Next-Generation Sequencing Identifies Differentially Expressed Genes in Embryonic Hearts Following Caffeine Treatment

Purpose: This study aimed to identify differentially expressed genes including alternative splice variants in embryonic ventricles following in utero caffeine treatment. Methods: Pregnant CD-1 mice were injected with 20 mg/kg of caffeine or vehicle control daily from embryonic day (E) 6.5-9.5. On E10.5, total RNA was isolated from embryonic ventricles and used for transcriptomic RNA sequencing with Illumina HiSeq 2000 (1X75bp). RNA-seq reads were aligned to the mouse genome (build mm10) with the Tophat for Illumina tool in the PSU galaxy platform. Counting and annotation of RNA-seq reads as well as alternative splicing analysis were performed with Partek Genomics Suite version 6.11. Differential expression of gene and transcript reads between treatments was analyzed with R package EdgeR. Genes/transcripts with false discovery rate (FDR) less than 0.05 and absolute fold change greater than 1.5 were considered as significant. Differentially expressed genes were defined as genes with altered expression at either gene or transcript level. Unique differentially expressed genes were identified by combining the results from annotations with the RefSeq Transcripts (2013-05-10) or Ensembl Transcripts release 71 databases. Results: Differential expression analysis revealed that 59 genes and 451 transcripts were significantly up-regulated, and 65 genes and 398 transcripts were down-regulated by prenatal caffeine treatment (fold change >1.5 or <-1.5; p-value with FDR<0.05). In total, 900 unique genes were identified to have altered expression either at the gene or transcription level. Further analysis with Partek GS revealed that 183 genes had abnormal alternative splicing at the exon level after in utero caffeine treatment. Conclusions: In utero caffeine exposure caused gene expression changes in embryonic ventricles and these changes may lead to long-term effects on cardiac morphology and function. Overall design: mRNA profiles in E10.5 heart ventricles treated with caffeine were generated by deep sequencing (n=2 for vehicle, n=3 for caffeine), using Illumina HiSeq 2000.

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Fang X, Mei W, Barbazuk WB, Rivkees SA, Wendler CC