Sharyn Stock-Myer1, Andrea Twomey, Paisu Tang, Anke Kohfahl, Mirjana Martic
1 Virtus Diagnostics, Melbourne IVF, 344 Victoria Parade, East Melbourne 3002, Sharyn.firstname.lastname@example.org
Pre-implantation Genetic Diagnosis (PGD) allows the diagnosis of known gene disorders from pre-implantation embryos significantly reducing the risk of ongoing affected pregnancy in a couple at known risk for a particular disorder. PGD for reciprocal translocations typically utilises either array CGH or Next Generation Sequencing to detect unbalanced segregants and allows embryos to be transferred that have normal copy number DNA. However, using these technologies it is impossible to distinguish embryos that are balanced and have the derivative chromosomes from those that have inherited normal chromosomes. Additionally, these technologies are unable to reliably detect pathogenic CNVs (below about 5 Mb in size) that may be inherited by embryos from known carrier parents.
Karyomapping, a recently developed PGD technology that utilises a SNP array, was developed as a universal tool for diagnosing single gene disorders by linkage analysis. Our aim was to attempt to use this method to distinguish embryos that are balanced from those that have inherited normal chromosomes, and also to diagnose very small CNVs by linkage (and in the case of deletions, also by direct detection).
To date, we have successfully used Karyomapping to perform PGD for duplications and deletions ranging from 0.2 – 2.5 Mb in size in 13 carrier couples and also for one translocation case. In this translocation case we were clearly able to see unbalanced segregants, as well distinguish embryos that had inherited balanced segregants with derivative chromosomes from those that had inherited normal chromosomes only.
Karyomapping is a reliable method for performing PGD for CNVs below the level of detection of other technologies. This method has also been used successfully to perform PGD for a translocation case and can enable the preferential transfer of embryos with normal chromosomes if available and clinically indicated.
Sharyn has been working for Melbourne IVF since 2002 when she was employed to establish PGD services for monogenic patients. She has continued running this program since that time, and in 2015 took over role of Scientific Director for Pre-implantation Genetics. She is honoured to be able to help couples in their dream to have a healthy child.