Viable phenotype of ILNEB syndrome without nephrotic impairment in siblings heterozygous for unreported integrin alpha3 mutations

Integrin mutations in blistering skin diseases and related genetically engineered mouse models

As major receptors for cellular adhesion, integrins in the epidermis are critical to maintain skin integrity. Integrins α6β4 and α3β1 are among the most highly and widely expressed integrins in the skin. Perhaps not surprisingly, mutation in subunits associated with these integrins cause variations of a blistering skin disease called junctional epidermolysis bullosa (JEB), which is characterized by blisters that form between the epidermis and dermis of the skin. This review highlights how the differences in structural roles and functions for these epidermal integrins lead to distinct JEB phenotypes resulting from their absence. Additionally, much has been learned by using genetically engineered mouse models, which are featured throughout the review, as they closely resemble the disorders of human patients that harbor analogous mutations.

Integrin α3 negative podocytes: A gene expression study

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New cell model to investigate the impact of loss of integrin α3 in podocytes.

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In this novel model, genes of the extracellular matrix and adhesome are mostly downregulated.

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Loss of integrin α3 results in changes of cell adhesion and spreading.

Integrin α3β1 is a cell adhesion receptor widely expressed in epithelial cells. Pathogenic variants in the gene encoding the integrin α3 subunit ITGA3 lead to a syndrome including interstitial lung disease, nephrotic syndrome, and epidermolysis bullosa (ILNEB). Renal involvement mainly consists of glomerular disease caused by loss of adhesion between podocytes and the glomerular basement membrane.

The aim of this study was to characterize the impact of loss of integrin α3 on human podocytes.

ITGA3 was stably knocked-out in the human podocyte cell line AB8/13, designated as Podo^A3−, and in human proximal tubule epithelial cell line HK2 using the targeted genome editing technique CRISPR/Cas9. Cell clones were characterized by Sanger sequencing, quantitative PCR, Western Blot and immunofluorescence staining. RNASeq of integrin α3 negative cells and controls was performed to identify differential gene expression patterns.

Differentiated Podo^A3− did not substantially change morphology and adhesion under standard culture conditions, but displayed significantly reduced spreading and adhesion when seed on laminin 511 in serum free medium. Gene expression studies demonstrated a distinct dysregulation of the adhesion network with downregulation of most integrin α3 interaction partners. In agreement with this, biological processes such as “extracellular matrix organization” and “cell differentiation” as well as KEGG pathways such as “ECM-receptor interaction”, “focal adhesion” and the “PI3K-Akt signaling pathway” were significantly downregulated in human podocytes lacking the integrin α3 subunit.

Epidermolysis Bullosa—A Different Genetic Approach in Correlation with Genetic Heterogeneity

Epidermolysis bullosa is a heterogeneous group of rare genetic disorders characterized by mucocutaneous fragility and blister formation after minor friction or trauma. There are four major epidermolysis bullosa types based on the ultrastructural level of tissue cleavage: simplex, junctional, dystrophic, and Kindler epidermolysis bullosa. They are caused by mutations in genes that encode the proteins that are part of the hemidesmosomes and focal adhesion complex. Some of these disorders can be associated with extracutaneous manifestations, which are sometimes fatal. They are inherited in an autosomal recessive or autosomal dominant manner. This review is focused on the phenomena of heterogeneity (locus, allelic, mutational, and clinical) in epidermolysis bullosa, and on the correlation genotype–phenotype.

Proteomic Analysis Reveals Differential Expression Profiles in Idiopathic Pulmonary Fibrosis Cell Lines

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, irreversible lung disorder of unknown cause. This disease is characterized by profibrotic activation of resident pulmonary fibroblasts resulting in aberrant deposition of extracellular matrix (ECM) proteins. However, although much is known about the pathophysiology of IPF, the cellular and molecular processes that occur and allow aberrant fibroblast activation remain an unmet need. To explore the differentially expressed proteins (DEPs) associated with aberrant activation of these fibroblasts, we used the IPF lung fibroblast cell lines LL97A (IPF-1) and LL29 (IPF-2), compared to the normal lung fibroblast cell line CCD19Lu (NL-1). Protein samples were quantified and identified using a label-free quantitative proteomic analysis approach by liquid chromatography-tandem mass spectrometry (LC-MS/MS). DEPs were identified after pairwise comparison, including all experimental groups. Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG), and Protein–Protein Interaction (PPI) network construction were used to interpret the proteomic data. Eighty proteins expressed exclusively in the IPF-1 and IPF-2 clusters were identified. In addition, 19 proteins were identified up-regulated in IPF-1 and 10 in IPF-2; 10 proteins were down-regulated in IPF-1 and 2 in IPF-2 when compared to the NL-1 proteome. Using the search tool for retrieval of interacting genes/proteins (STRING) software, a PPI network was constructed between the DEPs and the 80 proteins expressed exclusively in the IPF-2 and IPF-1 clusters, containing 115 nodes and 136 edges. The 10 hub proteins present in the IPP network were identified using the CytoHubba plugin of the Cytoscape software. GO and KEGG pathway analyses showed that the hub proteins were mainly related to cell adhesion, integrin binding, and hematopoietic cell lineage. Our results provide relevant information on DEPs present in IPF lung fibroblast cell lines when compared to the normal lung fibroblast cell line that could play a key role during IPF pathogenesis.

New Report of a Different Clinical Presentation of CD151 Splicing Mutation (c.351+2T>C): Could TSPAN11 be Considered as a Potential Modifier Gene for CD151?

CD151, a member of the tetraspanin family, is essential for normal development of skin and kidney. To date, only 2 pathogenic variants of the CD151 gene have been identified in a related disorder with recessive inheritance. Here, in the third study of CD151 mutations, we report 3 affected siblings presenting variable degrees of renal and dermal symptoms. Whole exome sequencing (WES) was performed on the proband, followed by data analysis and in silico assessments. Confirmation of the mutation in the other patients were carried out using Sanger sequencing. The consequence of the CD151 mutation was investigated by RNA extraction and Sanger sequencing of PCR products from cDNA. Multiple computational tools were applied for protein alignment, homology modeling, and molecular interaction analysis. WES revealed the variant c.351+2T>C, NM_139029 (GRCh37) in CD151, and this was confirmed by Sanger sequencing in all patients. This variant is the result of a substitution of nucleotide T with C that changes the position +2 of the donor splice site in intron 5, leading to total loss of exon 5 from the transcript. The mentioned variant was not found in population allele frequency databases, and prediction tools concurred in its damaging effect on the protein. Based on the criteria from ACMG guidelines, this variant is pathogenic. Interestingly, in terms of clinical findings, symptoms and severity of the disease in the patients in this study were different compared to the previous report of the mutation and the disease. In addition, in silico analysis in this study appears to suggest a candidate protein, Tetraspanin-11 (TSPAN11), that could partially modify CD151 functions. This study supports the pathogenic effect of the CD151 variant c.351+2T>C, highlights the extensive variable expressivity amongst patients, reinforces the contribution of genomic content to clinical characteristics of CD151 mutations, and accentuates the importance of modifier genes.

Epidermolysis Bullosa: Pediatric Perspectives

Epidermolysis bullosa (EB) is a group of rare congenital genetic conditions that result in painful blistering of the skin and mucous membranes, which occur with minor trauma or friction. There are many types and subtypes of EB that need to be distinguished, as the management and prognosis of each can vary significantly. We aim to perform an up-to-date literature review on congenital EB for healthcare providers in pediatrics. We performed a review of existing literature in the English language on EB via PubMed Clinical Queries, using key words such as "epidermolysis bullosa", "congenital" and "children". We reviewed EB based on the following subheadings: epidemiology, diagnosis, therapy, prognosis, and clinical prediction guidelines. EB is due to mutation in a number of genes, some types are autosomal dominant while others are autosomal recessive. The underlying mechanism is a defect in attachment between or within the epidermis and dermis of the skin. There are four main types: epidermolysis bullosa simplex, dystrophic epidermolysis bullosa, junctional epidermolysis bullosa, and Kindler syndrome. The diagnosis is suspected based on symptoms and confirmed by skin biopsy and definitive genetic testing. The severity of EB can range from mild to fatal. Severe complications may arise in some EB types and subtypes within the eye, ear, nose, upper airway, gastrointestinal and genitourinary tracts. There is no cure for the condition to date. Optimal management must be multidisciplinary, and involves wound care, pain control, controlling infections, nutritional support, and prevention and treatment of complications. EB presents in different forms. Treatment is supportive. The prognosis of milder forms is good. Children severely affected with EB and their families live a misery life with impaired quality of life. Health care workers must be aware of the suffering in these families and proactively support them.

Biallelic Missense Mutations in the Integrin Alpha 3 Gene Causes Skin Fragility Without Structural Defects in Lungs and Kidneys

Abstract is missing (Short communication)

A novel ITGA3 homozygous splice mutation in an ILNEB syndrome child with slow progression

BACKGROUND AND AIMS

ILNEB (interstitial lung disease, nephrotic syndrome, epidermolysis bullosa) syndrome is caused by ITGA3 mutations. Demises usually happened at infancy. This study reports a complete ILNEB syndrome child with slow disease progression.

MATERIALS AND METHODS

Clinical data and related specimens were collected. Genomic DNA was extracted for genetic sequencing. Integrin α3 expression was detected by western blotting and immunofluorescence staining.

RESULTS

The patient was male. He experienced recurrent rashes shortly after birth. His sparse eyebrows and eyelashes gradually lost. The patient was vulnerable to respiratory infections and had recurrent fever after vaccine immunization after 4 years. He was found with nephrotic syndrome and polycystic renal dysplasia at 8 years and progressed to end-stage renal disease at 12 years. A chest Computed Tomography revealed intestinal lung disease at 8 years. Continuous oxygen supplementation was needed at 13 years. Counts of lymphocyte subsets revealed elevated percentage of double-negative T cells and activated T cells. Next-generation sequencing revealed a novel homozygous splice mutation c.2219 + 4A > Cin ITGA3 that was predicted to be deleterious. The mutation resulted in exon17 skipping with the loss of 80 bp in the mRNA. The aberrant integrin α3 mRNA level was lower compared to the healthy control. Integrin α3 protein was not detected in urine epithelial cells and skin of the patient.

CONCLUSIONS

We report a patient harboring a novel ITGA3 homozygous splice mutation who presented with complete ILNEB syndrome but slow disease progression. Immune disorders were suspected.

First patient with ILNEB syndrome due to pathogenic variants in ITGA3 surviving to adulthood

Interstitial Lung disease, Nephrotic syndrome and Epidermolysis Bullosa, also referred to as ILNEB syndrome is an extremely rare autosomal recessive condition, caused by pathogenic variants in ITGA3. 11 patients have previously been diagnosed with ILNEB syndrome of whom 7 died in infancy or early childhood. We report the only patient with ILNEB syndrome who survived past adolescence, partly due to a double lung transplant. Additionally, our patient showed oral, nasal and gynecological symptoms not previously reported in patients with ILNEB syndrome.

Successful kidney transplantation in a patient with neonatal-onset ILNEB

BACKGROUND

ILNEB constitute an autosomal recessive disorder caused by homozygous or compound heterozygous mutation of the gene for the ITGA3. To date, 8 ILNEB patients have been reported, but all 6 neonatal-onset ILNEB patients suffered early death within 2 years. The most common cause of death among previously reported ILNEB patients was exacerbation of the respiratory condition.

METHODS

In this study, we describe a case of ILNEB with neonatal onset in a female patient and the genetic and histopathological testing performed.

RESULTS

Our patient had a compound heterozygous mutation in ITGA3. Compared to previously reported patients, this patient exhibited milder clinical and histopathological characteristics. After experiencing a life-threatening respiratory infection at 8 months old, the patient started periodic subcutaneous immunoglobulin treatment once every 1-2 weeks for nephrotic-range proteinuria-induced secondary hypogammaglobulinemia. At the age of 3 years, proteinuria gradually increased with severe edema despite strict internal management. Therefore, our patient underwent unilateral nephrectomy and insertion of a peritoneal dialysis catheter followed by another unilateral nephrectomy. One month later, she underwent an ABO-compatible living-donor kidney transplantation at the age of 4 years.

CONCLUSIONS

Our patient is a neonatal-onset ILNEB patient who survived for more than 2 years and underwent successful kidney transplantation.

Inherited epidermolysis bullosa: New diagnostics and new clinical phenotypes

Inherited epidermolysis bullosa (EB) is a group of heterogeneous genetic disorders characterized by skin fragility. EB comprises a large spectrum of phenotypes, ranging from severe cutaneous and extracutaneous involvement caused by lack of key adhesion proteins, to mild cutaneous fragility caused by subtle molecular defects. Disease-causing variants in 20 different genes account for the genetic and allelic heterogeneity of EB. Here, we discuss the development of laboratory methods that enabled these discoveries and the clinical and molecular features of some new EB entities elucidated during the past 5-6 years.

Update on Genetic Conditions Affecting the Skin and the Kidneys

Genetic conditions affecting the skin and kidney are clinically and genetically heterogeneous, and target molecular components present in both organs. The molecular pathology involves defects of cell-matrix adhesion, metabolic or signaling pathways, as well as tumor suppressor genes. This article gives a clinically oriented overview of this group of disorders, highlighting entities which have been recently described, as well as the progress made in understanding well-known entities. The genetic bases as well as molecular cell biological mechanisms are described, with therapeutic applications.