EPLINβ Is Involved in the Assembly of Cadherin-catenin Complexes in Osteoblasts and Affects Bone Formation

Abstract

Epithelial protein lost in neoplasm (EPLIN) is an actin-associated cytoskeletal protein that plays an important role in epithelial cell adhesion. EPLIN has two isoforms: EPLINα and EPLINβ. In this study, we investigated the role of EPLINβ in osteoblasts using EPLINβdeficient (EPLINβ GT/GT ) mice. The skeletal phenotype of EPLINβ GT/GT mice is indistinguishable from the wildtype (WT), but bone properties and strength were significantly decreased compared with WT littermates. Histomorphological analysis revealed altered organization of bone spicules and osteoblast cell arrangement, and decreased alkaline phosphatase activity in EPLINβ GT/GT mouse bones. Transmission electron microscopy revealed wider intercellular spaces between osteoblasts in EPLINβ GT/GT mice, suggesting aberrant cell adhesion. In EPLINβ GT/GT osteoblasts, α-and β-catenins and F-actin were observed at the cell membrane, but OB-cadherin was localized at the perinuclear region, indicating that cadherincatenin complexes were not formed. EPLINβ knockdown in MC3T3-e1 osteoblast cells showed similar results as in calvaria cell cultures. Bone formation markers, such as RUNX2, Osterix, ALP, and Col1a1 mRNA were reduced in EPLINβ knockdown cells, suggesting an important role for EPLINβ in osteoblast formation. In conclusion, we propose that EPLINβ is involved in the assembly of cadherin-catenin complexes in osteoblasts and affects bone formation.

Tmem161a regulates bone formation and bone strength through the P38 MAPK pathway

“…A number of molecules are involved in the regulation of osteoblasts and osteoclasts, and their disruption leads to bone metabolic diseases, such as osteoporosis 21 . To identify novel genes involved in bone metabolism, we developed an efficient screening system using mutant mouse strains registered with the Exchangeable Gene Trap Clones database 9 , 10 , 22 . This screening process identified Tmem161a as a gene involved in bone metabolism.…”

“…Femurs were obtained from 8-week-old WT and Tmem161a GT/GT male mice and analyzed by μCT using a μCT system (ScanXmate-L090H; Comscantecno, Kanagawa, Japan), as described previously 10 . Bone morphology was analyzed using a three-dimensional image analysis system (TRI/3D-BON; RATOC System Engineering, Tokyo, Japan) (n = 10) 10 . For cortical bone analyses, the mid-point of the femur was scanned.…”

“…We recently designed a new screening system to identify and analyze the function of novel genes involved in bone metabolism using mutant mouse strains registered in the Exchangeable Gene Trap Clones database 9 , 10 . The principle of gene trapping involves randomly inserting a trap vector containing a drug-resistance gene into the embryonic stem cell genome and disrupting only target genes with the inserted vector.…”

HMGB2 Promotes De Novo Lipogenesis to Accelerate Hepatocyte Proliferation During Liver Regeneration

“…The medium was supplemented with 10% (v/v) heat-inactivated fetal bovine serum (FBS) and penicillin-streptomycin-am-photericin B. Hepa 1-6 cells were divided into two groups, and transfected with HMGB2-small interfering RNA (siRNA) and PPARα siRNA (Integrated DNA Technologies, MMC.RNAI.N008252.3_2 nm, Coralville, IA) or control siRNA (Integrated DNA Technologies, DS Scrambled-Neg universal negative control duplex) using Lipofectamine RNAiMAX, as described previously. 23 Successfully transfected cells were prepared into a cell suspension using α-MEM with l -glutamine and phenol red with 10% FBS, 50-µg/ml ascorbic acid, and 5-mM β-glycerophosphate. The cells were seeded at a density of 2 × 10 4 cells per well in 24-well plates, followed by incubation in a constant temperature incubator (5% CO 2 , 37C, 95% humidity).…”