The clinical application of NGS-based SNP haplotyping for PGD of Hb H disease

This study investigated the usefulness of next-generation sequencing (NGS)-based single nucleotide polymorphism (SNP) haplotyping for preimplantation genetic diagnosis (PGD) of hemoglobin H (Hb H) disease. Multiple displacement amplification (MDA) was used for whole genome amplification (WGA) of biopsied trophectoderm (TE) cells. Gap-PCR and NGS-based SNP haplotyping was used to distinguish the two genotypes of -α^3.7/αα and -^SEA/αα for PGD of Hb H disease. One out of the ten blastocysts (B11) was successfully diagnosed as genotype -α^3.7/αα by Gap-PCR, whereas the others revealed allele dropout (ADO) (B1, B2, B4, B5, B7, B8, B12, and B15) or amplification failure (B10). However, NGS-based SNP haplotyping successfully diagnosed the -α^3.7/αα and -^SEA/αα genotypes from the MDA products of the biopsied TE cells. The haplotyping result showed that B4, B7, B8, B10, B11, B12, and B15 were carriers of the -α^3.7 deletion (-α^3.7/αα), whereas B1, B2, and B5 were carriers of the -^SEA deletion (-^SEA/αα). A blastocyst (B11) was transferred into the uterus in a subsequent frozen embryo transfer (FET) cycle after PGD. A healthy infant with a -α^3.7/αα genotype weighing 2,800 g was born by cesarean section at the 38^th week of gestation. This result indicates that NGS-based SNP haplotyping is a valid screening tool for the PGD of Hb H disease.