At Least 6.5% of De Novo Mutations Occur in Post-Zygotic Developing Human Embryo or Child; Implications for Genetic Counseling of At-Risk Parents

Until now, de novo genetic mutations, i.e., alterations in a gene found for the first time in one family member, were believed to be mainly the result of new mutations in the sperm or eggs (germline) of one of the parents and passed on to their child. Researchers from The Netherlands have now succeeded in determining that at least 6.5% of de novo mutations occur during the development of the child (post-zygotic) rather than from the germline of a parent. The research was published online on June 5, 2015 in the American Journal of Human Genetics. The AJHG article is titled “Post-Zygotic Point Mutations Are an Underrecognized Source of De Novo Genomic Variation.” Senior author Christian Gilissen, Ph.D., Assistant Professor in Bioinformatics at the Radboud University Medical Centre, Nijmegen, The Netherlands, will tell attendees of the European Society of Human Genetics (ESHG) Conference being held in Glasgow, UK, June 6-June 9, conference that, due to the technical difficulties of identifying and validating post-zygotic events, until now there have been very few estimates as to how common they are. "Determining exactly how many mutations occur during the development of the child has been challenging because conventional genetic sequencing is not sensitive enough to reliably identify post-zygotic mutations," he will say. Unlike germline mutations, the post-zygotic genetic changes are only present in a proportion of the cells of the individual. This is important because the proportion in which the de novo mutation is present in a patient, as well as the type of cells in which it occurs, may not only determine the clinical outcome of a disease for the patient, but also affect the risk of the parents having another child with the same disease in future pregnancies.
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