Identification and characterization of the major histocompatibility complex class II DQB (MhcMath-DQB1) alleles in Tibetan macaques (Macaca thibetana)

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.

Characterization of 17 full-length MHC-DQB1 alleles in Tibetan macaques (Macaca thibetana)

Seventeen full-length Math-DQB1 alleles were characterized in Tibetan macaques.

Promising potentials of Tibetan macaques in xenotransplantation

Organ transplantation is a crucial medical procedure, as it is often the only treatment for patients suffering from end-stage organ failure. Unfortunately, the shortage of donor organs limits the number of patients whose lives can be saved. Carrying out research on xenotransplantation with the aim of eventually replacing human organ transplants with those of animals is very promising, as it could effectively bridge the shortfall in donor organs. Thanks to the success of cloned pigs and to the emergence of gene-editing techniques, genetically modified pigs have come to be considered ideal animal donors for human xenotransplantation and have been widely used in basic research. Such research focuses on pig-to-nonhuman primates transplantation, as the recipients are suitable for preclinical studies because both their genes and organ sizes are similar to those of humans. Chinese transplantation scientists have carried out several experiments on Tibetan macaques, including successful preclinical transplants of material from genetically modified pigs, as well as research on such topics as intraocular pressure, Parkinson's disease, advanced cancer, islet transplantation, and liver transplantation. This article reviews basic and applied research on Tibetan macaques in xenotransplantation, as well as the issues of immune rejection and ethical concerns. We aim to demonstrate the various advantages of Tibetan macaques as transplant recipients compared to other nonhuman primate species and to provide a perspective for the future establishment of Tibetan macaques as principal recipients in preclinical studies of xenotransplantation.

Genetic diversity and differentiation of the rhesus macaque (Macaca mulatta) population in western Sichuan, China, based on the second exon of the major histocompatibility complex class II DQB (MhcMamu-DQB1) alleles

BACKGROUND

Rhesus macaques living in western Sichuan, China, have been separated into several isolated populations due to habitat fragmentation. Previous studies based on the neutral or nearly neutral markers (mitochondrial DNA or microsatellites) showed high levels of genetic diversity and moderate genetic differentiation in the Sichuan rhesus macaques. Variation at the major histocompatibility complex (MHC) loci is widely accepted as being maintained by balancing selection, even with a low level of neutral variability in some species. However, in small and isolated or bottlenecked populations, balancing selection may be overwhelmed by genetic drift. To estimate microevolutionary forces acting on the isolated rhesus macaque populations, we examined genetic variation at Mhc-DQB1 loci in 119 wild rhesus macaques from five geographically isolated populations in western Sichuan, China, and compared the levels of MHC variation and differentiation among populations with that previously observed at neutral microsatellite markers.

RESULTS

23 Mamu-DQB1 alleles were identified in 119 rhesus macaques in western Sichuan, China. These macaques exhibited relatively high levels of genetic diversity at Mamu-DQB1. The Hanyuan population presented the highest genetic variation, whereas the Heishui population was the lowest. Analysis of molecular variance (AMOVA) and pairwise FST values showed moderate genetic differentiation occurring among the five populations at the Mhc-DQB1 locus. Non-synonymous substitutions occurred at a higher frequency than synonymous substitutions in the peptide binding region. Levels of MHC variation within rhesus macaque populations are concordant with microsatellite variation. On the phylogenetic tree for the rhesus and crab-eating macaques, extensive allele or allelic lineage sharing is observed between the two species.

CONCLUSIONS

Phylogenetic analyses confirm the apparent trans-species model of evolution of the Mhc-DQB1 genes in these macaques. Balancing selection plays an important role in sharing allelic lineages between species, but genetic drift may share balancing selection dominance to maintain MHC diversity. Great divergence at neutral or adaptive markers showed that moderate genetic differentiation had occurred in rhesus macaque populations in western Sichuan, China, due to the habitat fragmentation caused by long-term geographic barriers and human activity. The Heishui population should be paid more attention for its lowest level of genetic diversity and relatively great divergence from others.