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

Simple Summary The lambing trait is an important production trait in sheep, and the FecB gene is one of the major genes affecting sheep reproduction. In order to explore the molecular regulatory mechanisms affecting lambing number in sheep, we used RNA-seq technology to detect the thyroid transcircRNA recombinome expression patterns during the luteal and luteal phases in different FecB genotypes of small-tail Han sheep (STH), identified reproduction-related circRNAs in the thyroid gland of STH sheep, and performed bioinformatic analysis, RT-qPCR validation of these genes, and dual luciferase reporter gene experimental validation to predict their potential functions in repopulation and better reveal the molecular mechanisms of thyroid organization during reproduction in sheep.Abstract 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 FecB BB (MM) and FecB ++ (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 GNAQ, VEGFC, MAPK1, STAT1, and HSD17B7, 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-TXLNA and circ_0012128-oar-miR-370-3p-FGFR1 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.