GABPβ2 expression during osteogenic differentiation from human osteoblast-like Saos-2 cells

The E26 transformation-specific (ETS) family of transcription factors plays an important role in osteogenic differentiation. Whether GA-binding protein β2 (GABPβ2), a member of the ETS family, is involved in osteogenic differentiation has not been previously reported. In the present study, directed differentiation of human osteoblast-like Saos-2 cells was induced and validated by examining alkaline phosphatase (ALP) activity, presence of mineralized nodule and other phenotypic characteristics of the cells on days 0, 3, 6 and 9, thus establishing their osteogenic potential. Real-time PCR revealed that similarly to the bone-specific transcription factor Runx2, the expression of Gabpb2 in Saos-2 cells also peaked on day 3 and was significantly reduced on days 6 and 9. Immunocytochemical staining showed that changes in the immunoreactivity of GABPβ2 also exhibited a similar trend to that of Runx2. Initially, Runx2 was predominantly localized in the nuclei, while GABPβ2 was relatively diffuse. Both exhibited a significant increase in immunoreactivity on day 3, with presence in both the nuclei and cytoplasm. By day 6, both showed a significant decrease in immunoreactivity and were mainly localized in the nuclei. Therefore, we surmise that GABPβ2, as an ETS family member, may play a regulatory role in early osteoblastic differentiation and potentially act in synergy with Runx2.