Immune Gene Families Research Articles

A chromosome-level, haplotype-resolved genome assembly and annotation for the Eurasian minnow (Leuciscidae: Phoxinus phoxinus) provide evidence of haplotype diversity.

In this study, we present an in-depth analysis of the Eurasian minnow (Phoxinus phoxinus) genome, highlighting its genetic diversity, structural variations, and evolutionary adaptations. We generated an annotated haplotype-phased, chromosome-level genome assembly (2n = 50) by integrating high-fidelity (HiFi) long reads and chromosome conformation capture data (Hi-C). We achieved a haploid size of 940 megabase pairs (Mbp) for haplome 1 and 929 Mbp for haplome 2 with high scaffold N50 values of 36.4 Mb and 36.6 Mb and BUSCO scores of 96.9% and 97.2%, respectively, indicating a highly complete genome assembly. We detected notable heterozygosity (1.43%) and a high repeat content (approximately 54%), primarily consisting of DNA transposons, which contribute to genome rearrangements and variations. We found substantial structural variations within the genome, including insertions, deletions, inversions, and translocations. These variations affect genes enriched in functions such as dephosphorylation, developmental pigmentation, phagocytosis, immunity, and stress response. In the annotation of protein-coding genes, 30,980 messenger RNAs and 23,497 protein-coding genes were identified with a high completeness score, which further underpins the high contiguity of our genome assemblies. We performed a gene family evolution analysis by comparing our proteome to 10 other teleost species, which identified immune system gene families that prioritize histone-based disease prevention over NB-LRR-related-based immune responses. Additionally, demographic analysis indicates historical fluctuations in the effective population size of P. phoxinus, likely correlating with past climatic changes. This annotated, phased reference genome provides a crucial resource for resolving the taxonomic complexity within the genus Phoxinus and highlights the importance of haplotype-phased assemblies in understanding haplotype diversity in species characterized by high heterozygosity.

Genomic insights into fibrinogen-related proteins and expression analysis in the Pacific white shrimp, Litopenaeusvannamei.

Fibrinogen-related domain (FReD) containing proteins are an evolutionarily conserved immune gene family characterized by the C-terminal fibrinogen (FBG) and diverse N-terminal domains. To understand the complexity of this family in crustaceans, we performed genome screening and identified 43 full-length FReDs encoding genes in Litopenaeus vannamei. Structural classification analysis revealed these putative FReDs could be divided into six types, including two reported types (LvFReDI and II) and four new types (LvFReDIII-VI). Sequence and phylogenetic analysis showed that FBG domains were highly conserved throughout and phylogeny clusters correlated strongly with gene type. We analyzed the temporal and spatial expression patterns of LvFReD genes based on the transcriptomes of developmental stages, adult tissues or pathogen infected tissues of L. vannamei. Most LvFReDs were expressed from larval in membrane stage, and exhibited tissue-specific expression patterns and immune-responsive transcription after challenge with bacteria or virus. Further time-course expression analysis suggested that LvFReDII genes with additional coiled-coil region were more sensitive to pathogens than LvFReDI genes. Our findings provided comprehensive gene sequence resources and expression profiles of FReD genes in shrimp, which give insights into clarifying the diversity and function of these genes in crustaceans.

Spatial variation in toll-like receptor diversity in koala populations across their geographic distribution

The koala (Phascolarctos cinereus) is an iconic Australian species that is listed as endangered in the northern parts of its range due to loss of habitat, disease, and road deaths. Diseases contribute significantly to the decline of koala populations, primarily Chlamydia and koala retrovirus. The distribution of these diseases across the species’ range, however, is not even. Toll-like receptors (TLRs) play a crucial role in innate immunity by recognising and responding to various pathogens. Variations in TLR genes can influence an individual’s susceptibility or resistance to infectious diseases. The aim of this study was to identify koala TLR diversity across the east coast of Australia using 413 re-sequenced genomes at 30 × coverage. We identified 45 single-nucleotide polymorphisms (SNP) leading to 51 alleles within ten TLR genes. Our results show that the diversity of TLR genes in the koala forms four distinct genetic groups, which are consistent with the diversity of the koala major histocompatibility complex (MHC), another key immune gene family. The bioinformatics approach presented here has broad applicability to other threatened species with existing genomic resources.

Using bioinformatics to investigate functional diversity: a case study of MHC diversity in koalas.

Conservation genomics can greatly improve conservation outcomes of threatened populations, including those impacted by disease. Understanding diversity within immune gene families, including the major histocompatibility complex (MHC) and toll-like receptors (TLR), is important due to the role they play in disease resilience and susceptibility. With recent advancements in sequencing technologies and bioinformatic tools, the cost of generating high-quality sequence data has significantly decreased and made it possible to investigate diversity across entire gene families in large numbers of individuals compared to investigating only a few genes or a few populations previously. Here, we use the koala as a case study for investigating functional diversity across populations. We utilised previous target enrichment data and 438 whole genomes to firstly, determine the level of sequencing depth required to investigate MHC diversity and, secondly, determine the current level of diversity in MHC genes in koala populations. We determined for low complexity, conserved genes such as TLR genes 10 × sequencing depth is sufficient to reliably genotype more than 90% of variants, whereas for complex genes such as the MHC greater than 20 × and preferably 30 × sequencing depth is required. We used whole genome data to identify 270 biallelic SNPs across 24 MHC genes as well as copy number variation (CNV) within class I and class II genes and conduct supertype analysis. Overall, we have provided a bioinformatic workflow for investigating variation in a complex immune gene family from whole genome sequencing data and determined current levels of diversity within koala MHC genes.

New insights into immune genes and other expanded gene families of the house fly, Musca domestica, from an improved whole genome sequence.

The house fly, Musca domestica, is a pest of livestock, transmits pathogens of human diseases, and is a model organism in multiple biological research areas. The first house fly genome assembly was published in 2014 and has been of tremendous use to the community of house fly biologists, but that genome is discontiguous and incomplete by contemporary standards. To improve the house fly reference genome, we sequenced, assembled, and annotated the house fly genome using improved techniques and technologies that were not available at the time of the original genome sequencing project. The new genome assembly is substantially more contiguous and complete than the previous genome. The new genome assembly has a scaffold N50 of 12.46 Mb, which is a 50-fold improvement over the previous assembly. In addition, the new genome assembly is within 1% of the estimated genome size based on flow cytometry, whereas the previous assembly was missing nearly one-third of the predicted genome sequence. The improved genome assembly has much more contiguous scaffolds containing large gene families.To provide an example of the benefit of the new genome, we used it to investigate tandemly arrayed immune gene families. The new contiguous assembly of these loci provides a clearer picture of the regulation of the expression of immune genes, and it leads to new insights into the selection pressures that shape their evolution.

Multiple pals gene modules control a balance between immunity and development in Caenorhabditis elegans.

The immune system continually battles against pathogen-induced pressures, which often leads to the evolutionary expansion of immune gene families in a species-specific manner. For example, the pals gene family expanded to 39 members in the Caenorhabditis elegans genome, in comparison to a single mammalian pals ortholog. Our previous studies have revealed that two members of this family, pals-22 and pals-25, act as antagonistic paralogs to control the Intracellular Pathogen Response (IPR). The IPR is a protective transcriptional response, which is activated upon infection by two molecularly distinct natural intracellular pathogens of C. elegans-the Orsay virus and the fungus Nematocida parisii from the microsporidia phylum. In this study, we identify a previously uncharacterized member of the pals family, pals-17, as a newly described negative regulator of the IPR. pals-17 mutants show constitutive upregulation of IPR gene expression, increased immunity against intracellular pathogens, as well as impaired development and reproduction. We also find that two other previously uncharacterized pals genes, pals-20 and pals-16, are positive regulators of the IPR, acting downstream of pals-17. These positive regulators reverse the effects caused by the loss of pals-17 on IPR gene expression, immunity, and development. We show that the negative IPR regulator protein PALS-17 and the positive IPR regulator protein PALS-20 colocalize inside and at the apical side of intestinal epithelial cells, which are the sites of infection for IPR-inducing pathogens. In summary, our study demonstrates that several pals genes from the expanded pals gene family act as ON/OFF switch modules to regulate a balance between organismal development and immunity against natural intracellular pathogens in C. elegans.

Tea polyphenols, astaxanthin, and melittin can significantly enhance the immune response of juvenile spotted knifejaw (Oplegnathus punctatus).

The frequent occurrence of diseases seriously hampers the sustainable development of the spotted knifejaw (Oplegnathus punctatus) breeding industry. Our previous genome-wide scan and cross-species comparative genomic analysis revealed that the immune gene family (Toll-like receptors, TLR) members of O. punctatus underwent a significant contraction event (tlr1, tlr2, tlr14, tlr5, and tlr23). To address immune genetic contraction may result in reduced immunity, we investigated whether adding different doses (0, 200, 400, 600, and 800mg/kg) of immune enhancers (tea polyphenols, astaxanthin, and melittin) to the bait after 30 days of continuous feeding could stimulate the immune response of O. punctatus. We found that the expression of tlr1, tlr14, tlr23 genes in immune organs (spleen and head kidney) was stimulated when tea polyphenols were added at 600mg/kg. The tlr2 (400mg/kg), tlr14 (200mg/kg), tlr5 (200mg/kg), and tlr23 (200mg/kg) genes expression of intestine were elevated in the tea polyphenol group. When the addition of astaxanthin is 600mg/kg, it can effectively stimulate the expression of tlr14 gene in immune organs (liver, spleen and head kidney). In the astaxanthin group, the expression of the genes tlr1 (400mg/kg), tlr14 (600mg/kg), tlr5 (400mg/kg) and tlr23 (400mg/kg) reached their highest expression in the intestine. Besides, the addition of 400mg/kg of melittin can effectively induce the expression of tlr genes in the liver, spleen and head kidney, except the tlr5 gene. The tlr-related genes expression in the intestine was not significantly elevated in the melittin group. We hypothesize that the immune enhancers could enhance the immunity of O. punctatus by increasing the expression of tlr genes, and thereby leading to increased resistance to diseases. Meanwhile, our findings further demonstrated that significant increases in weight gain rate (WGR), visceral index (VSI), and feed conversion rate (FCR) were observed at 400mg/kg, 200mg/kg and 200mg/kg of tea polyphenols, astaxanthin and melittin in the diet, respectively. Overall, our study provided valuable insights for future immunity enhancement and viral infection prevention in O. punctatus, as well as offered guidance for the healthy development of the O. punctatus breeding industry.

Population Genomics of Plasmodium falciparum and Malaria Control Implications in Abidjan (Cote d’ivoire)

Introduction: The onset of Plasmodium falciparum (P. falciparum) resistance to antimalarial drugs requires the careful surveillance of African parasite populations. Genomic tools are implemented to detect evolutionary changes that could impact malaria control and elimination strategies. Here, we evaluate the genome-wide pattern of selection and sequence variation in P. falciparum populations in Abidjan, Côte d’Ivoire. Methods: The study was conducted in three localities of Abidjan from 2013 to 2014. We collected 70 blood samples after receiving written informed consent from patients above two years of age. After extracting P. falciparum and human DNA from isolates, we performed whole-genome sequencing and used population genomics approaches to investigate the genetic diversity and complexity of infections and identify loci under positive directional selection. Results: We observed an excess of rare variants in the population, showing a clear mutation process in the isolates. Moderate Fst estimates (0.3) was detected for surfin, an immune invasion gene family. Seven iHS regions that had at least two SNPs with a score > 3.2 were identified. These regions code for genes that have been under strong directional selection. Two of these genes were the chloroquine resistance transporter (crt) on chromosome 7 and the dihydropteroate reductase (dhps) on chromosome 8. Our analyses showed that a recent selective sweep occurred for the erythrocyte membrane protein (Pfemp1). Conclusion: Our analyses identified genes under selective drug pressure and balancing selection on protective immune-specific genes. These findings demonstrate the effectiveness of genomics analyses to follow the evolution of malaria parasites and adopt appropriate strategies to eliminate malaria in Côte d’Ivoire.

The chromosome-level genome assembly of goldstripe ponyfish (Karalla daura) reveals its similarity to Chinese sillago on contracted immune gene families

The goldstripe ponyfish is a small tropical economic fish in the Leiognathidae family. The genome of this fish was assembled as 24 chromosomes with a total length of 577.66 Mb and 54.81 Mb unanchored contigs using HiFi and Hi-C sequencing technologies. There are 256.7 Mb of repeat elements, which cover 40.59% of the genome, and 21,506 coding genes, which cover 47.68%. According to phylogenetic analysis, the goldstripe ponyfish is closely related to the Sillaginidae family’s Chinese sillago. The distance between goldstripe ponyfish and Chinese sillago in the hierarchical clustering of gene family contractions and expansions is also the shortest, indicating a similarity even greater than that between croakers of the same family (Sciaenidae). The goldstripe ponyfish and Chinese sillago share 25 identical contracted gene families, the majority of which are immune recognition receptors, such as innate immunity-related C-type lectin and butyrophilin families, as well as acquired immunity-related T-cell receptor region V and the surface glycoprotein CD4, implying that these two fishes’ immune systems may adopt similar evolutionary strategy at the genomic level. Additionally, the positively selected genes of the Chinese sillago and the goldstripe ponyfish were enriched in biological functions involved in the cell cycle, such as telomeres, which may account for the disparities in body size and lifespan between the two species.

Major histocompatibility complex genomic investigation of endangered Chinese alligator provides insights into the evolution of tetrapod major histocompatibility complex and survival of critically bottlenecked species

BackgroundThe major histocompatibility complex (MHC) gene family, a vital immune gene family in vertebrates, helps animals defend against pathogens. The polymorphism of MHC genes is important for a species and is considered to be caused by the numerous alleles of MHC antigen-presenting genes. However, the mechanism of this process is unclear due to the lack of data on the MHC structure. The evolutionary trajectories of the tetrapod MHC are also unclear because of insufficient studies on the reptile MHC architecture. Here, we studied the Chinese alligator (Alligator sinensis), which experienced a population bottleneck, but the population increased rapidly in the past 30 years and is proposed to have a unique MHC system to face pathogenic challenges.ResultsWe successfully constructed a 2 Mb MHC region using bacterial artificial chromosome (BAC) library and genome data of the Chinese alligator and checked the antigen-presenting genes using transcriptome data and the rapid amplification of cDNA ends (RACE) technique. The MHC architecture reported here uncovers adjacent Class I and Class II subregions and a unique CD1 subregion. This newly added information suggested that the Class I-II structure pattern was more ancient in tetrapods and helped reconstruct the evolution of the MHC region architecture. We also found multiple groups of MHC class I (MHC-I) (12 duplicated loci, belonging to three groups, two of which were novel) and MHC class II (MHC-II) (11 duplicated loci, belonging to two groups) inside the 2 Mb MHC region, and there were three more duplicated MHC-I loci outside it. These highly duplicated antigen-presenting loci had differences in expression, amino acid length of antigen-presenting exons, and splice signal of exon and intron, which together promoted the polymorphism of duplicated genes. Although the MHC antigen-presenting genes were identified as monomorphic or oligomorphic in our previous population study, the loci with high copy numbers and many differences can make up for this loss, presenting another mechanism for polymorphism in antigen presentation. These MHC-I and MHC-IIB loci with low polymorphism for each locus, but high numbers in all, may also contribute to MHC antigen-presenting binding variability in a population.ConclusionTo summarize, the fine MHC region architecture of reptiles presented in this study completes the evolutionary trajectories of the MHC structure in tetrapods, and these distinctive MHC gene groups in the Chinese alligator may have helped this species to expand rapidly in the past recent years.

Best genome sequencing strategies for annotation of complex immune gene families in wildlife.

The biodiversity crisis and increasing impact of wildlife disease on animal and human health provides impetus for studying immune genes in wildlife. Despite the recent boom in genomes for wildlife species, immune genes are poorly annotated in nonmodel species owing to their high level of polymorphism and complex genomic organisation. Our research over the past decade and a half on Tasmanian devils and koalas highlights the importance of genomics and accurate immune annotations to investigate disease in wildlife. Given this, we have increasingly been asked the minimum levels of genome quality required to effectively annotate immune genes in order to study immunogenetic diversity. Here we set out to answer this question by manually annotating immune genes in 5 marsupial genomes and 1 monotreme genome to determine the impact of sequencing data type, assembly quality, and automated annotation on accurate immune annotation. Genome quality is directly linked to our ability to annotate complex immune gene families, with long reads and scaffolding technologies required to reassemble immune gene clusters and elucidate evolution, organisation, and true gene content of the immune repertoire. Draft-quality genomes generated from short reads with HiC or 10× Chromium linked reads were unable to achieve this. Despite mammalian BUSCOv5 scores of up to 94.1% amongst the 6 genomes, automated annotation pipelines incorrectly annotated up to 59% of manually annotated immune genes regardless of assembly quality or method of automated annotation. Our results demonstrate that long reads and scaffolding technologies, alongside manual annotation, are required to accurately study the immune gene repertoire of wildlife species.

Evaluation of Genetic Diversity and Parasite-Mediated Selection of MHC Class I Genes in Emberiza godlewskii (Passeriformes: Emberizidae)

The major histocompatibility complex (MHC) is a multi-copy immune gene family in vertebrates. Its genes are highly variable and code for antigen-presenting molecules. Characterization of MHC genes in different species and investigating the mechanisms that shape MHC diversity is an important goal in understanding the evolution of biological diversity. Here we developed a next-generation sequencing (NGS) protocol to genotype the MHC class I genes of 326 Godlewski’s buntings (Emberiza godlewskii) sampled in the Western mountain area of Beijing from 2014 to 2016. A total of 184 functional alleles were identified, including both non-classical and classical alleles, clustering into nine supertypes. Compared with other passerine birds, the number of MHC class I alleles per individual in Godlewski’s buntings is high (mean 16.1 ± 3.3, median 16). In addition, we demonstrated signatures of historical and contemporary selection on MHC genes. Reflecting historical selection, ten amino acid sites in the antigen-binding domain showed signatures of balancing selection, eight of which exhibit high amino acid polymorphism. In terms of contemporary selection, we found that specific MHC supertypes were nominally associated with the infection of two malaria parasite lineages. These findings indicate the action of historical and possibly also contemporary balancing selection and suggest negative frequency-dependent or fluctuating selection as possible selection mechanisms.

Transcriptomic Response to Perkinsus marinus in Two Crassostrea Oysters Reveals Evolutionary Dynamics of Host-Parasite Interactions.

Infectious disease outbreaks are causing widespread declines of marine invertebrates including corals, sea stars, shrimps, and molluscs. Dermo is a lethal infectious disease of the eastern oyster Crassostrea virginica caused by the protist Perkinsus marinus. The Pacific oyster Crassostrea gigas is resistant to Dermo due to differences in the host-parasite interaction that is not well understood. We compared transcriptomic responses to P. marinus challenge in the two oysters at early and late infection stages. Dynamic and orchestrated regulation of large sets of innate immune response genes were observed in both species with remarkably similar patterns for most orthologs, although responses in C. virginica were stronger, suggesting strong or over-reacting immune response could be a cause of host mortality. Between the two species, several key immune response gene families differed in their expansion, sequence variation and/or transcriptional response to P. marinus, reflecting evolutionary divergence in host-parasite interaction. Of note, significant upregulation of inhibitors of apoptosis (IAPs) was observed in resistant C. gigas but not in susceptible C. virginica, suggesting upregulation of IAPs is an active defense mechanism, not a passive response orchestrated by P. marinus. Compared with C. gigas, C. virginica exhibited greater expansion of toll-like receptors (TLRs) and positive selection in P. marinus responsive TLRs. The C1q domain containing proteins (C1qDCs) with the galactose-binding lectin domain that is involved in P. marinus recognition, were only present and significantly upregulated in C. virginica. These results point to previously undescribed differences in host defense genes between the two oyster species that may account for the difference in susceptibility, providing an expanded portrait of the evolutionary dynamics of host-parasite interaction in lophotrochozoans that lack adaptive immunity. Our findings suggest that C. virginica and P. marinus have a history of coevolution and the recent outbreaks may be due to increased virulence of the parasite.

Sequence Diversity, Locus Structure, and Evolutionary History of the SpTransformer Genes in the Sea Urchin Genome.

The generation of large immune gene families is often driven by evolutionary pressure exerted on host genomes by their pathogens, which has been described as the immunological arms race. The SpTransformer (SpTrf) gene family from the California purple sea urchin, Strongylocentrotus purpuratus, is upregulated upon immune challenge and encodes the SpTrf proteins that interact with pathogens during an immune response. Native SpTrf proteins bind both bacteria and yeast, and augment phagocytosis of a marine Vibrio, while a recombinant SpTrf protein (rSpTrf-E1) binds a subset of pathogens and a range of pathogen associated molecular patterns. In the sequenced sea urchin genome, there are four SpTrf gene clusters for a total of 17 genes. Here, we report an in-depth analysis of these genes to understand the sequence complexities of this family, its genomic structure, and to derive a putative evolutionary history for the formation of the gene clusters. We report a detailed characterization of gene structure including the intron type and UTRs with conserved transcriptional start sites, the start codon and multiple stop codons, and locations of polyadenylation signals. Phylogenetic and percent mismatch analyses of the genes and the intergenic regions allowed us to predict the last common ancestral SpTrf gene and a theoretical evolutionary history of the gene family. The appearance of the gene clusters from the theoretical ancestral gene may have been driven by multiple duplication and deletion events of regions containing SpTrf genes. Duplications and ectopic insertion events, indels, and point mutations in the exons likely resulted in the extant genes and family structure. This theoretical evolutionary history is consistent with the involvement of these genes in the arms race in responses to pathogens and suggests that the diversification of these genes and their encoded proteins have been selected for based on the survival benefits of pathogen binding and host protection.

Holosteans contextualize the role of the teleost genome duplication in promoting the rise of evolutionary novelties in the ray-finned fish innate immune system.

Over 99% of ray-finned fishes (Actinopterygii) are teleosts, a clade that comprises half of all living vertebrate species that have diversified across virtually all fresh and saltwater ecosystems. This ecological breadth raises the question of how the immunogenetic diversity required to persist under heterogeneous pathogen pressures evolved. The teleost genome duplication (TGD) has been hypothesized as the evolutionary event that provided the substrate for rapid genomic evolution and innovation. However, studies of putative teleost-specific innate immune receptors have been largely limited to comparisons either among teleosts or between teleosts and distantly related vertebrate clades such as tetrapods. Here we describe and characterize the receptor diversity of two clustered innate immune gene families in the teleost sister lineage: Holostei (bowfin and gars). Using genomic and transcriptomic data, we provide a detailed investigation of the phylogenetic history and conserved synteny of gene clusters encoding diverse immunoglobulin domain-containing proteins (DICPs) and novel immune-type receptors (NITRs). These data demonstrate an ancient linkage of DICPs to the major histocompatibility complex (MHC) and reveal an evolutionary origin of NITR variable-joining (VJ) exons that predate the TGD by at least 50 million years. Further characterizing the receptor diversity of Holostean DICPs and NITRs illuminates a sequence diversity that rivals the diversity of these innate immune receptor families in many teleosts. Taken together, our findings provide important historical context for the evolution of these gene families that challenge prevailing expectations concerning the consequences of the TGD during actinopterygiian evolution.

The Diverse Transformer (Trf) Protein Family in the Sea Urchin Paracentrotus lividus Acts through a Collaboration between Cellular and Humoral Immune Effector Arms.

Sea urchins are long-living marine invertebrates with a complex innate immune system, which includes expanded families of immune receptors. A central immune gene family in sea urchins encodes the Transformer (Trf) proteins. The Trf family has been studied mainly in the purple sea urchin Strongylocentrotus purpuratus. Here, we explore this protein family in the Mediterranean Sea urchin Paracentrotus lividus. The PlTrf genes and predicted proteins are highly diverse and show a typical Trf size range and structure. Coelomocytes and cell-free coelomic fluid from P. lividus contain different PlTrf protein repertoires with a shared subset, that bind specifically to E. coli. Using FACS, we identified five different P. lividus coelomocyte sub-populations with cell surface PlTrf protein expression. The relative abundance of the PlTrf-positive cells increases sharply following immune challenge with E. coli, but not following challenge with LPS or the sea urchin pathogen, Vibrio penaeicida. Phagocytosis of E. coli by P. lividus phagocytes is mediated through the cell-free coelomic fluid and is inhibited by blocking PlTrf activity with anti-SpTrf antibodies. Together, our results suggest a collaboration between cellular and humoral PlTrf-mediated effector arms in the P. lividus specific immune response to pathogens.

Genomic insight into diet adaptation in the biological control agent Cryptolaemus montrouzieri

BackgroundThe ladybird beetle Cryptolaemus montrouzieri Mulsant, 1853 (Coleoptera, Coccinellidae) is used worldwide as a biological control agent. It is a predator of various mealybug pests, but it also feeds on alternative prey and can be reared on artificial diets. Relatively little is known about the underlying genetic adaptations of its feeding habits.ResultsWe report the first high-quality genome sequence for C. montrouzieri. We found that the gene families encoding chemosensors and digestive and detoxifying enzymes among others were significantly expanded or contracted in C. montrouzieri in comparison to published genomes of other beetles. Comparisons of diet-specific larval development, survival and transcriptome profiling demonstrated that differentially expressed genes on unnatural diets as compared to natural prey were enriched in pathways of nutrient metabolism, indicating that the lower performance on the tested diets was caused by nutritional deficiencies. Remarkably, the C. montrouzieri genome also showed a significant expansion in an immune effector gene family. Some of the immune effector genes were dramatically downregulated when larvae were fed unnatural diets.ConclusionWe suggest that the evolution of genes related to chemosensing, digestion, and detoxification but also immunity might be associated with diet adaptation of an insect predator. These findings help explain why this predatory ladybird has become a successful biological control agent and will enable the optimization of its mass rearing and use in biological control programs.

Evidence for reduced immune gene diversity and activity during the evolution of termites.

The evolution of biological complexity is associated with the emergence of bespoke immune systems that maintain and protect organism integrity. Unlike the well-studied immune systems of cells and individuals, little is known about the origins of immunity during the transition to eusociality, a major evolutionary transition comparable to the evolution of multicellular organisms from single-celled ancestors. We aimed to tackle this by characterizing the immune gene repertoire of 18 cockroach and termite species, spanning the spectrum of solitary, subsocial and eusocial lifestyles. We find that key transitions in termite sociality are correlated with immune gene family contractions. In cross-species comparisons of immune gene expression, we find evidence for a caste-specific social defence system in termites, which appears to operate at the expense of individual immune protection. Our study indicates that a major transition in organismal complexity may have entailed a fundamental reshaping of the immune system optimized for group over individual defence.

Annotation of immune genes in the extinct thylacine (Thylacinus cynocephalus).

Advances in genome sequencing technology have enabled genomes of extinct species to be sequenced. However, given the fragmented nature of these genome assemblies, it is not clear whether it is possible to comprehensively annotate highly variable and repetitive genes such as those involved in immunity. As such, immune genes have only been investigated in a handful of extinct genomes, mainly in human lineages. In 2018 the genome of the thylacine (Thylacinus cynocephalus), a carnivorous marsupial from Tasmania that went extinct in 1936, was sequenced. Here we attempt to characterise the immune repertoire of the thylacine and determine similarity to its closest relative with a genome available, the Tasmanian devil (Sarcophilus harrisii), as well as other marsupials. Members from all major immune gene families were identified. However, variable regions could not be characterised, and complex families such as the major histocompatibility complex (MHC) were highly fragmented and located across multiple small scaffolds. As such, at a gene level we were unable to reconstruct full-length coding sequences for the majority of thylacine immune genes. Despite this, we identified genes encoding functionally important receptors and immune effector molecules, which suggests the functional capacity of the thylacine immune system was similar to other mammals. However, the high number of partial immune gene sequences identified limits our ability to reconstruct an accurate picture of the thylacine immune repertoire.

Discovery of core gene families associated with liver metastasis in colorectal cancer and regulatory roles in tumor cell immune infiltration

In this study, we aimed to uncover genes that drive the pathogenesis of liver metastasis in colorectal cancer (CRC), and identify effective genes that could serve as potential therapeutic targets for treating with colorectal liver metastasis patients based on two GEO datasets. Several bioinformatics approaches were implemented. First, differential expression analysis screened out key differentially expressed genes (DEGs) across the two GEO datasets. Based on gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, we identified the enrichment functions and pathways of the DEGs that were associated with liver metastasis in CRC. Second, immune infiltration analysis identified key immune signature gene sets associated with CRC liver metastasis, among which two key immune gene families (CD and CCL) identified as key DEGs were filtered by protein-protein interaction (PPI) network. Some of the members in these gene families were associated with disease free survival (DFS) or overall survival (OS) in two subtypes of CRC, namely COAD and READ. Finally, functional enrichment analysis of the two gene families and their neighboring genes revealed that they were closely associated with cytokine, leukocyte proliferation and chemotaxis. These results are valuable in comprehending the pathogenesis of liver metastasis in CRC, and are of seminal importance in understanding the role of immune tumor infiltration in CRC. Our study also identified potentially effective therapeutic targets for liver metastasis in CRC including CCL20, CCL24 and CD70.