Transcriptome Analysis Reveals Differentially Expressed circRNAs Associated with Fecundity in Small-Tail Han Sheep Thyroid with Different FecB Genotypes.

Litter size is an economically important trait in sheep, and it is a complex trait controlled by multiple genes in multiple organs. Among them, the regulation of lamb number trait by the thyroid gland is a very important part. However, the molecular mechanisms of the thyroid gland in sheep reproduction remain unclear. Here, RNA-seq was used to detect transcriptome expression patterns in the thyroid gland between follicular phase (FP) and luteal phase (LP) in (MM) and ++ (ww) STH sheep, respectively, and to identify differentially expressed circRNAs (DECs) associated with reproduction. Bioinformatic analysis of the source genes of these DECs revealed that they can be enriched in multiple signaling pathways involved in the reproductive process of animals. We found that the source genes of these DECs, such as , , , and may play important roles in the reproductive process of animals. To better understand the function of these DECs, we constructed circRNA-miRNA co-expression networks. Dual luciferase reporter assays suggested that a ceRNA regulatory mechanism between circ_0003259-oar-miR-133- and circ_0012128-oar-miR-370-3p- may hold. All of these DEC expression profiles in the thyroid gland provide a novel resource for elucidating the regulatory mechanisms underlying STH sheep prolificacy.