6). Case presentation: A 23-year-old woman with late-onset OTCD diagnosed by biochemical testing was subjected to subsequent genetic testing. Sanger sequencing revealed no pathogenic mutation throughout the coding exons of the OTC gene, but multiplex ligation-dependent probe amplification (MLPA) revealed duplication of exons 1-6. Further genetic analyses revealed an inversion of duplicated exon 1 and a tandem duplication of exons 2-6. Each of the junctions of the inversion harbored a microhomology and non-templated microinsertion, respectively, suggesting a replication-based mechanism. The duplication was also of de novo origin but segregation analysis indicated that it took place in the paternal chromosome. Conclusion: We report the first OTCD case harboring an exonic duplication in the OTC gene. The functional defects caused by this anomaly were determined via structural analysis of its complex rearrangements.",
author = "Katsuyuki Yokoi and Yoko Nakajima and Hidehito Inagaki and Makiko Tsutsumi and Tetsuya Ito and Hiroki Kurahashi",
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AU - Nakajima, Yoko

AU - Inagaki, Hidehito

AU - Tsutsumi, Makiko

AU - Ito, Tetsuya

AU - Kurahashi, Hiroki

PY - 2018/12/12

Y1 - 2018/12/12

N2 - Background: Ornithine transcarbamylase deficiency (OTCD) is an X-linked recessive disorder involving a defect in the urea cycle caused by OTC gene mutations. Although a total of 417 disease-causing mutations in OTC have been reported, structural abnormalities in this gene are rare. We here describe a female OTCD case caused by an exonic duplication of the OTC gene (exons 1-6). Case presentation: A 23-year-old woman with late-onset OTCD diagnosed by biochemical testing was subjected to subsequent genetic testing. Sanger sequencing revealed no pathogenic mutation throughout the coding exons of the OTC gene, but multiplex ligation-dependent probe amplification (MLPA) revealed duplication of exons 1-6. Further genetic analyses revealed an inversion of duplicated exon 1 and a tandem duplication of exons 2-6. Each of the junctions of the inversion harbored a microhomology and non-templated microinsertion, respectively, suggesting a replication-based mechanism. The duplication was also of de novo origin but segregation analysis indicated that it took place in the paternal chromosome. Conclusion: We report the first OTCD case harboring an exonic duplication in the OTC gene. The functional defects caused by this anomaly were determined via structural analysis of its complex rearrangements.

AB - Background: Ornithine transcarbamylase deficiency (OTCD) is an X-linked recessive disorder involving a defect in the urea cycle caused by OTC gene mutations. Although a total of 417 disease-causing mutations in OTC have been reported, structural abnormalities in this gene are rare. We here describe a female OTCD case caused by an exonic duplication of the OTC gene (exons 1-6). Case presentation: A 23-year-old woman with late-onset OTCD diagnosed by biochemical testing was subjected to subsequent genetic testing. Sanger sequencing revealed no pathogenic mutation throughout the coding exons of the OTC gene, but multiplex ligation-dependent probe amplification (MLPA) revealed duplication of exons 1-6. Further genetic analyses revealed an inversion of duplicated exon 1 and a tandem duplication of exons 2-6. Each of the junctions of the inversion harbored a microhomology and non-templated microinsertion, respectively, suggesting a replication-based mechanism. The duplication was also of de novo origin but segregation analysis indicated that it took place in the paternal chromosome. Conclusion: We report the first OTCD case harboring an exonic duplication in the OTC gene. The functional defects caused by this anomaly were determined via structural analysis of its complex rearrangements.

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