The Research On Molecular Regulatory Network And Gene Related Intramuscular Fat Deposition In Chicken

Intramusclar fat (IMF) content is one of pivotal traits of meat quality. In this article, the deposition pattern and mechanism of IMF, the differentially expressed genes and the construction of molecular regulatory network related to IMF in breast tissue and identification of new functional genes related to lipid metabolism were studied using Arbor Acres (AA, fast-growing breed) and Beijing-you chicken (BJY, slow-growing china local breed) as contrastive experimental materials. There are three experimental parts in this study.Trail 1: The preliminary exploration on deposition pattern and its molecular mechanism of IMF in breast tissues of fast-growing breed and local breed with the development. Two broiler breeds of female hatchlings (BJY 60 and AA 48 individuals, respectively) were randomly assigned to 5 and 4 pens of 12 birds in each breed. The experimental period was divided into 5 phases: 1, 2-21 d, 22-42 d, 43-90 d, and 91-120 (only for BJY) d. Birds were raised in the same nutrition standard and an environmentally management. Feed and water were provided ad libitum during the experiment. At 1, 21, 42, 90 and 120 days of age, 6 birds of each group with similar weight from two breeds were slaughtered, respectively. The results show that 1) the contents of IMF and TG, and TG/PLIP ratio were continued increased and had a peak at the 90 day of BJY chickens and 42 day of AA chickens. And PLIP content would gradually increase with the development. 2) There had the extremely significantly positive correlation between total fat in liver with the IMF content in breast tissue and FAS gene expression level in liver. 3) The enzyme activities of LPL, FAS and HSL would no significant effect to the differences of IMF in breast tissue or total fat in liver at different days.Trail 2: The differentially expressed genes and the construction of molecular regulatory network related to IMF in breast tissue. Using the chicken cDNA expression microarray in tissue, this trail systematic studied the differentially expressed genes profiles and molecular regulatory network on the difference of IMF at different days of BJY and AA chickens, and between IMF in breast and thigh tissues and abdominal fat of BJY chickens. The feeding, management and slaughtering of experimental animals are same to trail 1. After the total RNA of all samples was extracted, the RNA mixed pool of tissues was built respectively at different day age in two breeds to use in the microarray analysis.The results show that: 1) With the breast tissue development, the numbers of the differentially expressed genes, differentially expressed genes related to lipid metabolism, the differentially expressed genes with the correlation to lipid biochemical differences in BJY and AA chickens were 4255 and 3182, 59 and 70, 15 and 8, respectively. These genes mainly were the upstream regulatory genes. And the common differentially expressed genes with the correlation to lipid biochemical differences in BJY and AA chickens were CETP, GLTPD1 and SNX4. 2)Except for the lipid metabolic pathway (such as the PPAR signaling pathway), some pathways involved in the actin synthesis (such as Tight junction, ECM-receptor interaction, focal adhesion, regulation of actin cytoskeleton, et al.) may affect the IMF deposition. 3) Comparison between breast, thigh and abdominal fat tissues, the numbers of common differentially expressed genes and the differentially expressed genes related to lipid metabolism were ?499 and 107, these genes mainly were the downstream regulatory genes and would be the reason on the difference of lipid traits between breast, thigh and abdominal fat tissues. 4)Comparison between breast, thigh and abdominal fat tissues, the signaling pathways which the differentially expressed genes involved in, included the ECM-receptor interaction, tight junction, glycolysis/gluconeogenesis, regulation of actin cytoskeleton, Wnt signaling pathways, focal adhesion, CAMs and ErbB signaling pathway, except for the lipid metabolic pathway (such as the PPAR signaling pathway). They may affect the lipid deposition.Trail 3: The function identification of new candidate genes, FSH and FSHR, related to lipid metabolism. In this trail, the tissue samples come from the different days (1, 21, 42, 90 and 120 d) of BJY chickens in trail 1. Some researches were performed on the expression validation of FSH and FSHR gene at tissue level, the function identification of FSH and FSHR at cell level, and the signaling pathways involved in lipid metabolism which was regulated by FSH and FSHR, respectively. The results show that: 1) FSH gene did not express in fat tissue of chicken, but exist FSH protein. FSHR genes could express in fat tissue. 2) FSH can promote the lipid deposition in fat tissue of chicken by raising the FSHR gene expression. 3) FSH would influence the lipid metabolism by regulating the PPAR signaling pathway, retinol metabolic pathway and fatty acid metabolic pathway.