Abstract
Alternative splicing (AS) contributes to the complexity of the mammalian proteome and plays an important role in diseases, including infectious diseases. The differential AS patterns of these transcript sequences between the healthy (HS3A) and mastitic (HS8A) cows naturally infected by Staphylococcus aureus were compared to understand the molecular mechanisms underlying mastitis resistance and susceptibility. In this study, using the Illumina paired-end RNA sequencing method, 1352 differentially expressed genes (DEGs) with higher than twofold changes were found in the HS3A and HS8A mammary gland tissues. Gene ontology and KEGG pathway analyses revealed that the cytokine–cytokine receptor interaction pathway is the most significantly enriched pathway. Approximately 16k annotated unigenes were respectively identified in two libraries, based on the bovine Bos taurus UMD3.1 sequence assembly and search. A total of 52.62% and 51.24% annotated unigenes were alternatively spliced in term of exon skipping, intron retention, alternative 5′ splicing and alternative 3ʹ splicing. Additionally, 1,317 AS unigenes were HS3A-specific, whereas 1,093 AS unigenes were HS8A-specific. Some immune-related genes, such as ITGB6, MYD88, ADA, ACKR1, and TNFRSF1B, and their potential relationships with mastitis were highlighted. From Chromosome 2, 4, 6, 7, 10, 13, 14, 17, and 20, 3.66% (HS3A) and 5.4% (HS8A) novel transcripts, which harbor known quantitative trait locus associated with clinical mastitis, were identified. Many DEGs in the healthy and mastitic mammary glands are involved in immune, defense, and inflammation responses. These DEGs, which exhibit diverse and specific splicing patterns and events, can endow dairy cattle with the potential complex genetic resistance against mastitis.
Highlights
Bovine mastitis is an inflammation of the mammary gland invaded and infected by bacteria
The top 100 differentially expressed genes (DEGs) from the aforementioned genes were selected by the reads per kilobase of the exon model per million mapped reads (RPKM) calculation and further ranked based on the expression fold change value [log2(HS8A/HS3A)] of the genes (Table B in S2 File)
Out of the 100 top DEGs, 66% (66/100) genes were up-regulated in the HS8A, indicating that these genes play important roles bovine response to mastitis
Summary
Bovine mastitis is an inflammation of the mammary gland invaded and infected by bacteria. This disease results in considerable economic loss and engenders food safety and animal welfare concerns in the dairy industry [1]. Aureus), Streptococcus and Escherichia coli (E. coli). The major microorganisms responsible for mastitis are Staphylococcus aureus Obtaining insights into the processes of bovine defense and immune response to mastitis could provide new solutions to mastitis infection. A genetic strategy based on the molecular mechanism of cow mastitis demonstrates positive effects on the reduction of antibiotic use in dairy cow breeding and improves the safety of milk products [3]
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