Expression of miRNAs in ovine fetal gonads: potential role in gonadal differentiation

Abstract

BackgroundGonadal 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.MethodsWe 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.ResultsExpression 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.ConclusionsBased on our results we postulate that gene expression networks underlying fetal gonadal development are regulated by miRNAs.

Characterization and expression analysis of microRNAs in Qira black sheep and Hetian sheep ovaries using Solexa sequencing

“…Nevertheless, these data add new information to existing data on sheep miRNAs. Similarly, genome-wide miRNA expression profiles have also been examined in whole ovaries from mice (Ro et al, 2007;Mishima et al, 2008), cattle (Hossain et al, 2009;Tripurani et al, 2010;Huang et al, 2011), pig , goat (Zhang et al, 2013), and fetal sheep (Torley et al, 2011); however comparisons across different follicular stages, different stages of the estrous cycle or different breeds were not performed (Hossain et al, 2012b;McBride et al, 2012). Recent studies have also proposed roles for miRNAs in the regulation of follicular development and apoptosis (Baley and Li, 2012;Donadeu et al, 2012).…”

“…Regardless of species, let-7 family, miR-125b, miR-143, miR-145, and miR-199b, miR-21 and miR-99a have been found to be the most commonly abundant miRNA populations within ovaries (Hossain et al, 2009;Tripurani et al, 2010;Huang et al, 2011;Li et al, 2011;Torley et al, 2011;Zhang et al, 2013). The present study also showed that these miRNAs were expressed at high levels in both libraries, and miR-125b, miR-145, and miR-99a were significantly upregulated in Qira black sheep compared to Hetian sheep.…”

MicroRNAs in farm animals

“…Torley et al compared the expression of 128 miRNAs in sheep ovaries and testes at gestational day (GD) 42 and GD75 by real-time qRT-PCR, finding that 24 miRNAs were differentially expressed between ovaries and testes at GD42 while 43 miRNAs at GD75. Using in situ hybridization, Torley et al revealed that miR-22 was located in Sertoli cells and proposed that this miRNA might play a role in suppressing the estrogen-signaling pathway during fetal testicular development (Torley et al, 2011). Prenatal testosterone treatment leads to ovarian pathology.…”

The potential role of microRNAs in regulating gonadal sex differentiation in the chicken embryo

“…MiRNAs are known to regulate cell division and cell fate and identity (reviewed, Pauli et al 2011;Suh and Blelloch 2011). Furthermore, miRNAs have been detected in mammalian and avian gonads during development (Bannister et al 2009;Tripurani et al 2010;Torley et al 2011). Some of these gonadal miRNAs show sexually dimorphic expression patterns and are candidate regulators of sex-specific development.…”