Genomics and morphometrics reveal the adaptive evolution of pikas.

Pikas (Lagomorpha: Ochotonidae) are small mouse-like lagomorphs. To investigate their adaptation to different ecological environments during their dispersal from the Qinghai-Xizang (Tibet) Plateau (QTP), we collected 226 pikas and measured 20 morphological characteristics and recorded habitat information. We also sequenced the genome of 81 specimens, representing 27 putative pika species. The genome-wide tree based on 4 090 coding genes identified five subgenera, i.e., Alienauroa, Conothoa, Lagotona, Ochotona, and Pika, consistent with morphometric data. Morphologically, Alienauroa and Ochotona had similar traits, including smaller size and earlier divergence time compared to other pikas. Consistently, the habitats of Alienauroa and Ochotona differed from those of the remaining subgenera. Phylogenetic signal analysis detected 83 genes significantly related to morphological characteristics, including several visual and hearing-related genes. Analysis of shared amino acid substitutions and positively selected genes (PSGs) in Alienauroa and Ochotona identified two genes, i.e., mitochondrial function-related TSFM (p.Q155E) and low-light visual sensitivity-related PROM1 (p.H419Y). Functional experiments demonstrated that TSFM-155E significantly enhanced mitochondrial function compared to TSFM-155Q in other pikas, and PROM1-419Y decreased the modeling of dynamic intracellular chloride efflux upon calcium uptake. Alienauroa and Ochotona individuals mostly inhabit different environments (e.g., subtropical forests) than other pikas, suggesting that a shift from the larger ancestral type and changes in sensory acuity and energy enhancement may have been required in their new environments. This study increases our understanding of the evolutionary history of pikas.

Genome-wide analysis reveals signatures of complex introgressive gene flow in macaques (genus Macaca).

The genus Macaca serves as an ideal research model for speciation and introgressive gene flow due to its short period of diversification (about five million years ago) and rapid radiation of constituent species. To understand evolutionary gene flow in macaques, we sequenced four whole genomes (two M. arctoides and two M. thibetana) and combined them with publicly available macaque genome data for genome-wide analyses. We analyzed 14 individuals from nine Macaca species covering all Asian macaque species groups and detected extensive gene flow signals, with the strongest signals between the fascicularis and silenus species groups. Notably, we detected bidirectional gene flow between M. fascicularis and M. nemestrina. The estimated proportion of the genome inherited via gene flow between the two species was 6.19%. However, the introgression signals found among studied island species, such as Sulawesi macaques and M. fuscata, and other species were largely attributed to the genomic similarity of closely related species or ancestral introgression. Furthermore, gene flow signals varied in individuals of the same species (M. arctoides, M. fascicularis, M. mulatta, M. nemestrina and M. thibetana), suggesting very recent gene flow after the populations split. Pairwise sequentially Markovian coalescence (PSMC) analysis showed all macaques experienced a bottleneck five million years ago, after which different species exhibited different fluctuations in demographic history trajectories, implying they have experienced complicated environmental variation and climate change. These results should help improve our understanding of the complicated evolutionary history of macaques, particularly introgressive gene flow.

Effects of aging on gene expression in blood of captive Tibetan macaques ( Macaca thibetana) and comparisons with expression in humans.

Changes in gene expression occur as animals, including primates, age. Macaques have long been used as a model species for primate evolution and biomedical studies. Here, to study gene expression in Tibetan macaques (Macaca thibetana, TMs) and its differences to humans, we applied RNA-Seq to obtain the blood transcriptomes of 24 TMs. In total, 2 523 age-associated differentially expressed genes (DEGs) were identified. Several pathways and processes that regulate aging, including the FoxO signaling pathway, autophagy, and platelet activation, were significantly enriched in the up-regulated DEGs. Two significantly age-related modules were identified by weighted gene co-expression network analysis (WGCNA). The TMs and humans shared 279 common DEGs, including 111 up-regulated and 141 down-regulated genes with advancing age in the same expression direction. However, 27 age-related DEGs presented the opposite expression direction in TMs as that in humans. For example, INPPL1, with inhibitory effects on the B cell receptor signaling pathway, was up-regulated in humans but down-regulated in TMs. In general, our study suggests that aging is a critical factor affecting gene expression in the captive TM population. The similarities and differences in gene expression patterns between TMs and humans could provide new insights into primate evolution and benefit TM model development.

Blood transcriptome analysis reveals gene expression features of breast-feeding rhesus macaque ( Macaca mulatta) infants.

During the breast-feeding period, infants undergo remarkable changes, including rapid physiological and developmental growth. However, little is known about gene expression features and sex-specific gene expression in breast-feeding infants. In this study, we sequenced 32 blood transcriptomes from 16 breast-feeding rhesus macaque ( Macaca mulatta) infants and their lactating mothers. We identified 218 differentially expressed genes (DEGs) between infants and mothers, including 91 up-regulated and 127 down-regulated DEGs in the infant group. Functional enrichment analysis of the up-regulated DEGs and unique hub genes in infants showed primary enrichment in immunity, growth, and development. Protein-protein interaction analysis also revealed that genes at key positions in infants were mainly related to development and immunity. However, we only detected 23 DEGs between female and male infants, including three DEGs located on chromosome X and 14 DEGs located on chromosome Y. Of these DEGs, TMF1 regulated nuclear protein 1 ( Trnp1), which was highly expressed in female infants, is crucial for controlling the tangential and radial expansion of the cerebral cortex in mammals. Thus, our study provides novel insight into the gene expression features of breast-feeding infants in non-human primates (NHPs) and reveals sex-specific gene expression between these infants.

Identification and characterization of short tandem repeats in the Tibetan macaque genome based on resequencing data.

The Tibetan macaque, which is endemic to China, is currently listed as a Near Endangered primate species by the International Union for Conservation of Nature (IUCN). Short tandem repeats (STRs) refer to repetitive elements of genome sequence that range in length from 1-6 bp. They are found in many organisms and are widely applied in population genetic studies. To clarify the distribution characteristics of genome-wide STRs and understand their variation among Tibetan macaques, we conducted a genome-wide survey of STRs with next-generation sequencing of five macaque samples. A total of 1 077 790 perfect STRs were mined from our assembly, with an N50 of 4 966 bp. Mono-nucleotide repeats were the most abundant, followed by tetra- and di-nucleotide repeats. Analysis of GC content and repeats showed consistent results with other macaques. Furthermore, using STR analysis software (lobSTR), we found that the proportion of base pair deletions in the STRs was greater than that of insertions in the five Tibetan macaque individuals (P<0.05, t-test). We also found a greater number of homozygous STRs than heterozygous STRs (P<0.05, t-test), with the Emei and Jianyang Tibetan macaques showing more heterozygous loci than Huangshan Tibetan macaques. The proportion of insertions and mean variation of alleles in the Emei and Jianyang individuals were slightly higher than those in the Huangshan individuals, thus revealing differences in STR allele size between the two populations. The polymorphic STR loci identified based on the reference genome showed good amplification efficiency and could be used to study population genetics in Tibetan macaques. The neighbor-joining tree classified the five macaques into two different branches according to their geographical origin, indicating high genetic differentiation between the Huangshan and Sichuan populations. We elucidated the distribution characteristics of STRs in the Tibetan macaque genome and provided an effective method for screening polymorphic STRs. Our results also lay a foundation for future genetic variation studies of macaques.

Comparison of microsatellite distribution in genomes of Centruroides exilicauda and Mesobuthus martensii.

In this study, we characterized the distribution of microsatellites in the genomes and genes of Centruroides exilicauda and Mesobuthus martensii, carried out Gene Ontology (GO) analysis and GO enrichment analysis of coding sequences (CDSs) with microsatellite (SSR). In addition, over-represented GO functions related to environmental interactions, development process and methylation were identified to develop functional markers and facilitate further analysis of microsatellite function in the genes of scorpions. Location analysis indicated that microsatellites were predominantly concentrated at both ends of genes. Most genes containing microsatellite had the SSR present at only one locus, from which we infer that the number of SSRs per gene is limited even though intragenic tandem repeats can generate functional variability. Lastly, we identified 75 SSRs in 64 genes of 54 expanded gene families and 1 SSR in the toxin gene of Mesobuthus martensii, allowing future studies on the effect of microsatellites on gene function.