Systematic Screening of Drosophila Deficiency Mutations for Embryonic Phenotypes and Orphan Receptor Ligands

This paper defines a collection of Drosophila deletion mutations (deficiencies) that can be systematically screened for embryonic phenotypes, orphan receptor ligands, and genes affecting protein localization. It reports the results of deficiency screens we have conducted that have revealed new axon guidance phenotypes in the central nervous system and neuromuscular system and permitted a quantitative assessment of the number of potential genes involved in regulating guidance of specific motor axon branches. Deficiency “kits” that cover the genome with a minimum number of lines have been established to facilitate gene mapping. These kits cannot be systematically analyzed for phenotypes, however, since embryos homozygous for many deficiencies in these kits fail to develop due to the loss of key gene products encoded within the deficiency. To create new kits that can be screened for phenotype, we have examined the development of the nervous system in embryos homozygous for more than 700 distinct deficiency mutations. A kit of ∼400 deficiency lines for which homozygotes have a recognizable nervous system and intact body walls encompasses >80% of the genome. Here we show examples of screens of this kit for orphan receptor ligands and neuronal antigen expression. It can also be used to find genes involved in expression, patterning, and subcellular localization of any protein that can be visualized by antibody staining. A subset kit of 233 deficiency lines, for which homozygotes develop relatively normally to late stage 16, covers ∼50% of the genome. We have screened it for axon guidance phenotypes, and we present examples of new phenotypes we have identified. The subset kit can be used to screen for phenotypes affecting all embryonic organs. In the future, these deficiency kits will allow Drosophila researchers to rapidly and efficiently execute genome-wide anatomical screens that require examination of individual embryos at high magnification.     

Stabilization of DNA triple helices by a series of mono- and disubstituted amidoanthraquinones.

We have used quantitative DNase I footprinting to measure the relative affinities of four disubstituted and two monosubstituted amidoanthraquinone compounds for intermolecular DNA triplexes, and have examined how the position of the attached base-functionalized substituents affects their ability to stabilize DNA triplexes. All four isomeric disubstituted derivatives examined stabilize DNA triplexes at micromolar or lower concentrations. Of the compounds studied the 2,7-disubstituted amidoanthraquinone displayed the greatest triplex affinity. The order of triplex affinity for the other disubstituted ligands decreases in the order 2,7 > 1,8 = 1,5 > 2,6, with the equivalent monosubstituted compounds being at least an order of magnitude less efficient. The 1,5-disubstituted derivative also shows some interaction with duplex DNA. These results have been confirmed by molecular modelling studies, which provide a rational basis for the structure-activity relationships. These suggest that, although all of the compounds bind through an intercalative mode, the 2,6, 2,7 and 1,5 disubstituted isomers bind with their two side groups occupying adjacent triplex grooves, in contrast with the 1,8 isomer which is positioned with both side groups in the same triplex groove.     

Hereditary chondrodystrophy in the rabbit. Genetics and pathology of a new mutant, a model for metatropic dwarfism.

Thirty-one cases of a new hereditary chondrodystrophy in the rabbit have been shown to be associated with a fully penetrant autosomal recessive gene symbolized cd. The mutant is viable prenatally but does not survive after birth. It differs from the two other inherited chondrodystrophies, dachs and achondroplasia, but is very similar to the metatropic dwarf reported in man.     

The Sex Ratio of Heterodera glycines at Low Population Densities

The sex ratio of the Arkansas 1 isolate of Heterodera glycines was determined in experiments in which ''Lee'' soybean was inoculated with either one or two larvae. A 3:1 male to female sex ratio was established for this isolate under the test conditions used. No influence of one nematode on the penetration and development to adult of another nematode in the same root was detected in double larval inoculations.     

In vivo regulation of hepatic LDL receptor mRNA in the baboon. Differential effects of saturated and unsaturated fat

The effects of diets enriched with cholesterol and different fats upon plasma lipoproteins and hepatic low density lipoprotein (LDL) receptor mRNA levels were studied in a group of 18 normal baboons. Animals were fed diets containing 1% cholesterol and 25% fat as either coconut oil, peanut oil, or olive oil for a period of 20 weeks. Plasma total cholesterol, high density lipoprotein (HDL) cholesterol, beta-lipoprotein (LDL + very low density lipoprotein) cholesterol, apolipoprotein B and apolipoprotein A-I were measured in samples obtained at 4-week intervals. All three diet groups demonstrated a statistically significant increase in plasma cholesterol as compared to base line throughout the experiment. Hepatic LDL receptor (LDL-R) mRNA levels were quantified by dot blot hybridization in serial liver biopsies. Animals fed saturated fat sustained a significant reduction in hepatic LDL-R mRNA as compared to those fed either monounsaturated or polyunsaturated fat. A strong negative correlation between LDL-R mRNA and plasma total cholesterol (r = -0.71), HDL cholesterol (r = -0.76), and plasma apo A-I (r = -0.77) was observed only in those animals fed coconut oil. Weak negative correlations between LDL-R mRNA and other plasma parameters did not achieve statistical significance. We conclude that saturated and unsaturated oils may influence plasma cholesterol levels in part through differential effects on LDL receptor biosynthesis in baboons.     

Comparative 16S rRNA oligonucleotide analyses and murein types of round-spore-forming bacilli and non-spore-forming relatives

The phylogenetic incoherency of the genus Bacillus as presently described is demonstrated by analysis of both published and new data from comparative 16S rRNA cataloguing of nine Bacillus species and a number of related non-Bacillus taxa, i.e. Caryophanon latum, Filibacter limicola and Planococcus citreus. While the ellipsoidal-spore-forming bacilli, e.g. B. subtilis and allied species, formed a coherent cluster, the round-spore-forming bacilli showed a higher degree of relationship to the non-spore-forming organisms than these bacilli show among each other. Thus B. sphaericus clustered with C. latum, B. globisporus grouped with F. limicola, B. pasteurii with Sporosarcina ureae, and 'B. aminovorans' with P. citreus, respectively. These organisms formed two related subclusters which, in their phylogenetic depth, are comparable to that of the B. subtilis subline. With the exception of 'B. aminovorans', the 16S rRNA phylogeny was entirely consistent with the distribution of murein types. Even more distantly related to and grouping outside the main Bacillus cluster was B. stearothermophilus, which displayed a moderate relationship to Thermoactinomyces vulgaris. Taxonomic problems arising from the new insights into the intrageneric relationships of Bacillus are discussed.