Application of triplet repeat-primed-PCR and methylation specific multiplex ligation-dependent probe amplification in prenatal diagnosis of fragile X syndrome

Objective To explore the application value of triplet repeat-primed (TP)-PCR and methylation specific multiplex ligation-dependent probe amplification (MS-MLPA) for prenatal diagnosis of Fragile X syndrome. Methods The CGG repeat number and AGG interruption pattern were analyzed using TP-PCR and methylation status of CpG islands was detected by MS-MLPA from 2 FXS family members and 30 unrelated fetuses. Results The range of alleles was 23-40 CGG repeats in fetuses, and the most frequent allele and AGG interruption pattern were 29 CGG repeats and 9A9A9, respectively. CGG expansion was observed in both of the two permutation alleles during transmission. CpG islands of FMR1 were observed hypermethylated in patients with full mutation, while 30 controls and premature carriers were hypomethylation. Conclusion TP-PCR, in combination with MS-MLPA, represents a reliable diagnostic protocol in the prenatal diagnosis of FXS. Key words: Fragile X syndrome (FXS); Prenatal diagnosis; FMR1 gene; CGG repeat number; AGG interruption pattern