Roles of hypothalamic neuropeptide gene expression in body mass regulation in Eothenomys miletus (Mammalia: Rodentia: Cricetidae)

Molecular genetics and quantitative traits divergence among populations of Eothenomys miletus from Hengduan Mountain region

An important objective of evolutionary biology has always been to grasp the evolutionary and genetic processes that contribute to speciation. The present work provides the first detailed account of the genetic and physiological adaptation to changing environmental temperatures as well as the reasons causing intraspecific divergence in the Eothenomys miletus from the Hengduan Mountain (HM) region, one of the biodiversity hotspots. One hundred sixty-one E. miletus individuals from five populations in the HM region had their reduced-representation genome sequenced, and one additional individual from each community had their genomes resequenced. We then characterized the genetic diversity and population structure of each population and compared the phenotypic divergence in traits using neutral molecular markers. We detected significant phenotypic and genetic alterations in E. miletus from the HM region that were related to naturally occurring diverse habitats by combining morphometrics and genomic techniques. There was asymmetric gene flow among the E. miletus populations, indicating that five E. miletus populations exhibit an isolation-by-island model, and this was supported by the correlation between F ST and geographic distance. Finally, P ST estimated by phenotypic measures of most wild traits were higher than differentiation at neutral molecular markers, indicating directional natural selection favoring different phenotypes in different populations must have been involved to achieve this much differentiation. Our findings give information on the demographic history of E. miletus, new insights into their evolution and adaptability, and literature for studies of a similar nature on other wild small mammals from the HM region.

Comparative research of intestinal microbiota diversity and body mass regulation in Eothenomys miletus from different areas of Hengduan mountain regions

In order to investigate the effects of different areas on intestinal bacterial diversity and body mass regulation in Eothenomys miletus from Hengduan mountain regions, and to explore the community structure and diversity of intestinal microflora and their role in body mass regulation. E. miletus was collected from five areas including Deqin (DQ), Xianggelila (XGLL), Lijiang (LJ), Jianchuan (JC), and Dali (DL), we used 16S rRNA sequencing technology combined with physiological and morphological methods to study the intestinal microbiota diversity, abundance and community structure of the intestinal bacteria in winter, and to explore the influence of geographical factors, physiological indicators including food intake, resting metabolic rate (RMR), non-shivering thermogenesis (NST), neuropeptide Y (NPY), Agouti-Related Protein (AgRP), proopiomelanocortin (POMC), cocaine and amphetamine regulated transcription peptide (CART), and morphological indicators including body mass, body length and other nine indicators on the intestinal microflora diversity in E. miletus. The results showed that there were significant differences in metabolic indexes such as RMR, NST, NPY, AgRP, and morphological indexes such as body length, tail length and ear length among the five regions. Bacterial community in intestinal tract of E. miletus mainly includes three phyla, of which Firmicutes is the dominant phyla, followed by Bacteroidetes and Tenericutes. At the genus level, the dominant bacterial genera were S24-7(UG), Clostridiales (UG), and Lachnospiraceae (UG), etc. α diversity of intestinal microorganisms in DL and JC were significantly different from that in the other three regions. Genera of intestinal microorganisms in DL and JC were also the most. Moreover, Bacteroides, Ruminococcus, and Treponema could affect energy metabolism in E. miletus, which were closely related to the environment in which they lived. All of these results indicated that different areas in Hengduan Mountain had certain effects on the structure of intestinal microbial community in E. miletus, which were responded positively to changes in food abundance and other environmental factors. Furthermore, Firmicutes and Bacteroidetes play an important role in the body mass regulation in E. miletus.

Differential Expression of Metabolism-Related Genes in Plateau Pika (Ochotona curzoniae) at Different Altitudes on the Qinghai-Tibet Plateau

According to life history theory, animals living in extreme environments have evolved specific behavioral and physiological strategies for survival. However, the genetic mechanisms underpinning these strategies are unclear. As the highest geographical unit on Earth, the Qinghai-Tibet Plateau is characterized by an extreme environment and climate. During long-term evolutionary processes, animals that inhabit the plateau have evolved specialized morphological and physiological traits. The plateau pika (Ochotona curzoniae), one of the native small mammals that evolved on the Qinghai-Tibet Plateau, has adapted well to this cold and hypoxic environment. To explore the genetic mechanisms underlying the physiological adaptations of plateau pika to extremely cold ambient temperatures, we measured the differences in resting metabolic rate (RMR) and metabolism-related gene expression in individuals inhabiting three distinct altitudes (i.e., 3,321, 3,663, and 4,194 m). Results showed that the body mass and RMR of plateau pika at high- and medium-altitudes were significantly higher than those at the low-altitude. The expression levels of peroxisome proliferator-activated receptor α (pparα), peroxisome proliferator-activated receptor-γ coactivator-1α (pgc-1α), and the PR domain-containing 16 (PRDM16) in white (WAT) and brown (BAT) adipose tissues of plateau pika from high- and medium-altitudes were significantly higher than in pika from the low-altitude region. The enhanced expression levels of pgc-1α and pparα genes in the WAT of pika at high-altitude showed that WAT underwent "browning" and increased thermogenic properties. An increase in the expression of uncoupling protein 1 (UCP1) in the BAT of pika at high altitude indicated that BAT increased their thermogenic properties. The gene expression levels of pparα and pgc-1α in skeletal muscles were significantly higher in high-altitude pika. Simultaneously, the expression of the sarcolipin (SLN) gene in skeletal muscles significantly increased in high-altitude pika. Our results suggest that plateau pika adapted to an extremely cold environment via browning WAT, thereby activating BAT and enhancing SLN expression to increase non-shivering thermogenesis. This study demonstrates that plateau pika can increase thermogenic gene expression and energy metabolism to adapt to the extreme environments on the plateau.

Metabolomics of Eothenomys miletus from five Hengduan Mountains locations in summer

Climatic characteristics of Hengduan Mountains region were diverse, and Eothenomys miletus was a native species throughout this region. To investigate adaptive strategies of E. miletus to environmental factors in different locations in this region, five locations were selected, including Deqin (DQ), Xianggelila (XGLL), Lijiang (LJ), Jianchuan (JC) and Ailaoshan (ALS). Then, body mass, visceral organ masses, and serum and liver metabolomes of E. miletus from each location were examined. The results showed that body mass was significantly different among these five sites. Liver mass was lower in ALS than in other locations. PLS-DA analysis, metabolite tree maps and heat maps of serum and liver metabolites showed that samples from DQ and XGLL clustered together, as did the samples from LJ, JC and ALS. Serum concentrations of lipid and amino acid metabolites, concentrations of TCA cycle intermediates, lipid metabolites and amino acid metabolites in livers from DQ and XGLL were higher than those from other three regions. However, the concentrations of glycolytic metabolites were lower in DQ and XGLL. All these results indicated that E. miletus adapts to changes in environmental temperature and altitude of this region by adjusting body mass and serum and liver metabolite concentrations.