GEP, a local growth factor, is critical for odontogenesis and amelogenesis

Using ImageJ (Fiji) to Analyze and Present X-Ray CT Images of Enamel

X-ray micro CT has become a popular methodology for the nondestructive analysis of dental tissues and has been used extensively in the amelogenesis field. The aim of this chapter is to introduce ImageJ/Fiji to researchers new to CT scanning and the analysis of CT image data. The program can be applied to analyzing X-ray CT images of enamel but can be extrapolated to other tissues as well.

Progranulin: A conductor of receptors orchestra, a chaperone of lysosomal enzymes and a therapeutic target for multiple diseases

Progranulin (PGRN), a widely expressed glycoprotein with pleiotropic function, has been linked to a host of physiological processes and diverse pathological states. A series of contemporary preclinical disease models and clinical trials have evaluated various therapeutic strategies targeting PGRN, highlighting PGRN as a promising therapeutic target. Herein we summarize available knowledge of PGRN targeting in various kinds of diseases, including common neurological diseases, inflammatory autoimmune diseases, cancer, tissue repair, and rare lysosomal storage diseases, with a focus on the functional domain-oriented drug development strategies. In particular, we emphasize the role of extracellular PGRN as a non-conventional, extracellular matrix bound, growth factor-like conductor orchestrating multiple membrane receptors and intracellular PGRN as a chaperone/co-chaperone that mediates the folding and traffic of its various binding partners.

Functional characterization and molecular mechanism exploration of three granulin epithelin precursor splice variants in biomineralization of the pearl oyster Pinctada fucata

The granulin/epithelin precursor (GEP) encodes a glycoprotein precursor which exhibits pleiotropic tissue growth factor activity with multiple functions. Here, GEP was isolated and its role in the shell biomineralization process of the pearl oyster Pinctada fucata was investigated. Three forms of GEP mRNA were isolated from the pearl oyster (designated PfGEP-1, PfGEP-2 and PfGEP-3). Genomic DNA flanking the splicing region of the PfGEP variants was sequenced and it was found that PfGEP-2 splices out Exon 4, whereas PfGEP-3 splices out Exon 3 compared to PfGEP-1. PfGEP-1 (1505 amino acids) consists of 18 granulin domains, whereas PfGEP-2 (1459 amino acids) and PfGEP-3 (1471 amino acids) consist of 17.5 granulin domains, respectively. Analyses of PfGEP-1 and PfGEP-3 mRNA showed differential patterns in the tissues and developmental stages. Western blotting results showed that the three splice variants can translate to proteins in HEK293T cells. A knockdown experiment using PfGEP dsRNA showed decreased PfGEP-1/PfGEP-3 and PfMSX mRNA, and irregular crystallization of the nacreous layer using scanning electron microscopy. In luciferase assays, co-transfection of PfGEP-1 could activate as well as repress luciferase expression of the reporter plasmid driven by the PfMSX promoter, whereas PfGEP-3 stimulated the expression, elucidating the molecular mechanisms involved in the correlation between PfGEP and PfMSX. These results suggested that GEP variants might function differently during the biomineralization process, which provides new knowledge on the mechanism regulating nacre formation.

Progranulin protects against osteoarthritis through interacting with TNF-α and β-Catenin signalling

OBJECTIVE

Progranulin (PGRN) was previously isolated as an osteoarthritis (OA)-associated growth factor. Additionally, PGRN was found to play a therapeutic role in inflammatory arthritis mice models through antagonising tumour necrosis factor α (TNF-α). This study was aimed at investigating the role of PGRN in degradation of cartilage and progression of OA.

METHODS

Progression of OA was analysed in both spontaneous and surgically induced OA models in wild type and PGRN-deficient mice. Cartilage degradation and OA were evaluated using Safranin O staining, immunohistochemistry and ELISA. Additionally, mRNA expression of degenerative factors and catabolic markers known to be involved in cartilage degeneration in OA were analysed. Furthermore, the anabolic effects and underlying mechanisms of PGRN were investigated by in vitro experiments with primary chondrocytes.

RESULTS

Here, we found that deficiency of PGRN led to spontaneous OA-like phenotype in 'aged' mice. Additionally, PGRN-deficient mice exhibited exaggerated breakdown of cartilage structure and OA progression, while local delivery of recombinant PGRN protein attenuated degradation of cartilage matrix and protected against OA development in surgically induced OA models. Furthermore, PGRN activated extracellular signal-regulated kinases (ERK) 1/2 signalling and elevated the levels of anabolic biomarkers in human chondrocyte, and the protective function of PGRN was mediated mainly through TNF receptor 2. Additionally, PGRN suppressed inflammatory action of TNF-α and inhibited the activation of β-Catenin signalling in cartilage and chondrocytes.

CONCLUSIONS

Collectively, this study provides new insight into the pathogenesis of OA, and also presents PGRN as a potential target for the treatment of joint degenerative diseases, including OA.

Structure, function, and mechanism of progranulin; the brain and beyond

Mutation of human GRN, the gene encoding the secreted glycoprotein progranulin, results in a form of frontotemporal lobar degeneration that is characterized by the presence of ubiquitinated inclusions containing phosphorylated and cleaved fragments of the transactivation response element DNA-binding protein-43. This has stimulated interest in understanding the role of progranulin in the central nervous system, and in particular, how this relates to neurodegeneration. Progranulin has many roles outside the brain, including regulation of cellular proliferation, survival, and migration, in cancer, including cancers of the brain, in wound repair, and inflammation. It often acts through the extracellular signal-regulated kinase and phopshatidylinositol-3-kinases pathways. The neurobiology of progranulin has followed a similar pattern with proposed roles for progranulin (PGRN) in the central nervous system as a neuroprotective agent and in neuroinflammation. Here we review the structure, biology, and mechanism of progranulin action. By understanding PGRN in a wider context, we may be better able to delineate its roles in the normal brain and in neurodegenerative disease.

Cellular effects of progranulin in health and disease

Progranulin is a fascinating multifunctional protein, which has been implicated in cell growth, wound repair, tumorigenesis, inflammation, neurodevelopment, and more recently in neurodegeneration. The mechanism of action of this protein is still largely unknown, but the knowledge about the cellular effects on various cell types is expanding. In the current review, we will summarize what is known about the cell biology of progranulin. A better understanding of the biology of progranulin will impact diverse areas of research.