Whole transcriptome analyses of six thoroughbred horses before and after exercising using RNA-Seq

We sequenced the whole mRNA of six thoroughbred horse (Equus caballus) blood and muscle tissues before and after exercising, generating a total of 1.3 billion short reads with 90-bp pair-end sequences from 24 samples. Comparing with current genome annotation, we identified 32,361 unigene clusters spanning 51.83 Mb that contained 11,933 (36.87%) annotated genes. More than 60% (20,428) unigene clusters did not match any current equine gene model. We identified 189,973 single nucleotide variations (SNVs) from the aligned sequences against the horse reference. Most SNVs (171,558 SNVs; 90.31%) were novel compared with over 1.1 million equine SNPs from two databases. Some genes have significantly different expression levels under different environment. We define those identical genes which have different expression levels are ‘differentially expressed’ and carried out differentially expressed gene analysis before and after exercise conditions. We discovered, 62 up- and 80 down-regulated genes in the blood and 878 up- and 285 down-regulated genes in the muscle from the 24 samples. Six out of 28 previously exercise-related known genes, HIF1A, ADRB2, PPARD, VEGF, TNC, and BDNF, were highly expressed in the muscle after exercise. We discovered 56 functionally unknown transcription factors that are probably associated with an early regulatory exercise mechanism from 91 differentially expressed transcription factors. We found interesting RNA expression patterns where different alternative splicing forms of the same gene showed reversed expressions before and after exercising. Overall design: whole mRNA sequencing profiles of six thoroughbred horse (Equus caballus) blood and muscle tissues before and after exercising