Departamento de Reproducción Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Madrid 28040, Spain.
Proc Natl Acad Sci U S A. 2010 Feb 23;107(8):3394-9. doi: 10.1073/pnas.0913843107. Epub 2010 Feb 4.
Although genetically identical for autosomal Chrs (Chr), male and female preimplantation embryos could display sex-specific transcriptional regulation. To illustrate sex-specific differences at the mRNA level, we compared gene-expression patterns between male and female blastocysts by DNA microarray comparison of nine groups of 60 bovine in vitro-produced blastocysts of each sex. Almost one-third of the transcripts detected showed sexual dimorphism (2,921 transcripts; false-discovery rate, P < 0.05), suggesting that in the absence of hormonal influences, the sex Chrs impose an extensive transcriptional regulation upon autosomal genes. Six genes were analyzed by qPCR in in vivo-derived embryos, which displayed similar sexual dimorphism. Ontology analysis suggested a higher global transcriptional level in females and a more active protein metabolism in males. A gene homolog to an X-linked gene involved in network interactions during spliceosome assembly was found in the Y-Chr. Most of the X-linked-expressed transcripts (88.5%) were up-regulated in females, but most of them (70%) exhibited fold-changes lower than 1.6, suggesting that X-Chr inactivation is partially achieved at the blastocyst stage. Almost half of the transcripts up-regulated in female embryos exhibiting more than 1.6-fold change were present in the X-Chr and eight of them were selected to determine a putative paternal imprinting by gene expression comparison with parthenogenetic embryos. Five (BEX, CAPN6, BEX2, SRPX2, and UBE2A) exhibited a higher expression in females than in parthenotes, suggesting that they are predominantly expressed by the paternal inherited X-Chr and that imprinting may increase the transcriptional skew caused by double X-Chr dosage.
尽管常染色体在遗传上是相同的（Chr），但男性和女性的着床前胚胎可能表现出性别特异性的转录调控。为了说明在 mRNA 水平上的性别特异性差异，我们通过对 9 组每组 60 个体外培养的牛胚胎的 DNA 微阵列比较，比较了男性和女性囊胚的基因表达模式。检测到的几乎三分之一的转录本表现出性别二态性（2921 个转录本；错误发现率，P < 0.05），这表明在没有激素影响的情况下，性染色体对常染色体基因施加了广泛的转录调控。我们在体内衍生的胚胎中通过 qPCR 分析了 6 个基因，这些基因显示出类似的性别二态性。本体论分析表明，雌性的整体转录水平较高，雄性的蛋白质代谢更为活跃。在 Y 染色体上发现了一个与涉及剪接体组装过程中网络相互作用的 X 连锁基因的同源基因。大多数 X 连锁表达的转录本（88.5%）在雌性中上调，但大多数（70%）的倍数变化低于 1.6，这表明 X 染色体失活在囊胚阶段部分完成。在雌性胚胎中上调超过 1.6 倍的转录本中，有近一半存在于 X 染色体上，其中 8 个被选中，通过与孤雌胚胎的基因表达比较来确定潜在的父系印记。在女性中表达水平高于孤雌胚胎的五个（BEX、CAPN6、BEX2、SRPX2 和 UBE2A），这表明它们主要由父系遗传的 X 染色体表达，印记可能会增加由双 X 染色体剂量引起的转录偏斜。
