One Novel Frameshift Mutation on Exon 64 of

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ing occurs below the laminadensa of the dermal- epidermal junction after mechanical trauma [1]. It is caused by the COL7A1 gene mutation that en- codes type ...
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Annals of Clinical & Laboratory Science, vol. 45, no. 5, 2015

One Novel Frameshift Mutation on Exon 64 of COL7A1 Gene in an Iranian Individual Suffering Recessive Dystrophic Epidermolysis Bullosa Mahmoud Shekari Khaniani1, Nasrin Sohrabi1, Neda Mansoori Derakhshan2, and Sima Mansoori Derakhshan1 1Medical

Genetic Department, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz and 2Department of Genetics, Faculty of Sciences, Islamic Azad University, Tabriz Branch, Tabriz, Iran

Abstract. Recessive dystrophic epidermolysis bullosa (RDEB) is an extremely rare subtype of bullous dermatosis caused by the COL7A1 gene mutation. After genomic DNA extraction from the peripheral blood sample of all subjects (3 pedigree members and 3 unrelated control individuals), COL7A1 gene screening was performed by PCR amplification and direct DNA sequencing of all of the coding exons and flanking intronic regions. Genetic analysis of the COL7A1 gene in an affected individual revealed a novel mutation: c.5493delG (p.K1831Nfs*10) in exon 64 of the COL7A1 gene in homozygous state. This mutation was not discovered in 3 unrelated Iranian control individuals. These data suggest that c.5493delG may influence the phenotype of RDEB. The result of this case report contributes to the expanding database on COL7A1 mutations. Keywords: Recessive dystrophic epidermolysis bullosa, COL7A1 gene, Mutation analysis. Introduction

Materials and Methods

Recessive Dystrophic epidermolysis bullosa (RDEB) is a heritable skin disease in which blistering occurs below the laminadensa of the dermalepidermal junction after mechanical trauma [1]. It is caused by the COL7A1 gene mutation that encodes type VII collagen in autosomal dominant or recessive mode [2]. Common symptoms include skin blisters, scars, pseudosyndactyly, and onychodystrophy caused by slight trauma[3].

A 4-year-old girl was diagnosed with RDEB on the basis of typical skin lesions composed of multiple blisters with severely healed erosions and scarring on trauma-exposed body sites (Figure 1A). At birth, the newborn had reddened areas on the hands and toe tips, which began to blister after she was 1 week old. In this case, an RDEB inheritance pattern was assumed based on a negative previous family history, consanguineous marriage, and a characteristically severe phenotype in the affected child. After informed consent, genomic DNA was extracted by the salting out method [4] from the peripheral blood sample of all subjects (3 pedigree members and 3 unrelated control individuals). COL7A1 gene screening was performed by PCR amplification and direct DNA sequencing of the whole coding exons and flanking intronic regions. In a subsequent pregnancy, at 12 weeks of gestation, DNA from chorionic villus sample was obtained and is investigated for the known mutation.

Herein, we report a molecular genetic study of a child referred to Tabriz Ebne Sina Medical genetic center who was suspected to have RDEB. This study also reports the successful determination of the fetal genotype in subsequent pregnancy at risk for recurrence of RDEB in this family. Besides the 730 mutations reported, we identified one novel COL7A1 gene mutation in an Iranian family causing RDEB. Address correspondence to Sima Mansoori Derakhshan, MD, PhD, Medical Genetic Department, Medical Faculty, Tabriz University of Medical Sciences, Tabriz, Iran; phone: (+98 411) 3371587; cell phone: 09141779918; fax: (+98 411) 3371587; e-mail: mderakhshan2002@ gmail.com

Ethics. This study was approved by the Regional Committee of Ethics of the Tabriz University of Medical Sciences. Written informed consent was obtained from the parents of all the children who participated in this study.

0091-7370/15/0500-??? © 2015 by the Association of Clinical Scientists, Inc.

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Annals of Clinical & Laboratory Science, vol. 45, no. 5, 2015

Figure 1. (a) Patient was the first child of consanguineous unaffected parents of Iran origin with no family history of EB. Prenatal diagnosis showed that second child of parents was unaffected. (b) Direct sequencing of the whole coding exons and flanking intronic regions showed that Parents were heterozygous for the mutation c.5493delG, p.K1831Nfs*10 (arrow) in exon 64. The mutation created a premature termination codon (PTC) located 10 amino acids downstream in exon 64.

Results

Discussion

Genetic analysis of the COL7A1 gene in an affected individual revealed a novel mutation, c.5493delG (p.K1831Nfs*10) in exon 64 of the COL7A1 gene in homozygous state. Her parents were heterozygous for the mutation c.5493delG, p.K1831Nfs*10 (Figure 1B). This frameshift mutation leads to a premature termination codon (PTC) located 10 amino acids downstream in exon 64 (p.K1831Nfs*10) and is expected to result in a loss of function either by nonsense-mediated decay of mutant mRNA or by the formation of a nonfunctional, truncated protein. This mutation was not discovered in 3 unrelated Iranian control healthy individuals. In the prenatal stage, the fetus was found to be normal for this mutation and this finding has been validated by the birth of a healthy child.

The position of the PTC within COL7A1 correlates with the its clinical severity. When PTC are located upstream of the triple helical region, they result in severe clinical symptoms such as complete pseudosyndactyly while Downstream PTCs affect patients with partial pseudosyndactyly. The presence of some functional protein appears to be the most important factor in ameliorating the disease severity [5]. Because the therapeutic approaches are mainly symptomatic, and have limited success, the prevention of the disease by risk assessment and genetic counseling is the only effective strategy at the moment [6]. In this study, the clinical presentation of the affected child resulted from a homozygous frameshift mutation at codon 1831. To our knowledge, the deletion c.5493delG in exon 64 of the COL7A1 gene has not been reported in the

One Novel Frameshift Mutation on Exon 64 of COL7A1 Gene in Recessive Dystrophic Epidermolysis Bullosa

literature or the HGMD professional database 2013.3, and it is a novel mutation and associated with the severe RDEB phenotype. This report presented that molecular diagnosis can be beneficial to diagnose RDEB and predict prognosis. Moreover, this novel mutation of COL7A1 in an Iranian patient is an addition to the range of COL7A1 mutations related to RDEB.

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Acknowledgment We are grateful to the patient and parents for assisting us in carrying out this study and compiling this report.

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References 6. 1.

Fine J-D, Eady RAJ, Bauer EA, Bauer JW, Bruckner-Tuderman L, Heagerty A, et al. The classification of inherited epidermolysis bullosa (EB): Report of the Third International Consensus Meeting on Diagnosis and Classification of EB. Journal of the American Academy of Dermatology. 2008;58(6):931-50.

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