Differential Gene Expression in High and Low active Animals.

Abstract

It is well established that physical activity levels are significantly controlled by genetic factors; however, the specific genes and genetic mechanisms involved in the regulation of physical activity is unknown. PURPOSE: To compare the gene expression pattern of several potential candidate genes in both nucleus accumbens (brain) and gastrocnemius/soleus (G/S muscle) between two differentially active inbred strains of mice. METHODS: From previous experiments, nucleus acumbens and G/S tissue were used from 11 high active C57L/J (LJ) mice (8 male, 3 female) and 13 low active C3H/HeJ (C3H) mice (8 male, 5 female). As we had seen previously, while there was no difference in the weight of the mice between strains (LJ=23.7±2.6 gms, avg±SD vs. C3H=23.3±3.6 gms), over 21 days of wheel running activity, the LJ ran farther (11.1±3.0 km/day vs. 1.6±2.1 km/day), longer (367.2±56.3 min/day vs. 92.3±112.7 min/day), and faster (30.3±5.9 m/min vs. 14.6±2.9 m/min) than the C3H mice proving that the LJ mice had higher daily activity than the C3H mice. Standard quantitative RT-PCR techniques developed in our lab were used to determine potential differential expression of previously suggested candidate genes: dopamine receptor 2 (Drd2), nescient helix-loop-helix 2 (Nhlh2), alpha actinin 2 (Actn2), alpha actinin 3 (Actn3), melanocortin-4-receptor (Mc4r), aromatase (Cyp19a1), leptin receptor (Lepr), myostatin (Mstn), 3'-phosphoadenosine 5'-phosphosulfate synthase 2 (Papss2), and glucose transporter 4 (Slc2a4). All expression data was log transformed for normality purposes and the values were compared using one-way ANOVAs between strains within each tissue with the alpha value set = 0.05. RESULTS: Of the comparisons in the brain tissue, Lepr (p=0.02) and Mstn (p=0.0001) were expressed at higher levels in the LJ mice. In the G/S tissue, Nhlh2 (p=0.05) and Slc2a4 (p=0.0005) were both expressed at higher levels in the LJ mice. CONCLUSIONS: Our data suggest that Lepr and Mstn in the nucleus accumbens and Nhlh2 and Slc2a4 in the G/S are differentially expressed in high and low active animals. While this data does not establish a role for any of these genes in activity regulation, it does show that there is an association between these genes and activity; an association that further research should delineate. Supported by NIH R01AR050085 and the Huffines' Institute.