Livestock is an important food resource for the inhabitants of cold regions, such as northern Asia and alpine regions, where agriculture is limited. In these regions, cold stress largely affects livestock production, thereby reducing the productivity and survival of animals. Despite the importance of breeding cold-tolerant animals, few studies have investigated the effects of cold stress on cattle. Furthermore, whether severe cold stress alters gene expression or affects molecular genetic mechanisms remains unknown. Thus, we investigated gene expression changes in the peripheral blood samples of the Chinese Sanhe cattle exposed to severe cold. A total of 193 genes were found to exhibit significant alteration in expression (P < 0.05; fold change > 1.3), with 107 genes showing upregulation and 86 showing downregulation after cold exposure. The differences in the expression of 10 selected genes were further validated by real-time qRT-PCR. Further analyses showed that these differentially expressed genes (DEGs) were predominantly associated with important biological pathways and gene networks, such as lipid metabolism and cell death and survival, which are potentially associated with severe cold-stress resistance. Identification and description of these cold stress-induced DEGs might lead to the discovery of novel blood biomarkers that could be used to assess cold-stress resistance in cattle. To our knowledge, this is the first genomic evidence of differences in the transcript expression pattern in cattle exposed to severe cold stress. Our findings provide insights on the potential molecular mechanisms underlying cold-stress response in cattle.

ABSTRACT. Bovine mastitis is the most common and costly disease of dairy cattle. Cluster of differentiation 4 (CD4) is closely related to the immune response in mastitis. We quantified promoter CpG methylation levels of the CD4 gene in Chinese Holsteins with clinical mastitis (CM) and in healthy controls; these levels were quantitatively detected with bisulfite pyrosequencing assays and confirmed by cloning sequencing. We found that the bovine CD4 promoter had 16% more methyl groups in the cows with CM (75.0 ± 5.8%) compared to the controls (59.0 ± 8.5%). The decreased expression level of CD4 in CM cows may be downregulated by the increased DNA methylation levels in the CD4 promoter. Two-dimensional hierarchical clustering analyses showed large differences in promoter CD4 methylation between mastitic and healthy cows; the dendrogram clearly distinguished the cows with clinical mastitis from healthy controls based on methylation levels. The DNA methylation level of the CD4 gene was strongly influenced by mastitis status in all comparisons. We suggest that 6229 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 12 (4): 6228-6239 (2013) DNA methylation changes at the CD4 promoter in mastitic cows the DNA methylation level of the CD4 promoter can be used as a molecular marker for clinical mastitis in dairy cows.