Microsatellite markers within the α-globin gene cluster for robust preimplantation genetic diagnosis of severe α-thalassemia syndromes in Mediterranean populations.

In this study we report the development of a generic protocol for preimplantation genetic diagnosis (PGD) of severe α-thalassemia (α-thal) syndromes in α-thal carrier couples of Mediterranean origin. The in silico identification and design of primers for multiplex analysis of short tandem repeats (STRs), was followed by the optimization of polymerase chain reaction (PCR) conditions for multiplexed STR analysis within the α-globin gene cluster (16p3.3) and subsequent optimization and validation of a single-cell multiplex reaction including the selected STRs. Three simple dinucleotide repeats were selected based on their rate of heterozygosity, multiplex PCR efficiency and product size, and location within the α-globin gene cluster. The multiplex PCR was optimized in single lymphocytes with PCR efficiency ranging from 92.5 to 98% and an allele drop-out (ADO) rate of 0 to 9.0% for the three loci. The optimized method was applied in two clinical PGD cycles and genotypes were achieved in 17 out of 18 blastomeres (94%). Transfer of unaffected embryos led to a singleton pregnancy in one of the two couples. The triplex PCR validated for Greek and Cypriot populations is a robust generic method for α-thal PGD.