Transcriptome Analysis of Hypothalamic Gene Expression during Daily Torpor in Djungarian Hamsters (Phodopus sungorus)

Abstract

Animals living at high or temperate latitudes are challenged by extensive changes in environmental conditions over seasons. Djungarian hamsters (Phodopus sungorus) are able to cope with extremely cold ambient temperatures and food scarcity in winter by expressing spontaneous daily torpor. Daily torpor is a circadian controlled voluntary reduction of metabolism that can reduce energy expenditure by up to 65% when used frequently. In the past decades it has become more and more apparent, that the hypothalamus is likely to play a key role in regulating induction and maintenance of daily torpor, but the molecular signals, which lead to the initiation of daily torpor, are still unknown. Here we present the first transcriptomic study of hypothalamic gene expression patterns in Djungarian hamsters during torpor entrance. Based on Illumina sequencing we were able to identify a total number of 284 differentially expressed genes, whereby 181 genes were up- and 103 genes down regulated during torpor entrance. The 20 most up regulated group contained eight genes coding for structure proteins, including five collagen genes, dnha2 and myo15a, as well as the procoagulation factor vwf. In a proximate approach we investigated these genes by quantitative real-time PCR (qPCR) analysis over the circadian cycle in torpid and normothermic animals at times of torpor entrance, mid torpor, arousal and post-torpor. These qPCR data confirmed up regulation of dnah2, myo15a, and vwf during torpor entrance, but a decreased mRNA level for all other investigated time points. This suggests that gene expression of structure genes as well as the procoagulation factor are specifically initiated during the early state of torpor and provides evidence for protective molecular adaptions in the hypothalamus of Djungarian hamsters including changes in structure, transport of biomolecules and coagulation.

Aberrant Expression of Collagen Gene Family in the Brain Regions of Male Mice with Behavioral Psychopathologies Induced by Chronic Agonistic Interactions

“…It was previously shown that the expression of Col1a1 and C ol3a1 genes was definitely observed in the pituitary glands of rats in the cells surrounding the capillaries, which are supposed to be the basic components of ECM [57]. Interestingly, similar to our results, the transcriptome analysis of hypothalamic gene expression during daily torpor in Djungarian hamsters revealed upregulation of the Col18a1, Col5a3, Col17a1, and Col20a1 genes, which was specific for torpor as compared to normothermic hamsters [58]. Based on these data, one might preliminarily have hypothesized that the Col genes are involved in natural regulation, for example, of physiological adaptation under repeated stress in mice, winter torpor in hamsters, or CNS pathologies.…”

Aberrant expression of collagen family genes in the brain regions developing under agonistic interactions in male mice

“…It was previously shown that mRNA expression for the Col1a1 and Col3a1 genes was distinctly observed in pituitary glands of rats in cells located around capillaries in the gland and were supposed to be the main components of the ECM [Fujiwara et al 2010]. Interestingly, in the hypothalamus of Djungarian hamsters, transcriptome analysis revealed upregulation of the Col18a1 and Col5a3 similar with our results, and increase of the Col17a1, Col20a1 and Col26a1 gene expression, which were specific for torpor in comparison with normothermic hamsters [Cubuk et al 2017]. The preliminary hypothesis from this part of data may be the recognition of involvement Col* genes into natural regulation, for example, of physiological adaptation under repeated stress in mice, winter torpor in hamsters, or CNS pathologies associated with collagens during neurodevelopment [Ali et al 1998;Cheng et al 2009;Lepelletier, et al 2017].…”

Hypothalamic control systems show differential gene expression during spontaneous daily torpor and fasting-induced torpor in the Djungarian hamster (Phodopus sungorus)

“…Hypothalamic blocks were cut from frozen brain samples as described in Cubuk et al ., 2017[43]. Hypothalamic samples were homogenized in 1 ml TriFast by using a micropestle.…”

“…All primers were designed on P . sungorus specific sequences obtained from our previous Illumina study [43]. 18–25 bp long primers were designed using the online tool OligoAnalyzer 3.1 with a melting temperature of 60°C ± 1.1°C.…”