Clinical application of the single-molecule real-time technology for identification of triplicated α-globin genes and compound variant alleles
Objective To assess the clinical utility of single-molecule real-time technology(SMRT)in identifying triplicated α-globin genes and compound variant alleles.Methods A total of 36 samples with tripli-cated α-globin genes were collected.Among them,28 samples were confirmed by PCR flow-through hybridiza-tion and 8 samples were confirmed by Next Generation Sequencing(NGS).These 36 samples included tripli-cated α-globin genes compound variants with cis or trans arrangements unknown,such as αααanti4 2 compoundαcsα(2 cases),αααanti4.2 compound-α3.7(10 cases),and HKαα/--SEA pending confirmation(2 cases),SMRT technology was employed to detect thalassemia gene variants.Additionally,a pedigree with the genotype ofαααanti4.2 compound-α3.7 variant was recruited,including the proband(Ⅱ-1),its father(Ⅰ-1),and mother(Ⅰ-2).PCR flow-through hybridization and SMRT were employed to detect thalassemia gene variants.Results SMRT detected 35 out of 36 samples with triplicated α-globin genes,and 1 sample with quadrupllcated α-globin genes(ααααanti4.2).Among the 2 αααanti4 2 compound αCSα variant samples,both αααanti42 and αCSα were arranged in trans,with a genotype of αααanti4.2/αCSα.Among the 10 αααanti4.2 compound-α3.7 variant samples,9 samples hadαααanti4.2 and-α3.7 in a cis arrangement,with a genotype of HKαα/αα,and 1 sample had αααannti4.2 and-α3.7 in a trans arrangement,with a genotype of αααanti4.2/-α3.7.Compared with PCR flow-through hybridization,SMRT detected one case of a large segment deletion in the β-globin gene and two unknown variants,which led to an increase in the positive detection rate of approximately 10.71％(3/28).The pedigree analysis showed that the proband(Ⅱ-1)inherited αααanti4.2 and-α3.7 variants from his mother(Ⅰ-2),with a genotype of HKαα/αα,con-sistent with the SMRT detection results.Conclusion SMRT can accurately detect triplicated or quadrupllcat-ed α-globin genes,and compound variant alleles.It offers high accuracy,enables one-step identification of cis or trans arrangements,and provides comprehensive coverage of thalassemia gene variations,demonstrating its significant clinical value.
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