Telomere DNA is significantly reduced in aneuploid human oocytes and embryos

Abstract

OBJECTIVE: Since telomere DNA (telDNA) content is associated with genomic instability and is naturally reset during mammalian preimplantation embryogenesis, we tested the hypothesis that telomere DNA quantity is associated with the development of aneuploidy. DESIGN: Paired analysis of telDNA quantity in aneuploid and euploid human polar bodies and embryo biopsies. MATERIALS AND METHODS: A telDNA real-time PCR method was developed to evaluate single cells after whole genome amplification (WGA). Results from picogram amounts of DNA were compared to results obtained using large quantities of purified total DNA from the same cell lines. WGA DNA was available for analysis from oocyte (n=18) and embryo (n=44) biopsies that had undergone microarray based 24 chromosome aneuploidy screening. Paired analysis of sibling aneuploid and euploid polar bodies and embryonic cells from within the same patients' oocytes and embryos and within the same treatment cycle provided the greatest control over critical variables including maternal age. RESULTS: WGA of picograms of DNA from cells provided results equivalent to those obtained using large quantities of purified total DNA (Pearson R2=0.97). Embryo fragmentation rates, which were previously shown to correlate with telDNA length, weren't significantly different among aneuploid (9.2%) and euploid (9.7%) samples (P=0.75). Aneuploid human polar bodies displayed significantly less telDNA than euploid polar bodies (-3.07 fold, P=0.016). Aneuploid embryonic cells displayed significantly less telDNA than euploid embryonic cells at the cleavage stage (-2.60 fold, P=0.002) but not at the blast stage (-1.18 fold, P=0.340). CONCLUSION: These results indicate that reduced telomere length is associated with aneuploidy prior to embryonic genome activation. This further suggests that aneuploidy is not associated with resetting of telomere DNA length but is instead associated with telomere maintenance in the maternal genome during oogenesis and early embryo development.