胫前显性营养不良型大疱性表皮松解症基因突变研究

目的 探讨Ⅶ型胶原基因（COL7A1）在胫前显性营养不良型大疱性表皮松解症（DDEB-Pt）发病中的意义。 方法 收集中国汉族1例DDEB-Pt散发患者及其家庭成员和100例健康对照的外周血标本,用改良盐析法提取外周静脉血中的基因组DNA,通过PCR反应扩增和测序进行序列分析。 结果 测序结果显示,COL7A1基因73号外显子的第6109位碱基鸟嘌呤（G）转化为腺嘌呤（A）,使得三螺旋区第2037位密码子由GCT变成ACT,编码氨基酸由甘氨酸（Gly）变为精氨酸（Arg）,即c.G6109A（p.Gly2037Arg）甘氨酸替换突变。 结论 COL7A1 基因甘氨酸替换突变为致病性突变,是一新发突变。     

A novel missense mutation in the COL7A1 gene underlies epidermolysis bullosa pruriginosa

Epidermolysis bullosa (EB) pruriginosa is a subtype of dominant dystrophic EB (DDEB), characterized by severe pruritus and blistering localized to the extensor surface of the extremities. EB pruriginosa exhibits extensive clinical heterogeneity with variable expression and delayed age of onset. Mutations in the COL7A1 gene, especially in glycine residues within Gly-X-Y repeats, have been shown to cause this form of DDEB. Here, we report a novel COL7A1 mutation in a Taiwanese pedigree with EB pruriginosa. Using PCR and direct sequence analysis we have identified a G-->T transversion at nucleotide 7097 in exon 92 of COL7A1, converting a glycine residue to valine (G2366V). The mutation resides within a consecutive, uninterrupted stretch of 17 Gly-X-Y residues in the triple-helical domain of type VII collagen. Interestingly, an affected member of this family also displayed elevated IgE levels, previously reported in some patients with this disorder. Our finding further implicates COL7A1 mutation in the pathogenesis of EB pruriginosa and underscores the heterogeneous clinical symptoms of glycine mutations in DDEB.     

A novel missense mutation in the COL7A1 gene causes epidermolysis bullosa pruriginosa

Epidermolysis bullosa (EB) pruriginosa, characterized by severe itching and the presence of nodular prurigo‐like or lichenoid lesions, is a rare clinical type of dystrophic EB. Mutations in the COL7A1 gene encoding type VII collagen, the major component of anchoring fibrils, have been implicated in the pathogenesis of the disorder. In the present study, we screened a Chinese family with EB pruriginosa for COL7A1 mutations by PCR amplification of genomic sequences and direct nucleotide sequencing. The mutation consists of a G→T substitution at nucleotide 6724 in exon 85, which leads to the substitution of glycine by tryptophan at codon 2242. This report adds new variants to the known COL7A1 mutations underlying EB pruriginosa, and provides the basis for genetic counselling and prenatal diagnosis for affected families.     

A new glycine substitution mutation in the COL7A1 gene in a Chinese family with dominant dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is caused by mutations in the COL7A1 gene encoding type VII collagen, the major component of anchoring fibrils. The characteristic genetic lesion in dominant DEB (DDEB) is a glycine substitution in the collagenous domain of the protein. In this study, we identified a Chinese family with a four-generation pedigree of DDEB, in whom a novel glycine substitution mutation in COL7A1 was demonstrated. A heterozygous nucleotide G-->A transition at position 6208 in exon 74 of COL7A1 was detected, which resulted in a glycine to arginine substitution (G2070R) in the triple-helical domain of type VII collagen. This substitution was not found in 110 unrelated normal alleles. This report emphasizes the predominance of glycine substitution mutations in DDEB and contributes to the expanding database on COL7A1 mutations.     

显性营养不良型大疱性表皮松解症COL7A1基因突变分析

Objective: Dystrophic epidermolysis bullosa is an autosomal dominant or recessive disorder caused by mutations in the gene encoding type Ⅶ collagen (COL7A1 gene). To detect the mutation of COL7A1 in a DEB family. Methods: We performed full exon sequencing on DNA of the proband, and verified the COL7A1 mutation site of her sister by Sanger sequencing. Results: The proband and her sister had the same COL7A1 genotype, and the point mutation on exon 86 was c.6761G>A (p.Gly2254Glu). Conclusion: A new mutation locus of DEB family COL7A1 gene is found, which has not been reported in China at present. © 2022 China Journal of Leprosy and Skin Diseases. All rights reserved.     

2个痒疹样营养不良型大疱性表皮松解症家系基因突变分析

目的:检测2个痒疹样营养不良型大疱性表皮松解症家系的基因突变。方法: 应用聚合酶链反应(PCR)、RT-PCR、DNA直接测序明确突变位点。结果:发现家系1中先证者COL7A1基因的61号外显子5217位发生GC的改变,造成甘氨酸(GGT)被精氨酸(CGT)取代;家系2中先证者87号内含子c.6900+1GC的剪接突变,导致87号外显子被剪切,86号外显子与88号外显子直接拼接,Ⅶ型胶原的胶原区缺少了23个氨基酸;健康对照不存在此两种突变。结论: 2个家系发现的突变均为导致该疾病发生的特异性突变。     

Solitary angiokeratoma seen in a patient with pretibial epidermolysis bullosa

Solitary angiokeratoma was observed on the right leg of a 50-year-old Japanese female. In her childhood, she had repeatedly developed vesicles on the legs, and a possible diagnosis of pretibial epidermolysis bullosa was made, based on additional findings. Clinically, the condition resembled malignant melanoma and basal cell epithelioma. Possibly repeated injuries predisposed her to the development of solitary angiokeratoma.     

Dystrophic epidermolysis bullosa with one dominant and one recessive mutation of the COL7A1 gene in a child with deafness

Abstract:   Dystrophic epidermolysis bullosa can be inherited in autosomal dominant and recessive forms, the former usually expressed as a milder phenotype, although mild forms of recessive dystrophic epidermolysis bullosa can occur. We present a patient who was found to be a compound heterozygote, inheriting a dominant mutation from his father and a recessive mutation from his mother, resulting in a clinically severe case of dystrophic epidermolysis bullosa. Mutations in the gene for collagen VII ( COL7A1 ) have been documented in both types of dystrophic epidermolysis bullosa. Our patient has also been diagnosed with bilateral auditory neuropathy, a disorder coincidentally also mapped to a nearby gene on chromosome 3p21 (the transmembrane inner ear expressed gene, TMIE ).     

A recurrent frameshift mutation in exon 19 of the type VII collagen gene (COL7A1) in Mexican patients with recessive dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is an inherited blistering skin disorder caused by mutations in the type VII collagen gene (COL7A1). In this study, we determined the molecular basis of autosomal recessive DEB in a 19-year-old Hispanic Mexican woman by PCR amplification of genomic DNA, heteroduplex analysis, and automated sequencing of heteroduplex bandshifts. This approach revealed a homozygous frameshift mutation, 2470insG, in exon 19 of COL7A1 and resulted in attenuated basement membrane zone expression of type VII collagen, a reduced number of anchoring fibrils at the dermal-epidermal junction, and a sub-lamina densa level of blister formation. Clinically, the patient had widespread trauma-induced skin fragility and complete loss of the nails, but had less pseudosyndactyly of the fingers and toes and milder mucosal involvement compared to most patients with the generalized form of this genodermatosis. We also screened 7 other Hispanic-Mexican patients with recessive DEB, none of whom were known to be related to this individual, for the mutation 2470insG using heteroduplex analysis and direct sequencing and detected this mutation on 7/14 alleles. Haplotype analysis using intragenic COL7A1 and flanking polymorphisms and microsatellite markers revealed that all the mutant alleles had arisen on similar allelic backgrounds, consistent with propagation of a common Hispanic Mexican ancestral haplotype. In view of the high allelic frequency of the mutation 2470insG in the patients studied, we recommend initial screening for this mutation when attempting to identify the molecular pathology of recessive DEB in Hispanic Mexican patients.     

De Novo COL7A1 mutation in a patient with trisomy 21: coexistence of dystrophic epidermolysis bullosa and Down syndrome

Background Down syndrome (DS) is the most common autosomal chromosomal disorder. Epidermolysis bullosa (EB) is a rare genodermatosis characterized by skin and mucous membrane fragility, with formation of blisters and erosions after minor trauma. Dystrophic EB (DEB) is inherited as an autosomal dominant (DDEB) or recessive (RDEB) trait. Both forms are caused by mutations in COL7A1, the gene coding for the type VII collagen. We report a patient affected by both conditions: DS and DDEB. Methods A patient with DS developed generalized blisters at the age of three months. Cytogenetic study was performed to confirm DS. Skin biopsies were examined with immunohistochemical and electron microscopy techniques to determine EB subtype. Genomic DNA was extracted from peripheral blood samples. COL7A1 mutations were screened by heteroduplex analysis using conformation‐sensitive gel electrophoresis and sequencing. Results Karyotype analysis revealed trisomy 21. Histological study agreed with a DEB diagnosis. Mutational analysis showed a heterozygous c.6127G>T mutation in COL7A1, which is compatible with DDEB. Parental study suggests that c.6127G>T arises as a de novo mutation. Conclusions This report demonstrates that EB can be associated with other common conditions and reports the case of a patient who suffered two de novo independent genetic conditions. It also contributes to expanding the knowledge and database of clinical and molecular aspects of DDEB.     

反向型营养不良性大疱性表皮松解症COL7A1基因的突变

目的 报告1例反向型营养不良性大疱性表皮松解症,并进行组织学超微结构分析和分子遗传学诊断。方法 患者男,24岁。主诉反复皮肤水疱24年。出生后全身反复出现泛发水疱和大疱,以摩擦部位为主,夏重冬轻,伴有明显的瘙痒感,无光敏感现象。3 ～ 4岁后水疱、大疱减少,仅躯干、腹部余留水疱,症状逐年减轻。5岁时患肾炎,15岁时发展为肾衰竭,进行了肾移植手术,长期口服他克莫司和吗替麦考酚酯治疗,服药后皮损减轻。父母非近亲结婚,无相关家族史。皮肤科检查：全身未见水疱,腰背腹部可见大片边缘不规则色素减退萎缩性瘢痕,伴多个甲营养不良。收集先证者临床资料,通过免疫荧光抗原检测、透射电镜检查对患者进行分型,应用PCR扩增COL7A1基因并测序寻找致病突变,通过软件预测和逆转录PCR对突变结果在RNA水平进行验证。结果 患者皮损部皮肤Ⅶ型胶原表达量减少;皮肤裂隙位于真皮侧,致密板下锚纤维数量减少。COL7A1基因上存在同义杂合的c.C5499T剪接突变和c. C6205T（p.Arg2069Cys）错义突变,两突变分别来自父母。150例无关健康人对照中未发现相应突变。结论 c.C5499T的剪接突变和c. C6205T（p.Arg2069Cys）错义突变可能是导致患者反向型营养不良性大疱性表皮松解症的致病突变。