Evolution and developmental expression of nuclear receptor genes in the ascidian Herdmania

Nuclear receptors are a superfamily of metazoan transcription factors that have been shown to be involved in a wide range of developmental and physiological processes. A PCR-based survey of genomic DNA and developmental cDNAs from the ascidian Herdmania identifies eight members of this multigene family. Sequence comparisons and phylogenetic analyses reveal that these ascidian nuclear receptors are representative of five of the six previously defined nuclear receptor subfamilies and are apparent homologues of retinoic acid [NR1B], retinoid X [NR2B], peroxisome proliferator-activated [NR1C], estrogen related [NR3B], neuron-derived orphan (NOR) [NR4A3], nuclear orphan [NR4A], TR2 orphan [NR2C1] and COUP orphan [NR2F3] receptors. Phylogenetic analyses that include the ascidian genes produce topologically distinct trees that suggest a redefinition of some nuclear receptor subfamilies. These trees also suggest that extensive gene duplication occurred after the vertebrates split from invertebrate chordates. These ascidian nuclear receptor genes are expressed differentially during embryogenesis and metamorphosis.

A genomewide search for type 2 diabetes-susceptibility genes in indigenous Australians

The prevalence of type 2 diabetes among Australian residents is 7.5%; however, prevalence rates up to six times higher have been reported for indigenous Australian communities. Epidemiological evidence implicates genetic factors in the susceptibility of indigenous Australians to type 2 diabetes and supports the hypothesis of the thrifty genotype, but, to date, the nature of the genetic predisposition is unknown. We have ascertained clinical details from a community of indigenous Australian descent in North Stradbroke Island, Queensland. In this population, the phenotype is characterized by severe insulin resistance. We have conducted a genomewide scan, at an average resolution of 10 cM, for type 2 diabetes-susceptibility genes in a large multigeneration pedigree from this community. Parametric linkage analysis undertaken using FASTLINK version 4.1p yielded a maximum two-point LOD score of +2.97 at marker D2S2345. Multipoint analysis yielded a peak LOD score of +3.9

Homeotic genes influence the axonal pathway of a Drosophila embryonic sensory neuron

Each abdominal hemisegment of the Drosophila embryo has two sensory neurons intimately associated with a tracheal branch. During embryogenesis, the axons of these sensory neurons, termed the v'td2 neurons, enter the CNS and grow toward the brain with a distinctive pathway change in the third thoracic neuromere. We show that the axons use guidance cues that are under control of the bithorax gene complex (BX-C). Pathway defects in mutants suggest that a drop in Ultrabithorax expression permits the pathway change in the T3 neuromere, while combined Ultrabithorax and abdominal-A expression represses it in the abdominal neuromeres. We propose that the axons do not respond to a particular segmental identity in forming the pathway change; rather they respond to pathfinding cues that come about as a result of a drop in BX-C expression along the antero-posterior axis of the CNS.

The role of homeotic genes in determining the segmental pattern of chordotonal organs in Drosophila

The homeotic genes are instrumental in establishing segment-specific characteristics. In Drosophila embryos there is ample evidence that the homeotic genes are involved in establishing the differences in the pattern of sense organs between segments. The chordotonal organs are compound sense organs made up of several stretch receptive sensilla. A set of serially homologous chordotonal organs, Ich3 in the 1(st) thoracic segment, dch3 in the 2(nd) and 3(rd) thoracic segments and Ich5 in abdominal segments 1 to 7, is composed of different numbers of sensilla with different positions and orientations. Here we examine this set of sense organs and a companion set, vchA/B and vch 1, in the wild type and mutants for Sex combs reduced, Antennapedia, Ultrabithorax, and abdominal-A, using immunostaining. Mutant phenotypes indicate that Ultrabithorax and abdominal-A in particular influence the formation of these sense organs. Differential expression of abdominal-A and Ultrabithorax within compartments of individual parasegments can precisely modulate the types of sense organs that will arise from a segment.

Minor genes are involved in ascochyta blight resistance in lentils

In addition to a gene with major effect, minor genes were found to contribute to the genetic regulation of foliar resistance to Ascochyta blight in two crosses between two resistant and one susceptible lentil cultivars (lines). This was established by comparing inbred lines with and without the major resistance gene. The effects of minor genes were not large enough to change the phenotypic performance determined by its major gene qualitatively (from resistant to susceptible, or vice versa) based on the measurement scale used. However, they did substantially and significantly modify the resistance level. The major gene for foliar resistance was linked to the gene(s) for seed infection rate and/or had a positive pleiotrophic effect on seed infection rate. Similarly, the major gene for foliar resistance was linked to the gene(s) for seed yield/plant in disease free environments and/or had negative pleiotrophic effects on yield/plant. Selection for resistance and yield among inbreds with the same major resistance gene may be necessary to enhance the resistance level, and to reduce the negative effect on yield of the major resistance gene.

Phase variation in meningococcal lipooligosaccharide biosynthesis genes

Neisseria meningitidis expresses a range of lipooligosaccharide (LOS) structures, comprising of at least 13 immunotypes (ITs). Meningococcal LOS is subject to phase variation of its terminal structures allowing switching between ITs, which is proposed to have functional significance in disease. The objectives of this study were to investigate the repertoire of structures that can be expressed in clinical isolates, and to examine the role of phase-variable expression of LOS genes during invasive disease. Southern blotting was used to detect the presence of LOS biosynthetic genes in two collections of meningococci, a global set of strains previously assigned to lineages of greater or lesser virulence, and a collection of local clinical isolates which included paired throat and blood isolates from individual patients. Where the phase-variable genes lgtA, lgtC or IgtG were identified, they were amplified by PCR and the homopolymeric tracts, responsible for their phase-variable expression, were sequenced. The results revealed great potential for variation between alternate LOS structures in the isolates studied, with most strains capable of expressing several alternative terminal structures. The structures predicted to be currently expressed by the genotype of the strains agreed well with conventional immunotyping. No correlation was observed between the structural repertoire and virulence of the isolate. Based on the potential for LOS phase variation in the clinical collection and observations with the paired patient isolates, our data suggest that phase variation of LOS structures is not required for translocation between distinct compartments in the host. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies.

Inheritance and mapping of 11 avirulence genes in Phytophthora sojae

Two new crosses involving four races (races 7, 16, 17, and 25) of the soybean root and stem rot pathogen Phytophthora sojae were established (7/16 cross; 17/25 cross). An F-2 Population derived from each cross was used to determine the genetic basis of avirulence towards 11 different resistance genes in soybean. Avirulence was found to be dominant and determined by a single locus for Avr1b, 1d, 1k, 3b, 4, and 6, as expected for a simple gene-for-gene model. We also observed several cases of segregation, inconsistent with a single dominant gene being solely responsible for avirulence, which suggests that the genetic background of the different crosses can affect avirulence. Avr4 and 6 cosegregated in both the 7/16 and 17/25 crosses and, in the 7/16 cross, Avr1b and 1k were closely linked. Information from segregating RAPD, RFLP, and AFLP markers screened on F-2 progeny from the two new crosses and two crosses described previously (a total of 212 F-2 individuals, 53 from each cross) were used to construct an integrated genetic linkage map of P. sojae. This revised genetic linkage map consists of 386 markers comprising 35 RFLP, 236 RAPD, and 105 AFLP markers, as well as 10 avirulence genes. The map is composed of 21 major linkage groups and seven minor linkage groups covering a total map distance of 1640.4 cM. (C) 2002 Elsevier Science (USA). All rights reserved.

Coordinated expression of scleraxis and Sox9 genes during embryonic development of tendons and cartilage

Embryonic development of tendons is in close association with that of cartilage and bone. Although these tissues are derived from mesenchymal progenitor cells which also give rise to muscle and fat, their fates clearly diverse in early embryonic stages, Transcription factors may play pivotal roles in the process of determination and differentiation of tendon cells as well as other cells in the skeletal system. Scleraxis, a basic helix-loop-helix (bHLH) type transcription factor. is expressed in mesenchymal progenitors that later form connective tissues including tendons. Sox9 is an HMG-box containing transcription factor, which is expressed at high levels in chondrocytes. We hypothesized that the two transcription factors regulate the fate of cells that interact with each other at the interface between the two tissues during divergence of their differentiation pathways, To address this point, we investigated scleraxis and Sox9 rnRNA expression during mouse embyogenesis focusing on the coordinated development of tendons and skeletons, In the early stage of mesenchymal tissue development at 10.5 d.p.c., scleraxis and Sox9 transcripts were expressed in the mesenchymal progenitor cells in the appendicular and axial mesenchyme. At 11.5 d.p.c.. scleraxis transcripts were observed in the mesenchymal tissue surrounding skeletal primordia which express Sox9. From this stage, scleraxis expression was closely associated with, but distinct from, formation of skeletal primordia, At 13.5 d.p.c., scleraxis was expressed broadly in the interface between muscle and skeletal primordia while Sox9 expression is confined within the early skeletal primordia. Then. at 15.5 d.p.c., scleraxis transcripts were more restricted to tendons. These observations revealed the presence of temporal and spatial association of scleraxis expression during embryonic development of tendon precursor cells in close association with that of So,0 expression in chondrogenic cells in skeletal tissues. (C) 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.

A family of textilinin genes, two of which encode proteins with antihaemorrhagic properties

Two peptides, textilinins 1 and 2, isolated from the venom of the Australian common brown snake, Pseudonaja textilis textilis, are effective in preventing blood loss. To further investigate the potential of textilinins as anti-haemorrhagic agents, we cloned cDNAs encoding these proteins. The isolated full-length cDNA (430 bp in size) was shown to code for a 59 amino acid protein, corresponding in size to the native peptide, plus an additional 24 amino acid propeptide. Six such cDNAs were identified, differing in nucleotide sequence in the coding region but with an identical propeptide. All six sequences predicted peptides containing six conserved cysteines common to Kunitz-type serine protease inhibitors. When expressed as glutathione S-transferase (GST) fusion proteins and released by cleavage with thrombin, only those peptides corresponding to textilinin 1 and 2 were active in inhibiting plasmin with K-i values similar to those of their native counterparts and in binding to plasmin less tightly than aprotinin by two orders of magnitude. Similarly, in the mouse tail vein blood loss model only recombinant textilinin 1 and 2 were effective in reducing blood loss. These recombinant textilinins have potential as therapeutic agents for reducing blood loss in humans, obviating the need for reliance on aprotinin, a bovine product with possible risk of transmissible disease, and compromising the fibrinolytic system in a less irreversible manner.

Comparison of tafenoquine (WR238605) and primaquine in the post-exposure (terminal) prophylaxis of vivax malaria) in Australian Defence Force personnel

On return from duty in North Solomons Province (including Bougainville Island), Papua New Guinea, 586 Australian Defence Force personnel received either primaquine (14-d) or tafenoquine (3-d) post-exposure malaria prophylaxis. Within 12 months, 6 of the 214 volunteers receiving primaquine and 7 of 378 receiving tafenoquine had developed vivax malaria. Overall, volunteers preferred the shorter course of tafenoquine.

Novel genes regulated by Sonic Hedgehog in pluripotent mesenchymal cells

Sonic Hedgehog is a secreted morphogen involved in patterning a wide range of structures in the developing embryo. Disruption of the Hedgehog signalling cascade leads to a number of developmental disorders and plays a key role in the formation of a range of human cancers. The identification of genes regulated by Hedgehog is crucial to understanding how disruption of this pathway leads to neoplastic transformation. We have used a Sonic Hedgehog (Shh) responsive mouse cell line, C3H/10T1/2, to provide a model system for hedgehog target gene discovery. Following activation of cell cultures with Shh, RNA was used to interrogate microarrays to investigate downstream transcriptional consequences of hedgehog stimulation. As a result 11 target genes have been identified, seven of which are induced (Thrombomodulin, GILZ, BF-2, Nr4a1, IGF2, PMP22, LASP1) and four of which are repressed (SFRP-1, SFRP-2, Mip1-gamma, Amh) by Shh. These targets have a diverse range of putative functions and include transcriptional regulators and molecules known to be involved in regulating cell growth or apoptosis. The corroboration of genes previously implicated in hedgehog signalling, along with the finding of novel targets, demonstrates both the validity and power of the C3H/10T1/2 system for Shh target gene discovery.