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Recessive Dystrophic Epidermolysis bullosa due to Hemizygous 40 kb Deletion of COL7A1 and the Proximate PFKFB4 Gene Focusing on the Mutation c.425A>G Mimicking Homozygous Status. Diagnostics (Basel) 2022; 12:diagnostics12102460. [PMID: 36292148 PMCID: PMC9600310 DOI: 10.3390/diagnostics12102460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 09/17/2022] [Accepted: 09/28/2022] [Indexed: 11/17/2022] Open
Abstract
Background: Dystrophic Epidermolysis bullosa (DEB) is a rare inherited mechanobullous disease characterised by the hyperfragility of the skin and mucous membranes. It is (typically) caused by (loss-of-function) mutations in the COL7A1 gene that impair the formation of collagen type VII, which represents the major constituent of anchoring fibrils within the basement membrane zone of epithelialised tissues. In a 4-year-old patient diagnosed with the clinical features of recessive DEB, genotyping via Next-Generation EB Panel Sequencing initially revealed the homozygosity of the maternal c.425A>G mutation, while the paternal heterozygosity in exon 3 was lacking. This genetic profile suggested incongruent gene transmission due to uniparental isodisomy (UPD) or the occurrence of a hemizygous deletion of unknown size. Methods: Thus, the EB panel sequencing of genomic DNA, followed by a paternity test and analysis of microsatellite markers, as well as multiplex ligation-dependent probe amplification (MLPA) copy number analysis using patient and parental DNA, were performed. Results: This approach revealed a paternally derived hemizygous deletion spanning from exon 3 to exon 118. Linear amplification-mediated PCR (LAM-PCR) determined the breaking points within intron 2 of the COL7A1 gene, comprising a 40kb segment within intron 1 of the adjacent PFKFB4 gene. Conclusion: This report highlights the relevance of advanced molecular profiling to determine new/exceptional/unusual genotypes and the accurate mode of genetic transmission in DEB.
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Bremer J, van der Heijden EH, Eichhorn DS, Meijer R, Lemmink HH, Scheffer H, Sinke RJ, Jonkman MF, Pasmooij AMG, Van den Akker PC. Natural Exon Skipping Sets the Stage for Exon Skipping as Therapy for Dystrophic Epidermolysis Bullosa. MOLECULAR THERAPY. NUCLEIC ACIDS 2019; 18:465-475. [PMID: 31670143 PMCID: PMC6831832 DOI: 10.1016/j.omtn.2019.09.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 09/10/2019] [Accepted: 09/10/2019] [Indexed: 02/04/2023]
Abstract
Dystrophic epidermolysis bullosa (DEB) is a devastating blistering disease affecting skin and mucous membranes. It is caused by pathogenic variants in the COL7A1 gene encoding type VII collagen, and can be inherited dominantly or recessively. Recently, promising proof-of-principle has been shown for antisense oligonucleotide (AON)-mediated exon skipping as a therapeutic approach for DEB. However, the precise phenotypic effect to be anticipated from exon skipping, and which patient groups could benefit, is not yet clear. To answer these questions, we studied new clinical and molecular data on seven patients from the Dutch EB registry and reviewed the literature on COL7A1 exon skipping variants. We found that phenotypes associated with dominant exon skipping cannot be distinguished from phenotypes caused by other dominant DEB variants. Recessive exon skipping phenotypes are generally relatively mild in the spectrum of recessive DEB. Therefore, for dominant DEB, AON-mediated exon skipping is unlikely to ameliorate the phenotype. In contrast, the overall severity of phenotypes associated with recessive natural exon skipping pivots toward the milder end of the spectrum. Consequently, we anticipate AON-mediated exon skipping for recessive DEB caused by bi-allelic null variants should lead to a clinically relevant improvement of this devastating phenotype.
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Affiliation(s)
- Jeroen Bremer
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; Department of Dermatology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
| | - Elisabeth H van der Heijden
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Daryll S Eichhorn
- Department of Dermatology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Rowdy Meijer
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Henny H Lemmink
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Hans Scheffer
- Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Richard J Sinke
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Marcel F Jonkman
- Department of Dermatology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Anna M G Pasmooij
- Department of Dermatology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Peter C Van den Akker
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands; Department of Dermatology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
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