Melatonin Receptor Genes' Polymorphism And Their Expression Level In Different Tissues Of Chicken

Melatonin (MEL), is an important endocrine hormone secreted by pineal gland and retina, which widely exists in multiple tissues of many kinds of species. It is the important signal of the compatible correlation between illumination information and the reproductive system. Regulation of illumination on reproductive function relays on mediation of MEL which combined with melatonin receptor (MTNR) to adjust animals'circadian rhythm and breeding change. This study aims to understand the genetic variation of gene MTNR and its differential expression in different tissues between open antenatal and open postpartum, so as to give some advices to genetic improvement of native fowl breeds. The research results as follow:Taking WenChang chicken as the object of study, was used. we designed multiple primers, used cloning sequencing and direct sequencing to augment separately the 5′UTR and exon regions of MTNR1A, MTNR1B and MTNR1C, and study the correlation with early open production traits of WenChang chicken. The results suggest that there are 15 SNPs and 1 insertion/deletion in 5′UTR of MTNR1B. The domain effect from the point mutation of -778 on egg number in metaphase of WenChang chicken comes to 2.3 and 6.2 on total egg number in forty-six-week. For egg number in later stage and total egg number in forty-six-week, C is advantage alleles relative to A in -216,the values of additive effect are 2.5 and 3.2, the values of domain effect are 3.5 and 6.8, performance for super dominant in addition. Through the haplotype analysis between two loci, we found that the value from AA haplotype on total egg number in forty-six-week is the smallest in the four kind haplotypes; the hens'age at first laying with AA/AA posterior to individuals with AC/AA and GC/GC significantly. The exons of MTNR1A and MTNR1B are highly conserved, there are two loci named C378T and G381A in the exon3 of MTNR1C, but they don't lead to the change of amino acide.Taking geneβ-actin as interior label, using qRT-PCR method, we compared the differences of expression level of gene MTNR1A, MTNR1B and MTNR1C in heart, liver, oviduct, ovary, brain and SCN and the difference between open antenatal and open postpartum. The results indicate that: after open antenatal, gene MTNR1A shows up-regulated expression in different tissues (except down-regulated expression in brain), the differences of expression level are not significant among different tissues at open antenatal and after open antenatal, but significantly different after open postpartum, and the level in ovary is the highest. Compared the open antenatal, after open postpartum, gene MTNR1B and MTNR1C showed down-regulated expression in every kind of tissue, except up-regulated expression in optic chiasma. In the same tissue, the expression level of gene MTNR1B are not significantly different between open antenatal and open postpartum, but the difference are significant in different tissues at open antenatal or open postpartum, moreover the level of optic chiasma is always the highest and lowest in ovary. However for gene MTNR1C, it don't only show significant difference in different tissues at open antenatal or open postpartum, but also be significantly different among heart oviduct and tissues of brain after open antenatal.The results of this study may be helpful to investigate the mechanism of melatonin regulating chickens'reproductive performance .