FBLN1

Abstract: Fibulin-1 is an extracellular matrix protein often associated with fibronectin (FN) in vivo. In this study, the ability of fibulin-1 to modulate adhesion, spreading and motility-promoting activities of FN was investigated. Fibulin-1 was found to have pronounced inhibitory effects on the cell attachment and spreading promoted by FN. Fibulin-1 was also found to inhibit the motility of a variety of cell types on FN substrata. For example, the FN-dependent haptotactic motility of breast carcinoma (MDA MB231) cells, epidermal carcinoma (A431), melanoma (A375 SM), rat pulmonary aortic smooth muscle cells (PAC1) and Chinese hamster ovary (CHO) cells was inhibited by the presence of fibulin-1 bound to FN-coated Boyden chamber membranes. Cells transfected to overproduce fibulin-1 displayed reduced velocity, distance of movement and persistence time on FN substrata. Similarly, the incorporation of fibulin-1 into FN-containing type I collagen gels inhibited the invasion of endocardial cushion mesenchymal cells migrating from cultured embryonic heart explants. By contrast, incorporation of fibulin-1 into collagen gels lacking FN had no effect on the migration of endocardial cushion cells. These results suggest that the motility-suppressive effects of fibulin-1 might be FN specific. Furthermore, such effects are cell-type specific, in that the migration of gingival fibroblasts and endothelial cells on FN substrata is not responsive to fibulin-1. Additional studies found that the mechanism for the motility-suppressive effects of fibulin-1 does not involve perturbations of interactions between alpha5beta1 or alpha4 integrins, or heparan sulfate proteoglycans with FN. However, fibulin-1 was found to inhibit extracellular signal regulated kinase (ERK) activation and to suppress phosphorylation of myosin heavy chain. This ability to influence signal transduction cascades that modulate the actin-myosin motor complex might be the basis for the effects of fibulin-1 on adhesion and motility.

Abstract: Molecular analysis of the reciprocal chromosomal translocation t(12;22)(p11.2;q13.3) cosegregating with a complex type of synpolydactyly showed involvement of an alternatively spliced exon of the fibulin-1 gene (FBLN1 located in 22q13.3) and the C12orf2 (HoJ-1) gene on the short arm of chromosome 12. Investigation of the possible functional involvement of the fibulin-1 protein (FBLN1) in the observed phenotype showed that FBLN1 is expressed in the extracellular matrix (ECM) in association with the digits in the developing limb. Furthermore, fibroblasts derived from patients with the complex type of synpolydactyly displayed alterations in the level of FBLN1-D splice variant incorporated into the ECM and secreted into the conditioned culture medium. By contrast, the expression of the FBLN1-C splice variant was not perturbed in the patient fibroblasts. Based on these findings, we propose that the t(12;22) results in haploinsufficiency of the FBLN1-D variant, which could lead to the observed limb malformations.

Abstract: Asthma is a chronic inflammatory disease of the airways. It is characterized by allergic airway inflammation, airway remodelling, and airway hyperresponsiveness (AHR). Asthma patients, in particular those with chronic or severe asthma, have airway remodelling that is associated with the accumulation of extracellular matrix (ECM) proteins, such as collagens. Fibulin-1 (Fbln1) is an important ECM protein that stabilizes collagen and other ECM proteins. The level of Fbln1c, one of the four Fbln1 variants, which predominates in both humans and mice, is increased in the serum and airways fluids in asthma but its function is unclear. We show that the level of Fbln1c was increased in the lungs of mice with house dust mite (HDM)-induced chronic allergic airway disease (AAD). Genetic deletion of Fbln1c and therapeutic inhibition of Fbln1c in mice with chronic AAD reduced airway collagen deposition, and protected against AHR. Fbln1c-deficient (Fbln1c-/- ) mice had reduced mucin (MUC) 5 AC levels, but not MUC5B levels, in the airways as compared with wild-type (WT) mice. Fbln1c interacted with fibronectin and periostin that was linked to collagen deposition around the small airways. Fbln1c-/- mice with AAD also had reduced numbers of α-smooth muscle actin-positive cells around the airways and reduced airway contractility as compared with WT mice. After HDM challenge, these mice also had fewer airway inflammatory cells, reduced interleukin (IL)-5, IL-13, IL-33, tumour necrosis factor (TNF) and CXCL1 levels in the lungs, and reduced IL-5, IL-33 and TNF levels in lung-draining lymph nodes. Therapeutic targeting of Fbln1c reduced the numbers of GATA3-positive Th2 cells in the lymph nodes and lungs after chronic HDM challenge. Treatment also reduced the secretion of IL-5 and IL-13 from co-cultured dendritic cells and T cells restimulated with HDM extract. Human epithelial cells cultured with Fbln1c peptide produced more CXCL1 mRNA than medium-treated controls. Our data show that Fbln1c may be a therapeutic target in chronic asthma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Abstract: Hepatocellular carcinoma (HCC) is one of the most common cancers world-wide but the molecular mechanisms that underlie hepatocarcinogenesis are not fully determined. On the same surgical sample with HCC, we performed microarray-based gene expression profiling and karyotype analysis using a single nucleotide polymorphism (SNP) array. In addition, quantitative real-time reverse transcription polymerase chain reaction (PCR), methylation specific PCR (MSP) and immunohistochemical staining were conducted using specimens from 48 patients with HCC. Gene expression profiling showed the expression of fibulin 1 (FBLN1), located on 22q13, to be decreased in tumor tissue. Karyotype analysis revealed no loss of heterozygosity (LOH) since deletions were not detected in 22q, and one of the SNPs on 22q13 showed AB genotype in both cancerous tissue and in corresponding noncancerous tissue, indicating retention of heterozygosity. Quantitative real-time PCR showed FBLN1 mRNA levels in cancerous tissues to be significantly decreased compared with that in corresponding noncancerous tissues. The immunohistochemical staining results were consistent with both gene expression profiling and quantitative PCR data. Twenty-four out of 48 HCCs gave a positive result in MSP. Moreover, promoter hypermethylation of FBLN1 was significantly associated with advanced stage HCC, multiple tumors and increased tumor size. Our results indicated that FBLN1 is a novel candidate of tumor suppressor gene and that promoter hypermethylation of FBLN1 is associated with tumor progression in HCC. © 2011 Wiley-Liss, Inc.