Karyomapping—a comprehensive means of simultaneous monogenic and cytogenetic PGD: comparison with standard approaches in real time for Marfan syndrome

Excerpt

Preimplantation genetic diagnosis (PGD) of single gene defects by genetic analysis of single or small numbers of cells biopsied from in vitro fertilization (IVF) embryos is clinically well-established. Targeted haplotyping by multiplex fluorescent polymerase chain reaction (PCR) of closely linked or intragenic short tandem repeat (STR) markers combined with direct mutation detection improves the accuracy of single cell analysis significantly and minimizes potential errors caused by undetected allele dropout (ADO) or contamination [1]. Allele dropout refers to the failure of one of the two alleles of a heterozygous locus to amplify. This makes a heterozygous cell appear homozygous at the affected locus, potentially leading to misdiagnosis. Furthermore, using high order multiplex protocols, this approach has been extended to multiple loci, including analysis of the Human leukocyte antigen (HLA) region for selection of embryos tissue matched to existing sick children and diagnosis of translocation chromosome imbalance [2‐4]. However, the development of patient, disease or locus-specific protocols, and testing with single cells, is time-consuming and labour intensive. Also, this targeted approach only provides limited information on chromosome aneuploidy, which is recognized to be a major cause of IVF failure and pregnancy loss. …