Selection for growth rate and body size have altered the expression profiles of somatotropic axis genes in chickens.

Junjing Jia,Irfan Ahmed,Ying Huang,Guiping Zhao,Zhiqiang Xu,Shanrong Wang,Qihua Li,Zhengtian Li,Kun Wang,Sumei Zhao,Dahai Gu,Tengfei Dou,Zhengchang Su,Lixian Liu,Mir Zulqarnain Talpur,Hua Rong,Huiquan Tong,Xiaohua Duan,Shixiong Yan,Yong Liu,M.f.w Te Pas ,Chao Ge

doi:10.1371/journal.pone.0195378

Abstract

The growth hormone / insulin-like growth factor-1 (GH/IGF-1) pathway of the somatotropic axis is the major controller for growth rate and body size in vertebrates, but the effect of selection on the expression of GH/IGF-1 somatotropic axis genes and their association with body size and growth performance in farm animals is not fully understood. We analyzed a time series of expression profiles of GH/IGF-1 somatotropic axis genes in two chicken breeds, the Daweishan mini chickens and Wuding chickens, and the commercial Avian broilers hybrid exhibiting markedly different body sizes and growth rates. We found that growth rate and feed conversion efficiency in Daweishan mini chickens were significantly lower than those in Wuding chickens and Avian broilers. The Wuding and Daweishan mini chickens showed higher levels of plasma GH, pituitary GH mRNA but lower levels of hepatic growth hormone receptor (GHR) mRNA than in Avian broilers. Daweishan mini chickens showed significantly lower levels of plasma IGF-1, thigh muscle and hepatic IGF-1 mRNA than did Avian broilers and Wuding chickens. These results suggest that the GH part of the somatotropic axis is the main regulator of growth rate, while IGF-1 may regulate both growth rate and body weight. Selection for growth performance and body size have altered the expression profiles of somatotropic axis genes in a breed-, age-, and tissue-specific manner, and manner, and alteration of regulatory mechanisms of these genes might play an important role in the developmental characteristics of chickens.

Highlights

Growth rate, body size and weight are determined by genotype as well as by environmental factors including nutrition
The Avian broilers approached to the adult body weight (BW) much faster (Fig 1A) than the two indigenous breeds, while Wuding chickens still showed a slow linear increase in BW and Daweishan mini chickens had an even slower linear increase in BW during the entire experimental period
Consistent with this observation, the Avian broilers showed a sharp peak of growth rate at week 6, which decreased sharply with increasing in age, while Wuding chickens showed a slow linear increase in growth rate and Daweishan mini chickens had an even slower increase in growth rate from weeks 2 to 8, which decreased with increasing in age (Fig 1B)

Summary

Introduction

Body size and weight are determined by genotype as well as by environmental factors including nutrition. Rodents, and other vertebrate species have shown unequivocally that the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) pathway of the somatotropic axis is the major controller of linear skeletal growth rate and body size [2,3,4,5,6,7,8,9,10]. In addition to its direct effects on target tissues, plasma GH can indirectly exert its functions by stimulating IGF-1 production and secretion in the liver. Both GH and IGF-1 can stimulate the growth of tissues by regulating protein, carbohydrate and lipid metabolisms. Alterations in these interrelated pathways can lead to both growth retardation or tissue proliferation and a variety of metabolic disturbances [2]

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