Sequence variation at the major histocompatibility complex locus DQ beta in beluga whales (Delphinapterus leucas) [published erratum appears in Mol Biol Evol 1995 Nov;12(6):1174]

Genetic variation at the Major Histocompatibility Complex locus DQ beta was analyzed in 233 beluga whales (Delphinapterus leucas) from seven populations: St. Lawrence Estuary, eastern Beaufort Sea, eastern Chukchi Sea, western Hudson Bay, eastern Hudson Bay, southeastern Baffin Island, and High Arctic and in 12 narwhals (Monodon monoceros) sympatric with the High Arctic beluga population. Variation was assessed by amplification of the exon coding for the peptide binding region via the polymerase chain reaction, followed by either cloning and DNA sequencing or single-stranded conformation polymorphism analysis. Five alleles were found across the beluga populations and one in the narwhal. Pairwise comparisons of these alleles showed a 5:1 ratio of nonsynonymous to synonymous substitutions per site leading to eight amino acid differences, five of which were nonconservative substitutions, centered around positions previously shown to be important for peptide binding. Although the amount of allelic variation is low when compared with terrestrial mammals, the nature of the substitutions in the peptide binding sites indicates an important role for the DQ beta locus in the cellular immune response of beluga whales. Comparisons of allele frequencies among populations show the High Arctic population to be different (P < or = .005) from the other beluga populations surveyed. In these other populations an allele, Dele-DQ beta*0101-2, was found in 98% of the animals, while in the High Arctic it was found in only 52% of the animals. Two other alleles were found at high frequencies in the High Arctic population, one being very similar to the single allele found in narwhal.      

Ant community composition and functional traits in new grassland strips within agricultural landscapes

1. Ongoing intensification and fragmentation of European agricultural landscapes dramatically reduce biodiversity and associated functions. Enhancing perennial noncrop areas holds great potential to support ecosystem services such as ant‐mediated pest control.
2. To study the potential of newly established grassland strips to enhance ant diversity and associated functions, we used hand collection data and predation experiments to investigate differences in (a) ant community composition and (b) biocontrol‐related functional traits, and (c) natural pest control across habitats in cereal fields, old grasslands, and new grassland transects of three years of age.
3. Ant species diversity was similar between new and old grasslands, but significantly higher in new grasslands than in surrounding cereal fields. Contrary, ant community composition of new grasslands was more similar to cereal fields and distinct from the species pool of old grasslands. The functional trait space covered by the ant communities showed the same distribution between old and new grasslands. Pest control did not differ significantly between habitat types and therefore could not be linked to the prevalence of functional ant traits related to biocontrol services in new grasslands.
4. Our findings not only show trends of convergence between old and new grasslands, but also indicate that enhancing ant diversity through new grasslands takes longer than three years to provide comparable biodiversity and functionality.
5. Synthesis and applications: Newly established grasslands can increase ant species richness and abundance and provide a consistent amount of biocontrol services in agroecosystems. However, three years after their establishment, new grasslands were still dominated by common agrobiont ant species and lacked habitat specialists present in old grasslands, which require a constant supply of food resources and long colony establishment times. New grasslands represent a promising measure for enhancing agricultural landscapes but must be preserved in the longer term to promote biodiversity and resilience of associated ecosystem services.

     

Analysis of nuclear targeting activities of transport signals in the human immunodeficiency virus Rev protein

The human immunodeficiency Rev protein shuttles between the nucleus and cytoplasm, while accumulating to high levels in the nucleus. Rev has a nuclear localization signal (NLS; AA 35-50) with an arginine-rich motif (ARM) that interacts with importin beta and a leucine-rich nuclear export signal (NES; AA 75-84) recognized by CRM1/exportin 1. Here we explore nuclear targeting activities of the transport signals of Rev. GFP tagging and quantitative fluorescence microscopy were used to study the localization behavior of Rev NLS/ARM mutants under conditions inhibiting the export of Rev. Rev mutant M5 was actively transported to the nucleus, despite its known failure to bind importin beta. Microinjection of transport substrates with Rev-NES peptides revealed that the Rev-NES has both nuclear import and export activities. Replacement of amino acid residues "PLER" (77-80) of the NES with alanines abolished bidirectional transport activity of the Rev-NES. These results indicate that both transport signals of Rev have nuclear import capabilities and that the Rev NLS has more than one nuclear targeting activity. This suggests that Rev is able to use various routes for nuclear entry rather than depending on a single pathway.     

Elongation factor-1 alpha occurs as two copies in bees: implications for phylogenetic analysis of EF-1 alpha sequences in insects

We report the complete sequence of a paralogous copy of elongation factor-1 alpha (EF-1 alpha) in the honeybee, Apis mellifera (Hymenoptera: Apidae). This copy differs from a previously described copy in the positions of five introns and in 25% of the nucleotide sites in the coding regions. The existence of two paralogous copies of EF-1 alpha in Drosophila and Apis suggests that two copies of EF-1 alpha may be widespread in the holometabolous insect orders. To distinguish between a single, ancient gene duplication and parallel, independent fly and bee gene duplications, we performed a phylogenetic analysis of hexapod EF-1 alpha sequences. Unweighted parsimony analysis of nucleotide sequences suggests an ancient gene duplication event, whereas weighted parsimony analysis of nucleotides and unweighted parsimony analysis of amino acids suggests the contrary: that EF-1 alpha underwent parallel gene duplications in the Diptera and the Hymenoptera. The hypothesis of parallel gene duplication is supported both by congruence among nucleotide and amino acid data sets and by topology-dependent permutation tail probability (T-PTP) tests. The resulting tree topologies are also congruent with current views on the relationships among the holometabolous orders included in this study (Diptera, Hymenoptera, and Lepidoptera). More sequences, from diverse orders of holometabolous insects, will be needed to more accurately assess the historical patterns of gene duplication in EF-1 alpha.      

Molecular control of systemic bile acid homeostasis by the liver glucocorticoid receptor

Systemic bile acid (BA) homeostasis is a critical determinant of dietary fat digestion, enterohepatic function, and postprandial thermogenesis. However, major checkpoints for the dynamics and the molecular regulation of BA homeostasis remain unknown. Here we show that hypothalamic-pituitary-adrenal (HPA) axis impairment in humans and liver-specific deficiency of the glucocorticoid receptor (GR) in mice disrupts the normal changes in systemic BA distribution during the fasted-to-fed transition. Fasted mice with hepatocyte-specific GR knockdown had smaller gallbladder BA content and were more susceptible to developing cholesterol gallstones when fed a cholesterol-rich diet. Hepatic GR deficiency impaired liver BA uptake/transport via lower expression of the major hepatocyte basolateral BA transporter, Na(+)-taurocholate transport protein (Ntcp/Slc10a1), which affected dietary fat absorption and brown adipose tissue activation. Our results demonstrate a role of the HPA axis in the endocrine regulation of BA homeostasis through the liver GR control of enterohepatic BA recycling.     

Evolutionary history of the genus Listeria and its virulence genes

The genus Listeria contains the two pathogenic species Listeria monocytogenes and Listeria ivanovii and the four apparently apathogenic species Listeria innocua, Listeria seeligeri, Listeria welshimeri, and Listeria grayi. Pathogenicity of the former two species is enabled by an approximately 9 kb virulence gene cluster which is also present in a modified form in L. seeligeri. For all Listeria species, the sequence of the virulence gene cluster locus and its flanking regions was either determined in this study or assembled from public databases. Furthermore, some virulence-associated internalin loci were compared among the six species. Phylogenetic analyses were performed on a data set containing the sequences of prs, ldh, vclA, and vclB (all directly flanking the virulence gene cluster), as well as the iap gene and the 16S and 23S-rRNA coding genes which are located at different sites in the listerial chromosomes. L. grayi represents the deepest branch within the genus. The remaining five species form two groupings which have a high bootstrap support and which are consistently found by using different treeing methods. One lineage represents L. monocytogenes and L. innocua, while the other contains L. welshimeri, L. ivanovii and L. seeligeri, with L. welshimeri forming the deepest branch. Based on this perception, we tried to reconstruct the evolution of the virulence gene cluster. Since no traces of lateral gene transfer events could be detected the most parsimonious scenario is that the virulence gene cluster was present in the common ancestor of L. monocytogenes, L. innocua, L. ivanovii, L. seeligeri and L. welshimeri and that the pathogenic capability has been lost in two separate events represented by L. innocua and L. welshimeri. This hypothesis is also supported by the location of the putative deletion breakpoints of the virulence gene cluster within L. innocua and L. welshimeri.     

Mortality in over 350,000 Insured Swedish Dogs from 1995–2000: II. Breed-Specific Age and Survival Patterns and Relative Risk for Causes of Death

This study continues analysis from a companion paper on over 350,000 insured Swedish dogs up to 10 years of age contributing to more than one million dog-years at risk during 1995–2000. The age patterns for total and diagnostic mortality and for general causes of death (trauma, tumour, locomotor, heart and neurological) are presented for numerous breeds. Survival estimates at five, eight and 10 years of age are calculated. Survival to 10 years of age was 75% or more in Labrador and golden retrievers, miniature and toy poodles and miniature dachshunds and lowest in Irish wolfhounds (91% dead by 10 years). Multivariable analysis was used to estimate the relative risk for general and more specific causes of death between breeds accounting for gender and age effects, including two-way interactions. Older females had tumour as a designated cause of death more often than males in most breeds, but not in the Bernese mountain dog. Information presented in this and the companion paper inform our understanding of the population level burden of disease, and support decision-making at the population and individual level about health promotion efforts and treatment and prognosis of disease events.     

Non-regulatory CD8+CD45RO+CD25+ T-lymphocytes may compensate for the loss of antigen-inexperienced CD8+CD45RA+ T-cells in old age

The age-related decline in immune system functions is responsible for the increased prevalence of infectious diseases and the low efficacy of vaccination in elderly individuals. In particular, the number of peripheral naive T-cells declines throughout life and they exhibit severe functional defects at advanced age. However, we have recently identified a non-regulatory CD8+CD45RO+ CD25+ T-cell subset that occurs in a subgroup of healthy elderly individuals, who still exhibit an intact humoral immune response following influenza vaccination. Here, we demonstrate that CD8+CD45RO+CD25+ T-cells share phenotypic and functional characteristics with naive CD8+CD45RA+CD28+ T-cells from young individuals, despite their expression of CD45RO. CD8+CD45RO+ CD25+ T-cells also have long telomeres and upon antigenic challenge, they efficiently expand in vitro and differentiate into functional effector cells. The expanded population also maintains a diverse T-cell receptor repertoire. In conclusion, CD8+CD45RO+CD25+ T-cells from elderly individuals compensate for the loss of functional naive T-cells and may therefore be used as a marker of immunological competence in old age.     

Live imaging of <Emphasis Type="Italic">Drosophila</Emphasis>gonad formation reveals roles for Six4 in regulating germline and somatic cell migration

Background  

Movement of cells, either as amoeboid individuals or in organised groups, is a key feature of organ formation. Both modes of migration occur during Drosophila embryonic gonad development, which therefore provides a paradigm for understanding the contribution of these processes to organ morphogenesis. Gonads of Drosophila are formed from three distinct cell types: primordial germ cells (PGCs), somatic gonadal precursors (SGPs), and in males, male-specific somatic gonadal precursors (msSGPs). These originate in distinct locations and migrate to associate in two intermingled clusters which then compact to form the spherical primitive gonads. PGC movements are well studied, but much less is known of the migratory events and other interactions undergone by their somatic partners. These appear to move in organised groups like, for example, lateral line cells in zebra fish or Drosophila ovarian border cells.