Karyomapping – faster genetic testing for PGD patients
Dr Sharyn Stock-Myer | 27th Nov 2014
Genetic disorders (depending on their severity) can have a devastating psychological, social and economic impact on entire families. Many family members watch loved ones suffer through crippling conditions and lose hope of wanting to start a family of their own, for fear of passing on the gene that affected their family for generations.
Pre-implantation Genetic Diagnosis (PGD) is a treatment that involves removal of cells from a developing embryo and testing the cells for the genetic disorder or abnormality. Wide-spread usage of this technique is relatively new and research in this field is ongoing to develop more specific and accessible tests that will help prevent parents from passing on often devastating conditions to their children.
How do we test embryos for genetic disorders?
PGD is available for a large number of monogenic disorders – disorders due to a mutation in the DNA of a single gene – including conditions such as cystic fibrosis and Huntington disease.
To help reduce the risk of parents passing on a known genetic disorder to their children, in the past we developed a specific genetic test for the specific genetic condition and gene mutation for each couple. This approach could take up to six months to complete, with enormous stress experienced by the couple due to the wait and expense.
With karyomapping, waiting months to establish a test for each couple is now a thing of the past.
What exactly is karyomapping?
Karyomapping is a single nucleotide polymorphism (SNP) test that uses a DNA finger-printing technique to identify which embryos have inherited the altered gene.
DNA samples are collected, usually via a simple blood or saliva test, from the couple and other family members whose genetic status for the disease is known. Preliminary testing of those samples using Karyomapping allows a DNA fingerprint in the region of the faulty gene to be determined.
After this, as part of an IVF cycle, embryos are formed from the couples eggs and sperm. Cells are carefully removed from developing embryos and tested for the DNA fingerprint, revealing those embryos that have inherited the altered gene. If the fingerprint characteristic of the healthy embryo is detected, then the embryo is free of the genetic disorder and suitable for transfer to the woman’s womb during an IVF cycle.
Karyomapping also provides information across the entire genome, meaning we can identify some of the chromosomal errors that cause implantation failure and miscarriage. Karyomapping therefore has the potential to help us identify the embryos that have the best chance of pregnancy success, which we expect will improve our live birth rates for couples accessing this treatment.
Why are we the first to offer karyomapping in Australia?
We have been trialling karyomapping for Virtus Health patients for about one year through the Melbourne IVF PGD laboratory. The results to date indicate that karyomapping will be suitable for most couples with a known single gene disorder.
The Melbourne IVF PGD laboratory has earned an international reputation in the field of Preimplantation Genetic Diagnosis, after developing full karyotyping analysis from a single cell in the late-1990s.
This resulted in a world-first birth of a healthy baby from an embryo that had comprehensive chromosome testing. In 2010, we were also the first Australian fertility group to introduce 24sure arrayCGH – Advanced Embryo Selection - which enables all 24 chromosomes in a developing embryo to be analysed prior to implantation. This contributed to the developers of Karyomapping technology (Illumina) selecting our laboratory as the first in Australia to refine and validate Karyomapping before it become available to patients.
Is Karyomapping suitable for me?
If you know you are a carrier of a genetic disorder and you do not wish to pass this onto your children, then Karyomapping may be a good option for you.
It involves an appointment with our clinical genetics team. Then we will need to collect a DNA sample from you and specific family members with which to prepare for your treatment and confirm that Karyomapping is suitable. Once this is determined (only about 2-4 weeks) your IVF treatment can begin.
If Karyomapping is not suitable for you we will almost certainly still be able to offer you PGD using a different method, and this will be discussed with you.
What if I wish to proceed?
You should make an appointment with a fertility specialist at Melbourne IVF, IVFAustralia or Queensland Fertility Group and they will refer you to our genetics clinic for discussion regarding PGD and Karyomapping.
Read more: Karyomapping in New South Wales, Queensland, Victoria.
Dr Sharyn Stock-Myer has a doctorate in Human Genetics and is fascinated by genes and genetic conditions. She has worked at Melbourne IVF for more than 12 years and was the lead scientist in developing PGD for monogenic disorders there, and continues to run the monogenic PGD program. Sharyn enjoys being part of the PGD team at Melbourne IVF and is honoured to be able to assist couples in their dream to have a healthy child.