Differential Expression and Functional Analysis of CircRNA in the Ovaries of Low and High Fecundity Hanper Sheep

Abstract

Litter size is a considerable quality that determines the production efficiency of mutton sheep. Therefore, revealing the molecular regulation of high and low fertility may aid the breeding process to develop new varieties of mutton sheep. CircRNAs are the important factors regulating follicular development, but their mechanism role in the regulation of litter size in Hanper sheep is not clear. In the present study, ovarian tissues from the follicular (F) or luteal phase (L) of Hanper sheep that were either consecutive monotocous (M) or polytocous were collected. Then, we performed transcriptome sequencing to screen for differentially expressed circRNAs (DE-circRNAs) and elucidate their function. In total, 4256 circRNA derived from 2184 host genes were identified in which 183 (146 were upregulated, while 37 were downregulated) were differentially expressed in monotocous sheep in the follicular phase versus polytocous sheep in the follicular phase (MF vs. PF). Moreover, 34 circRNAs (14 were upregulated, while 20 were downregulated) were differentially expressed in monotocous sheep in the luteal phase versus polytocous sheep in the luteal sheep (ML vs. PL). This was achieved through DE-circRNAs function enrichment annotation analysis by GESA, GO, and KEGG, which function through the EGF-EGFR-RAS-JNK, TGF-β and thyroid hormone signaling pathway to affect the litter size of Hanper sheep in MF vs. PF and ML vs. PL. STEM results showed that MAPK signaling pathways play a key role in MF vs. PF and ML vs. PL. Through WGCNA analysis, AKT3 was a core gene in MF vs. PF and ML vs. PL. Moreover, competitive endogenous RNA (ceRNA) network analysis revealed the target binding sites for miRNA such as oar-miR-27a, oar-miR-16b, oar-miR-200a/b/c, oar-miR-181a, oar-miR-10a/b, and oar-miR-432 in the identified DE-cirRNAs.

Identification of Circular RNAs in the Ovaries of Hu Sheep and Local Fat-tailed Sheep during the Luteal Phase

“…These circular RNAs are mainly composed of three types (Fig 1D ), introns (8%3%), intergenic (3.4%8.4%) and exons (both 88.6%). The sequencing results in the ovaries of previous studies, such as pig (Wang et al, 2021), goat (La et al, 2019) and sheep (Liu et al, 2021) animals, were similar to the results obtained in the present study.…”

Analysis of Expression Profiles of CircRNA and MiRNA in Oviduct during the Follicular and Luteal Phases of Sheep with Two Fecundity (FecB Gene) Genotypes

“…miR-27a inhibits the proliferation and promotes the apoptosis of mouse granulosa cells by reducing key enzymes for estrogen synthesis [87]. The sequencing of follicular and luteal phase ovarian tissues from monotocous and polytocous sheep revealed that oar-miR-181a (target to novel_circ_0017815) and oar-miR-27a have a targeting relationship with circLTBP1 [88]. miR-181a was also found to be associated with the regulation of estradiol synthesis and follicular apoptosis [89,90].…”

Photoperiods induced the circRNA differential expression in the thyroid gland of OVX+E2 ewes

“…CircRNAs are known to promote the transcription of source genes by interacting with U1 small ribonucleoproteins (snRNPs) and RNA polymerase II ( 41 ). Therefore, identification of the potential functions of source genes associated with circRNAs may shed light out on their functions ( 42 ). In this study, the source genes of differentially expressed circRNAs found to been riched in Inositol phosphate metabolism, cGMP-PKG signaling pathway, Calcium signaling pathway, MAPK signaling pathway and Oocyte meiosis.…”

“…Oar-miR-377-3p is related to oocyte quality, this can directly affect the ability of the embryo to develop ( 64 ). Oar-miR-181a, oar-miR-432 and oar-miR-495-3p were identified to be associated with reproductive function ( 42 , 65 ). Oar-miR-21, oar-miR-370-3p, and oar-miR-10b are differentially expressed in sheep-related diseases ( 66 , 67 ), which have not been studied in seasonal reproduction, their differential expression under different photoperiods deserves further study.…”