Cutis laxa with pulmonary emphysema, conjunctivochalasis, nasolacrimal duct obstruction, abnormal hair, and a novel FBLN5 mutation

HHIP protein interactions in lung cells provide insight into COPD pathogenesis

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide. The primary causes of COPD are environmental, including cigarette smoking; however, genetic susceptibility also contributes to COPD risk. Genome-Wide Association Studies (GWASes) have revealed more than 80 genetic loci associated with COPD, leading to the identification of multiple COPD GWAS genes. However, the biological relationships between the identified COPD susceptibility genes are largely unknown. Genes associated with a complex disease are often in close network proximity, i.e. their protein products often interact directly with each other and/or similar proteins. In this study, we use affinity purification mass spectrometry (AP-MS) to identify protein interactions with HHIP , a well-established COPD GWAS gene which is part of the sonic hedgehog pathway, in two disease-relevant lung cell lines (IMR90 and 16HBE). To better understand the network neighborhood of HHIP , its proximity to the protein products of other COPD GWAS genes, and its functional role in COPD pathogenesis, we create HUBRIS, a protein-protein interaction network compiled from 8 publicly available databases. We identified both common and cell type-specific protein-protein interactors of HHIP. We find that our newly identified interactions shorten the network distance between HHIP and the protein products of several COPD GWAS genes, including DSP, MFAP2, TET2 , and FBLN5 . These new shorter paths include proteins that are encoded by genes involved in extracellular matrix and tissue organization. We found and validated interactions to proteins that provide new insights into COPD pathobiology, including CAVIN1 (IMR90) and TP53 (16HBE). The newly discovered HHIP interactions with CAVIN1 and TP53 implicate HHIP in response to oxidative stress.

Clinical and Molecular Delineation of Cutis Laxa Syndromes: Paradigms for Homeostasis

Cutis laxa (CL) syndromes are a large and heterogeneous group of rare connective tissue disorders that share loose redundant skin as a hallmark clinical feature, which reflects dermal elastic fiber fragmentation. Both acquired and congenital-Mendelian- forms exist. Acquired forms are progressive and often preceded by inflammatory triggers in the skin, but may show systemic elastolysis. Mendelian forms are often pleiotropic in nature and classified upon systemic manifestations and mode of inheritance. Though impaired elastogenesis is a common denominator in all Mendelian forms of CL, the underlying gene defects are diverse and affect structural components of the elastic fiber or impair metabolic pathways interfering with cellular trafficking, proline synthesis, or mitochondrial functioning. In this chapter we provide a detailed overview of the clinical and molecular characteristics of the different cutis laxa types and review the latest insights on elastic fiber assembly and homeostasis from both human and animal studies.

New insight into clinical heterogeneity and inheritance diversity of FBLN5-related cutis laxa

Background

FBLN5-related cutis laxa (CL) is a rare disorder that involves elastic fiber-enriched tissues and is characterized by lax skin and variable systemic involvement such as pulmonary emphysema, arterial involvement, inguinal hernias, hollow viscus diverticula and pyloric stenosis. This type of CL follows mostly autosomal recessive (AR) and less commonly autosomal dominant patterns of inheritance.

Results

In this study, we detected a novel homozygous missense variant in exon 6 of FBLN5 gene (c.G544C, p.A182P) by using whole exome sequencing in a consanguineous Iranian family with two affected members. Our twin patients showed some of the clinical manifestation of FBLN5-related CL but they did not present pulmonary complications, gastrointestinal and genitourinary abnormalities. The notable thing about this monozygotic twin sisters is that only one of them showed ventricular septal defect, suggesting that this type of CL has intrafamilial variability. Co-segregation analysis showed the patients’ parents and relatives were heterozygous for detected variation suggesting AR form of the CL. In silico prediction tools showed that this mutation is pathogenic and 3D modeling of the normal and mutant protein revealed relative structural alteration of fibulin-5 suggesting that the A182P can contribute to the CL phenotype via the combined effect of lack of protein function and partly misfolding-associated toxicity.

Conclusion

We underlined the probable roles and functions of the involved domain of fibulin-5 and proposed some possible mechanisms involved in AR form of FBLN5-related CL. However, further functional studies and subsequent clinical and molecular investigations are needed to confirm our findings.

Review of clinical and molecular variability in autosomal recessive cutis laxa 2A

ATP6V0A2-related cutis laxa, also known as autosomal recessive cutis laxa type 2A (ARCL2A), is a subtype of hereditary cutis laxa originally characterized by skin, skeletal, and neurological involvement, and a combined defect of N-glycosylation and O-glycosylation. The associated clinical spectrum subsequently expanded to a less severe phenotype dominated by cutaneous involvement. At the moment, ARCL2A was described in a few case reports and series only. An Italian adult woman ARCL2A with a phenotype restricted to skin and the two novel c.3G>C and c.1101dup ATP6V0A2 variants has been reported. A systematic literature review allowed us to identify 69 additional individuals from 64 families. Available data were scrutinized in order to describe the clinical and molecular variability of ARCL2A. About 78.3% of known variants were predicted null alleles, while 11 were missense and 2 affected noncanonical splice sites. Age at ascertainment appeared as the unique phenotypic discriminator with earlier age more commonly associated with facial dysmorphism (p .02), high/cleft palate (p .005), intellectual disability/global developmental delay (p .013), and seizures (p .024). No specific genotype-phenotype correlations were identified. This work confirmed the existence of an attenuated phenotype associated with ATP6V0A2 biallelic variants and offers an updated critique to the clinical and molecular variability of ARCL2A.

Autosomal recessive cutis laxa: a novel mutation in the FBLN5 gene in a family

FBLN5-related cutis laxa (CL) is a rare syndrome that can be inherited in an autosomal dominant or recessive manner. Autosomal recessive cutis laxa (ARCL), type IA, has been reported to be more severe. The disease is characterized by microcephaly, sagging cheeks, loose, wrinkled and redundant skin, emphysema, aorta or pulmonary artery abnormalities, inguinal hernia, and anomalies of internal organs. Homozygous mutations in the FBLN5 gene are responsible for the clinical manifestations. We report a family study of a child with ARCL. FBLN5 genes of the patient and parents were sequenced using next-generation sequencing technologies. Analyses showed that the patient was homozygous for the novel c.518A>G, p.R173H mutation in exon 6 of the FBLN5 gene, whereas the parents were heterozygous. The mutation was found to be 'possibly pathogenic' in bioinformatic analysis. We identified a novel FBLN5 mutation in a CL patient; pedigree and parental genetic analyses suggested ARCL. Our results also suggest that the mutation analysis provides useful evidence to support the clinical diagnosis and define the inheritance mode of CL in an apparently sporadic case.

A preliminary study on the establishment of an animal model of conjunctivochalasis

AIM

To explore a feasible method on the establishment of an animal model of conjunctivochalasis (CCH).

METHODS

Twelve clean-grade New Zealand white rabbits were divided into four groups (n=3/group): the control group (one received no interventions, and the others underwent subconjunctival injection of sterile water), the matrix metalloproteinases (MMPs) group (administered subconjunctival injection of MMP-3), the aging group (administered subcutaneous injection of D-galactose), the tumor necrosis factor-α (TNF-α) solution group (administered eye drops of TNF-α). Anterior segment photography, conjunctival tissue light microscopy and transmission electron microscopy (TEM) were performed after 12wk.

RESULTS

Among all groups, the MMPs group had the following changes: the looser connection between the inferior bulbar conjunctiva and sclera; the more disordered collagen fibers (Trichrome staining) and the broken elastic fibers (Aldehyde-fuchsin staining); the focal necrosis of fibroblasts (TEM).

CONCLUSION

Administration of MMPs may be a feasible method for the establishment of an animal model of CCH.

Conjunctivochalasis: a systematic review

Conjunctivochalasis (CCH) is a conjunctival condition characterized by loose, redundant conjunctival folds, most typically in the inferior bulbar conjunctiva of both eyes. Although CCH is a common cause of ocular irritation and discomfort, especially in the elderly, it is often overlooked in clinical practice. CCH may be associated with various ocular and nonocular conditions; however, the most important risk factor is aging. Although often asymptomatic, CCH may cause symptoms related to tear film instability and/or delayed tear clearance. Pathogenesis of CCH remains largely unknown but may involve different elements such as aged conjunctiva, unstable tear film, mechanical friction, ocular surface inflammation, and delayed tear clearance. Contradictory results have been reported on histopathologic changes in CCH, with some studies showing a normal microscopic structure. For symptomatic CCH, medical treatment may include lubrication and anti-inflammatory medications. For symptomatic patients who fail to respond to medical treatment, a surgical procedure may be considered. Although various surgical procedures have been used for CCH, more often, it consists of conjunctival cauterization or excision of the redundant conjunctiva, with or without amniotic membrane transplantation.

The role of elastic fibers in pathogenesis of conjunctivochalasis

The PubMed, MEDLINE databases and China National Knowledge Infrastructure (CNKI) were searched for information regarding the etiology and pathogenesis of conjunctivochalasis (CCh) and the synthesis and degradation of elastic fibers. After analysis of the literature, we found elastic fibers was a complex protein molecule from the structure and composition; the degradation of elastic fibers was one of the histopathological features of the disease; the vast majority of the factors related to the pathogenesis of CCh ultimately pointed to abnormal elastic fibers. By reasonably speculating, we considered that abnormal elastic fibers cause the conjunctival relaxation. In conclusion, we hypothesize that elastic fibers play an important role in the pathogenesis of CCh. Studies on the mechanism of synthesis, degradation of elastic fibers are helpful to clarify the pathogenesis of the disease and to find effective treatment methods.