Case Report: Uncommon Association of ITGB4 and KRT10 Gene Mutation in a Case of Epidermolysis Bullosa With Pyloric Atresia and Aplasia Cutis Congenita

Background: Epidermolysis bullosa is a rare form of genodermatosis produced by different gene mutations. The junctional form of the disease (JEB-PA) can associate pyloric atresia, renal abnormalities, and aplasia cutis congenita.

Case Description: A case of a male preterm newborn with suspicion of digestive tube malformation at fetal ultrasound and who was born by cesarian section. At birth, he presented extensive cutaneous aplasia on the lower limbs and bilaterally under ears; outer ear agenesis; nasal septum hypoplasia; micrognathia; multiple blisters on the face, trunk, and limbs; lower limb deformities and absence of toe nails. Pathological examination following a surgical procedure with unfavorable outcome showed pyloric atresia, junctional form of epidermolysis bullosa and aplasia cutis congenita. Homozygous variants in two genes were identified: c.3111+1G>A in ITGB4 (class 5) and c.1498G>T in KRT10 (class 3).

Conclusion: The particularity of our case is the novel finding of a coincidental occurrence in the context of consaguinity of two mutations in the ITGB4 and KRT10 genes, and clinical characteristics of epidermolysis bullosa.

A novel mutation in ITGB4 gene in a newborn with epidermolysis bullosa, pyloric atresia, and aplasia cutis congenita

Background

Epidermolysis bullosa with pyloric atresia (EB-PA), also known as Carmi syndrome, is an uncommon, autosomal recessive genodermatosis that typically affects the skin and gastrointestinal tract. EB-PA is caused by homozygous or compound heterozygous mutations in the integrin alpha 6 (ITGA6) gene on chromosome 2q31.1 or in the integrin beta 4 (ITGB4) gene on 17q25.1.

Case presentation

A male premature infant was born with aplasia cutis, atresia of the pylorus, and bilateral hydronephrosis. His clinical and imaging findings were compatible with EB-PA. A novel, small deletion of the last two bases in exon 6 and the first two nucleotides of intron 6 (c.565_566+2del) in ITGB4 gene was identified.

Conclusion

EB-PA-aplasia cutis congenita is known to be a non-treatable condition with a poor prognosis as the reported case. The novel mutation reported in this patient may lead to the lethal form of this disease. Identification of underlying genetic abnormality is critical to give genetic counseling.

Über die Problematik der klinischen Entscheidungsfindung aufgrund von Fallbeschreibungen – ethische Implikationen am Beispiel eines Falls von Carmi Syndrom

Bei extrem seltenen Erkrankungen bilden Fallbeschreibungen oft die einzige Datengrundlage für klinische Entscheidungen. Das Carmi Syndrom ist eine seltene Kombination von Epidermolysis bullosa und Pylorusatresie. Während der Betreuung einer betroffenen Patientin fielen unterschiedliche Wahrnehmungen über die publizierten Mortalitätsraten auf. Daraufhin wurde die Hypothese untersucht, ob sich die kumulativen Mortalitätsraten von Einzelfallbeschreibungen und Mehrfachfallbeschreibungen unterscheiden, um so eine mögliche Verzerrung der Prognose in ihren Auswirkungen auf klinische und ethische Einschätzungen des Falls zu überprüfen.

Ein Mädchen wurde in der Schwangerschaftswoche 33 mit Carmi Syndrom geboren. Zusammen mit dem klinischen Ethikkomitee wurden Behandlungsoptionen diskutiert, einschließlich einer palliativen Behandlung oder einer operativen Gastrojejunostomie. Da etwa ein Drittel der in Fallbeschreibungen publizierten Kinder nach einer Operation überlebten, entschieden wir uns auch vor dem Hintergrund unsicherer Prognosen für das chirurgische Vorgehen. Die Patientin starb 4 Wochen später nach multiplen Komplikationen.

Die Datenbank PubMed wurde nach Publikationen über Carmi Syndrom durchsucht. Das Outcome von Einzelfallbeschreibungen wurde mit dem von Mehrfachfallbeschreibungen verglichen.

Insgesamt wurden 102 Fälle von Carmi Syndrom identifiziert. Die Mortalität bei Einzelfallbeschreibungen belief sich auf 17 von 27 Fällen (63 %), während 62 von 74 Patienten von Mehrfachfallbeschreibungen starben (84 %, p = 0,036).

Beim Carmi Syndrom unterscheidet sich die publizierte Mortalität zwischen Einfach- und Mehrfachfallbeschreibungen, möglicherweise aufgrund einer Kombination von Selektions- und Publikationsbias. Die Unterschätzung der tatsächlichen Mortalitätsrate kann zu unangebracht intensiven Therapieansätzen führen. Kliniker und Ethiker sollten daher vorsichtig sein, ihre Entscheidungen bei seltenen oder neuartigen Erkrankungen auf kumulative Erfahrungen von Fallbeschreibungen, insbesondere von Einzelfallbeschreibungen, zu basieren, die positive Verläufe von Behandlungen zu betonen scheinen.

Genotype-phenotype correlations on epidermolysis bullosa with congenital absence of skin: A comprehensive review

Congenital absence of skin (CAS) is a clinical sign associated with the main types of epidermolysis bullosa (EB). Very few studies have investigated the genetic background that may influence the occurrence of this condition. Our objective was to investigate genotype-phenotype correlations on EB with CAS through a literature revision on the pathogenic variants previously reported. A total of 171 cases (49 EB simplex, EBS; 23 junctional EB, JEB; and 99 dystrophic EB, DEB), associated with 132 pathogenic variants in eight genes, were included in the genotype-phenotype analysis. In EBS, CAS showed to be a recurrent clinical sign in EBS with pyloric atresia (PA) and EBS associated with kelch-like protein 24; CAS was also described in patients with keratins 5/14 alterations, particularly involving severe phenotypes. In JEB, this is a common clinical sign in JEB with PA associated with premature termination codon variants and/or amino acid substitutions located in the extracellular domain of integrin α6β4 genes. In DEB with CAS, missense variants occurring close to non-collagenous interruptions of the triple-helix domain of collagen VII appear to influence this condition. This study is the largest review of patients with EB and CAS and expands the spectrum of known variants on this phenomenon.

Novel missense variant in TTN cosegregating with familial atrioventricular block

BACKGROUND

Cardiovascular diseases are the most common cause of death globally. In which atrioventricular block (AVB) is a common disorder with genetic causes, but the responsible genes have not been fully identified yet. To determine the underlying causative genes involved in cardiac AVB, here we report a three-generation Chinese family with severe autosomal dominant cardiac AVB that has been ruled out as being caused by known genes mutations.

METHODS

Whole-exome sequencing was performed in five affected family members across three generations, and co-segregation analysis was validated on other members of this family.

RESULTS

Whole-exome sequencing and subsequent co-segregation validation identified a novel germline heterozygous point missense mutation, c.49287C > A (p.N16429K), in the titin (TTN, NM_001267550.2) gene in all 5 affected family members but not in the unaffected family members, neither in the large population according to the Genome Aggregation Database (https://gnomad.broadinstitute.org/). The point mutation is predicted to be functionally deleterious by in-silico software tools. Our finding was further supported by the conservative analysis across species.

CONCLUSION

Based on this study, TTN was identified as a potential novel candidate gene for autosomal dominant AVB; this study expands the mutational spectrum of TTN gene and is the first to implicate TTN mutations as AVB disease causing in a Chinese pedigree.

Widespread aplasia cutis congenita in sibs with PLEC1 and ITGB4 variants

Aplasia cutis congenita (ACC) is a heterogeneous group of disorders characterized by localized or widespread absence of skin. ACC can occur isolated or as part of a syndrome. Here we report two consanguineous families, each with two affected offspring. Affected individuals showed widespread ACC while the skin in between had a normal appearance. Ears and nose of the four patients were underdeveloped, otherwise there were no unusual physical characteristics and no internal organ anomalies. "Whole" exome sequencing (WES) of the mother of Family 1 yielded a pathogenic heterozygote variant in ITGB4. The father and healthy offspring were heterozygous for the same variant. WES of the mother of Family 2 yielded a variant in PLEC1. The father and grandmother, who had a history of two offspring with fatal ACC, were heterozygous for the same variant. PLEC1 and ITGB4 have both been previously been reported in association with ACC. We compare findings in earlier reported individuals with variants in ITGB4 and PLEC1, and provide a short summary of other entities going along with ACC.

Integra®-Dermal Regeneration Template and Split-Thickness Skin Grafting: A Therapy Approach to Correct Aplasia Cutis Congenita and Epidermolysis Bullosa in Carmi Syndrome

The association of junctional epidermolysis bullosa with pyloric atresia (JEB-PA) and aplasia cutis congenita (ACC) was described by El Shafie et al. (J Pediatr Surg 14(4):446-449, 1979) and Carmi et al. (Am J Med Genet 11:319-328, 1982). Most patients die in the first weeks of life, and no curative treatment options are available so far. We describe a patient with JEB-PA and ACC (OMIM # 226730) who was treated for extensive areas of ACC by Integra^®-Dermal Regeneration Template and split-thickness skin grafting (STSG). Clinically, the dermal template changed into well-vascularized neodermis, and after STSG, full take of the transplants was detected. No infections of the huge ACC areas were seen. Further studies must validate this treatment option in severe and acute cases of JEB-PA with ACC. Based on clinical findings, we postulate that placement of Integra^®-Dermal Regeneration Template with STSG could be a new treatment option for patients having JEB-PA with ACC to prevent severe infection, compartment-syndrome-like conditions, and deformities. Based on literature findings, we assume that Integra^®-Dermal Regeneration Template with STSG could even be able to prevent new blistering and thereby be a treatment option in cases of ACC and JEB.

Epidermolysis Bullosa with Pyloric Atresia and Aplasia Cutis in a Newborn Due to Homozygous Mutation in ITGB4

BACKGROUND

Epidermolysis bullosa with pyloric atresia (EB-PA) is an autosomal recessive disorder due to mutations in ITGA6 and/or ITGB4, resulting in altered expression of α6β4 integrin. EB-PA can also occur with aplasia cutis.

CASE REPORT

We present a newborn with EB-PA and aplasia cutis, born of consanguineous parents, with a homozygous c.3793+1G>A mutation affecting ITGB4, previously described only in the heterozygous state with other mutations.

CONCLUSION

The previously unreported homozygous c.3793+1G>A mutation affecting ITGB4 causes a severe form of junctional epidermolysis bullosa with pyloric atresia and aplasia cutis.

Identification of two rare and novel large deletions in ITGB4 gene causing epidermolysis bullosa with pyloric atresia

Epidermolysis bullosa with pyloric atresia (EB-PA) is a rare autosomal recessive hereditary disease with a variable prognosis from lethal to very mild. EB-PA is classified into Simplex form (EBS-PA: OMIM #612138) and Junctional form (JEB-PA: OMIM #226730), and it is caused by mutations in ITGA6, ITGB4 and PLEC genes. We report the analysis of six patients with EB-PA, including two dizygotic twins. Skin immunofluorescence epitope mapping was performed followed by PCR and direct sequencing of the ITGB4 gene. Two of the patients presented with non-lethal EB-PA associated with missense ITGB4 gene mutations. For the other four, early postnatal demise was associated with complete lack of β4 integrin due to a variety of ITGB4 novel mutations (2 large deletions, 1 splice-site mutation and 3 missense mutations). One of the deletions spanned 278 bp, being one of the largest reported to date for this gene. Remarkably, we also found for the first time a founder effect for one novel mutation in the ITGB4 gene. We have identified 6 novel mutations in the ITGB4 gene to be added to the mutation database. Our results reveal genotype-phenotype correlations that contribute to the molecular understanding of this heterogeneous disease, a pivotal issue for prognosis and for the development of novel evidence-based therapeutic options for EB management.

Combining GWAS and RNA-Seq Approaches for Detection of the Causal Mutation for Hereditary Junctional Epidermolysis Bullosa in Sheep

In this study, we demonstrate the use of a genome-wide association mapping together with RNA-seq in a reduced number of samples, as an efficient approach to detect the causal mutation for a Mendelian disease. Junctional epidermolysis bullosa is a recessive genodermatosis that manifests with neonatal mechanical fragility of the skin, blistering confined to the lamina lucida of the basement membrane and severe alteration of the hemidesmosomal junctions. In Spanish Churra sheep, junctional epidermolysis bullosa (JEB) has been detected in two commercial flocks. The JEB locus was mapped to Ovis aries chromosome 11 by GWAS and subsequently fine-mapped to an 868-kb homozygous segment using the identical-by-descent method. The ITGB4, which is located within this region, was identified as the best positional and functional candidate gene. The RNA-seq variant analysis enabled us to discover a 4-bp deletion within exon 33 of the ITGB4 gene (c.4412_4415del). The c.4412_4415del mutation causes a frameshift resulting in a premature stop codon at position 1472 of the integrin β4 protein. A functional analysis of this deletion revealed decreased levels of mRNA in JEB skin samples and the absence of integrin β4 labeling in immunohistochemical assays. Genotyping of c.4412_4415del showed perfect concordance with the recessive mode of the disease phenotype. Selection against this causal mutation will now be used to solve the problem of JEB in flocks of Churra sheep. Furthermore, the identification of the ITGB4 mutation means that affected sheep can be used as a large mammal animal model for the human form of epidermolysis bullosa with aplasia cutis. Our approach evidences that RNA-seq offers cost-effective alternative to identify variants in the species in which high resolution exome-sequencing is not straightforward.

Do cell junction protein mutations cause an airway phenotype in mice or humans?

Cell junction proteins connect epithelial cells to each other and to the basement membrane. Genetic mutations of these proteins can cause alterations in some epithelia leading to varied phenotypes such as deafness, renal disease, skin disorders, and cancer. This review examines if genetic mutations in these proteins affect the function of lung airway epithelia. We review cell junction proteins with examples of disease mutation phenotypes in humans and in mouse knockout models. We also review which of these genes are expressed in airway epithelium by microarray expression profiling and immunocytochemistry. Last, we present a comprehensive literature review to find the lung phenotype when cell junction and adhesion genes are mutated or subject to targeted deletion. We found that in murine models, targeted deletion of cell junction and adhesion genes rarely result in a lung phenotype. Moreover, mutations in these genes in humans have no obvious lung phenotype. Our research suggests that simply because a cell junction or adhesion protein is expressed in an organ does not imply that it will exhibit a drastic phenotype when mutated. One explanation is that because a functioning lung is critical to survival, redundancy in the system is expected. Therefore mutations in a single gene might be compensated by a related function of a similar gene product. Further studies in human and animal models will help us understand the overlap in the function of cell junction gene products. Finally, it is possible that the human lung phenotype is subtle and has not yet been described.

Modulation of vascular endothelial cell senescence by integrin β4

Increasing evidence has demonstrated that the senescence of vascular endothelial cells (VECs) has critical roles in the pathogenesis of vascular dysfunction. Finding important factors that regulate VEC senescence will help provide novel therapeutic strategies for vascular disorders. Previously, we found that integrin β4 was involved in VEC senescence. However, the mechanism underlying VEC senescence mediated by integrin β4 remains poorly understand. In this study, we used a mouse in vivo model and showed that the level of integrin β4 in the endothelium of mouse thoracic aorta was increased during natural aging and atherosclerosis. Furthermore, we found that H-ras, caveolin-1, and AP-1 were implicated in the senescent signal pathway mediated by integrin β4 in human umbilical vein ECs (HUVECs). Knockdown of integrin β4 could attenuate HUVEC senescent features, including increased interleukin-8 (IL-8) release and decreased endothelial nitric oxide synthase (eNOS) and NO levels and mitochondrial membrane potential in vitro. Our findings provide new clues illustrating the mechanism of VEC senescence. Integrin β4 might be a potential target for therapy in cardiovascular diseases.