Sex determines the expression level of one third of the actively expressed genes in bovine blastocysts

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 107; no. 8; pp. 3394 - 3399
• Main Authors: Bermejo-Alvarez, P, Rizos, D, Rath, D, Lonergan, P, Gutierrez-Adan, A
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 23.02.2010; National Acad Sciences
• Subjects: Animals; Biological Sciences; Blastocyst; Blastocyst - metabolism; Cattle; Embryos; Female; Female animals; females; gender differences; Gene expression; Gene Expression Profiling; gene expression regulation; Gene Expression Regulation, Developmental; Genes; Genomic Imprinting; Male; Male animals; males; messenger RNA; microarray technology; Oligonucleotide Array Sequence Analysis; polymerase chain reaction; preimplantation embryos; Proteins; Sex chromosomes; Sex Factors; Sexual dimorphism; Spliceosomes - genetics; Stem cells; Transcription, Genetic; Ungulates; X chromosome; X Chromosome - genetics; X Chromosome Inactivation; X linked genes; Y chromosome; Y Chromosome - genetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0913843107

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.