Although excessive adiposity has become a major drawback in meat type chicken production, few of the genes involved in this process have been characterized so far. In order to identify putative genes involved in adiposity, we performed differential display analysis of RNAs extracted from the liver of divergently selected lean and fat chickens. Twenty-six differential products were selected and purified by single strand conformation polymorphism gel electrophoresis before sequencing and Northern blot analyses. An orthologous sequence of a mammalian cytochrome P450 2C subfamily member was proven to be differentially expressed in the liver of lean and fat chickens and could play an important role in the regulation of adiposity. In mammals, these genes are involved in detoxification of xenobiotics and metabolism of some important biological compounds. Four other genes were found differentially expressed to a lower extent. Some unidentified products were shown to be lean or fat specific, with sequence polymorphism and liver specific expression, strongly suggesting that the related gene could be directly involved in adiposity. Our data indicate that differential display can evidence genes with differential expression and with sequence polymorphism, making this strategy more accurate for differential analysis of messenger RNAs.
"Differential abundance of lipogenic genes in liver of the FL and LL chickens was determined earlier by differential mRNA display , quantitative RT-PCR [30,31] or targeted low-density array . Our preliminary analysis of the liver transcriptome in the FL and LL chickens during juvenile development revealed 1,805 differentially expressed (DE) genes . "
[Show abstract][Hide abstract] ABSTRACT: This descriptive study of the abdominal fat transcriptome takes advantage of two experimental lines of meat-type chickens (Gallus domesticus), which were selected over seven generations for a large difference in abdominal (visceral) fatness. At the age of selection (9 wk), the fat line (FL) and lean line (LL) chickens exhibit a 2.5-fold difference in abdominal fat weight, while their feed intake and body weight are similar. These unique avian models were originally created to unravel genetic and endocrine regulation of adiposity and lipogenesis in meat-type chickens. The Del-Mar 14K Chicken Integrated Systems microarray was used for a time-course analysis of gene expression in abdominal fat of FL and LL chickens during juvenile development (1--11 weeks of age).
Microarray analysis of abdominal fat in FL and LL chickens revealed 131 differentially expressed (DE) genes (FDR<=0.05) as the main effect of genotype, 254 DE genes as an interaction of age and genotype and 3,195 DE genes (FDR<=0.01) as the main effect of age. The most notable discoveries in the abdominal fat transcriptome were higher expression of many genes involved in blood coagulation in the LL and up-regulation of numerous adipogenic and lipogenic genes in FL chickens. Many of these DE genes belong to pathways controlling the synthesis, metabolism and transport of lipids or endocrine signaling pathways activated by adipokines, retinoid and thyroid hormones.
The present study provides a dynamic view of differential gene transcription in abdominal fat of chickens genetically selected for fatness (FL) or leanness (LL). Remarkably, the LL chickens over-express a large number of hemostatic genes that could be involved in proteolytic processing of adipokines and endocrine factors, which contribute to their higher lipolysis and export of stored lipids. Some of these changes are already present at 1 week of age before the divergence in fatness. In contrast, the FL chickens have enhanced expression of numerous lipogenic genes mainly after onset of divergence, presumably directed by multiple transcription factors. This transcriptional analysis shows that abdominal fat of the chicken serves a dual function as both an endocrine organ and an active metabolic tissue, which could play a more significant role in lipogenesis than previously thought.
"Many studies have been performed to investigate the differential expression of genes involved in lipid synthesis and secretion in the liver of lean and fat chickens (Daval et al., 2000; Carre et al., 2002; Bourneuf et al., 2006). Because most of these researches were performed at 8 weeks of age only, few studies were conducted to analyze the temporal expression of genes in the liver, so the genetic mechanisms that are involved in adiposity during the developmental stage are largely unknown. "
[Show abstract][Hide abstract] ABSTRACT: Excessive accumulation of lipids in the adipose tissue is one of the main problems faced by the broiler industry nowadays. In chicken, lipogenesis occurs essentially in the liver, in which much of the triglycerides that accumulate in avian adipose tissue are synthesized. In order to better understand the gene expression and its regulation in chicken liver, the gene expression profiles of liver at developmental stages of chicken (1 week, 4 weeks and 7 weeks of age) were investigated and differentially expressed genes between lean and fat chicken lines divergently selected for abdominal fat content for eight generations were screened. Our data indicated that 4 weeks of age was a very important stage on chicken liver lipogenesis compared to 1 week and 7 weeks of age, and the glycometabolism in chicken liver could be related to lipid metabolism and the difference of glycometabolism could be another potential reason for the fat and lean phenotype occurrence besides the difference of lipogenesis in chicken liver. Our result have established groundwork for further study of the basic genetic control of chicken obesity and will benefit chicken research communities as well as researches that use chicken as a model organism for developmental biology and human therapeutics.
"The exact mechanism responsible for differential expression in these lines remains to be determined but could be linked to the regulation of lipogenic gene expression, as suggested by SREBP1 and HNF4 differential expression. As expected (Carré et al., 2002), G1-8B or namely CYP2C45 (Baader et al., 2002) expression was found inversely correlated to adipose tissue in lean and fat chickens. Chicken CYP2C45 and mammalian CYP2C sub-family members are well known for xenobiotics detoxification role (Baader et al., 2002) but also play a role in bio-transformation of important biological regulators such as steroids and poly-unsaturated fatty acids. "
[Show abstract][Hide abstract] ABSTRACT: Excessive adiposity has become a major drawback in meat-type chicken production. However, few studies were conducted to analyze the liver expression of genes involved in pathways and mechanisms leading to adiposity. A previous study performed by differential display on RNAs extracted from chicken livers from lean and fat lines allowed us to isolate cDNA products of genes with putative differential expression. In this study, a cDNA microarray resource was developed from these products together with cDNAs from genes involved in or related to lipid metabolism. This resource was used to analyze gene expression in the liver from lean and fat chickens. Some genes were found with a difference in expression between lean and fat animals and/or correlated to adipose tissue weight. Cytochrome P450 2C45, thought to play a role in biotransformation of steroids and poly-unsaturated fatty acids, was more expressed in lean chickens whereas fatty acid synthase, stearoyl-CoA desaturase, sterol response element binding factor 1 and hepatocyte nuclear factor 4, respectively involved in lipogenesis and its regulation, were more expressed in fat chickens. These results indicate that mechanisms involved in the expression and regulation of lipogenic genes could play a key role in fatness ontogenesis in chickens from lean and fat lines.
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