Microarray analysis reveals abnormal chromosomal complements in over 70% of 14 normally developing human embryos

Area of Science:

• Reproductive biology
• Genetics
• Embryology

Background:

• Human fertility rates are low, with in vitro fertilization (IVF) success rates also being relatively low.
• Chromosomal abnormalities in human gametes and early preimplantation embryos are known to reduce developmental potential.

Purpose of the Study:

• To determine the rates of aneuploidy and mosaicism in human preimplantation embryos of good quality.

Main Methods:

• Analysis of 14 good-quality human embryos from young IVF patients (age <35 years) that resulted in healthy births.
• Blastomeres were collected after thawing cryopreserved Day 2 embryos, cultured, and disaggregated.
• Array-comparative genomic hybridization (aCGH) was performed on amplified DNA from 91 single blastomeres to detect aneuploidy and structural aberrations.

Main Results:

• High rates of aneuploidy were observed in good-quality embryos, with 71.4% exhibiting mosaicism.
• Of the 70 analyzed blastomeres, 44.3% had chromosomal abnormalities, including 29% with structural aberrations.
• Only 28.6% of the embryos were uniformly diploid; none had the same aneuploidy pattern in all cells.

Conclusions:

• High-level mosaicism and structural aberrations are prevalent in good-quality IVF embryos, not just those with poor development.
• These findings necessitate further research into the origins and implications of chromosomal abnormalities in human preimplantation development.