Intraindividual Genetic Variation in Human Fetuses with a Preimplantation Origin

Intraindividual copy number variations (CNVs) happen post-zygotically, however their origin is largely unknown. They might appear either through aging or may resist following the common chromosome instability at the preimplantation stage. To uncover a part of this question we investigated fetal mosaicism and its origin. According to distribution pattern of frequent CNVs in derivatives of different germ layers, their origin is early development including preimplantation, whereas CNVs with low frequency occur in later stages. Both fetuses share CNVs, some in the same tissues and some other in different tissues. Functional analysis showed that altered genes were involved in embryonic development pathways. Each organ inherits CNVs with an unpredictable pattern due to extensive cell mixing/migration in embryonic development. Since we have found frequent intraindividual reciprocal CNVs as events with preimplantation origin in both fetuses, mosaic embryo transfer should be performed with caution because it may increase susceptibility to develop early/late onset diseases with genetic component even though recent reports seems to encourage IVF clinics for mosaic embryo transfer. Two normal fetuses were achieved following therapeutic abortion due to maternal indications on the 19th week of natural pregnancy. We studied DNA from 22 tissues of each fetus for copy number changes. The reciprocal aberrations, according to comparison of tissues of each fetus, were subsequently validated using qPCR.