title: Imbalance between the expression dosages of X-chromosome and autosomal genes in mammalian oocytes.
abstract: Oocytes have unique characteristics compared with other cell types. In mouse and human oocytes, two X chromosomes are maintained in the active state. Previous microarray studies have shown that the balance of the expression state is maintained in haploid oocytes. Here, we investigated transcripts using RNA-sequence technology in mouse and human oocytes. The median expression ratio between X chromosome and autosomal genes (X:A) in immature mouse oocytes increased as the gene expression levels increased, reaching a value of 1. However, the ratio in mature oocytes was under 1 for all expression categories. Moreover, we observed a markedly low ratio resulting from the bimodal expression patterns of X-linked genes. The low X:A expression ratio in mature oocyte was independent of DNA methylation. While mature human oocytes exhibited a slightly low X:A expression ratio, this was the result of the skewed high frequency of lowly expressed X-linked genes rather than the bimodal state. We propose that this imbalance between the expression dosages of X-chromosome and autosomal genes is a feature of transcripts in mammalian oocytes lacking X-chromosome inactivation.
authors.affiliation: Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukuda
authors.affiliation: DNA Chip Research Inc. 1-1-43 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Motohiko
authors.initials: M
authors.lastname: Tanino
authors.affiliation: DNA Chip Research Inc. 1-1-43 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Matoba
authors.affiliation: Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Umezawa
authors.affiliation: Center for Regenerative Medicine, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo 157-8535, Japan.|Department of Stem Cell Research, Fukushima Medical University, 1 Hikarigaoka, Fukushima City, Fukushima 960-1295, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Akutsu
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D033481:Chromosomes, Mammalian; D016000:Cluster Analysis; D019175:DNA Methylation; D018628:Gene Dosage; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D005808:Genes, Recessive; D050172:Genes, X-Linked; D006801:Humans; D051379:Mice; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D009866:Oogenesis / Q000235:genetics; D014158:Transcription, Genetic; D014960:X Chromosome; D049951:X Chromosome Inactivation