Sox-Oct motifs contribute to maintenance of the unmethylated H19 ICR in YAC transgenic mice

Abstract

Abnormal methylation at the maternally inherited H19 imprinted control region (H19 ICR) is one of the causative alterations leading to pathogenesis of Beckwith-Wiedemann syndrome (BWS). Recently, it was shown in human BWS patients, as well as mouse cell culture experiments, that Sox-Oct motifs (SOM) in the H19 ICR might play a role in protecting the maternal ICR from de novo DNA methylation. By grafting a mouse H19 ICR fragment into a human β-globin yeast artificial chromosome (YAC) followed by analysis in transgenic mice (TgM), we showed previously that the fragment carried sufficient information to establish and maintain differential methylation after fertilization. To examine possible functions of the SOM in the establishment and/or maintenance of differential methylation, two kinds of YAC-TgM were generated in this study. In the ΔSOM TgM, carrying the mouse H19 ICR bearing an SOM deletion, a maternally inherited transgenic ICR exhibited increased levels of methylation around the deletion site, in comparison to the wild-type control, after implantation. In the λ + CTCF + b (LCb) TgM, carrying a 2.3 kb λ DNA fragment supplemented with the fragment b including the SOM and four CTCF binding sites, maternally and some of the paternally inherited LCb fragments were significantly less methylated when compared with a control λ + CTCF fragment that was supplemented only with additional CTCF sites; the λ + CTCF was substantially methylated regardless of the parent of origin after implantation. These results demonstrated that the SOM in the maternal H19 ICR was required for maintaining surrounding sequences in the unmethylated state in vivo.

Exhaustive methylation analysis revealed uneven profiles of methylation atIGF2/ICR1/H1911p15 loci in Russell Silver syndrome

“…This hypothesis is supported by recent findings demonstrating the importance of OCT4/SOX2 binding in the protection of the maternal allele from hypermethylation at Igf2/ ICR1 /H19 domain in blastocysts 21 22 37. We have identified two novel unreported de novo variations in two patients, but they are unlikely to be the cause of the hypomethylation since they do not disturb a known cis -acting element and also they did not induce any particular methylation profile across the domain.…”

“…Mutations and small deletions of OCT4-binding and SOX2-binding sites have been described within the ICR1 in patients with BWS, and are associated with a gain of ICR1 methylation 18–20. These results suggest that OCT4/SOX2 bind to the maternal allele and protect it from gain of methylation during the early stages of fetal development 21 22…”

De novoDNA methylation through 5'-segment of theH19ICR maintains its imprint during early embryogenesis

“…Another possibility is that an epigenetic mark to designate its paternal origin might be set in this region of the H19 ICR during spermatogenesis. Importantly, this is the first example of regulatory sequences that ensure a stable methylation level of the paternal H19 ICR during preimplantation periods, because all the cis regulatory elements identified to date (such as CTCF or Sox-Oct binding motifs) function to maintain the unmethylated state of maternal H19 ICR following implantation (Matsuzaki et al, 2010;Sakaguchi et al, 2013;Schoenherr et al, 2003;Zimmerman et al, 2013).…”

“…1A) is DNA-methylated by the DNMT3A-DNMT3L complex in prospermatogonia, the status of which is maintained on the paternal allele following fertilization (Kaneda et al, 2004;Tremblay et al, 1997), and it is thus classified as a gDMR. Whereas indispensable roles for CTCF (Matsuzaki et al, 2010;Schoenherr et al, 2003) and Sox-Oct binding motifs (Sakaguchi et al, 2013;Zimmerman et al, 2013) in maintaining maternal H19 ICR hypomethylation during postimplantation periods are well established, little is known about the underlying mechanisms that maintain paternal H19 ICR hypermethylation during preimplantation periods.…”

Epigenetic Deregulation of Genomic Imprinting in Humans: Causal Mechanisms and Clinical Implications

“…Recently, it was experimentally confirmed that SOX2-OCT4 motifs (octamer motifs and their flanking sequences) in the ICR determine the cell type, DNA region and allele specificity of DNA methylation [82,83]. Another pluripotency factor, which contributes to the maintenance of the differential DNA methylation, at least in the mouse, is ZFP42 (also called REX1) [66].…”