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Title:Transcription profiles of differentially marbled beef cattle
Author(s):Clark, Daniel L.
Advisor(s):Carr, Tom R.
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Marbling
Transcription Profiles
Beef
Intramuscular Fat
Abstract:The objective of this study was to identify specific bovine genes expressed within skeletal muscle that are associated with the amount of intramuscular fat deposition. Twenty-eight steers and heifers were harvested at the University of Illinois Meat Science lab over the course of 4 months in early 2009. Samples of longissimus muscle were removed within 90 minutes post-mortem and stored at -80ºC prior to RNA extraction. At 24 h post-mortem, cattle were graded and pH, drip loss, color measurements were recorded. Steaks were removed for analysis of shear force and intramuscular fat content. Four pairs of animals were identified based on similar adjusted backfat thickness but differing in amounts of intramuscular fat within each pair. The high marbled group averaged 9.7% intramuscular fat while the low marbled group had just 4.8% intramuscular fat. RNA was extracted from muscle samples devoid of visible fat and microarray analysis was performed using the Agilent two-color bovine array using a paired design with dye flip. Based on this analysis, 9 genes were selected as differentially expressed due to intramuscular fat content, and expression was subsequently confirmed by qPCR. Expression levels of MYH3, HOXD10, MXRA8 and CASQ2 were increased in animals with high marbling, whereas levels of NPNT, MRC1, DNER, and CYPB4 were decreased in high marbling animals. The remaining gene, ACTN2 was determined to be a false positive from the array and was therefore excluded from further study. RNA was then extracted from the remaining animals and expression of the above 8 genes was determined by qPCR with 18srRNA as a housekeeping gene. Despite the positive results of the preliminary study, associations between gene expression and intramuscular fat content did not extend to the larger population of beef cattle. A significant negative association existed between expression of MRC1 and marbling level (P=0.04), but the amount of variability explained by this relationship was low (R2=0.17). Interestingly, expression of MRC1 was also negatively associated with a* (P=0.01, R=-0.49) and b* (P=0.02, R=-0.44). Therefore, this study was unable to identify a particular gene set whose expression correlated well with marbling levels in the larger population of beef cattle.
Issue Date:2010-08-20
URI:http://hdl.handle.net/2142/16885
Rights Information:Copyright 2010 Daniel L. Clark
Date Available in IDEALS:2010-08-20
Date Deposited:2010-08


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