Genetic and epigenetic X-chromosome variations in a parthenogenetic human embryonic stem cell line

Abstract

Purpose To assess the genetic and epigenetic status of parthenogenetic human embryonic stem cells (phESCs). Methods Cytogenetics, X chromosome inactivation (XCI) and gene expression patterns were analyzed in one phESC line (FY-phES-018) that was derived from our laboratory. Results FY-phES-018 cells displayed the classical characteristics of normal hESCs. These cells had a 46, XX karyotype, and no inactive X chromosomes were observed before passage 20. After being cultured long term in vitro, some cells lost one X, and the proportion of cells with only one X gradually increased. At passage 35, almost all the cells displayed a 45, XO karyotype. Interestingly, at passage 45, the recovery of the X-chromosome was observed, and XCI became detectable; the mosaic ratio of 46, XX to 45, XO was 67:33. After passage 60, most cells displayed the 46, XX karyotype again with a mosaic ratio of 97:3. Some aberrant genomic imprinting was also observed in these cells. Conclusions The phESCs line FY-phES-018 is both genetically and epigenetically unstable; therefore, further research is needed before using these cells.

Chromosomal Abnormalities in Embryonic and Somatic Stem Cells

“…On the contrary, human pESCs [Kim et al, 2007;Revazova et al, 2007;Brevini et al, 2009Brevini et al, , 2012 appear to be more variable. Some cell lines are stable, showing a normal karyotype after long-term culture (>50-100 passages) after standard G-banding analysis [Lin et al, 2007;Mai et al, 2007]; others lose 1 copy of the X chromosome with a frequency that increases during passages [Liu et al, 2011]. Chromosome deletions and translocations have also been reported in the hPES-2 cell line, when cultivated for 120 passages [Mai et al, 2007].…”

Mutation Frequency Dynamics inHPRTLocus in Culture-Adapted Human Embryonic Stem Cells and Induced Pluripotent Stem Cells Correspond to Their Differentiated Counterparts

“…The HPRT locus is located on the X chromosome, and controversy exists regarding X chromosome inactivation in hESCs [36,37] and iPSCs [38]. It appears that the X chromosome inactivation in hESCs may depend on the cell line, subculture, and passage number [39][40][41][42]. The X chromosome has been reported in both the inactive form [43][44][45][46][47] and as two active copies [48,49].…”

Research with parthenogenetic stem cells will help decide whether a safer clinical use is possible

“…As derived mainly from diploid embryos, almost all pESC lines established to date have two X chromosomes that are active at least at early passages (Liu et al ., ). It is tempting to suggest that the presence of two active X chromosomes might provide pESC lines with metabolic and growth advantages that will grant them more resilience to adapt to non‐optimal culture conditions.…”

“…To date, although the biological characterization of pESCs is well documented, available data about the genetic and epigenetic behaviour of these cells is limited (for a review see Liu et al ., ). Recent evidence suggests that, outside their controlled in vitro culture environment, pESCs might turn into tumorigenic cells (Brevini et al ., ).…”