PROGRESS TOWARDS UNIVERSAL PGT- HOW CLOSE ARE WE TO COMPREHENSIVE PGT?

REFERENCES 1. Riesewijk et al., Mol Hum Reprod 2003 2. Díaz-Gimeno et al., Fertil Steril 2011 3. Díaz-Gimeno et al., Fertil Steril 2013 4. Ruiz-Alonso et al., Fertil Steri 2013 5. Ruiz-Alonso et al., Hum Reprod 2014 6. Hashimoto et al., Reprod Med Biol 2017 7. Mahajan et al., J Hum Reprod Sci 2015 8. Tan et al., J Assist Reprod Genet 2018 9. Simon et al., Fertil Steril 2016 10. Moreno et al., Am J Obstet Gynecol 2016 11. Moreno et al., Am J Obstet Gynecol 2018

doi: 10.1016/j.rbmo.2019.04.024

INVITED LECTURES PROGRESS TOWARDS UNIVERSAL PGT- HOW CLOSE ARE WE TO COMPREHENSIVE PGT?

Don Leigh1,2 1  NGS

Pty Ltd, Australia 2  Calmette Hospital & 1st People's Hospital, Kunming, Yunnan, China

“Are we there yet?”- these are the words that many parents would have heard when taking children on some sort of trip. The journey began over 30 years ago when the first PGTs were done. It was simple back then- the answers required were generally simple (or at least straightforward) and you only went looking for directed answers. PGS was for chromosomes and PGD was for a gene(s)- and generally, never the two would meet. Early chromosome testing was based on FISH and the targets were polar bodies or blastomeres from cleavage embryos- apart from some technical expertise in getting the sample, analysis was essentially down to the operator's ability to count to 1 (2nd PB) or 2 (1st PB and blastomeres). Life was good- but unfortunately the results were often not so productive with implantation rates resisting change and only some groups reporting decreased miscarriage rates for some patient cohorts. The naysayers reached a crescendo around 2005 when it was proclaimed that not only was PGS not helping but it was hurting patient's chances of a pregnancy.

RBMO VOLUME 39 ISSUE s1 2019

Three years of gloom followed with claim and counter claim on the appropriateness of PGS. PGD fared a bit better with the simple logic of Mendelian genetics and obvious success in outcomes- although some mishaps in the early days led some groups to possibly over emphasize and focus on DNA contamination, ADO and recombination eventslife for PGD though was generally good. The darkness of those 3 years of doubt and dispute were substantially dispelled when a British Knight led the field into the new era of comprehensive chromosome screening where every chromosome could now be seen to be both problematic and mischievous. Finally, the full impact of identifying any and all chromosome changes was seen- a dramatic increase in implantation rate and decreased miscarriage rates for most groups tested. There were still some shadowy areas of understanding but the light was again shining and things were, maybe, good again. Was it just a breakthrough in analysis that flicked the switch? No, there were some underlying bits to the puzzle that were not given the amount of the credit for the improvements that they possibly deserved. Two other steps in addition to CCS were essential for the realization of these new outcomes- vitrification with concomitant cryo-transfer and blastocyst stage biopsy. The naysayers retreated, not totally but sufficiently far to encourage the bulk of the world to adopt the new processes. “Are we there yet?”. No, but getting closer. In the meantime, PGD continued on its singular path but now it had to also face the multitude of positive findings associated with the benefits of CCSfind not only the correct genetics for an embryo but also the correct chromosome compliment. How to combine the two for the best of both world's outcomes? Approaches to improved PGS (now

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referred to as PGT-A, PGT-SR) and combining PGD (now PGT-M) into a single will be discussed. “Are we there yet?” doi: 10.1016/j.rbmo.2019.04.025

PREIMPLANTATION GENETIC TESTING (PGT) FOR DE NOVO MUTATIONS (DNM)

S Rechitsky, A Kuliev Reproductive Genetic Innovations, 2910 MacArthur Boulevard, Northbrook, IL 60062, USA

Introduction: PGT-M may presently be applicable for any inherited disorder for which sequence information or relevant haplotypes are available for the detection by direct mutation analysis or haplotyping in oocytes or embryos. However, these approaches cannot be applied in cases of de novo mutations (DNM) in parent(s) or affected children, as neither origin nor relevant haplotypes are available for tracing the inheritance of this DNM in single cells biopsied from embryos or in oocytes. On the other hand, with the improved awareness of PGT, an increasing number of couples request PGT, without any family history of the genetic disease that has been first diagnosed in one of the parents or in their affected children. So special PGT strategies are required for the genetic conditions determined by DNM. Materials and Methods: We developed PGT strategies for DNM which were applied for 277 families with 83 different genetic conditions. The majority, 256 of them, were determined by dominant mutations, with only 4 by autosomal recessive and 21 - by X-linked DNM. It is of interest, that despite the expected predominance of dominant DNM of a paternal origin, with the increasing proportion of older paternal partners in the modern society, there was a comparable proportion of DNM of the paternal (138 couples) and maternal origin (110 couples). The latter presents a