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High‐altitude adaptation in vertebrates as revealed by mitochondrial genome analyses

ABSTRACT: Abstract The high‐altitude environment may drive vertebrate evolution in a certain way, and vertebrates living in different altitude environments might have different energy requirements. We hypothesized that the high‐altitude environment might impose different influences on vertebrate mitochondrial genomes (mtDNA). We used selection pressure analyses and PIC (phylogenetic independent contrasts) analysis to detect the evolutionary rate of vertebrate mtDNA protein‐coding genes (PCGs) from different altitudes. The results showed that the ratio of nonsynonymous/synonymous substitutions (dN/dS) in the mtDNA PCGs was significantly higher in high‐altitude vertebrates than in low‐altitude vertebrates. The seven rapidly evolving genes were shared by the high‐altitude vertebrates, and only one positive selection gene (ND5 gene) was detected in the high‐altitude vertebrates. Our results suggest the mtDNA evolutionary rate in high‐altitude vertebrates was higher than in low‐altitude vertebrates as their evolution requires more energy in a high‐altitude environment. Our study demonstrates the high‐altitude environment (low atmospheric O2 levels) drives vertebrate evolution in mtDNA PCGs. We studied the influence of different altitudes on the evolution of 104 vertebrate mtDNA PCGs for the first time. Our results demonstrated that the rapid evolution and positive selection sites of mitochondrial genes are one of the important factors for vertebrates to adapt to plateau environment through this research and the high‐altitude environment drove the evolution of vertebrate mtDNA PCGs.

SUBMITTER: Wang X

PROVIDER: S-EPMC8571627 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Since their arrival in the Tibetan Plateau during the Neolithic Age, Tibetans have been well-adapted to extreme environmental conditions and possess genetic variation that reflect their living environment and migratory history. To investigate the origin of Tibetans and the genetic basis of adaptation in a rigorous environment, we genotyped 30 Tibetan individuals with more than one million SNP markers. Our findings suggested that Tibetans, together with the Yi people, were descendants of Tibeto-Burmans who diverged from ancient settlers of East Asia. The valleys of the Hengduan Mountain range may be a major migration route. We also identified a set of positively-selected genes that belong to functional classes of the embryonic, female gonad, and blood vessel developments, as well as response to hypoxia. Most of these genes were highly correlated with population-specific and beneficial phenotypes, such as high infant survival rate and the absence of chronic mountain sickness. Genetic features of Tibetans have been broadly investigated, but the properties of copy number variation (CNV) have not been well examined. To get a preliminary view of CNV in Tibetans, we scanned 29 Tibetan genomes with the Illumina Human-1 M high-resolution genotyping microarray and identified 139 putative copy number variable regions (CNVRs), consisting of 70 deletions, 61 duplications, and 8 multi-allelic loci. Thirty-four of the 139 CNVRs showed differential allele frequencies versus other East-Asian populations, with P values ,0.0001. These results indicated a distinct pattern of CNVR allele frequency distribution in Tibetans. The Tibetan CNVRs are enriched for genes in the disease class of human reproduction (such as genes from the DAZ, BPY2, CDY, and HLA-DQ and -DR gene clusters) and biological process categories of ‘‘response to DNA damage stimulus’’ and ‘‘DNA repair’’ (such as RAD51, RAD52, and MRE11A). These genes are related to the adaptive traits of high infant birth weight and darker skin tone of Tibetans, and may be attributed to recent local adaptation. Our results provide a different view of genetic diversity in Tibetans and new insights into their high-altitude adaptation.

Project description:Purpose: The goal of this study was to reveal epigenetic differences in the microRNA transcriptomes of two organs (heart and lung) between yak and cattle. Methods: Three unrelated 2-year old adult females for both of yaks and cattle (Luxi Huang cattle) were used in this study. Two of significant hypoxia-responsive tissues (heart and lung) were rapidly collected from each carcass, washed three times with physiological saline, immediately frozen in liquid nitrogen. All frozen samples were stored at –80 °C until RNA extraction.The total RNA were extracted with Trizol (Ambion, USA). NanoDrop ND-2000 spectrophotometer (Nano Drop, DE, USA) and Bioanalyzer 2100 (Agilent Technologies, Santa Clara, CA, USA) were used to monitor the concentration and integrity of RNA, respectively. In brief, several successive steps consist the Illumina sequencing. The small RNA with length of 14-40 nt were first purified by polyacrylamide gel electrophoresis (PAGE), and then specific adapters were ligated to the purified small RNA. The ligated RNA were reverse transcribed to cDNA libraries. Finally, each library were sequenced on Genome Analyzer. Results: We identified 808 widely-expressed conserved and 697 species-specific novel miRNAs in two species. In addition, although two organs showed similar high expression miRNAs, larger differentiation was present in lung than heart between two species. In addition, miRNAs with significantly differentiated patterns of expression in two organs exhibited obvious co-operation effect in high altitude adaptation in form of miRNA family and cluster. Functional analysis revealed that a large amount of differentially expressed miRNAs were enriched in hypoxia-related pathways, such as VEGF signaling pathway, HIF-1α signaling pathway, insulin signaling pathway, DNA damage response, apoptosis, fatty acid metabolism and glucose metabolism. These results suggested the diverse degrees of epigenetic variation in different tissues between yak and cattle, and revealed extensive roles of miRNAs in high altitude adaptation. Conclusions: In this study, we illustrated the differences in the microRNA transcriptomes level for heart and lung between yak and cattle, and suggested extensive roles of miRNAs in high altitude adaptation. The work performed here will provide a typical demonstration for future deciphering the mechanism of high altitude adaptation

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High‐altitude adaptation in vertebrates as revealed by mitochondrial genome analyses

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