Background: Excessive deposition of abdominal fat poses serious problems in broilers owing to rapid growth. Recently, the evolution of the existing knowledge on long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) have established their indispensable roles in multiple physiological metabolic processes, including adipogenesis and fat deposition. However, not much has been explored on their profiles in the abdominal fat tissues of broilers to date. In the study, we aimed to characterize the vital candidates of lncRNAs and circRNAs and their underlying regulations for abdominal fat deposition in broilers. Results: The present study sequenced the lncRNAs and circRNAs expression profiles in the abdominal fat tissues isolated from 7-week-old broilers, who were divergently selected for their fatness. It identified a total of 3359 lncRNAs and 176 circRNAs, demonstrating differential expressed (DE) 30 lncRNAs and 17 circRNAs between the fat- and lean-line broilers (|log2FC| ≥ 1, P < 0.05). Subsequently, the 20 cis-targets and 48 trans-targets of the candidate DE lncRNAs were identified for depositing abdominal fat by adjacent gene analysis and co-expression analysis, respectively. In addition, the functional enrichment analysis showed the DE lncRNAs targets and DE circRNAs host genes to be mainly involved in the cellular processes, amino/fatty acid metabolism, and immune inflammation-related pathways and GO terms. Finally, the vital 16 DE lncRNAs located in cytoplasm and specifically expressed in fat/lean line and their targets were used to construct the lncRNA-miRNA-mRNA competing endogenous RNA (ceRNA) regulatory network, comprising 7 DE lncRNAs, 28 miRNAs, 11 DE mRNAs. Notably, three lncRNAs including XR_001468036.2, XR_003077610.1 and XR_001466431.2 with the most connected degrees might play hub regulatory roles in abdominal fat deposition of broilers. Conclusions: This study characterized the whole expression difference of lncRNAs and circRNAs between the two lines broilers with divergently ability of abdominal fat. The vital candidate DE lncRNAs/circRNAs and ceRNA regulations were identified related to the deposition of abdominal fat in chicken. These results might further improve our understanding of regulating the non-coding RNAs in obesity.

Reducing abdominal fat (AF) in broilers is a key objective in broiler breeding, as excessive AF deposition has an unfavorable effect on reproductive and growth traits. Fatty acid synthase gene (FASN) encodes the fatty acid synthase, which promotes fatty acid synthesis and lipid synthesis. Our previous study identified a 7-bp InDel variant (g.4944396_4944402delGACTTCA, rs1060467633) in intron 42 of chicken FASN, demonstrating a marked association with chicken AF. To investigate the underlying mechanism of this association, we conducted dual-luciferase reporter assay, bioinformatics analysis and electrophoretic mobility shift assay (EMSA). Luciferase reporter showed that the deletion allele had significantly higher activity than the insertion allele (p < 0.05), indicating its potential role in regulating gene expression. Bioinformatics analysis and EMSA indicated that the insertion allele created binding site for cAMP-responsive element-binding protein 1 (CREB1). Luciferase reporter confirmed that the insertion allele suppresses FASN expression through CREB1, with a stronger inhibitory effect than the deletion allele. In conclusion, rs1060467633, as a functional variant, regulates FASN expression and AF deposition by altering the binding to CREB1 in chickens.

Preadipocyte differentiation is an essential process in adipogenesis. METTL14, an essential constituent of the N⁶-methyladenosine (m⁶A) methyltransferase complex, plays an important role in mammalian preadipocyte differentiation. However, its role in avian adipogenesis remains unclear. More importantly, the m⁶A mechanism by which METTL14 regulates preadipocyte differentiation has not been elucidated. Here, we found that the level of METTL14 expression was substantially elevated within the adipose tissue of the abdominal region of fat chickens relative to lean chickens. Knockdown of METTL14 inhibited preadipocyte differentiation, whereas overexpression of METTL14 promoted this process. Through the integration of MeRIP-seq and RNA-seq, we confirmed that chBMI1, chTMED3, and chMFAP2 were functionally essential targets of METTL14-dependent m⁶A modification in adipogenesis. METTL14-mediated chBMI1 mRNA stabilization and the degradation of chTMED3 and chMFAP2 mRNAs depend on IGF2BP1/2 and YTHDF2, respectively. Overall, our findings establish that METTL14 promotes chicken preadipocyte differentiation by modulating the stability of target mRNAs through a dual-reader m⁶A mechanism.