COMUNICACIONES ORALES CO-029 GENE CONVERSION IN HUMAN EMBRYOS INDUCED BY GENE EDITING N. Marti Gutierrez (1), D. Liang (1), Y. Lee (2), H. Ma (1), A. Koski (1), A. Mikhalchenko (1), S. Heitner (1), E. Kang (2), P. Amato (1), S. Mitalipov (1) (1) Oregon Health & Science University - Portland (Oregon), (2) CHA University - Gyeonggi (South Korea) INTRODUCTION: around target region, we evaluated the presence or loss of sin- gle-nucleotide polymorphisms (SNPs) adjacent to the target DNA double strand breaks (DSBs) at specific loci can be effi- region. ciently induced by genome editing tools. Most DSBs are repai- red by either non-homologous end joining (NHEJ) or homology RESULT: directed repair (HDR) using synthetic DNA templates We show high frequency of GC by targeting the mutant alleles in OBJECTIVE: several heterozygous loci of human preimplantation embryos. Moreover, when targeting both alleles at homozygous loci we Our study aims to evaluate if DNA DSBs in human preimplanta-found that 40.2% (129/321) blastomeres appeared with identi- tion embryos also repaired by an alternative mechanism knowncal indel mutations on both parental alleles, indicating that GC as gene conversion (GC), where intact endogenous homolo- and NHEJ compete and interplay with each other within the gous sequences are used as templates. same cell. GC results in extensive loss of heterozygosity (LOH) within the targeted genomic region. In contrast to GC, frequen- MATERIAL AND METHOD: cy of HDR via exogenous synthetic DNA templates is limited. Pre-tested sgRNAs and Cas9 protein were co-injected into hu- CONCLUSION: man MII oocytes or zygotes to target heterozygous and ho- mozygous wild-type (WT) loci. Injected embryos were culturedOur study demonstrates that GC and NHEJ are the two major for 3 days and then individual blastomeres of cleaving embryosDNA DSB repair mechanisms in human preimplantation embr- were isolated and analysed by sequencing at a single-cell level.yos. While gene conversion could be applicable for gene correc- Since gene conversion results in loss of heterozygosity (LOH)tion, extensive LOH presents a safety concern. CO-030 DETECCIÓN DE CONTAMINACIÓN MATERNA EN NIPGT-A MEDIANTE GENOTIPADO C. Pérez Pelegrín BIOARRAY - Elche (Alicante) INTRODUCCIÓN: materna avanzada (> 35 años), fallo recurrente de implantación (>2 fallos de implantación) y abortos de repetición (>2 abor- El estudio de PGT-A (de sus siglas en inglés, Preimplantationtos). Para un estudio de PGT-A convencional, se requiere de una Genetic Testing for Aneuploidies) es una herramienta bastantebiopsia del embrión en estadio de blastocisto (día 5 o 6 tras fe- extendida en reproducción asistida, que puede resultar muy cundación), para recoger 5-8 células del trofoectodermo para beneficiosa para un perfil de parejas concreto, como son: edadsu posterior amplificación de genoma completo o WGA (Whole 112 ASEBIR. Revista de Embriología Clínica y Biología de la Reproducción. Noviembre 2021 Vol. 26 Nº 2