The genetic effects of the dopamine D1 receptor gene on chicken egg production and broodiness traits

Haiping Xu,Meixia Fang,Qinghua Nie,Min Zhou,Hua Zeng,Xu Shen,Xiquan Zhang

doi:10.1186/1471-2156-11-17

Abstract

BackgroundThe elevation of egg production and the inhibition of incubation behavior are the aims of modern poultry production. Prolactin (PRL) gene is confirmed to be critical for the onset and maintenance of these reproductive behaviors in birds. Through PRL, dopamine D1 receptor (DRD1) was also involved in the regulation of chicken reproductive behavior. However, the genetic effects of this gene on chicken egg production and broodiness have not been studied extensively. The objective of this research was to evaluate the genetic effects of the DRD1 gene on chicken egg production and broodiness traits.ResultsIn this study, the chicken DRD1 gene was screened for the polymorphisms by cloning and sequencing and 29 variations were identified in 3,342 bp length of this gene. Seven single nucleotide polymorphism (SNPs) among these variations, including a non-synonymous mutation (A+505G, Ser169Gly), were located in the coding region and were chosen to analyze their association with chicken egg production and broodiness traits in 644 Ningdu Sanhuang individuals. Two SNPs, G+123A and C+1107T, were significantly associated with chicken broody frequency (P < 0.05). Significant association was also found between the G+1065A - C+1107T haplotypes and chicken broody frequency (P < 0.05). In addition, the haplotypes of G+123A and T+198C were significantly associated with weight of first egg (EW) (P = 0.03). On the other hand, the distribution of the DRD1 mRNA was observed and the expression difference was compared between broodiness and non-broodiness chickens. The DRD1 mRNA was predominantly expressed in subcutaneous fat and abdominal fat of non-broodiness chicken, and then in heart, kidney, oviduct, glandular stomach, hypothalamus, and pituitary. In subcutaneous fat and abdominal fat, the level of non-broodiness was 26 to 28 times higher than that of broodiness. In pituitary, it was 5-fold higher. In heart, oviduct, and kidney, a 2-3 times decrease from non-broodiness to broodiness was displayed. In glandular stomach and hypothalamus, the level seen in non-broodiness and broodiness was almost the same.ConclusionThe polymorphisms of the DRD1 gene and their haplotypes were associated with chicken broody frequency and some egg production traits. The mRNA distribution was significant different between broodiness and non-broodiness chickens.

Highlights

The elevation of egg production and the inhibition of incubation behavior are the aims of modern poultry production
At least five distinct dopamine receptors subtypes, DRD1-DRD5, have been identified and classically divided into two classes referred to as D1-like (DRD1 and DRD5) and D2-like (DRD2, DRD3, and DRD4) receptors based on their pharmacological, biochemical, and physiological differences [20,21,22]
Polymorphisms of the Chicken DRD1 Gene and Transcription Factor Binding Sites Prediction in the 5’ Flanking Region Twenty-seven single nucleotide polymorphisms (SNPs) and 2 indel variations were identified in a total of 3,342 bp region of the chicken DRD1 gene, among which 7 SNPs were located in coding region and others in the 5’ regulatory region

Summary

Introduction

The elevation of egg production and the inhibition of incubation behavior are the aims of modern poultry production. Through PRL, dopamine D1 receptor (DRD1) was involved in the regulation of chicken reproductive behavior. PRL is postulated to play a critical role in the onset and maintenance of incubation behavior in birds [9,10,11,12] Some other factors, such as dopamine, have pivotal effects on PRL secretion [13,14,15]. Sartsoongnoen found that an association existed between DA neurons and the regulation of the reproductive system in Thai chickens [32] All these studies suggested that dopamine receptor was involved in the regulation of avian reproductive behavior. The DRD1 gene was chosen as a candidate gene to analyze the genetic effect on chicken egg production and broodiness traits

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Conclusion