Low genetic variation in the MHC class II DRB gene and MHC-linked microsatellites in endangered island populations of the leopard cat (Prionailurus bengalensis) in Japan

Current Genetic Structure Analysis of Leopard Cats Reveals a Weak Disparity Trend in Subpopulations in Beijing, China

Simple Summary

Habitat fragmentation is an important factor leading to the decline in the leopard cat population in Beijing. Habitat loss may further result in population shrinkage, which increases the risk of inbreeding and genetic decline. To reveal the segregation effects of highway construction and infrastructure expansion on population genetic variation, this study analyzed the genetic structure of leopard cats in five nature reserves in the mountain surroundings of Beijing. The results showed that a mild disparity trend exists in Baihuashan and Songshan subpopulations, due to habitat segregation and dispersal difficulties. We suggest that the genetic structures of the leopard cat population be monitored every 5 years to detect any changes. If needed, individuals can be artificially exchanged among different subpopulations to maintain the viability of this wild cat in Beijing.

Abstract

In the face of habitat shrinkage and segregation, the survival of wild cats looks bleak. Interpreting their population genetic structure during habitat fragmentation is critical in planning effective management strategies. To reveal the segregation effects of road construction and human settlements on the population genetic structure, we analyzed non-invasive fecal DNA samples from leopard cats (Prionailurus bengalensis) from five nature reserves in mountainous areas around Beijing. We focused on microsatellite markers. A total of 112 individual leopard cats were identified among 601 samples of scat, and moderate population genetic diversity was detected. Microsatellite-marker-based genetic differentiation (Fst) and gene flow (Nm) showed a weak trend toward discrepancies in the Baihuashan and Songshan subpopulations, which indicated habitat fragmentation effects on individual dispersal. Because the segregated subpopulations may suffer a high risk of genetic diversity loss, we suggest that their genetic structure be monitored with more molecular markers to detect any changes, and that female individuals be artificially introduced as needed to maintain the viability of the leopard cat subpopulations in Beijing.

Genetic Diversity and Differentiation of MHC Class I Genes in Red-Crowned Crane Populations

The red-crowned crane (Grus japonensis) has been demoted to “vulnerable species” because its populations have apparently stabilized in Japan and Korea. Low variation and genetic drift may cause damage to the nascent recovery of the G. japonensis population. The major histocompatibility complex (MHC) is one of the most polymorphic gene families in the vertebrate genome and can reflect information on the adaptive evolution of endangered species. In this study, variations in MHC I exon 3 of captive G. japonensis in China were assessed and compared with those in cranes from Japan. Forty MHC alleles of 274 base pairs were isolated from 32 individuals from two captive populations in China. There was high variability in the nucleotide and amino acid composition, showing the proportion of polymorphic sites of 18.98 and 32.97%, respectively. Comparative analyses of the Chinese and Japanese populations based on 222 base pair sequences revealed more alleles and higher variation in the Chinese population. The lack of significant geographical differentiation of G. japonensis was supported by the genetic differentiation coefficient (0.04506) between the Chinese and Japanese populations. Positive selection of antigen-binding sites was observed, which contributed to maintaining the diversity of MHC class I genes. Phylogenetic analysis suggested the persistence of trans-species polymorphisms among MHC class I genes in Gruidae species. Our results may contribute to optimizing the management of G. japonensis populations and population recovery of this threatened species.

Comparative Genomics of the Major Histocompatibility Complex (MHC) of Felids

This review summarizes the current knowledge on the major histocompatibility complex (MHC) of the family Felidae. This family comprises an important domestic species, the cat, as well as a variety of free-living felids, including several endangered species. As such, the Felidae have the potential to be an informative model for studying different aspects of the biological functions of MHC genes, such as their role in disease mechanisms and adaptation to different environments, as well as the importance of genetic diversity for conservation issues in free-ranging or captive populations. Despite this potential, the current knowledge on the MHC in the family as a whole is fragmentary and based mostly on studies of the domestic cat and selected species of big cats. The overall structure of the domestic cat MHC is similar to other mammalian MHCs following the general scheme "centromere-MHC class I-MHC class III-MHC class II" with some differences in the gene contents. An unambiguously defined orthologue of the non-classical class I HLA-E gene has not been identified so far and the class II DQ and DP genes are missing or pseudogenized, respectively. A comparison with available genomes of other felids showed a generally high level of structural and sequence conservation of the MHC region. Very little and fragmentary information on in vitro and/or in vivo biological functions of felid MHC genes is available. So far, no association studies have indicated effects of MHC genetic diversity on a particular disease. No information is available on the role of MHC class I molecules in interactions with Natural Killer (NK) cell receptors or on the putative evolutionary interactions (co-evolution) of the underlying genes. A comparison of complex genomic regions encoding NK cell receptors (the Leukocyte Receptor Complex, LRC and the Natural Killer Cell Complex, NKC) in the available felid genomes showed a higher variability in the NKC compared to the LRC and the MHC regions. Studies of the genetic diversity of domestic cat populations and/or specific breeds have focused mainly on DRB genes. Not surprisingly, higher levels of MHC diversity were observed in stray cats compared to pure breeds, as evaluated by DRB sequencing as well as by MHC-linked microsatellite typing. Immunogenetic analysis in wild felids has only been performed on MHC class I and II loci in tigers, Namibian leopards and cheetahs. This information is important as part of current conservation tasks to assess the adaptive potential of endangered wild species at the human-wildlife interface, which will be essential for preserving biodiversity in a functional ecosystem.

Genetic Diversity and Relatedness among Captive African Painted Dogs in North America

African painted dogs (Lycaon pictus, APD) are highly endangered, with fewer than 7000 remaining in nature. Captive breeding programs can preserve a genetically diverse population and provide a source of individuals for reintroductions. However, most programs are initiated from few founders and suffer from low genetic diversity and inbreeding. The aims of this study were to use molecular markers to assess genetic variation, inbreeding, and relatedness among APDs in the North American captive population, to use these data to realign studbook records, and to compare these data to wild populations and to the European captive population to facilitate the development of a global management plan. We sequenced mitochondrial and major histocompatibility (MHC) class II loci and genotyped 14 microsatellite loci from 109 APDs from 34 institutions in North America. We identified three likely studbook errors and resolved ten cases of uncertain paternity. Overall, microsatellite heterozygosity was higher than reported in Europe, but effective population size estimates were lower. Mitochondrial sequence variation was extremely limited, and there were fewer MHC haplotypes than in Europe or the wild. Although the population did not show evidence of significant inbreeding overall, several individuals shared high relatedness values, which should be incorporated into future breeding programs.

Genetic Diversity and Genetic Structure of the Wild Tsushima Leopard Cat from Genome-Wide Analysis

Simple Summary

The Tsushima leopard cat, Prionailurus bengalensis euptilurus, is a small regional population of the Amur leopard cat and is only found on Tsushima Island in Japan. A breeding program will require adequate information on parentage, kinship, and inbreeding for this population. Hence, there is an urgent need to develop this information in order to conserve the population and its genetic diversity. We performed GRAS-Di analysis to investigate the genetic diversity and genetic structure of the Tsushima leopard cat. We identified between 133 and 158 single-nucleotide polymorphism (SNP) markers in three different genotyping methods. These SNP markers can be used in identification of individuals and parentage. In addition, structure analysis using these markers demonstrated the similar genetic composition of the samples from 48 Tsushima leopard cats, and indicated Tsushima leopard cats have no subpopulations. We have provided genetic markers that are useful for conservation of the Tsushima leopard cat, such as individual identification and parentage. Moreover, we have also clarified units for conservation of the Tsushima leopard cat population from structure analysis.

Abstract

The Tsushima leopard cat (Prionailurus bengalensis euptilurus) lives on Tsushima Island in Japan and is a regional population of the Amur leopard cat; it is threatened with extinction. Its genetic management is important because of the small population. We used genotyping by random amplicon sequencing-direct (GRAS-Di) to develop a draft genome and explore single-nucleotide polymorphism (SNP) markers. The SNPs were analyzed using three genotyping methods (mapping de novo, to the Tsushima leopard cat draft genome, and to the domestic cat genome). We examined the genetic diversity and genetic structure of the Tsushima leopard cat. The genome size was approximately 2.435 Gb. The number of SNPs identified was 133–158. The power of these markers was sufficient for individual and parentage identifications. These SNPs can provide useful information about the life of the Tsushima leopard cat and the pairings and for the introduction of founders to conserve genetic diversity with ex situ conservation. We identified that there are no subpopulations of the Tsushima leopard cat. The identifying units will allow for a concentration of efforts for conservation. SNPs can be applied to the analysis of the leopard cat in other regions, making them useful for comparisons among populations and conservation in other small populations.

Molecular evolution of MHC class II DRB exon 2 in Japanese and Russian raccoon dogs, Nyctereutes procyonoides (Carnivora: Canidae)

Raccoon dogs, Nyctereutes procyonoides, are native to East Asia, but have been introduced into western Russia and eastern Europe. To determine allelic diversity and elucidate the evolution of major histocompatibility complex (MHC) class II genes in the raccoon dog, we analysed a 237-bp region of DRB exon 2 from 36 individuals of native and introduced populations from Japan and Russia. We detected 23 DRB alleles (Nypr-DRBs), 22 of which were novel. Some alleles were found across the species’ range, while others were geographically restricted. For both native and introduced populations, the ratio of non-synonymous to synonymous substitution rates for codons at predicted antigen-binding sites was significantly greater than 2, indicating that Nypr-DRBs have evolved under positive selection. Mixed effect model evolution analysis and an algorithm to detect recombination showed five positively selected codons and one recombination breakpoint, respectively. Overall, our results suggest that the diversity of MHC class II DRB in N. procyonoides was influenced and maintained by recombination, pathogen-driven positive selection, geographical barriers and the founder effect. A Bayesian phylogenetic tree revealed no evidence of trans-species polymorphism (TSP), but instead showed monophyly for the Nypr-DRB alleles within a larger clade of canid sequences. The lack of TSP may have been due to long-term divergence of raccoon dogs from other canids, or to their having encountered different sets of pathogens due to occupying a different ecological niche.

Evolution of MHC class I genes in Eurasian badgers, genus Meles (Carnivora, Mustelidae)

Because of their role in immune defense against pathogens, major histocompatibility complex (MHC) genes are useful in evolutionary studies on how wild vertebrates adapt to their environments. We investigated the molecular evolution of MHC class I (MHCI) genes in four closely related species of Eurasian badgers, genus Meles. All four species of badgers showed similarly high variation in MHCI sequences compared to other Carnivora. We identified 7-21 putatively functional MHCI sequences in each of the badger species, and 2-7 sequences per individual, indicating the existence of 1-4 loci. MHCI exon 2 and 3 sequences encoding domains α1 and α2 exhibited different clade topologies in phylogenetic networks. Non-synonymous nucleotide substitutions at codons for antigen-binding sites exceeded synonymous substitutions for domain α1 but not for domain α2, suggesting that the domains α1 and α2 likely had different evolutionary histories in these species. Positive selection and recombination seem to have shaped the variation in domain α2, whereas positive selection was dominant in shaping the variation in domain α1. In the separate phylogenetic analyses for exon 2, exon 3, and intron 2, each showed three clades of Meles alleles, with rampant trans-species polymorphism, indicative of the long-term maintenance of ancestral MHCI polymorphism by balancing selection.