Global expression profiling and pathway analysis in two different population groups in relation to high altitude

Modified Metabolism and Response to UV Radiation: Gene Expression Variations Along an Elevational Gradient in the Asiatic Toad (Bufo gargarizans)

High-elevation adaptation provides an excellent system for examining adaptive evolution, and adaptive variations may manifest at gene expression or any other phenotypic levels. We examined gene expression profiles of Asiatic toads (Bufo gargarizans) along an elevational gradient from both wild and common-garden acclimated populations. Asiatic toads originated from high altitudes have distinctive gene expression patterns. We identified 18 fixed differentially expressed genes (DEGs), which are different in both wild and acclimated samples, and 1217 plastic DEGs, which are different among wild samples. The expression levels of most genes were linearly correlated with altitude gradient and down-regulated in high-altitude populations. Expression variations of several genes associated with metabolic process are fixed, and we also identified a co-expression module that is significantly different between acclimated populations and has functions related to DNA repair. The differential expression of the vast majority genes, however, are due to phenotypic plasticity, revealing the highly plastic nature of gene expression variations. Expression modification of some specific genes related to metabolism and response to UV radiation play crucial role in adaptation to high altitude for Asiatic toads. Common-garden experiments are essential for evaluating adaptive evolution of natural populations.

Temporal transcriptome analysis suggest modulation of multiple pathways and gene network involved in cell-cell interaction during early phase of high altitude exposure

High altitude (HA) conditions induce several physiological and molecular changes, prevalent in individuals who are unexposed to this environment. Individuals exposed towards HA hypoxia yields physiological and molecular orchestration to maintain adequate tissue oxygen delivery and supply at altitude. This study aimed to understand the temporal changes at altitude of 4,111m. Physiological parameters and transcriptome study was conducted at high altitude day 3, 7, 14 and 21. We observed changes in differentially expressed gene (DEG) at high altitude time points along with altered BP, HR, SpO2, mPAP. Physiological changes and unsupervised learning of DEG's discloses high altitude day 3 as distinct time point. Gene enrichment analysis of ontologies and pathways indicate cellular dynamics and immune response involvement in early day exposure and later stable response. Major clustering of genes involved in cellular dynamics deployed into broad categories: cell-cell interaction, blood signaling, coagulation system, and cellular process. Our data reveals genes and pathways perturbed for conditions like vascular remodeling, cellular homeostasis. In this study we found the nodal point of the gene interactive network and candidate gene controlling many cellular interactive pathways VIM, CORO1A, CD37, STMN1, RHOC, PDE7B, NELL1, NRP1 and TAGLN and the most significant among them i.e. VIM gene was identified as top hub gene. This study suggests a unique physiological and molecular perturbation likely to play a critical role in high altitude associated pathophysiological condition during early exposure compared to later time points.