The role of HMGA2 in mesenchymal biology

Abstract

The human HMGA2 gene is located at chromosomal band 12q14-15. In normal cells it encodes for the HMGA2 protein (109 amino acids). HMGA2 is a transcription factor that binds to the AT rich sequences on DNA and thereby changing its conformation. The gene consists of five exons and between the third and the fourth exon, there is an intron with a size of 140Kb which may be broken in tumours. Such rearrangements have been identified in benign neoplasms and several types of malignant mesenchymal tumours. Mesenchymal stem cells (MSCs) are multipotent stem cells capable of differentiating into adipocytes among others. In this study we have induced adipogenic differentiation in the immortalized MSC line iMSC#3b. We found that theses cell lines are capable of differentiating into adipocytic lineage but difficult to transfect, and changed to another MSC line, hMSCtert20. hMSC-Tert20-HMGA2 clone t4 cell line was used for overexpression of HMGA2 during adipogenic differentiation and expression levels were measured by real time RT-PCR. It turned out that forced expression of exogeneous HMGA2 led to further overexpression during differentiation in most of the measurements. The effect of overexpression of HMGA2 was investigated on one of the markers of adipogenic differentiation Peroxisome proliferator-activated receptor γ (PPARγ). Also PPARγ expression was enhanced during differentiation by overexpressing HMGA2. It was also possible to see a slight increase in its expression in cells not induced for adipogenesis. We have also attempted to confirm the HMGA2 and NF-kB interaction. We used antibodies against HMGA2 and NF-kB-p65 to to investigate the expected interaction by immunoprecipitation. No interaction could be detected in the samples (HMGA2 and NF-kB) investigated, but this could be due to low sensitivity.