Abstract
Circular RNA (circRNA), as a novel endogenous biomolecule, has been emergingly demonstrated to play crucial roles in mammalian lipid metabolism and obesity. However, little is known about their genome-wide identification, expression profile, and function in chicken adipogenesis. In present study, the adipogenic differentiation of chicken abdominal preadipocyte was successfully induced, and the regulatory functional circRNAs in chicken adipogenesis were identified from abdominal adipocytes at different differentiation stages using Ribo-Zero RNA-seq. A total of 1,068 circRNA candidates were identified and mostly derived from exons. Of these, 111 differentially expressed circRNAs (DE-circRNAs) were detected, characterized by stage-specific expression, and enriched in several lipid-related pathways, such as Hippo signaling pathway, mTOR signaling pathway. Through weighted gene co-expression network analyses (WGCNA) and K-means clustering analyses, two DE-circRNAs, Z:35565770|35568133 and Z:54674624|54755962, were identified as candidate regulatory circRNAs in chicken adipogenic differentiation. Z:35565770|35568133 might compete splicing with its parental gene, ABHD17B, owing to its strictly negative co-expression. We also constructed competing endogenous RNA (ceRNA) network based on DE-circRNA, DE-miRNA, DE-mRNAs, revealing that Z:54674624|54755962 might function as a ceRNA to regulate chicken adipogenic differentiation through the gga-miR-1635-AHR2/IRF1/MGAT3/ABCA1/AADAC and/or the novel_miR_232-STAT5A axis. Translation activity analysis showed that Z:35565770|35568133 and Z:54674624|54755962 have no protein-coding potential. These findings provide valuable evidence for a better understanding of the specific functions and molecular mechanisms of circRNAs underlying avian adipogenesis.
Highlights
Excessive body fat accumulation has been triggered by the overemphasis on genetic selection for growth rate and feed conversion in broilers and laying hens, especially abdominal fat accumulation, leading to significantly reduced feed utilization, eggs performance, fertilization rate and hatchability, increased difficulty of meat product processing, coupled with enhanced nitrogen and phosphate content in excrement, causing serious pollution to the ecological environment
As commercial broilers have been utilized as a good biomedical model to study the basic mechanisms of adipogenesis, obesity, and obesity-related diseases (Abdalla et al, 2018), it is of great significance to study the formation and regulatory mechanisms underlying chicken abdominal fat deposition mediated by circular RNA (circRNA), which could provide feasible breeding programs for animal production and facilitate the development of new therapeutic methods for obesity in humans
A total of 1,068 circRNAs were identified in abdominal adipocytes over five differentiation stages, which was different from those of chicken granulosa cells (11,642 circRNAs) (Shen et al, 2019), embryonic muscle (13,377 circRNAs) (Ouyang et al, 2018b), and spleen (2,169 circRNAs) (Wang L. et al, 2020), which might be a consequence of the tissue-specific expression of circRNAs or our more restrictive qualification standard for circRNAs (Salzman et al, 2013)
Summary
Excessive body fat accumulation has been triggered by the overemphasis on genetic selection for growth rate and feed conversion in broilers and laying hens, especially abdominal fat accumulation, leading to significantly reduced feed utilization, eggs performance, fertilization rate and hatchability, increased difficulty of meat product processing, coupled with enhanced nitrogen and phosphate content in excrement, causing serious pollution to the ecological environment Abdominal fat deposition refers to a complex and precisely orchestrated process involving a network of genes, transcriptional factors, even epigenetic modification and regulation, for instance, non-coding RNAs (ncRNA) containing circular RNA (circRNA), long-chain non-coding RNA (lncRNA) and microRNA (miRNA), which has been gradually realized to exert crucial roles in various biological processes through regulating gene expression. CircRNAs are widely perceived to cis or trans regulate gene expression level via diverse mechanisms, including sponging miRNA, scaffolding protein, modulating their parental gene transcription by interacting with transcription complexes, competing with precursor mRNA (pre-mRNA) splicing, and encoding protein or peptide, eventually conducing its role in various biological processes (Han et al, 2018; Kristensen et al, 2019)
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