SEQUENOM mass spectrometry analysis of Xist DNA methylation in Dicer-deficient XY embryonic stem cell lines. Schematic representation of the Xist promoter region and 5'end of exon 1 (CpG regions 1 and 2, see Figure 2 for a detailed description). Graphs show the percentage of methylation of specific Xist CpG sites in the two groups of Dicerlox/lox and deficient embryonic stem (ES) cell lines ((A) and (B)). Average data for at least three independent DNA samples is shown for each CpG site. The wt 129/1 XY ES cell line is included as a reference control on each graph. The dots are joined by lines when consecutive sites were analysed. CpG sites numbered in grey below the graphs indicate that the data points are not available due to low or high fragment mass or due to duplication or overlay of two or more fragments. The average data for two or three CpG sites (for example, A7/8/9) is shown in cases when the sites reside close to each other and could not be resolved as separate fragments. (C) Dynamic of Xist CpG island hypomethylation in the DTCM23 floxed cell line exposed to tamoxifen for 50 (blue) or 168 hours (lilac).