Genetic Parameters for Yolk Cholesterol and Transcriptional Evidence Indicate a Role of Lipoprotein Lipase in the Cholesterol Metabolism of the Chinese Wenchang Chicken

Abstract

The yolk cholesterol has been reported to affect egg quality and breeding performance in chickens. However, the genetic parameters and molecular mechanisms regulating yolk cholesterol remain largely unknown. Here, we used the Wenchang chicken, a Chinese indigenous breed with a complete pedigree, as an experimental model, and we examined 24 sire families (24 males and 240 females) and their 362 daughters. First, egg quality and yolk cholesterol content were determined in 40-week-old chickens of two consecutive generations, and the heritability of these parameters was analyzed using the half-sib correlation method. Among first-generation individuals, the egg weight, egg shape index, shell strength, shell thickness, yolk weight, egg white height, Haugh unit, and cholesterol content were 45.36 ± 4.44 g, 0.81 ± 0.12, 3.07 ± 0.92 kg/cm2, 0.340 ± 0.032 mm, 15.57 ± 1.64 g, 3.36 ± 1.15 mm, 58.70 ± 12.33, and 274.3 ± 36.73 mg/egg, respectively. When these indexes were compared to those of the following generation, no statistically significant difference was detected. Although yolk cholesterol content was not associated with egg quality in females, an increase in yolk cholesterol content was correlated with increased yolk weight and albumin height in sire families (p < 0.05). Moreover, the heritability estimates for the yolk cholesterol content were 0.328 and 0.530 in female and sire families, respectively. Therefore, the yolk cholesterol content was more strongly associated with the sire family. Next, chickens with low and high yolk cholesterol contents were selected for follicular membrane collection. Total RNA was extracted from these samples and used as a template for transcriptional sequencing. In total, 375 down- and 578 upregulated genes were identified by comparing the RNA sequencing data of chickens with high and low yolk cholesterol contents. Furthermore, Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated the involvement of energy metabolism and immune-related pathways in yolk cholesterol deposition. Several genes participating in the regulation of the yolk cholesterol content were located on the sex chromosome Z, among which lipoprotein lipase (LPL) was associated with the peroxisome proliferator-activated receptor signaling pathway and the Gene Ontology term cellular component. Collectively, our data suggested that the ovarian steroidogenesis pathway and the downregulation of LPL played critical roles in the regulation of yolk cholesterol content.

Silencing acetyl-CoA carboxylase A and sterol regulatory element-binding protein 1 genes through RNAi reduce serum and egg cholesterol in chicken

“…An amount of 0.1 g of egg powder was taken in 1.5 ml eppendorf tube. A volume of nine times of anhydrous ethanol was added to the tube and the mixture was mechanically homogenized for 30 s using vortex 31 . Then, the mixture was centrifuged at 2500 g for 10 min at 4 °C.…”

Green Tea Powder Decreased Egg Weight Through Increased Liver Lipoprotein Lipase and Decreased Plasma Total Cholesterol in an Indigenous Chicken Breed

“…Reduced plasma VLDL concentration might decrease egg yolk weight. The yolk weight is positively correlated with egg weight [25]. Thus, a significantly lower egg weight detected in chickens from the GTP group might be because of the decreased plasma lipid concentration.…”

“…During egg laying, lipogenic, and genes related to egg yolk formation in the liver were highly expressed, which caused high plasma lipid concentration in layers [24]. High plasma VLDL will then pass through the granulose basal lamina and reach the receptors located on the oocyte surface for providing yolk precursors [25]. Reduced plasma VLDL concentration might decrease egg yolk weight.…”

Comparative Yolk Proteomic Analysis of Fertilized Low and High Cholesterol Eggs during Embryonic Development

“…Eggs quality was analyzed according to the Chen et al procedure [ 32 ]. Egg weight was determined by digital scale weight balance (accuracy: 0.01 g) and egg strength was measured by eggshell force gauge (Robotmation Co., Ltd., Tokyo, Japan).…”

“…For egg yolk cholesterol analysis, the Chen et al procedure was followed [ 32 ]. Briefly, 0.1 g of the yolk sample was taken in a 1.5 mL tube with anhydrous ethanol and homogenized mechanically for 30 s at 50 Hz.…”