Hypoxic response patterns in lung tissue: An integrated analysis of comparative physiological and transcriptomic studies from Neodon fuscus and Lasiopodomys brandtii

Oxygen (O₂) is essential for the survival and reproduction of most species. However, in recent years, with global climate change and the increasing impact of human activities on the ecosystem, the frequency of extreme environmental events, such as heat waves, cold waves, droughts, and floods, has increased, resulting in dramatic changes in environmental oxygen concentration (hypoxic environment, etc.), threatening the survival of animals and pushing them toward extreme adaptation. In this context, how organisms, especially those with differences in original habitats, adapt to low oxygen environment is particularly important. In this study, we systematically analyzed hypoxic response patterns in lung tissues of small rodents Neodon fuscus, Lasiopodomys brandtii, and Mus musculus with different experiences of natural hypoxia tolerance through laboratory simulation of hypoxia environment, combined with hematological, histological, and transcriptomic analysis. Our results show that all three species exhibit increased antioxidant defense and damage repair ability to a certain extent under hypoxia, although the specific molecular mechanisms are not the same. L. brandtii showed better damage repair ability than the others, which is likely to be closely related to the intermittent hypoxia environment experienced in the natural environment, and genes such as Glrx5, Prdx2, Col1a1, Lama1, and Eln may play a crucial role in this process. In addition, we found that both N. fuscus and L. brandtii appropriately enhanced oxygen transport in tissues under hypoxic conditions, with a series of functional genes related to hemoglobin synthesis and vascular smooth muscle contraction were significantly up-regulated in both species of voles, such as Actg2, Ptgir, Alas2, Hba, Hbb and Bpgm. Our results, to a certain extent, reveal the differences and similarities of hypoxic response patterns in lung tissues of small rodents with different hypoxic life histories and provide a relatively perfect analytical paradigm for related studies.

Diverse energy metabolism patterns in females in Neodon fuscus, Lasiopodomys brandtii, and Mus musculus revealed by comparative transcriptomics under hypoxic conditions

The effects of global warming and anthropogenic disturbance force animals to migrate from lower to higher elevations to find suitable new habitats. As such migrations increase hypoxic stress on the animals, it is important to understand how plateau- and plain-dwelling animals respond to low-oxygen environments. We used comparative transcriptomics to explore the response of Neodon fuscus, Lasiopodomys brandtii, and Mus musculus skeletal muscle tissues to hypoxic conditions. Results indicate that these species have adopted different oxygen transport and energy metabolism strategies for dealing with a hypoxic environment. N. fuscus promotes oxygen transport by increasing hemoglobin synthesis and reduces the risk of thrombosis through cooperative regulation of genes, including Fga, Fgb, Alb, and Ttr; genes such as Acs16, Gpat4, and Ndufb7 are involved in regulating lipid synthesis, fatty acid β-oxidation, hemoglobin synthesis, and electron-linked transmission, thereby maintaining a normal energy supply in hypoxic conditions. In contrast, the oxygen-carrying capacity and angiogenesis of red blood cells in L. brandtii are promoted by genes in the CYP and COL families; this species maintains its bodily energy supply by enhancing the pentose phosphate pathway and mitochondrial fatty acid synthesis pathway. However, under hypoxia, M. musculus cannot effectively transport additional oxygen; thus, its cell cycle, proliferation, and migration are somewhat affected. Given its lack of hypoxic tolerance experience, M. musculus also shows significantly reduced oxidative phosphorylation levels under hypoxic conditions. Our results suggest that the glucose capacity of M. musculus skeletal muscle does not provide sufficient energy during hypoxia; thus, we hypothesize that it supplements its bodily energy by synthesizing ketone bodies. For the first time, we describe the energy metabolism pathways of N. fuscus and L. brandtii skeletal muscle tissues under hypoxic conditions. Our findings, therefore, improve our understanding of how vertebrates thrive in high altitude and plain habitats when faced with hypoxic conditions.

Complete mitochondrial genomes confirm the generic placement of the plateau vole, Neodon fuscus

The plateau vole, Neodon fuscus is endemic to China and is distributed mainly in Qinghai Province. It is of public health interest, as it is, a potential reservoir of Toxoplasma gondii and the intermediate host of Echinococcus multilocularis. However, genetic data of this species are lacking, and its name and taxonomy are still a controversy. In the present study, we determined the nucleotide sequence of the entire mitochondrial (mt) genome of N. fuscus and analyzed its evolutionary relationship. The mitogenome was 16328 bp in length and contained 13 protein-coding genes, 22 genes for transfer RNAs (tRNA), two ribosomal RNA genes and two major noncoding regions (O_L region and D-loop region). Most genes were located on the heavy strand. All tRNA genes had typical cloverleaf structures except for tRNA^{Ser (GCU)}. The mt genome of N. fuscus was rich in A+T (58.45%). Maximum likelihood (ML) and Bayesian methods yielded phylogenetic trees from 33 mt genomes of Arvicolinae, in which N. fuscus formed a sister group with Neodon irene and Neodon sikimensis to the exclusion of species of Microtus and other members of the Arvicolinae. Further phylogenetic analyses (ML only) based on the cytb gene sequences also demonstrated that N. fuscus had a close relationship with N. irene. The complete mitochondrial genome was successfully assembled and annotated, providing the necessary information for the phylogenetic analyses. Although the name Lasiopodomys fuscus was used in the book ‘Wilson & Reeder’s Mammal Species of the World’, we have confirmed here that its appropriate name is N. fuscus through an analysis of the evolutionary relationships.