Investigation of multilocus imprinting disturbance (MLID) in 101 Beckwith-Wiedemann spectrum patients.

Beckwith-Wiedemann spectrum (BWSp) is an overgrowth disorder caused by both genetic and epigenetic defects within the 11p15.5 chromosomal region. The most common cause of BWSp is DNA methylation anomalies in two imprinting control regions (ICR1, the telomeric centre that includes H19/IGF2:IG-DMR and ICR2, the centromeric centre that includes KCNQ1OT1:TSS-DMR) located within the 11p15.5 locus. Previous studies demonstrated that a subset of BWSp patients had methylation defects extending beyond 11p15.5 to other chromosomal loci, an entity known as multilocus imprinting disturbances (MLID). In this study, the multilocus methylation status of 101 BWSp patients was analysed by both various methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA-ME034) and methylation microarrays. MS-MLPA-ME034 detected MLID in 16 (15.8%) of the patients, which increased to 59 (58.4%) using methylation microarrays. ICR2 hypomethylation was observed in all MLID cases, and 28 imprinted differentially methylated regions (DMRs) were additionally detected. Recurrent loci associated with the genes such as GNAS, MEST, and DIRAS3, previously reported in MLID patients, were also observed as hypomethylated in our cohort. Seven out of the 48 (14.6%) MLID-BWSp patients with complete data on type of conception were born following assisted reproductive technologies (ART), indicating an appreciable proportion of MLID among ART-conceived pregnancies. This study underscores the value of genome-wide methylation analyses in revealing molecular complexity, improving diagnostic accuracy, and informing prenatal care in BWSp with MLID. Future research should further explore the long-term clinical implications of MLID and the underlying molecular mechanisms.