title: Expression of miRNAs in ovine fetal gonads: potential role in gonadal differentiation.
abstract: BACKGROUND
  Gonadal differentiation in the mammalian fetus involves a complex dose-dependent genetic network. Initiation and progression of fetal ovarian and testicular pathways are accompanied by dynamic expression patterns of thousands of genes. We postulate these expression patterns are regulated by small non-coding RNAs called microRNAs (miRNAs). The aim of this study was to identify the expression of miRNAs in mammalian fetal gonads using sheep as a model.
  
  
  METHODS
  We determined the expression of 128 miRNAs by real time PCR in early-gestational (gestational day (GD) 42) and mid-gestational (GD75) sheep ovaries and testes. Expression data were further examined and validated by bioinformatic analysis.
  
  
  RESULTS
  Expression analysis revealed significant differences between ovaries and testes among 24 miRNAs at GD42, and 43 miRNAs at GD75. Bioinformatic analysis revealed that a number of differentially expressed miRNAs are predicted to target genes known to be important in mammalian gonadal development, including ESR1, CYP19A1, and SOX9. In situ hybridization revealed miR-22 localization within fetal testicular cords. As estrogen signaling is important in human and sheep ovarian development, these data indicate that miR-22 is involved in repressing estrogen signaling within fetal testes.
  
  
  CONCLUSIONS
  Based on our results we postulate that gene expression networks underlying fetal gonadal development are regulated by miRNAs.
authors.affiliation: Animal Reproduction and Biotechnology Laboratory, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Katie J
authors.initials: KJ
authors.lastname: Torley
authors.forename: Juliano C
authors.initials: JC
authors.lastname: da Silveira
authors.forename: Peter
authors.initials: P
authors.lastname: Smith
authors.forename: Russell V
authors.initials: RV
authors.lastname: Anthony
authors.forename: D N Rao
authors.initials: DN
authors.lastname: Veeramachaneni
authors.forename: Quinton A
authors.initials: QA
authors.lastname: Winger
authors.forename: Gerrit J
authors.initials: GJ
authors.lastname: Bouma
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics; D047628:Estrogen Receptor alpha / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006066:Gonads / Q000196:embryology*; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D010053:Ovary / Q000196:embryology; D055758:SOX9 Transcription Factor / Q000235:genetics; D012733:Sex Differentiation / Q000235:genetics*; D034561:Sheep, Domestic / Q000235:genetics; D013737:Testis / Q000196:embryology
chemical_list: D047628:Estrogen Receptor alpha; D035683:MicroRNAs; D055758:SOX9 Transcription Factor; D001141:Aromatase