Comparison of gene expression in male and female blastocysts

It is basically understood that male and female development is initiated by gonad differentiation into either testis or ovary. However, male embryos are reported to develop faster than female during preimplantation, implying sex differences at this stage. To learn more about when sex differentiation begins, we compared the global gene expression pattern of male and female embryos at the blastocyst stage. First, Blastocyst samples were sexed, using a novel method for non-invasive sexing of preimplantation stage mouse embryos by tagging the X chromosome with an EGFP transgene, Next, gene expression patterns of the male and female were compared using DNA microarray. Ｓamples were collected from three independent preparations and the experiments were triplicated. Scanned microarray results were processed with Feature Extraction software (ver. 7.5, Agilent). 　The hybridization experiments were duplicated in a reciprocal labeling manner to reduce dye integration bias, and total of six hybridizations were carried out using each 22K-1 and 22K-2 array.　 Combining plural array results and statistical analyses were carried out by Luminator software (Rosetta).