Higashimoto Ken, Urano Takeshi, Sugiura Kazumitsu, Yatsuki Hitomi, Joh Keiichiro, Zhao Wei, Iwakawa Mayumi, Ohashi Hirofumi, Oshimura Mitsuo, Niikawa Norio, Mukai Tsunehiro, Soejima Hidenobu
Division of Molecular Biology & Genetics, Department of Biomolecular Sciences, Saga Medical School, Nabeshima, Saga, Japan.
Am J Hum Genet. 2003 Oct;73(4):948-56. doi: 10.1086/378595. Epub 2003 Aug 29.
To clarify the chromatin-based imprinting mechanism of the p57(KIP2)/LIT1 subdomain at chromosome 11p15.5 and the mouse ortholog at chromosome 7F5, we investigated the histone-modification status at a differentially CpG methylated region of Lit1/LIT1 (DMR-Lit1/LIT1), which is an imprinting control region for the subdomain and is demethylated in half of patients with Beckwith-Wiedemann syndrome (BWS). Chromatin-immunoprecipitation assays revealed that, in both species, DMR-Lit1/LIT1 with the CpG-methylated, maternally derived inactive allele showed histone H3 Lys9 methylation, whereas the CpG-unmethylated, paternally active allele was acetylated on histone H3/H4 and methylated on H3 Lys4. We have also investigated the relationship between CpG methylation and histone H3 Lys9 methylation at DMR-LIT1 in patients with BWS. In a normal individual and in patients with BWS with normal DMR-LIT1 methylation, histone H3 Lys9 methylation was detected on the maternal allele; however, it disappeared completely in the patients with the DMR-LIT1 imprinting defect. These findings suggest that the histone-modification status at DMR-Lit1/LIT1 plays an important role in imprinting control within the subdomain and that loss of histone H3 Lys9 methylation, together with CpG demethylation on the maternal allele, may lead to the BWS phenotype.
为阐明11号染色体p15.5处p57(KIP2)/LIT1亚结构域以及7F5号染色体上小鼠直系同源物基于染色质的印记机制，我们研究了Lit1/LIT1差异甲基化CpG区域（DMR-Lit1/LIT1）的组蛋白修饰状态，该区域是该亚结构域的印记控制区域，在一半的贝克威思-维德曼综合征（BWS）患者中发生去甲基化。染色质免疫沉淀试验表明，在两个物种中，具有CpG甲基化的母源非活性等位基因的DMR-Lit1/LIT1显示组蛋白H3赖氨酸9甲基化，而CpG未甲基化的父源活性等位基因在组蛋白H3/H4上发生乙酰化且在H3赖氨酸4上发生甲基化。我们还研究了BWS患者中DMR-LIT1处CpG甲基化与组蛋白H3赖氨酸9甲基化之间的关系。在正常个体以及DMR-LIT1甲基化正常的BWS患者中，母源等位基因上检测到组蛋白H3赖氨酸9甲基化；然而，在DMR-LIT1印记缺陷的患者中，该甲基化完全消失。这些发现表明，DMR-Lit1/LIT1处的组蛋白修饰状态在该亚结构域的印记控制中起重要作用，并且母源等位基因上组蛋白H3赖氨酸9甲基化的缺失以及CpG去甲基化可能导致BWS表型。
