Kuerbitz Steven J, Pahys Joshua, Wilson Alison, Compitello Nicole, Gray Todd A
Department of Pediatrics and Department of Genetics, Case Western Reserve University and Ireland Cancer Center, Cleveland, OH 44109, USA.
Carcinogenesis. 2002 Apr;23(4):559-64. doi: 10.1093/carcin/23.4.559.
Recent studies have demonstrated imprinting of the human neuronatin (NNAT) gene. NNAT maps to 20q11.2-q12, a region exhibiting loss of heterozygosity in acute myeloid leukemia and myelodysplastic/myeloproliferative disease. To investigate possible epigenetic dysregulation of genes in this region relevant to leukemogenesis, we analyzed methylation of the NNAT gene in normal tissues and in leukemias. We found a differential methylation pattern, typical of imprinted genes, at sites in the CpG island containing NNAT exon 1 in normal pituitary, peripheral blood cells and bone marrow-derived CD34-positive hematopoietic progenitor cells. Substantial or complete loss of the unmethylated NNAT allele was observed in leukemia cell lines and in 20 of 29 (69%) acute myeloid or lymphoid leukemia samples. While most highly expressed in brain, NNAT mRNA was also detected in normal hematopoietic progenitor cells and in leukemia cells exhibiting the normal methylation pattern, although not in hypermethylated leukemia cells. Demethylation by treatment of hypermethylated leukemia cells with 5-aza-2'-deoxycytidine resulted in reactivation of NNAT expression, concomitant with a reversion to the normal methylation pattern. The data demonstrate that hypermethylation of the NNAT locus is a frequent event in both myeloid and lymphoid acute leukemias of childhood. Aberrant hypermethylation of the NNAT locus suggests that the dysregulation of genes at 20q11.2-q12 in leukemia may be the result of epigenetic as well as genetic events.
近期研究已证实人类神经调节蛋白（NNAT）基因存在印记现象。NNAT基因定位于20q11.2 - q12，该区域在急性髓系白血病和骨髓增生异常/骨髓增殖性疾病中表现出杂合性缺失。为了研究该区域与白血病发生相关基因可能存在的表观遗传失调，我们分析了正常组织和白血病中NNAT基因的甲基化情况。我们发现在正常垂体、外周血细胞和骨髓来源的CD34阳性造血祖细胞中，包含NNAT外显子1的CpG岛位点存在典型的印记基因差异甲基化模式。在白血病细胞系以及29例急性髓系或淋巴细胞白血病样本中的20例（69%）中，观察到未甲基化的NNAT等位基因大量或完全缺失。虽然NNAT mRNA在脑中表达最高，但在正常造血祖细胞和呈现正常甲基化模式的白血病细胞中也能检测到，不过在高甲基化的白血病细胞中未检测到。用5 - 氮杂 - 2'-脱氧胞苷处理高甲基化的白血病细胞导致去甲基化，从而使NNAT表达重新激活，同时甲基化模式恢复正常。数据表明，NNAT基因座的高甲基化在儿童髓系和淋巴细胞急性白血病中是常见事件。NNAT基因座的异常高甲基化表明，白血病中20q11.2 - q12基因的失调可能是表观遗传以及遗传事件的结果。
