Beygo Jasmin, Küchler Alma, Gillessen-Kaesbach Gabriele, Albrecht Beate, Eckle Jonas, Eggermann Thomas, Gellhaus Alexandra, Kanber Deniz, Kordaß Ulrike, Lüdecke Hermann-Josef, Purmann Sabine, Rossier Eva, van de Nes Johannes, van der Werf Ilse M, Wenzel Maren, Wieczorek Dagmar, Horsthemke Bernhard, Buiting Karin
Institut für Humangenetik, Universitätsklinikum Essen, Universität Duisburg-Essen, Essen, Germany.
Institut für Humangenetik, Universität zu Lübeck, Lübeck, Germany.
Eur J Hum Genet. 2017 Aug;25(8):935-945. doi: 10.1038/ejhg.2017.91. Epub 2017 Jun 21.
The chromosomal region 14q32 contains several imprinted genes, which are expressed either from the paternal (DLK1 and RTL1) or the maternal (MEG3, RTL1as and MEG8) allele only. Imprinted expression of these genes is regulated by two differentially methylated regions (DMRs), the germline DLK1/MEG3 intergenic (IG)-DMR (MEG3/DLK1:IG-DMR) and the somatic MEG3-DMR (MEG3:TSS-DMR), which are methylated on the paternal and unmethylated on the maternal allele. Disruption of imprinting in the 14q32 region results in two clinically distinct imprinting disorders, Temple syndrome (TS14) and Kagami-Ogata syndrome (KOS14). Another DMR with a yet unknown function is located in intron 2 of MEG8 (MEG8-DMR, MEG8:Int2-DMR). In contrast to the IG-DMR and the MEG3-DMR, this somatic DMR is methylated on the maternal chromosome and unmethylated on the paternal chromosome. We have performed extensive methylation analyses by deep bisulfite sequencing of the IG-DMR, MEG3-DMR and MEG8-DMR in different prenatal tissues including amniotic fluid cells and chorionic villi. In addition, we have studied the methylation pattern of the MEG8-DMR in different postnatal tissues. We show that the MEG8-DMR is hypermethylated in each of 13 non-deletion TS14 patients (seven newly identified and six previously published patients), irrespective of the underlying molecular cause, and is always hypomethylated in the four patients with KOS14, who have different deletions not encompassing the MEG8-DMR itself. The size and the extent of the deletions and the resulting methylation pattern suggest that transcription starting from the MEG3 promoter may be necessary to establish the methylation imprint at the MEG8-DMR.
染色体区域14q32包含多个印记基因，这些基因仅从父本（DLK1和RTL1）或母本（MEG3、RTL1as和MEG8）等位基因表达。这些基因的印记表达由两个差异甲基化区域（DMR）调控，即生殖系DLK1/MEG3基因间（IG）-DMR（MEG3/DLK1:IG-DMR）和体细胞MEG3-DMR（MEG3:TSS-DMR），它们在父本等位基因上甲基化，在母本等位基因上未甲基化。14q32区域印记的破坏会导致两种临床上不同的印记障碍，即坦普尔综合征（TS14）和加贺美-绪方综合征（KOS14）。另一个功能未知的DMR位于MEG8的内含子2中（MEG8-DMR，MEG8:Int2-DMR）。与IG-DMR和MEG3-DMR不同，这个体细胞DMR在母本染色体上甲基化，在父本染色体上未甲基化。我们通过对不同产前组织（包括羊水细胞和绒毛膜绒毛）中的IG-DMR、MEG3-DMR和MEG8-DMR进行深度亚硫酸氢盐测序，进行了广泛的甲基化分析。此外，我们研究了MEG8-DMR在不同产后组织中的甲基化模式。我们发现，13例非缺失型TS14患者（7例新确诊患者和6例先前已发表的患者）中的每一例，无论潜在分子病因如何，MEG8-DMR均呈高甲基化，而4例KOS14患者（具有不同的不包含MEG8-DMR本身的缺失）中的MEG8-DMR总是呈低甲基化。缺失的大小和范围以及由此产生的甲基化模式表明，从MEG3启动子开始的转录可能是在MEG8-DMR上建立甲基化印记所必需的。
