Relative changes in mRNA transcript levels of <i>gata4</i> and <i>nkx2–5</i> in the heart of <i>I. tridecemlineatus</i> over the torpor-arousal cycle.

<p>Sampling points were: euthermic in the cold room (EC), entrance into torpor (EN), early torpor (ET), late torpor (LT), early arousal (EA), and interbout arousal (IA); see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117747#sec002" target="_blank">Materials and Methods</a> for more extensive explanations. Representative bands on agarose gels are shown for selected pairs of sampling points that are labeled to the left (lanes 1–4) and right (lanes 5–8) of the gel. Transcript levels for each gene were standardized against band densities for <i>α-tubulin</i> amplified from the same sample. Relative transcript levels are shown in histograms expressed as mean standardized band densities (± S.E.M., n = 4 independent RNA isolations from different animals) for each of the six sampling points. Data were analyzed using analysis of variance with a post hoc Tukey test (p<0.05); for each gene, values that are not statistically different from each other share the same letter notation.</p

Relative changes in the protein levels of Troponin I, troponin C, and ANP in the heart of <i>I. tridecemlineatus</i> over the torpor-arousal cycle.

<p>Other information as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117747#pone.0117747.g002" target="_blank">Fig. 2</a>.</p

Relative changes in binding of the transcription factors GATA4 and Nkx2–5 as well as the phosphorylated form of GATA4 (Ser 261) to DNA binding elements in the heart of <i>I. tridecemlineatus</i> over the torpor-arousal cycle.

<p>Optical density readings were corrected by subtraction of blanks containing no protein and values were expressed relative to EC. Histograms show mean relative values ± S.E.M., n = 4 independent biological replicates for each of the five experimental conditions. Other information as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117747#pone.0117747.g001" target="_blank">Fig. 1</a>.</p

The regulation of troponins I, C and ANP by GATA4 and Nkx2-5 in heart of hibernating thirteen-lined ground squirrels, Ictidomys tridecemlineatus

Hibernation is an adaptive strategy used by various mammals to survive the winter under situations of low ambient temperatures and limited or no food availability. The heart of hibernating thirteen-lined ground squirrels (Ictidomys tridecemlineatus ) has the remarkable ability to descend to low, near 0°C temperatures without falling into cardiac arrest. We hypothesized that the transcription factors GATA4 and Nkx2-5 may play a role in cardioprotection by facilitating the expression of key downstream targets such as troponin I, troponin C, and ANP (atrial natriuretic peptide). This study measured relative changes in transcript levels, protein levels, protein post-translational modifications, and transcription factor binding over six stages: euthermic control (EC), entrance into torpor (EN), early torpor (ET), late torpor (LT), early arousal (EA), and interbout arousal (IA). We found differential regulation of GATA4 whereby transcript/protein expression, post-translational modification (phosphorylation of serine 261),

Relative changes in the protein levels of the transcription factors GATA4 and Nkx2–5 as well as the phosphorylation state of GATA4 (Ser 261) in the heart of <i>I. tridecemlineatus</i> over the torpor-arousal cycle.

<p>Representative Western blots are shown for selected pairs of sampling points that are labeled to the left (lanes 1–4) and right (lanes 5–8) of the gel. Histograms show mean standardized band densities (± S.E.M., n = 4 independent protein isolations from different animals). Other information as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117747#pone.0117747.g001" target="_blank">Fig. 1</a>.</p

Relative changes in mRNA transcript levels for <i>troponin I</i>, <i>troponin C</i> and <i>anp</i> in the heart of <i>I. tridecemlineatus</i> over the torpor-arousal cycle.

<p>Other information as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117747#pone.0117747.g001" target="_blank">Fig. 1</a>.</p