Quantitative analysis of methylation status at 11p15 and 7q21 for the genetic diagnosis of Beckwith-Wiedemann syndrome and Silver-Russell syndrome

Methylation-specific (MS) multiplex ligation-dependent probe amplification (MLPA) at two differentially methylated regions (DMRs) at chromosome 11p15, H19-DMR and LIT1-DMR, and microsatellite analysis for uniparental disomy (UPD) at chromosome 7 or 11, have been recommended for the genetic diagnosis of the Beckwith-Wiedemann syndrome (BWS) and the Silver-Russell syndrome (SRS). In this study, the efficacy of the MS pyrosequencing method at H19-DMR and LIT1-DMR at 11p15 and SGCE-DMR at 7q21 was evaluated for the genetic diagnosis of BWS (n=18) and SRS (n=20) patients. Epigenetic alterations or UPD were detected in 83% of BWS and 50% of SRS individuals by MS-MLPA, but the detection rate increased to 95% of BWS and 70% of SRS by MS pyrosequencing. Thirteen BWS patients (72%) harbored loss-of-methylation (LOM) at LIT1-DMR and two patients (11%) harbored gain-of-methylation (GOM) at H19-DMR, whereas two patients (11%) had both LOM at LIT1-DMR and GOM at H19-DMR, reflecting paternal UPD 11. Thirteen SRS patients (65%) harbored LOM at H19-DMR, whereas one patient (5%) had GOM at SGCE-DMR, reflecting maternal UPD 7. Birth anthropometric profiles were significantly correlated to methylation scores at either H19-DMR or LIT1-DMR. In conclusion, MS pyrosequencing enhanced the detection rate of molecular defects in BWS and SRS. Moreover, it indicates that methylation status at 11p15.5 might have an important role in fetal growth.