1. Volume 24, Issue 3, Pages 324-333 (February 2013)
In Vivo Epigenomic Profiling of Germ Cells Reveals Germ Cell Molecular Signatures 
Jia-Hui Ng, Vibhor Kumar, Masafumi Muratani, Petra Kraus, Jia-Chi Yeo, Lai-Ping Yaw, Kun Xue, Thomas Lufkin, Shyam Prabhakar, Huck-Hui Ng 
Developmental Cell 
Volume 24, Issue 3, Pages (February 2013)
DOI: /j.devcel
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2. Developmental Cell 2013 24, 324-333DOI: (10.1016/j.devcel.2012.12.011)
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3. Figure 1
Robustness of Modified Small-Scale ChIP-Seq Method to Map Histone Modifications using a Small Number of Purified Cells
(A) Experimental workflow of small-scale ChIP-seq. Germ cells were FACS-purified based on Pou5f1-GFP expression. Following ChIP, the reverse-crosslinked immunoprecipitated DNA was amplified by 15 cycles of WGA. Amplification adaptors were cleaved by two rounds of BpmI restriction digestion prior to ChIP-seq library preparation.
(B) qPCR results of small-scale H3K4me3 ChIP performed on 10,000, 25,000, and 100,000 mouse ESCs after WGA amplification. Pou5f1 DE and Pou5f1 Pro refer to the distal enhancer and proximal promoter of the Pou5f1 gene, respectively. Data represent the mean ± SEM (n = 3).
(C) UCSC browser view showing the similarity of mouse ESC H3K4me3 ChIP-seq tag count signals without (standard) and with 15 cycles (technical duplicates: WGA1 and WGA2) of WGA.
(D) Scatterplot of mouse ESC H3K4me3 ChIP-seq signals and Venn diagram illustrating overlap of peaks (using top 10,000 peaks) between amplified (WGA1 and WGA2) and nonamplified samples (Standard). Each point represents total tag count in a randomly chosen 1-kb genomic region; 100,000 bins are shown in the scatterplot.
See also Figure S1 and Table S1.
Developmental Cell  , DOI: ( /j.devcel )
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4. Figure 2
Identification of Active Promoters and Enhancers in Germ Cells
(A) UCSC browser view of active promoter regions (indicated by orange horizontal bar) marked by H3K4me3 and H3K27ac in E13.5 germ cells.
(B) Plot of H3K4me3 (meK4) and H3K27ac (acK27) ChIP-seq signals for E13.5 germ cells, adult liver, ProB cells, ESC, and NPC. Top regions for H3K4me3 and H3K27ac peaks in E13.5 germ cells are shown. A window of 8 kb (−4 kb to +4 kb) around the peak center is shown. Promoters that are marked by the H3K27ac histone modification in E13.5 germ cells only (germ cell promoter signatures) are indicated below the dotted line.
(C) Enriched mouse phenotypes for nearest genes within 30 kb of E13.5 germ cell promoter signatures (q < 9E-09).
(D) UCSC browser view of enhancer regions (indicated by red horizontal bar) marked by H2BK20ac and H3K27ac in E13.5 germ cells.
(E) Plot of H3K27ac (acK27) and H2BK20ac (acK20) ChIP-seq signals, which are hallmarks of active enhancers, for E13.5 germ cells, liver, ProB, ESC, and NPC. A window of 8 kb (−4 kb to +4 kb) around the peak center is shown. Enhancers that are marked by the H3K27ac histone modification in E13.5 germ cells only (germ cell enhancer signatures) are indicated below the dotted line.
(F) Enriched mouse phenotypes for nearest genes within 30 kb of E13.5 germ cell enhancer signatures (q < 0.001).
(G) The position weight matrix of the top three enriched motifs found at germ cell enhancer signatures.
See also Figure S2 and Tables S2, S3, and S4.
Developmental Cell  , DOI: ( /j.devcel )
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5. Figure 3
Identification of Nr5a2 as a Potential Regulator of Germ Cell Biology
(A) Microarray heatmaps of class 1 (early) and class 2 (late) genes that are differentially expressed in E11.5, E13.5, and E15.5 germ cells.
(B) Frequency of top ten enriched motifs found at H3K27ac-marked regions that are within 10 kb class 1 and class 2 genes. Motifs were searched using the TRANSFAC and JASPER databases.
(C) A higher overlap was observed between Nr5a2 binding (mouse ESC ChIP-seq peaks) and germ cell enhancer regions. The frequencies of transcription factor binding at cell-type-specific enhancer regions are expressed as fold relative to ProB’s frequency. Asterisks indicate significant (p < 0.002) enrichment of binding at germ cell enhancer regions compared to NPC and ProB. Nr5a2 binding of germ cell enhancers in ESCs represents a combination of (1) enhancers that are shared between ESCs and germ cells and (2) germ cell enhancers that could be primed or “bookmarked” by Nr5a2 in ESCs, but are not active in ESCs.
(D) Nr5a2 and p300 ChIP-qPCR at germ cell enhancer regions (N1–N10) that overlap with Nr5a2 peaks. Data represent the mean ± SEM.
(E) Nr5a2 knockdown negatively affects in vitro germ cell differentiation. Luciferase and Nr5a2 knockdown cells purified from day 0 and day 7 EBs were cultured in ESM (ES cell medium) and EGM (RA) (embryonic germ cell media supplemented with retinoic acid), respectively. Quantitation of AP+ colonies is expressed as a ratio of the respective control frequencies. Data represent the mean ± SEM for ESM (n = 2) and EGM (RA) (n = 3).
See also Figure S3.
Developmental Cell  , DOI: ( /j.devcel )
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6. Figure 4 H3K27me3-Marked Regions that Are Present in Germ Cells
(A) Plot of H3K4me3 (mK4) and H3K27me3 (mK27) ChIP-seq signals for germ cells (E11.5 and E13.5), ESC, NPC, MEF, and whole brain (Mikkelsen et al., 2007). A window of 12 kb (−6 kb to +6 kb) around the peak center is shown. The union of H3K27me3-marked regions in the examined cell types was clustered into seven distinct classes, with class 7 representing regions with H3K27me3 enriched in germ cells.
(B) UCSC browser view of a class 7 region. Highlighted regions indicate genomic locations that have H3K27me3 in E13.5 germ cells, but not in ESC, MEF, NPC, and whole brain.
(C) The frequency of top H3K27me3 sites (above 95th percentile in each cell type) that overlap with repeats. This fraction can be written as (bins with H3K27me3 above 95 percentile and lying on a repeat family) / (bins with H3K27me3 above 95 percentile). Asterisks indicate significantly lower frequencies than E13.5 germ cells (two proportion z-test: p < 0.001).
(D) Model illustrating major categories of genes that distinguish ESCs from E11.5 and E13.5 germ cells.
See also Figure S4.
Developmental Cell  , DOI: ( /j.devcel )
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