title: The X-linked imprinted gene family Fthl17 shows predominantly female expression following the two-cell stage in mouse embryos.
abstract: Differences between male and female mammals are initiated by embryonic differentiation of the gonad into either a testis or an ovary. However, this may not be the sole determinant. There are reports that embryonic sex differentiation might precede and be independent of gonadal differentiation, but there is little molecular biological evidence for this. To test for sex differences in early-stage embryos, we separated male and female blastocysts using newly developed non-invasive sexing methods for transgenic mice expressing green fluorescent protein and compared the gene-expression patterns. From this screening, we found that the Fthl17 (ferritin, heavy polypeptide-like 17) family of genes was predominantly expressed in female blastocysts. This comprises seven genes that cluster on the X chromosome. Expression analysis based on DNA polymorphisms revealed that these genes are imprinted and expressed from the paternal X chromosome as early as the two-cell stage. Thus, by the time zygotic genome activation starts there are already differences in gene expression between male and female mouse embryos. This discovery will be important for the study of early sex differentiation, as clearly these differences arise before gonadal differentiation.
authors.affiliation: Medical Top Track Program, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan. kobayashi.mtt@mri.tmd.ac.jp
authors.forename: Shin
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Fujihara
authors.forename: Nathan
authors.initials: N
authors.lastname: Mise
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kaseda
authors.forename: Kuniya
authors.initials: K
authors.lastname: Abe
authors.forename: Fumitoshi
authors.initials: F
authors.lastname: Ishino
authors.forename: Masaru
authors.initials: M
authors.lastname: Okabe
mesh_terms: D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism; D005260:Female; D005293:Ferritins / Q000235:genetics*; D020869:Gene Expression Profiling; D018392:Genomic Imprinting; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D012733:Sex Differentiation / Q000235:genetics*; D014960:X Chromosome; D049951:X Chromosome Inactivation
chemical_list: D005293:Ferritins