Genome-wide analysis of genomic impinting in cancer

众所周知，多种遗传和表观遗传变化影响癌症的发生和发展。为了了解印记基因在癌症中的功能相互作用，我们研究了1)新的印记基因的分离，2)LIT1印记基因的功能分析和3)在一些恶性细胞中的印记基因的分析。1)我们在人类中鉴定了143个差异甲基化区域DMR基因。此外，我们使用人类单染色体杂交体分离了两个新的印记基因，它们表现出父亲和母亲的等位基因特异性表达。此外，我们还发现在几个胶质瘤细胞系中观察到了这些基因的印迹增益(GOI)。这一结果表明印记基因的下调可能在胶质瘤的发展中起重要作用。2)印记非编码RNA LIT1是KCNQ1OT1的产物，参与人类染色体Ilpl5.5上印记簇中的顺式限制性沉默。虽然LIT1基因是一个印迹中心(IC)，但其功能尚不清楚。RNA原位杂交提供的证据表明，LIT1 RNA稳定地定位于L1T1区域，并在印迹结构域的转录沉默中发挥重要作用。3)LIT1的错误调控与Beckwith-Wiedemann综合征和包括结直肠癌在内的各种癌症有关。为了阐明L1T1是否与癌症的发生有关，我们研究了它在食道癌和结直肠癌中的表达情况。结果表明，DNA甲基化和组蛋白H3K9甲基化状态与LIT1在结直肠癌中的LOI无关。另一方面，CDKN1C印迹表达的沉默与DMR-L/77的CpG缺失和组蛋白甲基化相关，提示LIT1可能在食管癌的发生发展中起重要作用。

It is well known that a variety of genetic and epigenetic changes influence the development and progression of cancer. To understand the interaction of the functional role of imprinted genes for cancers, we investigated 1) isolation of novel imprinted genes, 2) functional analysis of LIT1 imprinted gene and 3) analysis of imprinted genes in some malignant cells, including glioma, esophageal and colorectal cancers.1) We have identified 143 loci of differential methylated region DMR in human. In addiotion, we isolated 2 novel imprinted gens that exhibit paternal and maternal allele-specific expression using human monochromosomal hybrids. Furthermore, we found that GOI (gain of imprinting) of these imrpinted genes were observed in several glioma cell lines. This result suggests that downregulation of the imprinted genes may be important in the development of glioma.2) The imprinted noncoding RNA LIT1, a product of the KCNQ1OT1, is involved in cis-limited silencing within an imprinted cluster on human chromosome Ilpl5.5. Although the locus serves as an imprinting center (IC), the function of the LIT1 gene product is unclear. RNA in situ hybridization provides evidence suggesting that the LIT1 RNA stably localizes to the L1T1 region and plays an important role in transcriptional silencing of the imprinting domain.3) Misregulation of LIT1 is associated with both Beckwith-Wiedemann syndrome and various cancers including colorectal cancers. To clarify whether L1T1 is correlated with development of cancers, we investigated its expression profiles in esophageal and colorectal cancer. As the results, DNA methylation and histone H3K9 methylation status is not responsible for LOI of LIT1 in colorectal cancers. On the other hand, silencing of imprinted CDKN1C expression was associated with loss of CpG and histone methylation at DMR-L/77 in esophageal cancer, suggeting that LIT1 may be important in the development of this tumor.