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) and methylation microarrays. MS-MLPA detected MLID in 15.84% of the patients, which increased to 44.55% using methylation arrays. ICR2 hypomethylation was observed in all MLID cases, and 25 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. As eight of the 45 BWSp-MLID patients were born following assisted reproductive technology (ART), our findings highlight the increased prevalence of MLID in pregnancies conceived through ART. This study underscores the value of genome-wide methylation analyses for uncovering the molecular complexity, enhancing diagnostic accuracy, and improving prenatal care in BWSp with MLID. Future research should investigate the long-term clinical impact of MLID and the molecular mechanisms involved.