The sleeping kidney: microRNA expression profiling of kidney tissue during daily torpor in mice

MicroRNA (miRNA), a class of short non-coding RNA, serves as a metabolically cheap and fast acting mechanism to inhibit translation of complementary mRNA. These molecules play a central role in regulating metabolic changes during torpor in small mammals, such as the house mouse (Mus musculus). The present study sequenced mouse kidney RNA to identify changes in miRNA expression in kidney, comparing active control mice (C57BL/6 strain) with mice in varying stages of torpor. Out of a total 962 miRNAs, 82 were differentially expressed when comparing torpid states to the control with 65, 14, and 2 miRNAs differentially expressed in deep torpor, early torpor, and recovery from torpor mice, respectively. In silico analysis of these targets demonstrated a clear downregulation of gene sets associated with cancer and active metabolism. This suggests that miRNA may play important roles in suppressing cell division and proliferation during torpor, along with maintaining a hypometabolic state. Machine learning techniques identified two specific miRNAs (miR-101c, miR-101a-3p) that can strongly distinguish between torpid and active states in kidney among other differentially regulated miRNA. The present study highlights the role of miRNA in transcriptional regulation of cell signaling and metabolic pathways in kidney throughout mouse torpor.