The genetic polymorphisms of melanocortin-4 receptor gene are associated with carcass quality traits in a Chinese indigenous beef cattle breed
Introduction
Melanocortin receptor belong to the smallest G-protein coupled receptor (GPCR) family, which has seven-transmembrane α-helix (Ju et al., 2018). In mammals, there were five melanocortin receptor subtypes with different functions (Mountjoy, 2010). The genes of this family were involved in several signaling pathways, including cyclic adenosine monophosphate, mitogen-activated protein kinase, protein kinase C and Janus kinase/signal transducer and activator of transcription (JAK/STA) (Gonçalves et al., 2018), and then played pivotal roles in pigmentation, feeding behavior, energy balance, steroidogenesis, and sexual behavior (Lubrano-Berthelier et al., 2003).
Melanocortin-4 receptor (MC4R) was polypeptides secreted from ventromedial hypothalamic nucleus in mammals, which possessed of seven transmembrane G protein coupled receptor (Gantz et al., 1993). It was predominant expression in central nervous system, including cerebral cortex, thalamus, hypothalamus, brainstem, and notochord (Cone, 2005). MC4R belonged to the GPCR superfamily and activated adenylate kinase, leading to an increase in intracellular cAMP levels (Tao, 2010). As an important regulatory element of leptin sympathetic nervous activity, MC4R gene cooperated with α-melanocyte to stimulated alpha-melanocyte-stimulating hormone and agouti-related protein (Zhang et al., 2015). It also cooperated with neuropeptide Y to regulated energy expenditure and glucose homeostasis in hypothalamus, thereby influencing body weight and feed intake of mammals (Liu et al., 2002). In MC4R knockout mice, the secretion level of insulin and feed intake increased, which caused agouti obesity syndrome in mice (Marie et al., 2000). Moreover, The involvement of MC4R in viscera and insulin sensitivity regulation by governing fat generation was well characterized (Haupt et al., 2009).
Growing findings have led credence to hypothesis that MC4R gene was an excellent candidate gene for meat-related traits in livestock (Cai et al., 2015; Zuo et al., 2014). The objective of this study was to analyze the effects of single and combined genotypes of MC4R gene in Chinese well-known indigenous cattle (Qinchuan cattle) population. Results gleaned from this study could possibly provide the theoretical basis for beef cattle breeding.
Section snippets
Ontogenic expression
Fifteen tissues of Qinchuan cattle were collected from three adult individuals of 2 years old and three calves of 7 days old, respectively. Total RNA was extracted using a Total RNA kit (TaKaRa, Dalian, China) and then reverse transcribed using PrimeScript™ RT Reagent Kit (TaKaRa, Dalian, China) according to the manufacturer's instruction.
The relative expression level of MC4R gene (NM_174110.1) was calculated using Applied Biosystems 7500 Fast Real-Time PCR System (Applied Biosystems, USA) by
Expression analysis
The MC4R gene is widely expressed in various tissues, with predominantly expression levels in central nervous system and genital system (Wan et al., 2012). The results presented in Fig. 1 demonstrated that the bovine MC4R gene was ubiquitously expressed in various tissues and organs. In addition, relative mRNA expression of MC4R was significantly affected by age (P < .05 or P < .01). More specifically, remarkably higher mRNA expression was detected in the muscle and kidney as compared with
Conclusions
In summary, three SNPs in the MC4R gene were identified in Qinchuan cattle. The association analysis of two single markers (g.927C > T and g.1069C > G) and diplotype Hap1/4 revealed prominent effects on carcass quality traits. Our investigation provides evidence that MC4R gene could be used as molecular markers for better carcass quality traits of cattle by further marker-assisted selection.
Authors contributions
Gui Yao Liu and Sayed Haidar Abbas Raza designed the experiment performed the experiments and wrote the manuscript. Ayman Hassan Abd El-Aziz and Ahmed Sabek, Hamed Shoorei, Motahareh Amjadi mainly assisted in analyzing the data Sayed Haidar Abbas Raza provided constructive suggestions for the discussion, and Lin-sheng Gui Project administration, Supervision and assisted in the language modification.
Acknowledgments
The research was supported by the National Natural Science Foundation (31960649), and the Open Project of State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University (2018-ZZ-8).
Declaration of Competing Interest
The authors declare no conflict of interest.
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These authors contributed equally to this study.