RNA-Seq analysis of seasonal and individual variation in blood transcriptomes of healthy managed bottlenose dolphins.
The blood transcriptome can reflect both systemic exposures and pathological changes in other organs of the body because immune cells recirculate through the blood, lymphoid tissues, and affected sites. In human and veterinary medicine, blood transcriptome analysis has been used successfully to identify markers of disease or pathological conditions, but can be confounded by large seasonal changes in expression. In comparison, the use of transcriptomic based analyses in wildlife has been limited. Here we report a longitudinal study of four managed bottlenose dolphins located in Waikoloa, Hawaii, serially sampled (approximately monthly) over the course of 1 year to establish baseline information on the content and variation of the dolphin blood transcriptome.



Illumina based RNA-seq analyses were carried out using both the Ensembl dolphin genome and a de novo blood transcriptome as guides. Overall, the blood transcriptome encompassed a wide array of cellular functions and processes and was relatively stable within and between animals over the course of 1 year. Principal components analysis revealed moderate clustering by sex associated with the variation among global gene expression profiles (PC1, 22 % of variance). Limited seasonal change was observed, with < 2.5 % of genes differentially expressed between winter and summer months (FDR < 0.05). Among the differentially expressed genes, cosinor analysis identified seasonal rhythmicity for the observed changes in blood gene expression, consistent with studies in humans. While the proportion of seasonally variant genes in these dolphins is much smaller than that reported in humans, the majority of those identified in dolphins were also shown to vary with season in humans. Gene co-expression network analysis identified several gene modules with significant correlation to age, sex, or hematological parameters.



This longitudinal analysis of healthy managed dolphins establishes a preliminary baseline for blood transcriptome analysis in this species. Correlations with hematological parameters, distinct from muted seasonal effects, suggest that the otherwise relatively stable blood transcriptome may be a useful indicator of health and exposure. A robust database of gene expression in free-ranging and managed dolphins across seasons with known adverse health conditions or contaminant exposures will be needed to establish predictive gene expression profiles suitable for biomonitoring.
National Centers for Coastal Ocean Sciences, National Ocean Service, NOAA, 331 Fort Johnson Rd, Charleston, SC, 29412, USA. jeanine.morey@noaa.gov.
Jeanine S
JS
Morey
National Centers for Coastal Ocean Sciences, National Ocean Service, NOAA, 331 Fort Johnson Rd, Charleston, SC, 29412, USA.
Marion G
MG
Neely
Department of Life Sciences and Biotechnology, University of Ferrara, via L. Borsari 46, 44121, Ferrara, Italy.
Denise
D
Lunardi
Department of Computer Science, College of Charleston, Charleston, SC, 29424, USA.
Paul E
PE
Anderson
National Centers for Coastal Ocean Sciences, National Ocean Service, NOAA, 331 Fort Johnson Rd, Charleston, SC, 29412, USA.
Lori H
LH
Schwacke
Dolphin Quest, Waikoloa, Hawaii, USA.
Michelle
M
Campbell
National Centers for Coastal Ocean Sciences, National Ocean Service, NOAA, 331 Fort Johnson Rd, Charleston, SC, 29412, USA. vandolahfm@cofc.edu.|Present Address: Graduate Program in Marine Biology, University of Charleston, Charleston, SC, 29412, USA. vandolahfm@cofc.edu.
Frances M
FM
Van Dolah
D000818:Animals; D015415:Biomarkers; D050681:Bottle-Nosed Dolphin / Q000235:genetics*; D016000:Cluster Analysis; D019295:Computational Biology / Q000379:methods; D005260:Female; D020869:Gene Expression Profiling; D063990:Gene Ontology; D053263:Gene Regulatory Networks; D023281:Genomics / Q000379:methods; D006304:Health Status; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008297:Male; D058977:Molecular Sequence Annotation; D012621:Seasons; D017423:Sequence Analysis, RNA; D012737:Sex Factors; D059467:Transcriptome
D015415:Biomarkers
Blood transcriptome; Bottlenose dolphin; Globin-reduction; RNA-seq; Tursiops truncatus