A Novel Family of Major Histocompatibility Complex Class I Genes in Marsupials and Monotremes

The Major Histocompatibility Complex (MHC) class I family of genes encode for molecules that have well-conserved structures, but have evolved to perform a diverse functions. The availability of an opossum genome from the grey, short-tailed opossum, Monodelphis domestica, has allowed for analysis of MHC class I genes in a marsupial. Traditional methods for gene discovery uncovered 13 MHC class I genes in the opossum. Utilization of a novel method to search for MHC domain structures discovered a family of 17 novel MHC class I genes. These genes, named ModoUT1-17, were located in a cluster on chromosome 1, unlinked to the MHC. UT homologues are only found in marsupial and monotreme genomes, consistent with being ancient in mammals yet lost in eutherians. Twelve of the ModoUT loci are transcribed in the opossum thymus. The majority of UT transcription is in the thymus or skin, with limited expression in other tissues. Full-length sequencing of eleven transcribed ModoUT genes revealed between five and eight exons, with typical class I gene structure and few alternative splice variants. A survey of ModoUT polymorphism in different M. domestica populations found low levels of polymorphism. Limited positive selection occurs in any of the ModoUT genes, suggesting they may not be under pathogen-mediated pressure. Also uncovered in M. domestica genome search was the presence of two additional loci of the ModoUA gene, now designated ModoUA3 and ModoUA4. The ModoUA gene is thought to be the class I molecule involved in peptide presentation. These new genes were uncovered in a region of the genome that was expanded and more complete than in earlier genome assemblies. The occurrence of five to six alleles in individual M. domestica indicates three loci being transcribed. The ModoUA1 and ModoUA3 genes are highly similar and alleles cannot be distinguished, while ModoUA4 is easily identifiable, although less common and also relatively non-polymorphic and not under positive selection. The use of later assemblies and novel search methods confirmed the existence of three related MHC class I genes in the opossum, making opossums more typical of mammals by having multiple classical MHC class I loci

Nestmate Recognition and Cuticular Hydrocarbon Profiles in the Ant Formica argentea

Nestmate recognition, the ability to recognize a nestmate from a non-nestmate, is critical to the ecological success of eusocial insects. Although cuticular hydrocarbons are thought to serve as cues in nestmate recognition, little is known about how specific hydrocarbons vary between colonies and which ones are responsible for evoking nestmate recognition behaviors. The aim of my study was, using the ant Formica argentea, to investigate cuticular hydrocarbons in great detail by addressing the following questions: (1) What cuticular hydrocarbons are present? (2) Can any one group of compounds statistically classify workers by nest? (3) Which structural classes of hydrocarbons evoke a nestmate recognition response? (4) Do increased differences in cuticular hydrocarbon profiles predict aggression? (5) How do different structural classes of hydrocarbons change with time? After chemical analyses I found that the cuticular hydrocarbon profile of F. argentea workers contain a mixture of n-alkanes, alkenes, and methylalkanes which stay fairly constant within a nest but vary in relative proportion between nests. Additionally, using the only the C29 methyl-alkanes in a hierarchical cluster analysis was enough to correctly classify workers by nest. Behavioral experiments demonstrated that both methylalkanes and alkenes increased aggression in workers while n-alkanes did not. Differences in cuticular hydrocarbon profiles between pairs were a good predictor of aggression with differences between particular methyl-alkanes weighing more heavily on the statistical analysis. When kept in a uniform environment the average relative proportions n-alkanes, alkenes, and methyl-alkanes, varied with time, while the relative proportion of the C29 methyl-alkanes remained constant. These finding indicate that all structural classes of cuticular hydrocarbons should not be grouped together or treated equally in nestmate recognition analyses. This study improves our understanding of nestmate recognition and cuticular hydrocarbon profiles in eusocial insects

Vector competence of Aedes aegypti, Culex tarsalis, and Culex quinquefasciatus from California for Zika virus.

Zika virus (ZIKV) has emerged since 2013 as a significant global human health threat following outbreaks in the Pacific Islands and rapid spread throughout South and Central America. Severe congenital and neurological sequelae have been linked to ZIKV infections. Assessing the ability of common mosquito species to transmit ZIKV and characterizing variation in mosquito transmission of different ZIKV strains is important for estimating regional outbreak potential and for prioritizing local mosquito control strategies for Aedes and Culex species. In this study, we evaluated the laboratory vector competence of Aedes aegypti, Culex quinquefasciatus, and Culex tarsalis that originated in areas of California where ZIKV cases in travelers since 2015 were frequent. We compared infection, dissemination, and transmission rates by measuring ZIKV RNA levels in cohorts of mosquitoes that ingested blood meals from type I interferon-deficient mice infected with either a Puerto Rican ZIKV strain from 2015 (PR15), a Brazilian ZIKV strain from 2015 (BR15), or an ancestral Asian-lineage Malaysian ZIKV strain from 1966 (MA66). With PR15, Cx. quinquefasciatus was refractory to infection (0%, N = 42) and Cx. tarsalis was infected at 4% (N = 46). No ZIKV RNA was detected in saliva from either Culex species 14 or 21 days post feeding (dpf). In contrast, Ae. aegypti developed infection rates of 85% (PR15; N = 46), 90% (BR15; N = 20), and 81% (MA66; N = 85) 14 or 15 dpf. Although MA66-infected Ae. aegypti showed higher levels of ZIKV RNA in mosquito bodies and legs, transmission rates were not significantly different across virus strains (P = 0.13, Fisher's exact test). To confirm infectivity and measure the transmitted ZIKV dose, we enumerated infectious ZIKV in Ae. aegypti saliva using Vero cell plaque assays. The expectorated plaque forming units PFU varied by viral strain: MA66-infected expectorated 13±4 PFU (mean±SE, N = 13) compared to 29±6 PFU for PR15-infected (N = 13) and 35±8 PFU for BR15-infected (N = 6; ANOVA, df = 2, F = 3.8, P = 0.035). These laboratory vector competence results support an emerging consensus that Cx. tarsalis and Cx. quinquefasciatus are not vectors of ZIKV. These results also indicate that Ae. aegypti from California are efficient laboratory vectors of ancestral and contemporary Asian lineage ZIKV

Marsupials and monotremes possess a novel family of MHC class I genes that is lost from the eutherian lineage

Major histocompatibility complex (MHC) class I genes are found in the genomes of all jawed vertebrates. The evolution of this gene family is closely tied to the evolution of the vertebrate genome. Family members are frequently found in four paralogous regions, which were formed in two rounds of genome duplication in the early vertebrates, but in some species class Is have been subject to additional duplication or translocation, creating additional clusters. The gene family is traditionally grouped into two subtypes: classical MHC class I genes that are usually MHC-linked, highly polymorphic, expressed in a broad range of tissues and present endogenously-derived peptides to cytotoxic T-cells; and non-classical MHC class I genes generally have lower polymorphism, may have tissue-specific expression and have evolved to perform immune-related or non-immune functions. As immune genes can evolve rapidly and are subject to different selection pressure, we hypothesised that there may be divergent, as yet unannotated or uncharacterised class I genes. Results: Application of a novel method of sensitive genome searching of available vertebrate genome sequences revealed a new, extensive sub-family of divergent MHC class I genes, denoted as UT, which has not previously been characterized. These class I genes are found in both American and Australian marsupials, and in monotremes, at an evolutionary chromosomal breakpoint, but are not present in non-mammalian genomes and have been lost from the eutherian lineage. We show that UT family members are expressed in the thymus of the gray short-tailed opossum and in other immune tissues of several Australian marsupials. Structural homology modelling shows that the proteins encoded by this family are predicted to have an open, though short, antigen-binding groove. Conclusions: We have identified a novel sub-family of putatively non-classical MHC class I genes that are specific to marsupials and monotremes. This

The pathology and pathogenicity of a novel Haemoproteus spp. infection in wild Little Penguins (Eudyptula minor)

One hundred and thirty four Little Penguin (Eudyptula minor) carcases found since 2004 in south west Australia were necropsied. The livers and spleens from ten of the penguins exhibited varying degrees of multifocal, randomly scattered areas of necrosis and varying numbers of parasites were associated with these areas. Hepatomegaly and splenomegaly were noted in many of these ten cases. Necrosis and parasites were also observed in the cardiac muscle of four of the cases and in the lung tissue in one of the penguins. Using PCR, the parasites were positively identified in four of the cases as Haemoproteus spp. and morphologically identical tissue stage parasites associated with histopathological changes were observed in all ten dead penguins. This is the first study to demonstrate both the in situ presence of the Haemoproteus parasite in any member of the Sphensicidae family and mortality due to its presence. We postulate the involvement of anomalous environmental conditions in a potential increase in local vectors