Differential transcriptional regulation of the NANOG gene in chicken primordial germ cells and embryonic stem cells

Background:NANOG is a core transcription factor(TF)in embryonic stem cells(ESCs)and primordial germ cells(PGCs).Regulation of the NANOG gene by TFs,epigenetic factors,and autoregulatory factors is well characterized in ESCs,and transcriptional regulation of NANOG is well established in these cells.Although NANOG plays a key role in germ cells,the molecular mechanism underlying its transcriptional regulation in PGCs has not been studied.Therefore,we investigated the mechanism that regulates transcription of the chicken NANOG(cNANOG)gene in PGCs and ESCs.Results:We first identified the transcription start site of cNANOG by 5′-rapid amplification of cDNA ends PCR analysis.Then,we measured the promoter activity of various 5′flanking regions of cNANOG in chicken PGCs and ESCs using the luciferase reporter assay.cNANOG expression required transcriptional regulatory elements,which were positively regulated by POU5F3(OCT4)and SOX2 and negatively regulated by TP53 in PGCs.The proximal region of the cNANOG promoter contains a positive transcriptional regulatory element(CCAAT/enhancer-binding protein(CEBP)-binding site)in ESCs.Furthermore,small interfering RNA-mediated knockdown demonstrated that POU5F3,SOX2,and CEBP played a role in cell type-specific transcription of cNANOG.Conclusions:We show for the first time that different trans-regulatory elements control transcription of cNANOG in a cell type-specific manner.This finding might help to elucidate the mechanism that regulates cNANOG expression in PGCs and ESCs.

Regulatory elements and transcriptional control of chicken vasa homologue(CVH)promoter in chicken primordial germ cells

Background： Primordial germ cells（PGCs）, the precursors of functional gametes, have distinct characteristics and exhibit several unique molecular mechanisms to maintain pluripotency and germness in comparison to somatic cells. They express germ cel-specific RNA binding proteins（RBPs） by modulating tissue-specific cis-and trans-regulatory elements. Studies on gene structures of chicken vasa homologue（CVH）, a chicken RNA binding protein, involved in temporal and spatial regulation are thus important not only for understanding the molecular mechanisms that regulate germ cel fate, but also for practical applications of primordial germ cells. However, very limited studies are available on regulatory elements that control germ cel-specific expression in chicken. Therefore, we investigated the intricate regulatory mechanism（s） that governs transcriptional control of CVH.Results： We constructed green fluorescence protein（GFP） or luciferase reporter vectors containing the various 5′ flanking regions of CVH gene. From the 5′ deletion and fragmented assays in chicken PGCs, we have identified a CVH promoter that locates at-316 to ＋275 base pair fragment with the highest luciferase activity. Additional y, we confirmed for the first time that the 5′ untranslated region（UTR） containing intron 1 is required for promoter activity of the CVH gene in chicken PGCs. Furthermore, using a transcription factor binding prediction, transcriptome analysis and siR NA-mediated knockdown,we have identified that a set of transcription factors play a role in the PGC-specific CVH gene expression.Conclusions： These results demonstrate that cis-elements and transcription factors localizing in the 5′ flanking region including the 5′ UTR and an intron are important for transcriptional regulation of the CVH gene in chicken PGCs. Final y,this information wil contribute to research studies in areas of reproductive biology, constructing of germ cel-specific synthetic promoter for tracing primordial germ cells as wel as understanding the transcriptional regulation for maintaining germness in PGCs.