Whole-genome sequencing in IVF Clinics

IVF Clinics are slowly adopting more extensive genetic screening of embryos. During Invitro Fertilization one two two dozen embryos can be generated for one cycle. This provides an opportunity to select the best embryo for implantation.

For over two decades, preimplantation genetic testing (PGT) has been availablefor couples who are aware they carry a genetic condition or have had a child affected by a genetic disease. In vitro fertilization (IVF) used in conjunction with monogenic PGT is available for couples to prevent transmission of known hereditary monogenic disorders. PGT for aneuploidy screens embryos for large segmental or whole-chromosome copy number changes and is commonly used for older women (over 35 years) who have a history of infertility, miscarriages or chromosomally abnormal conception. For couples seeking to ascertain their risk of having an affected child, around 6,000 diseases exist that may be genetically screened for. A mutation or disease-causing variant in one or both copies of approximately 5,000 human genes can cause a syndromic disease or phenotype. Between 0.5–5% of infants are born with a genetic condition or disorder15,16. The preconception genetic screening panels that are available to determine a couple’s carrier status for disease-causing genetic variants are limited to a subset of high-risk genes. Currently, preconception screening and PGT are performed as separate unlinked tests. An estimated 74 de novo SNP mutations are introduced at embryogenesis, which, when expressed dominantly or as a compound heterozygote, result in severe pathogenic phenotypes. With the declining cost and increased availability of whole-genome sequencing, some IVF clinics and IVF researchers are exploring the design of combined preconception screening and embryo PGT using whole-genome sequencing to detect disease-causing genetic variants in couples and their embryos in accordance with recommended practice guidelines. The purpose of this study was to develop a method of whole-genome sequencing analysis that could be used to screen human embryos for pathogenic variants. To achieve this, we firstly used parental genome sequences to identify the transmitted variants. Embryo biopsy samples that had undergone multiple displacement amplification and parental genomic DNA samples obtained from blood were used as templates for generating DNA libraries that were subsequently sequenced. Sequenced genomes of embryos and parents were analysed using variant annotation databases and functional prediction algorithms to detect the transmission or introduction of pathogenic mutations. SOURCES - Nature Scientific Reports Written By Brian Wang, Nextbigfuture.com