Platypus globin genes and flanking loci suggest a new insertional model for beta-globin evolution in birds and mammals

Background  

Vertebrate alpha (α)- and beta (β)-globin gene families exemplify the way in which genomes evolve to produce functional complexity. From tandem duplication of a single globin locus, the α- and β-globin clusters expanded, and then were separated onto different chromosomes. The previous finding of a fossil β-globin gene (ω) in the marsupial α-cluster, however, suggested that duplication of the α-β cluster onto two chromosomes, followed by lineage-specific gene loss and duplication, produced paralogous α- and β-globin clusters in birds and mammals. Here we analyse genomic data from an egg-laying monotreme mammal, the platypus (Ornithorhynchus anatinus), to explore haemoglobin evolution at the stem of the mammalian radiation.     

Autoantibody systems in rheumatoid arthritis: specificity, sensitivity and diagnostic value

The diagnosis of rheumatoid arthritis (RA) is primarily based on clinical symptoms, so it is often difficult to diagnose RA in very early stages of the disease. A disease-specific autoantibody that could be used as a serological marker would therefore be very useful. Most autoimmune diseases are characterized by a polyclonal B-cell response targeting multiple autoantigens. These immune responses are often not specific for a single disease. In this review, the most important autoantibody/autoantigen systems associated with RA are described and their utility as a diagnostic and prognostic tool, including their specificity, sensitivity and practical application, is discussed. We conclude that, at present, the antibody response directed to citrullinated antigens has the most valuable diagnostic and prognostic potential for RA.     

Regulation of phenylacetic acid degradation genes of Burkholderia cenocepacia K56-2

Background  

Metabolically versatile soil bacteria Burkholderia cepacia complex (Bcc) have emerged as opportunistic pathogens, especially of cystic fibrosis (CF). Previously, we initiated the characterization of the phenylacetic acid (PA) degradation pathway in B. cenocepacia, a member of the Bcc, and demonstrated the necessity of a functional PA catabolic pathway for full virulence in Caenorhabditis elegans. In this study, we aimed to characterize regulatory elements and nutritional requirements that control the PA catabolic genes in B. cenocepacia K56-2.     

Assessment of the relative contribution of asexual propagation in a population of the coral-excavating sponge Cliona delitrix from the Bahamas

Cliona delitrix is a very destructive coral-excavating sponge in Caribbean coral reef systems, particularly for Montastraea species. Little is known about how these excavating sponges propagate across coral reefs. In this study a hypothesis was tested that coral breakage caused by the bioeroding activity facilitates the asexual propagation of this sponge and in turn favors the spread of the most aggressive sponge genotypes. An allozyme analysis, involving 12 loci systems of 52 sponge individuals from a total of 13 Montastraea heads, found that no two sponges possessed identical multi-locus genotypes. Contrary to the pattern expected for fragmenting species, the incidence of clonality and asexual propagation at the population level was minimal. The lack of correlation between genetic and physical distances for the studied sponges also suggests that population maintenance appears to derive from larval dispersal, with a spatial range of dispersal larger than the average distance between the coral heads (10–10² m).     

Microsatellite evolution in congeneric mammals: domestic and bighorn sheep

We compared genotypes at eight (AC)n microsatellite loci in domestic sheep (Ovis aries) and wild Rocky Mountain bighorn sheep (O. canadensis). The domestic sheep had greater genetic variation, higher allele-size variances, and larger allele sizes than the wild sheep. Accumulating evidence from higher taxonomic comparisons shows that these parameters are biased if microsatellite loci are selected in one taxon and used in another. Our results demonstrate similar biases between congeneric species. We compared standard measures of genetic variation, differentiation, and distance within and between species (H, D, FST) to newer measures based on allele-size variance (SW, SB, RST). The size-based distances better detected species-level divergence, but standard measures better distinguished allopatric populations. Empirical calibration of these measures at the subspecies level is needed to establish their useful ranges.      

Nucleotide sequence of the Acinetobacter calcoaceticus trpGDC gene cluster

A plasmid library of Acinetobacter calcoaceticus HindIII fragments was constructed, and clones that complemented an Escherichia coli pabA mutant were selected. Plasmids containing a 3.9-kb fragment of A. calcoaceticus DNA that also complemented E. coli trpD and trpC-(trpF+) mutants were obtained. We infer that complementation of E. coli pabA mutants was the result of the expression of the amphibolic anthranilate- synthase/p-aminobenzoate-synthase glutamine-amidotransferase gene and that the plasmid insert carried the entire trpGDC gene cluster. In E. coli minicells, the plasmid insert directed the synthesis of polypeptides of 44,000, 33,000, and 20,000 daltons, molecular masses that are consistent with the reported molecular masses of phosphoribosylanthranilate transferase, indoleglycerol-phosphate synthase, and anthranilate-synthase component II, respectively. A 3,105- bp nucleotide sequence was determined. Comparison of the A. calcoaceticus trpGDC sequences with other known trp gene sequences has allowed insight into (1) the evolution of the amphibolic trpG gene, (2) varied strategies for coordinate expression of trp genes, and (3) mechanisms of gene fusions in the trp operon.      

A model for nonexercising hindlimb muscles in exercising animals

Nonexercising muscles appear to be metabolically active during exercise. Animal models for this purpose have not been established. However, we have been able to teach animals to run on their forelimbs while their hindlimbs are suspended above the treadmill with no visible limb movement. To document that indeed this mode of exercise does not provoke additional muscle activity, we have compared the levels of neural activation of the soleus and plantaris muscles using a computer analysis of the electromyographic interference pattern, recorded from bipolar fine wire electrodes implanted across each muscle. Via computer analyses of the electromyographic interference patterns the frequencies and amplitudes of motor unit action potentials were obtained. The data were sampled during 20 s of every minute of observation. Comparisons were made in four conditions: (i) resting on the treadmill while bearing weight on the hindlimbs (normal rest), (ii) running on the treadmill (15 m/min, 8% grade) on all four limbs (normal exercise), (iii) resting while the hindlimbs were suspended in a harness above the treadmill (suspended rest), and (iv) exercising with the forelimbs (15 m/min, 8% grade) while the hindlimbs were suspended above the treadmill (suspended exercise). All four experimental conditions were carried out for 90 min each and were performed by each animal. The results clearly show that muscle activities (frequencies and amplitudes), when the hindlimbs are suspended above the treadmill, at rest or during exercise, are lower than the activities in these same muscles when the animals are at rest, supporting only their body weight. Activities in the same muscles during exercise were from 300 to 2000% greater than during hindlimb suspension.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distributions of two recently inserted long interspersed elements of the L1 repetitive family at the Alb and beta h3 loci in wild mice populations

The presence of the L1 sequences, L1Md4 next to the pseudogene beta h3 and I12 found in the twelfth intron of the albumin gene, in certain strains of laboratory mice but not of others has led to the suggestion that these sequences were recent insertions into the Mus mus domesticus genome. To be sure that they are really recent insertions and not relics of an ancestral chromosome, we investigated the presence or absence of these sequences in populations of wild mice belonging to the semispecies M. m. domesticus and M. m. musculus as well as in other species of the genus Mus and in related murids. The sequence I12 in the albumin gene was found in 34% of the chromosomes of the wild mice belonging to M. m. domesticus and to a lesser extent (6%) in M. m. musculus. Of 114 M. m. domesticus chromosomes, L1Md4 was found in only nine, seven of which came from the same locality. Its presence was associated with the haplotype Hbbp, which is relatively rare in European populations of M. musculus. Since there was no evidence for the presence of these two L1 sequences in more distantly related species, we conclude that they are recent insertions in the M. musculus genome.