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:RCV-000802701.1;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.Endpoint 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.

Clinical characteristics and mutation analysis of propionic acidemia in Thailand

Background:Propionic acidemia(PA)is caused by a deficiency of propionyl CoA carboxylase.A characteristic urine organic acid profile includes 3-hydroxypropionate,methylcitrate,tiglylglycine,and propionylglycine.The diagnosis of PA is confirmed by detection of mutations in the PCCA or PCCB genes.We herein report the clinical and molecular findings of four Thai patients with PA.Methods:Clinical findings of four Thai patients with PA were retrospectively reviewed.Urine organic acids were analyzed by gas chromatography-mass spectrometry.PCR-sequencing analyses of encoding exons and intron/exon boundaries of the PCCA and PCCB genes were performed.Results:All patients had neonatal onset of PA.One patient died of cardiomyopathy,and another one of pneumonia and metabolic decompensation.The remainder experienced significant neurocognitive impairment.Mutation analysis of the PCCA gene identified homozygous c.1284+1G>A in patient 1,c.230G>A(p.R77Q)and c.1855C>T(p.R619X)in patient 2,homozygous c.2125T>C(p.S709P)in patient 3,and only one mutant allele,c.231+1G>T in patient 4.No PCCB mutation was identified.Four mutations including c.230G>A,c.231+1G>T,c.1855C>T,and c.2125T>C have not been reported previously.Conclusions:The clinical and molecular study of these Thai patients provided additional knowledge of the genotype and phenotype characteristics of PA.The results of the study suggested that PCCA mutations in Asian populations were distinct from those of other populations.