73. SIMULTANEOUS PGT-M APPLICATIONS FOR MULTIPLE GENETIC CONDITIONS

Abstract

Introduciton Pre-implantation genetic diagnosis for monogenic disorders (PGT-M) have been extensively applied for genetic conditions resulting from mutations at single genetic locus . Vast amount of data have arised from Whole Exom Sequencing (WES) and Whole Genome Sequencing (WGS) technologies it is not always straight forward to filter out the mutation responsible for the disorder. Furthermore consanguinity increases the risk of cooccurence of two or more etiologically different genetic diseases in a single family. For this reason increased number of patients referred to PGT-M applications started to demand simultaneous testing of multiple genetic disorders. Drastically some families referred for one condition later had further offsprings with additional single gene defects. We are reporting PGT-M application for two or more genetic conditions performed in our center. Materials and Methods PGT-M was performed by testing blastocyst/blastomere samples depending on the familial pathogenic variants. For this purpose biopsied cells were lysed and fragment analysis for haplotyping and sequence analysis for mutation detection have been performed following multiplex nested PCR. PGT-M testing was performed simultaneously for multiple genetic conditions in 17 couples. 6 infromative STR markers were used for each loci in addition to mutation site. Results was performed for 17 couples and 36 disorders including (Beta Thallasemia, DMD, Glycogen storage disease, Mitochondrial complex I deficiency, Maple syrup urine disease etc.) For 2 couples 3 different conditions were screened simultaneously. While 5 out 7 embryos was appropriate for transfer in one of these patients only 1 out of 8 embyos was transferable for the second case. For 15 couples where 2 conditions were screened 32 embryos out of 104 were appropriate for transfer. Embryo transfer was performed in all patients except for one patient who had only 1 embryo for . Conclusion Insufficient information in databeses regarding the pathogenicity of variants for rare diseases leads to a difficults in counselling patients for PGT-M. Frequent use of WES/WGS for families has become an effective tool for detecting the mutations to enable PGT-M application for families without previous diagnosis of their affected child. Unfortunately in many cases unusal phenotypes in consangenous couples forces us to exclude all variants including variants of unknown significance (VUS) that may be associated with phenotype. This a challanging approach since PGT-M should be designed for each condition together with linked STR markers for each of them to achieve high confidence results. Additionally the more we try to exclude the less likely we will find an appropriate embryo for transfer and families should be informed of this possibility before consenting to PGT-M applications. Because of this delineation of VUS will enable us to interprete patients history and give more efficient counselling to PGT-M patients thus limiting the number of embryos excluded due to these variants.