title: Masculine epigenetic sex marks of the CYP19A1/aromatase promoter in genetically male chicken embryonic gonads are resistant to estrogen-induced phenotypic sex conversion.
abstract: Sex of birds is genetically determined through inheritance of the ZW sex chromosomes (ZZ males and ZW females). Although the mechanisms of avian sex determination remains unknown, the genetic sex is experimentally reversible by in ovo exposure to exogenous estrogens (ZZ-male feminization) or aromatase inhibitors (ZW-female masculinization). Expression of various testis- and ovary-specific marker genes during the normal and reversed gonadal sex differentiation in chicken embryos has been extensively studied, but the roles of sex-specific epigenetic marks in sex differentiation are unknown. In this study, we show that a 170-nt region in the promoter of CYP19A1/aromatase, a key gene required for ovarian estrogen biosynthesis and feminization of chicken embryonic gonads, contains highly quantitative, nucleotide base-level epigenetic marks that reflect phenotypic gonadal sex differentiation. We developed a protocol to feminize ZZ-male chicken embryonic gonads in a highly quantitative manner by direct injection of emulsified ethynylestradiol into yolk at various developmental stages. Taking advantage of this experimental sex reversal model, we show that the epigenetic sex marks in the CYP19A1/aromatase promoter involving DNA methylation and histone lysine methylation are feminized significantly but only partially in sex-converted gonads even when morphological and transcriptional marks of sex differentiation show complete feminization, being indistinguishable from gonads of normal ZW females. Our study suggests that the epigenetic sex of chicken embryonic gonads is more stable than the morphologically or transcriptionally characterized sex differentiation, suggesting the importance of the nucleotide base-level epigenetic sex in gonadal sex differentiation.
authors.affiliation: Molecular Profiling Laboratory, Massachusetts General Hospital Center for Cancer Research and Harvard Medical School, Charlestown, Massachusetts, USA.
authors.forename: Haley L
authors.initials: HL
authors.lastname: Ellis
authors.forename: Keiko
authors.initials: K
authors.lastname: Shioda
authors.forename: Noël F
authors.initials: NF
authors.lastname: Rosenthal
authors.forename: Kathryn R
authors.initials: KR
authors.lastname: Coser
authors.forename: Toshi
authors.initials: T
authors.lastname: Shioda
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics*; D030161:Avian Proteins / Q000235:genetics*; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics*; D018899:CpG Islands; D019175:DNA Methylation / Q000187:drug effects; D012734:Disorders of Sex Development / Q000139:chemically induced / Q000196:embryology; D044127:Epigenesis, Genetic / Q000187:drug effects; D004997:Ethinyl Estradiol / Q000008:administration & dosage; D005260:Female; D005262:Feminization / Q000139:chemically induced / Q000196:embryology; D005819:Genetic Markers; D008297:Male; D010053:Ovary / Q000187:drug effects / Q000196:embryology; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019849:Sex Determination Processes; D012733:Sex Differentiation / Q000187:drug effects / Q000235:genetics; D013737:Testis / Q000187:drug effects / Q000196:embryology
chemical_list: D030161:Avian Proteins; D005819:Genetic Markers; D012333:RNA, Messenger; D004997:Ethinyl Estradiol; D001141:Aromatase