X chromosomes characterization of MCF7 cell line.

A) FISH analysis on metaphases using X painting probe. The percentages of MCF7 cells with two (left) or three (right) X chromosomes are indicated. B) Barr body staining. The percentages of HMEC, used as positive control, with (right) or without (left) a detectable Barr body (arrow) are indicated. No positive cell was observed in MCF7. C) High level of homozygosity (87%) detected by genotyping of the indicated panel of STRs. D) DNA FISH using a mix of telomeric (red, green and orange) and X alpha-satellite (blue) probes. The orange spots decorate the Xq telomeric region: two on X chromosomes, positive for X-alpha satellite probe (white arrows) and one on a rearranged chromosome, negative for X-alpha-satellite probe (red arrow). Telomeric red and green probes were used as hybridization control. E) Methylation analysis of ZMYM3 gene subjected to XCI (DXS6673E locus). Electropherograms show the allelic patterns obtained by PCR of HMEC and MCF7 DNAs undigested (top) and digested with methylation-sensitive enzymes (bottom). After digestion, HMEC show a methylated allele, whereas in MCF7 the locus is completely demethylated, resulting in the lack of amplification.