Abstract
The analysis of gene expression patterns during ovarian follicle development will advance our understanding of avian reproductive physiology and make it possible to improve laying performance. To gain insight into the molecular regulation of ovarian development, a systematic profiling of miRNAs and mRNAs at four key stages was conducted, using ovarian tissues from hens at 60 days of age (A), 100 days (B), 140 days-not yet laying (C), and 140 days-laying (D). Comparisons of consecutive stages yielded 73 differentially expressed miRNAs (DEMs) (14 for B vs. A, 8 for C vs. B, and 51 for D vs. C) and 2596 differentially expressed genes (DEGs) (51 for B vs. A, 20 for C vs. B, and 2579 for D vs. C). In addition, 174 DEMs (22 for C vs. A, 74 for D vs. A, and 78 for D vs. B) and 3205 DEGs (118 for C vs. A, 2284 for D vs. A, and 2882 for D vs. B) were identified between nonconsecutive stages. Some DEGs are involved in the Wnt and TGF-beta signaling pathways, which are known to affect ovarian development and ovulation. An integrative analysis of the miRNA and mRNA profiles identified 3166 putative miRNA-mRNA regulatory pairs containing 84 DEMs and 1047 DEGs. Functional annotation of the networks provides strong evidence that the miRNA regulatory networks may play vital roles in ovarian development and ovulation. Ten DEMs and 10 genes were validated by real-time quantitative PCR. The candidate miRNA-mRNA pairs gga-miR-200a-3p-SFRP4, gga-miR-101-3p-BMP5, gga-miR-32-5p-FZD4, and gga-miR-458b-5p-CTNNB1 potentially associated with ovarian development.
Highlights
Decades of traditional selective breeding by the poultry industry have resulted in marked improvement in commercial egg-laying breeds (Johnson et al, 2015)
The present study focused on identifying differentially expressed genes (DEGs) and miRNAs at four critical time points during ovarian development in Jining Bairi hens, an indigenous chicken breed that is well known for early sexual maturity at around 100 days
In order to visualize the pattern of miRNA expression during ovarian development, we conducted a time-course analysis using four samples, obtained at 60 days (A), 100 days (B), 140 days, and 140 days. 8,275,891, 7,091,297, 9,022,100, and 10,724,020 raw reads were collected from the four libraries, respectively
Summary
Decades of traditional selective breeding by the poultry industry have resulted in marked improvement in commercial egg-laying breeds (Johnson et al, 2015). The recent development of highthroughput genotyping platforms is likely to enable additional gains in egg production traits through molecular breeding, especially in the indigenous chicken breeds found in developing countries. Ovarian development and folliculogenesis in chicken is a complex and highly coordinated process, resulting in the maturation of oocytes and the differentiation and proliferation of granulosa and theca cells (Qin et al, 2015; Lyu et al, 2016). Since this biological program is expected to exert a major influence on egg production traits, the cell signaling and associated transcriptional mechanisms that regulate ovarian development are of particular interest. The selected follicle develops rapidly through five (F5 to F1) stage prior to ovulation (Johnson and Woods, 2009)
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