Epigenetic Study of XIST Gene from Female and Male Cells by Pyrosequencing

국문 초록 (Abstract)

목 적: X 염색체 불활성화는 여성과 남성 사이에 X 염색체의 유전자 발현 유지를 위해 여성의 X 염색체 중 하나가 불활성화 되는 현상이다. 이러한 X 염색체 불활성화는 해독되지 않는 XIST 유전자에 의해 조절된다. XIST 유전자는 오직 불활성화된 X 염색체 에서만 발현되고, 활성화된 X 염색체 에서는 발현되지 않는다. 따라서 체세포에서 활성화된 X 염색체의 XIST 유전자는 promoter 부분이 메틸화 되어있고, 불활성화된 X 염색체에서는 메틸화가 거의 되어 있지 않다. 연구방법: 본 연구에서는 정상 여성과 정상 남성의 XIST 유전자의 promoter와 5'-end 지역의 메틸화 차이를 측정하기 위해 정상여성과 남성의 혈액에서 DNA를 추출하여 파이로시퀀싱 (Pyrosequencing) 방법을 통해 XIST 유전자의 총 8부분의 CpG 영역 (-1696, -1679, -1475, -1473, -1469, +947, +956, +971)을 분석하였다. 결 과: 총 8부분의 CpG 영역을 분석한 결과, promoter 부분인 CpG 1-5 영역 (-1696, -1679, -1475, -1473, -1469)에서는 여성과 남성의 메틸화 정도에 차이가 없었다. 그러나 5'-end 부분인 CpG6-8 영역 (+947, +956, +971)에서는 여성이 45.2% 49.9% 44.2%, 남성이 90.6%, 96.7%, 87.8%으로 메틸화 정도가 차이를 나타냈다. 결 론: 따라서 본 연구에 사용한 방법은 XIST 유전자의 메틸화 패턴의 차이를 기존의 방법보다 신속하고 정확하게 분석할 수 있다는 장점이 있기 때문에 유용하게 사용될 수 있을 것이다.

다국어 초록 (Multilingual Abstract)

Objective: X inactivation is the silencing one of the two X chromosomes in female mammals for gene dosage on the X-chromosome between female and male. X inactivation is controlled by X inactive-specific transcript (XIST) gene, untranslated RNA. XIST is expressed only from the inactive X (Xi), not expressed from the active X (Xa). The Xist promoter is methylated on the silent Xist allele on the Xa in somatic cells, and less methylated on the Xist-expressing Xi. We investigated the difference of XIST methylation pattern of the promoter and 5'-region of XIST from male (XY) and female (XX) subjects. Methods: The direct quantification of XIST methylation is required for clinical application of normal XX and XY blood. Methylation percentage of eight CpG sites (-1696, -1679, -1475, -1473, -1469, +947, +956, +971) of XIST gene were diagnosed by pyrosequencing. Results: We directly quantitated the methylation percentage of the promoter and 5'-end of XIST by pyrosequencing. The average methylation percentages at CpG6-8 sites (+947, +956, +971) were 45.2% at CpG6, 49.9% at CpG7, and 44.2% at CpG8 from normal female and normal male were 90.6%, 96.7%, 87.8%, respectively. Nether CpG 1-5sites (-1696, -1679, -1475, -1473, -1469) had any effect on XX and XY. Conclusion: This method is sensitive for quantifying the small percentage change in the methylation status of XIST, and may be used for diagnosis.

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