#160 : Detection of Alpha Thalassemia Silent Carriers Having Point Mutation Among Infertile Patients by Gene Sequencing

Abstract

Background and Aims: Thalassemia is a highly prevalent genetic disease in Vietnam. Importantly, silent carriers pose a risk of having children with two mutated alleles hence serious health conditions requiring hematological treatments for the lifetime. Early detection of silent carriers would assist doctors in counseling and offering preimplantation genetic testing for monogenic defects (PGT-M), in this case for thalassemia, which would help carrier couples eventually have healthy babies. Approximately 5% of [Formula: see text]-thalassemia diseases are caused by point mutations while 95% are caused by deletions. Although rare, [Formula: see text]-thalassemia point mutations can be missed when conventional screening methods fail to detect them. DNA sequencing is considered a gold standard method for identifying novel, unreported point mutations. This study aims to apply sequencing to detect point mutations in infertile [Formula: see text]-thalassemia silent carriers. Method: Couples seeking fertility treatments were invited and consented to take part in the study. The control group had five healthy people possessing normal complete blood count results as well as a healthy family history. The study group consisted of nine people, who had hypochromic microcytic anemia (MCH [Formula: see text] 27 pg; MCV [Formula: see text] 80 fL) without any detected deletion mutations. DNA was extracted from whole blood samples. PCR products were then sequenced using SeqStudio Genetic Analyzer 3500 and analyzed by CLC Sequencing Analysis Software v6 together with Mutation Taster (http://www.mutationtaster.org/) and CAAD (https://cadd.gs.washington.edu/). Results: The study identified four variants of the HBA2 gene in nine heterozygous carriers. Among them, 5/9 carried the -[Formula: see text] [Formula: see text]variant, 2/9 had the -[Formula: see text] [Formula: see text], one carried the c.2delT variant, and one bore a new variant, c.-2C[Formula: see text]T, which has not been reported elsewhere. Conclusion: DNA sequencing is effective in detecting point mutations of the [Formula: see text]-thalassemia gene in carriers. The results can significantly contribute to the fertility treatment plan in order to have healthy babies.