Comparisons of lung and gluteus transcriptome profiles between yaks at different ages

Abstract

The yak, Bos grunniens, is the only large mammal in the Qinghai-Tibet Plateau and has been bred to provide meat, milk, and transportation. Previous studies indicate that the immune system contributes to the yak's adaptation to high-altitude environments. In order to further investigate changes in immune function during yak development, we compared the transcriptome profiles of gluteus and lung tissues among yaks at 6, 30, 60, and 90 months of age. Analyses of significantly differentially expressed genes (DEGs) in lung tissues revealed that immune function was more activated at 6-months and less activated at 90-months than in the 30 and 60-month-old animals. DEG exploration in gluteal tissues revealed that immune functions were more highly activated at both 6 and 90-months, compared with 30 and 60-months. Immune system activation in the muscle and lung tissues of 30-month-old yaks may increase their resistance to infections, while decreased may be due to aging. Furthermore, the higher immune activation status in the gluteal tissues in 90-month-old yaks could be due to muscle injury and subsequent regeneration, which is supported by the fact that 5 unigenes related with muscle injury and 3 related to muscle regeneration displayed greater expression levels at 90-months than at 30 and 60-months. Overall, the present study highlights the important role of the immune system in yak development, which will facilitate future investigations.

Figure 1

Real-time quantitative PCR validation of differentially expressed genes. H2B: histone H2B; H2A: histone H2A; CDK1: cyclin-dependent kinase 1; CD79A: CD79A antigen; CCNA2: cyclin (A) CD20: B-lymphocyte antigen CD20; LIPE: Hormone-sensitive lipase; FGB: Fibrinogen; AQP12: Aquaporin 12; TetA: Tetracycline resistance protein; AAAAD: AAA+ ATPase domain; MCHR1: Melanin-concentrating hormone 1. Student’s t-tests were performed to determine differences in each unigene between age groups. Different letters above the bars indicated significant differences.

Figure 2

Relative expression levels of differentially expressed genes associated with immune function in lung tissue. All data were calculated based on the FPKM values and were normalized by defining the highest FPKM value among the four age groups as one. Errors donate standard deviation. Student’s t-tests were performed to determine differences in each unigene between age groups. *Significantly different from 6-month old group (P < 0.05). ^#Significantly different from 90-month (P < 0.05).

Figure 3

Relative expression levels of differentially expressed genes associated with the cell cycle in lung tissue. All data were calculated based on the FPKM values and were normalized by defining the highest FPKM value among the four age groups as one. Errors donate standard deviation. Student’s t-tests were performed to determine differences in each unigene between age groups. *Significantly different from 6-month old group (P < 0.05). ^#Significantly different from 90-month old group (P < 0.05).

Figure 4

Relative expression levels of differentially expressed genes associated with immune function in gluteal tissue. All data were calculated based on the FPKM values and were normalized by defining the highest FPKM value among the four age groups as one. Errors donate standard deviation. Student’s t-tests were performed to determine differences in each unigene between age groups. *Significantly different from 6-month old group (P < 0.05). ^#Significantly different from 90-month old group (P < 0.05).