Alpha 6 beta 4 integrin abnormalities in junctional epidermolysis bullosa with pyloric atresia

Junctional epidermolysis bullosa with pyloric atresia (JEB-PA) (MIM 226730) is an autosomal recessive disorder resulting from mutations in the genes encoding alpha 6 beta 4 integrin (ITGA6 and ITGB4). Clinically, it is characterized by mucocutaneous fragility and gastrointestinal atresia, which most commonly affects the pylorus. Additional features of JEB-PA include involvement of the urogenital tract, aplasia cutis and failure to thrive. While most affected individuals have a poor prognosis resulting in death in infancy, others have milder clinical features and a better prognosis. We report two previously undescribed homozygous ITGB4 mutations in two unrelated families, which resulted in severe skin blistering, pyloric atresia and lethality in infancy. Delineation of the mutations was used to undertake DNA-based prenatal diagnosis in subsequent pregnancies at risk for recurrence in both families. We review all previously published ITGA6 and ITGB4 mutation reports to help define genotype--phenotype correlation in this rare genodermatosis.     

Expression of integrin alpha 6 beta 4 in junctional epidermolysis bullosa.

The integrin alpha 6 beta 4 is a member of the integrin family of adhesion receptors. The integrin alpha 6 beta 4 is preferentially expressed in stratified squamous epithelia, where it is localized in hemidesmosomes. A reduced number of rudimentary hemidesmosomes is often found in skin from patients with junctional epidermolysis bullosa (JEB). In this study we have investigated the expression of alpha 6 beta 4 in skin specimens of patients with junctional (one non-lethal, two lethal) and dystrophic (two) epidermolysis bullosa, using immunofluorescent (IF) staining with five different monoclonal antibodies against the alpha 6 and beta 4 subunits. The intensity of IF staining of the integrin alpha 6 beta 4 and bullous pemphigoid antigen (BPA) was unreduced along the epidermal basement membrane zone (EBMZ) of all EB patients, compared to that in skin of healthy human controls. However, in the skin of two patients with lethal (Herlitz) JEB, who did not express GB3, IF staining of integrin alpha 6 beta 4 and BPA showed a "stitchy" discontinuous linear pattern along the EBMZ with interruptions at the borders of adjoining basal keratinocytes. The same results were obtained by immunoelectron microscopy. They corresponded with freeze-induced partial cell detachment from the basement membrane at the ultimate baso-lateral edge of the basal keratinocytes in lethal JEB skin. The basal lamellipodia at that location almost completely lacked tonofilaments and hemidesmosomes. Furthermore, in JEB there was a split between the intra- and extracellular epitopes of the integrin alpha 6 beta 4 receptor, whereas the integrin remains intact in salt-split skin. This suggests that the defect is in alpha 6 beta 4 itself or perhaps its ligand.     

Compound heterozygosity for novel splice site mutations of ITGA6 in lethal junctional epidermolysis bullosa with pyloric atresia

Junctional epidermolysis bullosa with pyloric atresia (PA‐JEB) is a rare congenital bullous disease with gastrointestinal disturbance that has been associated with mutations in ITGA6 or ITGB4 encoding the α6 or β4 subunit of integrin, respectively. Only six ITGA6 mutations in PA‐JEB have been reported while many ITGB4 mutations have been identified, and all the ITGA6 mutations were homozygous. Here, we report a case of lethal type PA‐JEB, in which immunofluorescence showed the lack of both α6 and β4 integrins resulting from compound heterozygous splice site mutation in ITGA6, c.387G>T and c.2506‐1G>C. Maternal c.387G>T induced the skipping of the entire exon 3 and both exons 3 and 4, resulting in premature termination codon and in‐frame deletion, respectively. Paternal c.2506‐1G>C caused the skipping of the exon 20 and resulted in in‐frame deletion. As a reason why the present case showed lethal phenotype despite the in‐frame deletion mutation, rapid degradation of neo‐synthesized α6 protein and/or impaired transport of integrin were suggested from previous reports, and the lack of localization of integrin α6β4 to the epidermal basement membrane resulted in skin fragility. Our case expands the variety of integrin α6 mutations in PA‐JEB.     

DNA-based prenatal diagnosis of plectin-deficient epidermolysis bullosa simplex associated with pyloric atresia

Background Mutations in the plectin gene (PLEC) generally lead to epidermolysis bullosa simplex (EBS) associated with muscular dystrophy. It has been recently demonstrated that PLEC mutations can also cause a different clinical subtype, EBS associated with pyloric atresia (EBS‐PA), which shows early lethality. Prenatal diagnosis (PND) of EBS‐PA using mutation screening of PLEC has not been described. Objective This study aimed to perform DNA‐based PND for an EBS‐PA family. Materials and methods The EBS‐PA proband was compound‐heterozygous for a paternal c.1350G>A splice‐site mutation and a maternal p.Q305X nonsense mutation. Genomic DNA was obtained from amniocytes taken from an at‐risk fetus of the proband’s family. Direct sequencing and restriction enzyme digestion of polymerase chain reaction products from the genomic DNA were performed. Results Mutational analysis showed that the fetus harbored both pathogenic mutations, suggesting that the fetus was a compound‐heterozygote and therefore affected with EBS‐PA. The skin sample obtained by autopsy from the abortus confirmed the absence of plectin expression at the dermal–epidermal junction. Conclusions This is the first successful DNA‐based PND for an EBA‐PA family.     

KRT5基因新生突变致重度型单纯型大疱性表皮松解症一家系

目的:报道1例重度型单纯型大疱性表皮松解症,并检测其基因突变。方法:收集患者及其父母资料和外周血,提取基因组DNA,全外显子组测序筛查患儿致病基因,随后采用Sanger测序对家系成员进行验证。结果:患者KRT5基因第7号外显子第1 429位碱基发生G→A（c.1429G>A）杂合突变,导致KRT5基因所编码的蛋白第47...     

Categorizing immunofluorescence mapping in epidermolysis bullosa with pyloric atresia: Use as a broad prognostic indicator

Epidermolysis bullosa with pyloric atresia is a form of junctional epidermolysis bullosa associated with gastrointestinal abnormalities, which may include pyloric atresia. Genotype phenotype correlation is poorly understood and prognosis is difficult, if not impossible, to predict. Immunofluorescence mapping is an ideal candidate for developing a broad prognostic indicator for epidermolysis bullosa with pyloric atresia without the need for genetic mutation analysis. However, the tool developed in this paper does have limitations due to the small number of cases available and the effects of deleterious mutations in highly conserved cysteine residues on the predicted length of survival.     

Generalized,severe epidermolysis bullosa simplex caused by a Keratin 5 p.E477K mutation

Epidermolysis bullosa simplex (EBS) is a skin fragility disorder resulting from mutations of structural proteins in the epidermis. We provide a brief report of long‐term survival and reproduction in a mother with EBS due to keratin 5 (KRT5) c.1429G > A (p.E477K) mutation, which causes a particularly severe form of the disease.     

A heterozygous mutation in ITGB4 causing a mild phenotype of junctional epidermolysis bullosa

Mutations in ITGB4 are known to cause autosomal recessive junctional epidermolysis bullosa (JEB), which is manifested by severe blistering and granulation tissue, usually complicating pyloric atresia and even leading to death. ITGB4-associated autosomal dominant epidermolysis bullosa has rarely been documented. Herein, we identified a heterozygous pathogenic variant (c.433G>T; p.Asp145Tyr) in ITGB4 causing a mild phenotype of JEB in a Chinese family.     

Deletion of a cytoplasmic domain of integrin beta4 causes epidermolysis bullosa simplex

Integrin alpha6beta4 is a hemidesmosomal transmembrane molecule involved in maintaining basal cell-matrix adhesion through interaction of the large intracytoplasmic tail of the beta4 subunit with the keratin intermediate filament network, at least in part through its binding with plectin and BP180/type XVII collagen. Here we report a patient with predominant features of epidermolysis bullosa simplex due to a mutation in the integrin beta4 gene. The patient, a 49-y-old female, had mild blistering of hands and feet from birth on, dystrophy of the nails with onychogryposis, and enamel hypoplasia. She had no alopecia and no history of pyloric atresia. Electron microscopy and antigen mapping of a skin blister revealed that the level of separation was intraepidermal, low in the basal keratinocytes through the attachment plaque of the hemidesmosome. Immuno-fluorescence microscopy revealed absent binding of monoclonal antibody 450-11 A against the third fibronectin III repeat on the intracellular domain of integrin beta4, whereas binding was reduced with monoclonal antibodies recognizing epitopes on amino-terminal and carboxy-terminal ends of the polypeptide. At the molecular level the phenotype was caused by a novel 2 bp deletion 4733delCT in ITGB4, resulting in in-frame skipping of exon 36 and a deduced 50 amino acid deletion (1450-1499) within the third fibronectin type III repeat in the cytoplasmic domain of the integrin beta4 polypeptide. Immunoblot analysis demonstrated a 5 kDa shorter beta4 polypeptide. The 4733delCT mutation was heterozygously present in the DNA. The patient is also expected to be heterozygous for a null allele, as no full-size protein was detected in vitro and the epitope 450-11 A was absent in vivo. These data show that deletion of the third fibronectin type III repeat in the cytoplasmic domain of integrin beta4, which is thought to interact with BP180/type XVII collagen, is clinically pathogenic and results in a mild phenotype with predominant features of epidermolysis bullosa simplex.     

Detection of novel LAMA3 mutation in Herlitz junctional epidermolysis bullosa in a Jordanian family

The Herlitz junctional epidermolysis bullosa (H‐JEB) subtype usually presents as a severe lethal inherited variant of epidermolysis bullosa (EB) caused by a homozygous mutation in the genes LAMA3, LMAB3, or LAMAC3. Each gene encodes one of the three chains of heterotrimer laminin‐332 proteins (including the alpha‐3 chain, beta‐3 chain and gamma‐2‐chain) responsible for the adherence of the epidermis to the underlying dermis. The aim of this report is to add to the existing knowledge about EB by describing a novel mutation in a gene responsible for genodermatosis. A case of a Jordanian male neonate, born to healthy, first cousin consanguineous parents, who developed nonhealing blistering skin and mucous membrane lesions, crusted erosions with significant granulation tissue and dystrophic nails immediately after birth is described. The patient was diagnosed as having a novel LAMA3 mutation causing (H‐JEB) by immunofluorescence mapping and molecular analysis. Both parents and this baby's sibling were shown to be heterozygous carriers of the same mutation. Pre‐implantation diagnosis using molecular analysis for subsequent pregnancies in this family is crucial for managing any new pregnancy.     

Immunofluorescence analysis of villous trophoblasts: a tool for prenatal diagnosis of inherited epidermolysis bullosa with pyloric atresia

Genetic mutations invalidating the genes for integrin alpha6beta4 and, in some cases, plectin are associated with junctional and simplex epidermolysis bullosa with pyloric atresia (PA-JEB and PA-EBS), respectively. These recessive inherited conditions are characterized by pregnancies with fetal bullae, pyloric atresia, polyhydramnios, and neonatal mucocutaneous blistering, which often results in early postnatal demise. To date, first-trimester DNA-based prenatal diagnosis is not applicable to affected kindred carrying as yet unidentified genetic mutations. Here, we show that first-trimester chorionic villi strongly express both integrin alpha6beta4 and plectin, which persist throughout the pregnancy. Based on this observation, we implemented 25 prenatal diagnoses in kindred at risk for PA-EB by immunomapping, which identified three PA-JEB-affected fetuses and 22 healthy ones. In 19 cases, including the three PA-JEB pregnancies that were prematurely terminated, the results were confirmed by chorionic villous DNA-based tests, which also led to the identification of seven previously unreported mutations in the alpha6beta4 integrin genes. Our prediction was further sustained by the birth of 22 healthy babies. These results validate chorionic villi immunofluorescence examination as a tool for prenatal diagnosis of PA-JEB and PA-EBS and indicate that this procedure could be devised for EB with muscular dystrophy, which is also associated with genetic mutations in plectin.     

Bullous pemphigoid in a patient with suspected non-Herlitz junctional epidermolysis bullosa

A 56-year-old man with lifelong trauma-induced blisters, nail dystrophy and dental enamel hypoplasia presented with a new spontaneous blistering eruption. Clinicopathologically, he had evidence of both an inherited and an acquired blistering disorder: non-Herlitz junctional epidermolysis bullosa (nHJEB) and bullous pemphigoid (BP). HIstological examination of a skin biopsy found reduced (but not absent) collagen XVII in nonlesional skin, in vivo bound anticollagen XVII antibodies in perilesional skin, and prominent eosinophils in perilesional and lesional skin, with subepidermal blistering. Circulating anticollagen XVII antibodies were also present. Treatment with oral corticosteroids and mycophenolate mofetil led to clinical control of the BP but had no effect on the mechanobullous blistering. Our patient is unusual in that his skin retains some labelling for collagen XVII rather than having the complete absence of immunoreactivity expected in patients with generalized nHJEB. Moreover, we were unable to identify any pathogenic mutations in the COL17A1 gene encoding collagen XVII (or in other EB-associated basement membrane genes). It is plausible that the long-term consequences of basement membrane disruption in our patient, perhaps associated with atypical inherited COL17A1 pathology, might result in a conformationally altered and more immunogenic protein with the subsequent development of anticollagen XVII antibodies and BP as a secondary pathology.     

一例交界型大疱性表皮松解症患儿LAMA3基因突变检测

目的：检测1例交界型大疱性表皮松解症患儿LAMA3基因突变情况。方法：提取1例交界型大疱性表皮松解症患儿及其父母的外周血DNA，通过靶向捕获-高通量测序检测患儿的基因突变，用Sanger测序法进行父母验证，同时通过cDNA测序来验证异常的RNA剪接。结果：在患儿LAMA3基因上检测到两个新的影响RNA剪接的突变，即c.1478+5G>A(导致在mRNA上c.1381_1478del)和c.4647+5G>C(导致在mRNA上c.4647_4648ins74)，患儿的这2个突变分别遗传自其父亲和母亲。结论：本次检测到的LAMA3基因上的2个致病突变，可能因严重破坏层粘连蛋白-332的功能性α3肽链的合成而导致患儿发病。     

Differential expression of pyloric atresia in junctional epidermolysis bullosa with ITGB4 mutations suggests that pyloric atresia is due to factors other than the mutations and not predictive of a poor outcome: three novel mutations and a review of the literature

Junctional epidermolysis bullosa with pyloric atresia (JEB-PA) is an autosomal recessive blistering disease including lethal and non-lethal variants due to mutations in ITGB4 and ITGA6. It is unclear whether PA is caused directly by the mutations in these genes or by other factors. Skin biopsies from patients with JEB were processed for immunofluorescence mapping. When staining for integrin beta4 or alpha6 was absent or reduced, ITGB4 was screened for mutations. A review of known mutations of ITGB4 and the phenotypes of patients with JEB-PA was undertaken. Three novel ITGB4 mutations were identified in 3 families with JEB-PA: 2 splice-site and one insertion mutation. Two families with lethal phenotypes (EB-050 and EB-049) were due to combinations of premature termination codons and missense mutations (658delC/R252C and 3903dupC/G273D, respectively). The third family EB-013 has 2 JEB affected siblings; a brother with PA and a sister without PA. Both were homo notzygous for ITGB4 264G>A/3111-1G>A. Two cases had no gastrointestinal symptoms or signs of PA. PA is an inconstant feature of the subtype of epidermolysis bullosa known as JEB-PA. It is most likely that multiple factors influence the development of PA and its presence is not predictive of a poor outcome. It is possible that institutions that do not routinely screen immunofluore notscence mapping for integrin alpha6beta4 staining in the absence of PA are missing this form of epidermolysis bullosa.