CCDC69 Regulates Adipocyte Differentiation and Cellular Morphology in SGBS Cells, a Human Preadipocyte Cell Line

CCDC69 was previously identified as a gene upregulated during adipogenic differentiation of human Simpson–Golabi–Behmel syndrome (SGBS) preadipocytes but not mouse 3T3-L1 preadipocytes. Here, we investigated the role of CCDC69 in adipogenesis using SGBS cells. CCDC69 expression during adipogenic differentiation was assessed by quantitative reverse transcription PCR and Western blotting. CCDC69 function was examined by adenovirus-mediated overexpression and knockdown, followed by analyses of lipid accumulation, adipocyte marker expression, cell morphology, and cytoskeletal organization. CCDC69 expression increased during adipogenesis. CCDC69 overexpression enhanced adipogenesis, as indicated by increased lipid accumulation, a higher proportion of cells containing lipid droplets, and increased expression of adipocyte marker genes and proteins. Unexpectedly, CCDC69 knockdown also enhanced adipogenesis. Time-course analysis showed that CCDC69 overexpression suppressed PPARG mRNA expression during early adipogenesis but increased its expression at later stages, whereas knockdown increased PPARG expression at later stages. CCDC69 overexpression induced a flattened cell morphology accompanied by reduced fibrillar α-tubulin structures and F-actin stress fibers and increased punctate F-actin structures, whereas knockdown increased the number of small, round cells. These findings indicate that CCDC69 may regulate adipogenesis in a stage-dependent manner and is associated with adipocyte morphology and cytoskeletal organization.