Characterization of Circular RNAs in Chinese Buffalo (Bubalus bubalis) Adipose Tissue: A Focus on Circular RNAs Involved in Fat Deposition

SIMPLE SUMMARY: Buffalo play a vital role in several southeastern and middle-eastern Asian countries and Africa. Fat deposition has received increased attention because of its importance to meat quality. However, information on the development of buffalo adipose tissue is poorly understood and requires further investigation. This study characterized circular RNA (circRNA) profiles of adipose tissues in different developmental stages in buffalo. Co-expression analysis and functional enrichment revealed a considerable number of circRNAs which may function in fat deposition. Further qRT-PCR analysis identified two circRNAs with a significant association with PR/SET domain 16, a fat metabolism gene. Our results identified candidate regulators of fat deposition in buffalo, which may be valuable for buffalo breeding. ABSTRACT: Circular RNAs (circRNAs) have been identified as a novel type of regulators involved in multiple biological processes. However, circRNAs with a potential function in fat deposition in buffalo are poorly understood. In this study, six RNA libraries of adipose tissue were constructed for three young and three adult Chinese buffaloes with paired-ends RNA sequencing using the Illumina HiSeq 3000 platform. A total of 5141 circRNAs were computationally identified. Among them, 252 circRNAs were differentially expressed (DE) between the young and adult buffaloes. Of these, 54 were upregulated and 198 were downregulated in the adult group. Eight DE circRNAs were further identified by quantitative real-time-PCR (qRT-PCR) and Sanger sequencing. Co-expression analysis revealed that 34 circRNAs demonstrated a strong correlation with fat deposition-associated genes (|r| > 0.980). Among these, expressional correlation between two circRNAs (19:45387150|45389986 and 21:6969877|69753491) and PR/SET domain 16 was further verified using qRT-PCR, and a strong correlation was revealed (1 > |r| > 0.8). These results strongly suggest that circRNAs 19:45387150|45389986 and 21:6969877|69753491 are potential regulators of buffalo fat deposition. In summary, this study characterized the circRNA profiles of adipose tissues at different stages for the first time and revealed two circRNAs strongly correlated with fat deposition-associated genes, which provided new candidate regulators for fat deposition in buffalo.