HOM-C evolution in Drosophila: is there a need for Hox gene clustering?

The conservation of Homeotic (Hox) gene clustering and colinearity in many metazoans indicates that functional constraints operate on this genome organization. However, several studies have questioned its relevance in Drosophila. Here, we analyse the genomic organization of Hox and Hox-derived genes in 13 fruitfly species and the mosquito Anopheles gambiae. We found that at least seven different Homeotic complex (HOM-C) arrangements exist among Drosophila species, produced by three major splits, five microinversions and six gene transpositions. This dynamism contrasts with the stable organization of the complex in many other taxa. Although there is no evidence of an absolute requirement for Hox gene clustering in Drosophila, we found that strong functional constraints act on the individual genes.     

Evolution of the β-globin gene cluster in man and the primates

The arrangement of primate β-related globin genes has been determined by restriction endonuclease mapping of genomic DNA from species ranging from prosimians to man. The arrangement of the entire ?γγδβ-globin gene cluster in the gorilla and the yellow baboon is indistinguishable from that of man. Restriction site differences between these species are consistent with a surprisingly low overall rate of intergenic DNA sequence divergence of approximately 1% in 5 million years. A new world monkey (owl monkey) has a single γ-globin gene, suggesting that the ^Gγ-^Aγ-globin gene duplication in man is ancient, and occurred about 20 to 40 million years ago. The β-globin gene cluster in the brown lemur, a prosimian, is remarkably short (about 20,000 base-pairs) and contains single ?-, γ- and β-globin genes. The γ- and β-globin genes in this animal are separated by a curious gene containing the 3′ end of a β-globin gene preceded by sequences related to the 5′ end of the ?-globin gene.     

Is gene therapy a good therapeutic approach for HIV-positive patients?

Background

Vaccination of neonates is generally difficult due to the immaturity of the immune system and consequent higher susceptibility to tolerance induction. Genetic immunization has been described as an alternative to trigger a stronger immune response in neonates, including significant Th1 polarization. In this investigation we analysed the potential use of a genetic vaccine containing the heat shock protein (hsp65) from Mycobacterium leprae (pVAXhsp65) against tuberculosis (TB) in neonate mice. Aspects as antigen production, genomic integration and immunogenicity were evaluated.

Methods

Hsp65 message and genomic integration were evaluated by RT-PCR and Southern blot, respectively. Immunogenicity of pVAXhsp65 alone or combined with BCG was analysed by specific induction of antibodies and cytokines, both quantified by ELISA.

Results

This DNA vaccine was transcribed by muscular cells of neonate mice without integration into the cellular genome. Even though this vaccine was not strongly immunogenic when entirely administered (three doses) during early animal's life, it was not tolerogenic. In addition, pVAXhsp65 and BCG were equally able to prime newborn mice for a strong and mixed immune response (Th1 + Th2) to pVAXhsp65 boosters administered later, at the adult life.

Conclusion

These results suggest that pVAXhsp65 can be safely used as a priming stimulus in neonate animals in prime-boost similar strategies to control TB. However, priming with BCG or pVAXhsp65, directed the ensuing immune response triggered by an heterologous or homologous booster, to a mixed Th1/Th2 pattern of response. Measures as introduction of IL-12 or GM-CSF genes in the vaccine construct or even IL-4 neutralization, are probably required to increase the priming towards Th1 polarization to ensure control of tuberculosis infection.     

What's in a name? Are MSG and umami the same?

The Japanese word `umami' has a long past. It was already inuse during the Edo period (Tokugawa Shogunate) of Japanese history,which ended in 1868 (Mason, 1993). In Japanese, `umami' oftenconnotes a cognitive category (Yamaguchi and Ninomiya, 1998) oftaste, or perhaps flavor, with definitions that include deliciousness, flavor,relish,     

Electrophoretic and chromatographic evidence for allelic polymorphisms in the river buffalo α-globin gene complex

Isoelectric focusing in the ultranarrow immobilized (7.1–7.5) pH gradient (IPG) of hemoglobin and high-performances liquid chromatography (HPLC) of globin chains were used to investigate Hb polymorphism in Italian river buffalo. Six different phenotypes, each characterized by two or four different Hbs, were detected by IPG, whereas two different^IIα-globin chains were separated from two different^Iα-chains by HPLC. Two α-chains (^Iα¹ and^IIα³), and Hbs with similar mobilities (Hb1 andHb3), were associated with the AA Hb phenotype: two α-chains (^Iα² and^IIα⁴), and Hbs with different mobilities (Hb2 andHb4), were associated with the BB phenotype: two sets of doublet Hbs were associated with the AB phenotype, thus suggesting allelic polymorphisms at the two α loci. An allele at the β locus is responsible for increasing to as many as eight the number of different Hbs, thus further complicating the notable Hb polymorphism of the river buffalo.     

Arthropodization in the Hirudinea: evidence for a phylogenetic link with insects and other Uniramia?

The Hirudinea have a number of arthropod-like characters, including a true haemocoel and compound eyes. This 'arthropodization' may have bearing on the origin of the arthropod phylum Uniramia. Certain traits shared by Clitellata and Uniramia are interpreted as primitive and compatible with the view that a monophyletic link exists between these two groups: 'internal' fertilization, egg protected by cocoon/chorion, egg yolky with direct development not invoking a planktotrophic larval stage, formation and fate of presumptive areas in early embryology, uniramous lobopodial-like structures and the presence of uniramous mouthparts. Still other traits shared by Hirudinea and Hexapoda are interpreted as advanced and evidence for a paraphyletic relationship between leeches and pterygote insects: oogenesis with nurse cells, cephalization and segmental constancy. It is proposed that a major theme in uniramian evolution is the invasion of land from freshwater by a pre-lobopodial clitellate-like ancestor, the lobopodium being an adaptation to terrestrial locomotion. These views give new significance to the poorly studied fossil segmented worms from freshwater and terrestrial palaeohabitats.     

Expression of pair rule gene orthologs in the blastoderm of a myriapod: evidence for pair rule-like mechanisms?

ABSTRACT: BACKGROUND: A hallmark of Drosophila segmentation is the stepwise subdivision of the body into smaller and smaller units, and finally into the segments. This is achieved by the function of the well-understood segmentation gene cascade. The first molecular sign of a segmented body appears with the action of the pair rule genes, which are expressed as transversal stripes in alternating segments. Drosophila development, however, is derived, and in most other arthropods only the anterior body is patterned (almost) simultaneously from a pre-existing field of cells; posterior segments are added sequentially from a posterior segment addition zone. A long-standing question is to what extent segmentation mechanisms known from Drosophila may be conserved in short-germ arthropods. Despite the derived developmental modes, it appears more likely that conserved mechanisms can be found in anterior patterning. RESULTS: Expression analysis of pair rule gene orthologs in the blastoderm of the pill millipede Glomeris marginata (Myriapoda: Diplopoda) suggests that these genes are generally involved in segmenting the anterior embryo. We find that the Glomeris pairberry-1 (pby-1) gene is expressed in a pair rule pattern that is also found in insects and a chelicerate, the mite Tetraynchus urticae. Other Glomeris pair rule gene orthologs are expressed in double segment wide domains in the blastoderm, which at subsequent stages split into two stripes in adjacent segments. CONCLUSIONS: The expression patterns of the millipede pair rule gene orthologs resemble pair rule patterning in Drosophila and other insects, and thus represent evidence for the presence of an ancestral pair rule-like mechanism in myriapods. We discuss the possibilities that blastoderm patterning may be conserved in long-germ and short-germ arthropods, and that a posterior double segmental mechanism may be present in short-germ arthropods.     

How many and when? Optimising targeted gene flow for a step change in the environment

Targeted gene flow is an emerging conservation strategy that involves introducing individuals with particular traits to places where these traits are of benefit. One obvious application is to adapt a recipient population to a known threat, but questions remain as to how best to achieve this. Here, we vary timing and size of the introduction to maximise our objective – survival of the recipient population's genome. We explore a generic population model as well as a specific example – the northern quoll, an Australian marsupial predator threatened by the toxic cane toad. We reveal a trade‐off between preserving the recipient genome and reducing population extinction risk, but key management levers can often optimise this so that nearly 100% of the recipient population's genome is preserved. Any action was better than none but the size of the benefit was sensitive to outbreeding depression, recombination rate, and the timing and size of the introduction.     

A genome-wide screen identifies a single β-defensin gene cluster in the chicken: implications for the origin and evolution of mammalian defensins

Background  

Defensins comprise a large family of cationic antimicrobial peptides that are characterized by the presence of a conserved cysteine-rich defensin motif. Based on the spacing pattern of cysteines, these defensins are broadly divided into five groups, namely plant, invertebrate, α-, β-, and θ-defensins, with the last three groups being mostly found in mammalian species. However, the evolutionary relationships among these five groups of defensins remain controversial.     

Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds?

Among vertebrates, the sense of smell is mediated by olfactory receptors (ORs) expressed in sensory neurons within the olfactory epithelium. Comparative genomic studies suggest that the olfactory acuity of mammalian species correlates positively with both the total number and the proportion of functional OR genes encoded in their genomes. In contrast to mammals, avian olfaction is poorly understood, with birds widely regarded as relying primarily on visual and auditory inputs. Here, we show that in nine bird species from seven orders (blue tit, Cyanistes caeruleus; black coucal, Centropus grillii; brown kiwi, Apteryx australis; canary, Serinus canaria; galah, Eolophus roseicapillus; red jungle fowl, Gallus gallus; kakapo, Strigops habroptilus; mallard, Anas platyrhynchos; snow petrel, Pagodroma nivea), the majority of amplified OR sequences are predicted to be from potentially functional genes. This finding is somewhat surprising as one previous report suggested that the majority of OR genes in an avian (red jungle fowl) genomic sequence are non-functional pseudogenes. We also show that it is not the estimated proportion of potentially functional OR genes, but rather the estimated total number of OR genes that correlates positively with relative olfactory bulb size, an anatomical correlate of olfactory capability. We further demonstrate that all the nine bird genomes examined encode OR genes belonging to a large gene clade, termed gamma-c, the expansion of which appears to be a shared characteristic of class Aves. In summary, our findings suggest that olfaction in birds may be a more important sense than generally believed.     

Is LEAFY a useful marker gene for the flower-inflorescence boundary in the Euphorbia cyathium?

The flower-like reproductive structure of Euphorbia s.l. (Euphorbiaceae) is widely believed to have evolved from an inflorescence, and is therefore interpreted as a special type of pseudanthium, termed a cyathium. However, fuzzy morphological boundaries between the inflorescence, individual flowers, and organs have fuelled the suggestion that the cyathium does not merely superficially resemble a flower but could actually share developmental genetic pathways with a conventional flower. To test this hypothesis, immunolocalizations of FLORICAULA/LEAFY (LFY), a protein associated with floral identity in many angiosperm species, were performed in developing cyathia of different species of Euphorbia. Expression of the LFY protein was found not only in individual floral primordia (as predicted from results in the model organisms Arabidopsis and Anthirrhinum), but also in the cyathium primordium and in the primordia of partial male inflorescences. These results provide further evidence that the evolution of floral traits in pseudanthial inflorescences often involves expression of floral development genes in the inflorescence apex. This finding blurs the conventional rigid distinction between flowers and inflorescences.     

β-Thalassemia major resulting from a compound heterozygosity for the β-globin gene mutation: further evidence for multiple origin and migration of the thalassemia gene

Summary We describe in a Japanese family -thalassemia resulting from a compound heterozygosity for a -globin gene mutation. One mutation is a C-to-T transition at IVS-2 nucleotide position 654 on the background of Mediterranean haplotype IX. Another mutation is a G-to-A transition at IVS-2 nucleotide position 1, associated with a novel haplotype XL The occurrence of these mutations on various chromosomal backgrounds provides strong evidence for an interplay of gene migration, interallelic gene conversion, and multiple origins of the same mutation.     

Physiological thermoregulation in a crustacean? Heart rate hysteresis in the freshwater crayfish Cherax destructor

Differential heart rates during heating and cooling (heart rate hysteresis) are an important thermoregulatory mechanism in ectothermic reptiles. We speculate that heart rate hysteresis has evolved alongside vascularisation, and to determine whether this phenomenon occurs in a lineage with vascularised circulatory systems that is phylogenetically distant from reptiles, we measured the response of heart rate to convective heat transfer in the Australian freshwater crayfish, Cherax destructor. Heart rate during convective heating (from 20 to 30 degrees C) was significantly faster than during cooling for any given body temperature. Heart rate declined rapidly immediately following the removal of the heat source, despite only negligible losses in body temperature. This heart rate 'hysteresis' is similar to the pattern reported in many reptiles and, by varying peripheral blood flow, it is presumed to confer thermoregulatory benefits particularly given the thermal sensitivity of many physiological rate functions in crustaceans.     

Concept of immunomics: a new frontier in the battle for gene function?

At the beginning of the 21^st century, biology will try to address the function of a large number of new genes. From the perspective of technologies applied today to functional genomics, this task appears to be more complex than the effort invested in the sequencing of the human genome. Conceptually, a high-throughput approach permitting correlation between newly discovered genes and functional properties of their protein products has yet to be developed. To address relationships between tens of thousands of genes and their cognate proteins, novel interdisciplinary technologies need to emerge. In this paper, a new idea of immunomics is presented and an experimental strategy is outlined to circumvent some of the restrictions associated with methodologies currently in use. It is proposed that cloned segments of genomic DNA are used for genetic immunization to obtain a large collection of antibodies, and to generate microarrays of these antibodies for tracing differentially expressed cellular proteins.     

Molecular analysis of the gene encoding α-lytic protease: evidence for a preproenzyme

A 1.7-kb EcoRI fragment containing the structural gene for α-lytic protease has been cloned from Lysobacter enzymogenes 495 chromosomal DNA: the first example of a gene cloned from this organism. The protein sequence deduced from the nucleotide sequence encoding this serine protease matches the published amino acid sequence [Olson et al., Nature 228 (1970) 438–442] precisely. Sequence analysis and S 1 mapping indicate that, like subtilisin [e.g. Wells et al., Nucleic Acids Res. 11 (1983) 7911–7925] α-lytic protease is synthesized as a pre-pro protein (41 kDa) that is subsequently processed to its mature extracellular form (20 kDa). This first finding of a large N-terminal protease precursor in a Gram-negative bacterial protease strengthens the hypothesis that large precursors may be a general property of extracellular bacterial proteases, and suggests that the N- or C-terminal location of the precursor segment may be significant.