The Presence of the Y-Chromosome, Not the Absence of the Second X-Chromosome, Alters the mRNA Levels Stored in the Fully Grown XY Mouse Oocyte

The oocytes of B6.YTIR sex-reversed female mouse mature in culture but fail to develop after fertilization because of their cytoplasmic defects. To identify the defective components, we compared the gene expression profiles between the fully-grown oocytes of B6.YTIR (XY) females and those of their XX littermates by cDNA microarray. 173 genes were found to be higher and 485 genes were lower in XY oocytes than in XX oocytes by at least 2-fold. We compared the transcript levels of selected genes by RT-PCR in XY and XX oocytes, as well as in XO oocytes missing paternal X-chromosomes. All genes tested showed comparable transcript levels between XX and XO oocytes, indicating that mRNA accumulation is well adjusted in XO oocytes. By contrast, in addition to Y-encoded genes, many genes showed significantly different transcript levels in XY oocytes. We speculate that the presence of the Y-chromosome, rather than the absence of the second X-chromosome, caused dramatic changes in the gene expression profile in the XY fully-grown oocyte.

B6.YTIR性反转雌性小鼠的卵母细胞可在体外培养中成熟，但受精后因细胞质缺陷无法继续发育。为鉴定存在功能缺陷的组分，我们通过cDNA微阵列（cDNA microarray）比较了B6.YTIR（XY）雌性小鼠与同窝XX雌性小鼠完全成熟卵母细胞的基因表达谱。结果显示，相较于XX卵母细胞，XY卵母细胞中有173个基因的表达量至少上调2倍，485个基因的表达量至少下调2倍。我们通过逆转录聚合酶链式反应（RT-PCR）对XY、XX以及缺失父源性X染色体的XO卵母细胞中的部分候选基因的转录水平进行了检测。所有待测基因在XX与XO卵母细胞中的转录水平均无显著差异，表明XO卵母细胞的mRNA积累过程调控正常。相较而言，除Y染色体编码的基因外，XY卵母细胞中大量基因的转录水平均存在显著差异。我们推测，正是Y染色体的存在而非第二条X染色体的缺失，导致XY完全成熟卵母细胞的基因表达谱发生了显著改变。