He Shuyang, Pant Disha, Schiffmacher Andrew, Bischoff Steve, Melican David, Gavin William, Keefer Carol
Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, USA.
Mol Reprod Dev. 2006 Dec;73(12):1512-22. doi: 10.1002/mrd.20525.
Transcription factors, POU5F1/OCT4 and NANOG, whose expression is restricted to the inner cell mass (ICM) in mouse and human blastocysts, are used to characterize undifferentiated embryonic stem cells (ESC) in vitro. However, POU5F1 may not be a useful marker in domestic animals due to its expression in both ICM and trophectoderm (TE), while NANOG mRNA and protein expression have only been described fully in mice. In an effort to identify ESC markers for domestic animals, expression patterns of NANOG, POU5F1, and the cell surface markers (SSEA1, SSEA4, TRA-1-60, TRA-1-81) were examined in preimplantation goat embryos, a species that has proven to be a superior choice for the production of transgenic proteins in milk (biopharming). Our results indicate that while goat embryos express POU5F1, SSEA1, and SSEA4 proteins, their expression is not strictly restricted to the ICM. In a unique staining pattern, NANOG protein was localized to the nucleoplasm and nucleoli in ICM cells, but was localized strictly to nucleoli in TE. This pattern may reflect down-regulation of protein by sequestration/degradation utilizing a nucleolar mechanism known to operate in stem cells. Furthermore, NANOG mRNA in TE was also significantly down-regulated as compared with that in ICM. Taken together, this novel expression pattern of NANOG in goat preimplantation embryos suggests that NANOG could serve as marker of pluripotency in goats and may be useful in derivation and characterization of caprine ESC. This study is the first to characterize both NANOG mRNA and protein expression in any species other than the mouse.
转录因子POU5F1/OCT4和NANOG在小鼠和人类囊胚中仅在内细胞团（ICM）中表达，被用于体外鉴定未分化的胚胎干细胞（ESC）。然而，由于POU5F1在ICM和滋养外胚层（TE）中均有表达，在家畜中它可能不是一个有用的标志物，而NANOG mRNA和蛋白表达仅在小鼠中有完整描述。为了鉴定家畜的ESC标志物，研究人员检测了植入前山羊胚胎中NANOG、POU5F1和细胞表面标志物（SSEA1、SSEA4、TRA-1-60、TRA-1-81）的表达模式，山羊已被证明是通过乳汁生产转基因蛋白（生物制药）的优良选择。我们的结果表明，虽然山羊胚胎表达POU5F1、SSEA1和SSEA4蛋白，但它们的表达并不严格局限于ICM。以一种独特的染色模式，NANOG蛋白定位于ICM细胞的核质和核仁，但在TE中严格定位于核仁。这种模式可能反映了利用干细胞中已知的核仁机制通过隔离/降解导致的蛋白下调。此外，与ICM相比，TE中的NANOG mRNA也显著下调。综上所述，NANOG在山羊植入前胚胎中的这种新表达模式表明，NANOG可作为山羊多能性的标志物，可能有助于山羊ESC的分离和鉴定。本研究首次在小鼠以外的任何物种中对NANOG mRNA和蛋白表达进行了表征。
