Wu Jinghai, Srinivasan Seetha V, Neumann Jon C, Lingrel Jerry B
Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati Medical Center, 231 Albert Sabin Way, Cincinnati, Ohio 45267, USA.
Biochemistry. 2005 Aug 23;44(33):11098-105. doi: 10.1021/bi050166i.
Kruppel-like transcription factor 2 (KLF2), a critical gene for mouse embryogenesis, was recently identified as an inhibitor of adipogenesis. However, it is still unknown whether KLF2 is a natural repressor of adipocyte differentiation and if KLF2 affects the formation of preadipocytes. It may also be important for preadipocyte formation, as KLF2 is crucial for lung development and blood vessel formation. In this study, we show that differentiation of preadipocytes not only results in a concomitant decrease in the levels of KLF2 protein but also significantly reduces KLF2 promoter activity. We have generated tet-responsive lines of 3T3L1 that express physiological levels of KLF2 and show that reexpression of KLF2 prevents preadipocyte differentiation, thereby confirming the inhibition of adipogenesis by KLF2, partially via the restoration of Pref-1. In addition, we studied the contribution of KLF2-negative cells to the formation and subsequent differentiation of preadipocytes. We demonstrate that embryoid bodies derived from KLF2(-)(/)(-) ES cells can differentiate into adipocytes as evidenced by the accumulation of lipids and expression of several biochemical markers. Moreover, mouse embryonic fibroblasts (MEFs) derived from KLF2(-)(/)(-) mouse embryos differentiate efficiently into adipocytes. Interestingly, quantification of lipid accumulation in MEFs indicated that KLF2(-)(/)(-) cells are more prone to differentiate at the early stage of the process, suggesting that KLF2 is a natural repressor of differentiation in vivo. Taken together, these studies demonstrate that KLF2 does not affect the commitment of multipotent stem cells into the preadipocytic lineage but rather maintains their preadipocyte state and thereby negatively regulates their transition into adipocytes.
Kruppel样转录因子2（KLF2）是小鼠胚胎发育的关键基因，最近被鉴定为脂肪生成的抑制剂。然而，KLF2是否是脂肪细胞分化的天然抑制因子以及KLF2是否影响前脂肪细胞的形成仍不清楚。由于KLF2对肺发育和血管形成至关重要，它对前脂肪细胞的形成可能也很重要。在本研究中，我们发现前脂肪细胞分化不仅导致KLF2蛋白水平随之降低，还显著降低KLF2启动子活性。我们构建了表达生理水平KLF2的3T3L1四环素反应细胞系，并表明KLF2的重新表达可阻止前脂肪细胞分化，从而证实KLF2对脂肪生成的抑制作用，部分是通过恢复Pref-1实现的。此外，我们研究了KLF2阴性细胞对前脂肪细胞形成及随后分化的作用。我们证明，源自KLF2（-/-）胚胎干细胞的胚状体可分化为脂肪细胞，脂质积累和几种生化标志物的表达证明了这一点。此外，源自KLF2（-/-）小鼠胚胎的小鼠胚胎成纤维细胞（MEF）可高效分化为脂肪细胞。有趣的是，对MEF中脂质积累的定量分析表明，KLF2（-/-）细胞在该过程的早期更易于分化，这表明KLF2是体内分化的天然抑制因子。综上所述，这些研究表明KLF2不影响多能干细胞向脂肪前体细胞系的定向分化，而是维持它们的前脂肪细胞状态，从而负向调节它们向脂肪细胞的转变。
