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Title:Reductions in expression of growth regulating genes are observed in skeletal muscle and organs with age
Author(s):Jones, Jennifer
Advisor(s):Dilger, Anna C.
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
gene expression
Abstract:A set of growth regulating genes has been identified that decline in expression in organs with age. This downregulation is thought to coordinate organ growth cessation observed as humans and animals mature. The objective of this study was to observe the expression of 7 of these growth regulating genes (Ezh2, Gpc3, Mdk, Mest, Mycn, Peg3, and Plagl1) in male and female skeletal muscle, heart, and liver with age. It was hypothesized that the expression of these genes would differ not only between sexes, but also between tissues. Female and male C57BL/6J mice were sacrificed at 1, 7, 21, 35, and 49 days of age. Samples collected consisted of heart and liver from all mice, all muscles from both hind limbs of 1- and 7-day-old mice, and specific muscles (bicep femoris, gastrocnemius, tibialis anterior, and triceps brachii) from 21-, 35-, and 49-day-old mice. Expression was determined by quantitative real-time PCR, normalized to Rn18s, standardized to a single 1-day-old male liver sample present on each plate, and compared to the average of 1-day-old male expression for each tissue. Data were analyzed using the Proc Mixed procedure in SAS as repeated measures with significant differences (P < 0.05) determined by a Bonferroni-adjusted pdiff. Orthogonal contrasts were used to differentiate between linear, quadratic, and cubic patterns of expression among tissues. In general, expression declined from 1 or 7 days of age when compared to 49 days of age for all the genes in all the tissues except for expression of Ezh2 and Mycn, which was not altered by age in liver. Some differences in expression were observed between sexes with the majority of the differences occurring at 49 days. Expression was usually increased in females compared with males at this time point. Occasionally, males had greater expression than females; this was observed in liver at 1 day of age for Gpc3, Mest, and Plagl1 and muscle at 35 days of age for Mest. There were some similarities in the patterns of gene expression between muscle and heart or liver, but, there was not a single gene that had the same pattern of expression in all 3 tissues. Overall, these data suggest that the downregulation of these growth regulating genes with age might play a role in the coordinated cessation of muscle growth similar to organ growth with limited differences between sexes.
Issue Date:2013-02-03
Rights Information:Copyright 2012 Jennifer Jones
Date Available in IDEALS:2013-02-03
Date Deposited:2012-12

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