Identification of the sequences responsible for maternalH19-ICR hypermethylation with Beckwith-Wiedemann syndrome-like overgrowth in mice

Abstract

AbstractBeckwith-Wiedemann syndrome (BWS) is caused by a gain of methylation (GOM) at the imprinting control region within theIgf2-H19domain on the maternal allele (H19-ICR GOM). Mutations in the binding sites of several transcription factors are involved inH19-ICR GOM and BWS. However, the responsible sequence(s) forH19-ICR GOM with BWS-like overgrowth has not been identified in mice. Here, we report that a mutation in the SOX-OCT binding site (SOBS) causes partialH19-ICR GOM, which does not extend beyond CTCF binding site 3 (CTS3). Moreover, simultaneously mutating both SOBS and CTS3 causes complete GOM of the entireH19-ICR, leading to the misexpression of the imprinted genes, and frequent BWS-like overgrowth. In addition, CTS3 is critical for CTCF/cohesin-mediated chromatin conformation. These results indicate that SOBS and CTS3 are the sequences responsible forH19-ICR GOM leading to BWS-like overgrowth and are essential for maintaining the unmethylated state of maternalH19-ICR.