Human embryonic stem cells harboring an unbalanced reciprocal translocation t(11;22) as a valuable model for studying single gene dosage effects.

Aim: Carriers of balanced reciprocal translocations have an increased risk for repeated implantation failures and offspring with congenital malformations. Preimplantation genetic diagnosis (PGD) for such carriers ensures the transfer of chromosomally balanced embryos, and can significantly increase the probability of a healthy offspring. Research into chromosomal imbalances is limited since some segregation variants, particularly monosomies, are embryonically lethal. In the current work, we aimed to derive a HESC line that harbors partial monosomy, with the intent of studying developmental abnormalities and gene dosage effects. Methods & Results: Following PGD-FISH, three embryos with an unbalanced translocation developed into expanded blastocysts, and one HESC line with der(11)t(11;22)(q23;q12) was established, labeled Lis05_t(11;22). Lis05_t(11;22) harbored a partial monosomy, but it was still able to self-renew in vitro while remaining undifferentiated (currently at P53), demonstrating a typical HESC line morphology and expressing a panel of pluripotent markers. Full karyotyping confirmed partial monosomies 11 and 22 with no other chromosomal aberrations. Cell proliferation and colony formation assays demonstrated that even though Lis05_t(11;22) line demonstrated a self-renewal capacity, its proliferation rate was significantly lower than that of a wild type HESC (WT-HESC) line. Although the Lis05_t(11;22) line carried a non-balanced translocation known to be lethal during early embryonic development, it spontaneously differentiated into embryoid bodies. However, the expression levels of nine specific markers for the three germ layers and the trophectoderm, varied considerably in the Lis05_t(11;22)-differentiated cells compared to WT-HESCs, as demonstrated by qRT-PCR. Comparison of gene expression patterns between the partial monosomy Lis05_t(11;22) and the WT-HESCs by Affymetrix cDNA micro-array analysis revealed differential gene expression in chromosomes and regions other than the monosomic ones, of genes related mainly to development. Discussion: Monosomic HESC lines derived from unbalanced translocated embryos are a valuable model for studying single gene dosage effects as well as the pathophysiological mechanisms underlying developmental abnormalities. [ABSTRACT FROM AUTHOR]