Project description:Identify shifts in gene expression relevant to torpor phenotypes and recovery following torpor in five tissues of the 13-lined ground squirrel. Sampled tissues and time points overlap with prior hibernation RNA-seq studies in 13-lined ground squirrel and other species, allowing for the analysis of conserved gene expression patterns in torpor.
Project description:Thirteen-lined ground squirrels (TLGS) are obligate hibernators that cycle between torpor (low metabolic rate and body temperature) and interbout euthermia (IBE; typical euthermic body temperature and metabolism) from late autumn to spring. Many physiological changes occur throughout hibernation, including a reduction in liver mitochondrial metabolism during torpor, which is reversed during arousal to interbout euthermia. Nuclear-encoded microRNA (small post-transcriptional regulator molecules) differ in abundance throughout TLGS hibernation and have been shown to regulate mitochondrial gene expression in mammalian cell culture (where they are referred to as mitomiRs). This study characterized differences in mitomiR profiles from TLGS liver mitochondria isolated during summer, torpor, and IBE, and predicted their mitochondrial targets. Using small RNA sequencing, differentially abundant mitomiRs were identified between hibernation states and, using qPCR analysis we quantified expression of predicted mitochondrial mRNA targets. Most differences in mitomiR abundances were seasonal (i.e. between summer and winter) with only one mitomiR differentially abundant between IBE and torpor. Multiple factor analysis revealed unique clustering of hibernation states, predominantly driven by mitomiR abundances, and nine of these differentially abundant mitomiRs had predicted mitochondrial RNA targets, including subunits of electron transfer system complexes I and IV, 12S rRNA and two tRNAs. Overall, mitomiRs were predicted to suppress expression of their mitochondrial targets and may have some involvement in regulating protein translation in mitochondria. This study found differences in mitomiR abundances between seasons and hibernation states of TLGS and suggests potential mechanisms in regulating the mitochondrial electron transfer system.
Project description:Hibernation is a seasonally adaptive strategy that allows hibernators to live through extreme cold condition and was viewed as a highly regulated physiological event. In spite of the profound reduction of blood flow to retina, hibernation causes no lasting retinal injury and hibernators show increased tolerance to ischemic insults during hibernation period. To understand the molecular changes of retina in response to hibernation we applied transcriptomic analysis to explore the changes of gene expression of 13-lined ground squirrel retinas during hibernation.