Whole-genome amplification/preimplantation genetic testing for propionic acidemia of successful pregnancy in an obligate carrier Mexican couple: A case report

BACKGROUND: Identifying a potential single monogenetic disorder in healthy couples is costly due to the Assisted Reproduction facilities' current methodology for screening, which focuses on the detecting multiple genetic disorders at once. Here, we report the successful application of a low-cost and fast preimplantation genetic testing for monogenic/single gene defects (PGT-M) approach for detecting propionic acidemia (PA) in embryos obtained from a confirmed heterozygous propionyl-CoA carboxylase alpha subunit (PCCA) couple. CASE SUMMARY: A fertile 32-years old Mexican couple with denied consanguinity sought antenatal genetic counseling. They were suspected obligate PA carriers due to a previous deceased PA male newborn with an unknown PCCA/propionyl-CoA carboxylase beta subunit (PCCB) genotype. Next-Generation Sequencing revealed a heterozygous genotype for a pathogenic PCCA variant (c.2041-1G>T, ClinVar:RCV000802701.1; dbSNP:rs1367867218) in both parents. The couple requested in vitro fertilization (IVF) and PGT-M for PA. From IVF, 12 oocytes were collected and fertilized, of which two resulted in high-quality embryos. Trophectoderm biopsies and Whole Genome Amplification by a fragmentation/amplification-based method were performed and revealed that the two embryos were euploid. End-point polymerase chain reaction and further Sanger sequencing of the exon-intron borders revealed a wild-type PCCA male embryo and a heterozygous c.2041-1G>T female embryo. Both embryos were transferred, resulting in a clinical pregnancy and the delivery of a healthy male newborn (38 wk, weight: 4080 g, length: 49 cm, APGAR 9/9). The absence of PA was confirmed by expanded newborn screening. CONCLUSION: We show that using PGT-M with Whole Genome Amplification templates, coupled with IVF, can reduce the transmission of a pathogenic variant of the PCCA gene.