Genotypic basis of low viability in vestigial mutants of Drosophila melanogaster

The role of a marker mutation and other genes in a decrease in viability was studied in the Drosophila melanogaster vg line. In flies of the C-S line, chromosome 2 was substituted by the homologous chromosome of the vg flies. In addition, the flies of the mutant phenotype with mutant genes partially or completely substituted by the wild-type C-S genes were obtained in saturating crosses C-S x vg. In the reciprocal variant of chromosome 2 substitution, the flies of the C-S phenotype with chromosomes 1, 3, and 4 from the vg line were obtained. Chromosome 2 of the vg line, introduced into C-S fly karyotype, proved to substantially reduce the heat resistance and life span of flies. In the case of reciprocal replacement (C-S line chromosome 2 substituted for the homologous chromosome of vg flies), a significant increase in viability was observed, which, however, never reached the level characteristic of the C-S line. As the vg genotype became saturated with C-S genes, the heat resistance and life span of flies increased substantially. However, even the complete saturation of mutant chromosomes with wild-type genes never resulted in the equal viability of vg and C-S flies. These data suggest that the low viability of the vg mutant is largely accounted for by the gene composition of the second chromosome and, primarily, by the presence of the vg gene. Nevertheless, there is evidence that, along with the pleiotropic effect of the marker mutation, other genes not linked to chromosome 2 are responsible for the studied physiological properties of the vg flies.     

Mutation "outbursts" of various genes in natural populations of Drosophila melanogaster

The evaluation and treatment of older men with benign prostatic hyperplasia (BPH) is complicated by the highly variable clinical presentation of men with BPH, which ranges from minor urinary symptoms to acute urinary retention. Treatment choices have expanded with recent advances in medical and surgical therapies. Surgical treatment includes open prostatectomy and transurethral prostatectomy as well as newer technologies that are less invasive and that result in fewer long-term side effects. Response to treatment depends on the patient and should be directed at symptom relief.     

The mechanism of the development of the synapse as the basis for its involution

The electron microscopic investigation of human brain synaptic organization in normal aging and in ischemic heart pathology in different life periods was performed. A significant quantity of desmosome-like and mixed contacts was shown. Their ultrastructural organization was similar to that of developing synapses during prenatal ontogenesis and in newborn rats. The analysis of the experimental results suggests that an appearance of desmosome-like contacts in the human brain results from synapse involution. This is supported by the observation of formation of mixed contacts which may be a transitional stage between symmetrical or asymmetrical specialized synapse and desmosome. Thus, the mechanism of synaptic involution appears to be a mirror reflection of the mechanism of its development.     

High frequency of spontaneous occurrence of mutations affecting viability in chromosome 2 of Drosophila melanogaster line "HA"

The frequency of spontaneous mutations affecting viability was estimated in the chromosome II in LA strain of Drosophila melanogaster. The strain has been selected for low sexual activity for more than 180 generations and maintained by close inbreeding. Spontaneous mutation rate in LA strain has appeared to be extremely high--the frequency of lethal and semilethal mutations in the chromosome II in by an order higher than usual mutation frequencies. Most of the mutations originating are distributed between a limited number of loci in the b--c region.     

The transmission of fragmented chromosomes in Drosophila melanogaster

We investigated the fate of dicentric chromosomes in the mitotic divisions of Drosophila melanogaster. We constructed chromosomes that were not required for viability and that carried P elements with inverted repeats of the target sites (FRTs) for the FLP site-specific recombinase. FLP-mediated unequal sister-chromatid exchange between inverted FRTs produced dicentric chromosomes at a high rate. The fate of the dicentric chromosome was evaluated in the mitotic cells of the male germline. We found that dicentric chromosomes break in mitosis, and the broken fragments can be transmitted. Some of these chromosome fragments exhibit dominant semilethality. Nonlethal fragments were broken at many sites along the chromosome, but the semilethal fragments were all broken near the original site of sister-chromatid fusion, and retained P element sequences near their termini. We discuss the implications of the recovery and behavior of broken chromosomes for checkpoints that detect double-strand break damage and the functions of telomeres in Drosophila.     

Study of the vertical transmission and horizontal transmission of "Drosophila melanogaster" and "Drosophila immigrans" picornavirus (author's transl)

The contamination of drosophila eggs, of larvae of the 3 instars and of adults, was studied using several strains of P and C viruses of D. melanogaster and of iota virus of D. immigrans. The infected adults contaminated other flies if they were rich in viral particles and if the contact was long enough. Infection of the adults occurred in the presence of concentrated viral suspensions. The larvae were easily infected when they grew in contaminated media; the more sensitive stage was the first instar. Transovarian transmission was observed only in naturally infected flies propagating viruses of serotype I or III. C viruses were not hereditarily transmitted. Persistence of the Picornaviruses of drosophila populations can be explained by the additive effects of the 3 mechanisms of contamination.     

The autosomal FLP-DFS technique for generating germline mosaics in Drosophila melanogaster

The production of female germline chimeras is invaluable for analyzing the tissue specificity of recessive female sterile mutations as well as detecting the maternal effect of recessive zygotic lethal mutations. Previously, we developed the "FLP-DFS" technique to efficiently generate germline clones. This technique uses the X-linked germline-dependent dominant female sterile mutation ovoD1 as a selection for the detection of germline recombination events, and the FLP-FRT recombination system to promote site-specific chromosomal exchange. This method allows the efficient production of germline mosaics only on the X chromosome. In this paper we have built chromosomes that allow the use of this technique to the autosomes. We describe the various steps involved in the development of this technique as well as the properties of the chromosomes utilized.     

Analysis of somatic mosaicism in the Drosophila melanogaster radiosensitive mutant rad(2)201G1

Using heterozygosity for bw mutations, the frequency of somatic mosaicism has been studied in Drosophila melanogaster flies, homozygous for radiosensitive mutation, rad(2)201G1, and in those not carrying the mutation. Data obtained for control and after irradiation of larvae with 150, 450 and 750 R showed that homozygotes for the rad(2)201G1 were characterized by elevated levels of both spontaneous and induced mosaicism.     

The genetics of glutamate oxaloacetate transaminase in Drosophila melanogaster

A survey of 29 laboratory populations of Drosophila melanogaster for glutamate oxaloacetate transaminase (GOT) variation revealed that the Got-1 locus was polymorphic in three stocks recently collected from nature. The Got-1 locus was fixed for the same allozyme in the remaining 26 laboratory populations. Testcross matings to multiply marked stocks established that Got-1 is located at 4.8 centimorgans on chromosome 2.     

The K+ channel gene ether a go-go is required for the transduction of a subset of odorants in adult Drosophila melanogaster

The functional identity of an olfactory receptor neuron is determined in part by its repertoire of responses to odorants. As an approach toward understanding the contributions of particular conductances to olfactory neuron excitability and odor discrimination, we have investigated the role of the putative cyclic nucleotide-modulated K+ channel subunit encoded by the ether a go-go (eag) gene in odorant responsiveness in Drosophila melanogaster. Four independent mutant eag alleles exhibited reduced antennal sensitivity to a subset of nine odorants, all having short aliphatic side chains: ethyl butyrate (EB), propionic acid, 2-butanone, and ethyl acetate. Significantly fewer eag antennal neurons responded to EB compared with control neurons; the proportion sensitive to 2-heptanone was similar to controls. Two aspects of the character of EB-induced excitability were affected by mutations in eag. First, fewer EB-induced inhibitory responses were observed in eag mutants, and second, fewer excitatory odorant responses dependent on extracellular Ca2+ were observed. Furthermore, modulation of neuronal excitability by membrane-permeant cyclic nucleotide analogs was largely eag dependent. Focal application of high K+ saline to sensillae altered the excitability of the majority of neurons from wild-type but not eag antennae, suggesting that Eag may have a dendritic localization.     

The effect of 5-bromo-2'-deoxyuridine on the lifespan and behavior of Drosophila melanogaster

In this study, we have examined the effect of 5-bromo-2'-deoxyuridine incorporated into DNA of Drosophila nerve cells after incubation of larvae in the analog-containing medium on the duration of lifespan and behavior (photoactivity) of adult flies. 5-Bromo-2'-deoxyuridine incorporated into DNA decreases the lifespan of adult animals. In contrast to the control, the curves describing the probability of death become bimodal at higher doses of the analog (above 35 (g/ml). As the dose of 5-bromo-2'-deoxyuridine decreases, photoactivity of the flies diminishes, and the distribution into fractions with different activity becomes broader. The data obtained provide evidence that the modification of DNA with 5-bromo-2'-deoxyuridine drastically changes the expression of tissue-specific genes in nerve ganglia of Drosophila and at the same time diminishes the duration of insects lifespan. These observations suggest that genome of the nerve cells appears to be a probable initial substrate of Drosophila aging.     

The accumulation of P-element-induced recombinants in the germline of male Drosophila melanogaster

P-element-induced recombination in Drosophila melanogaster occurs premeiotically. Recombinants are therefore expected to accumulate in the stem cells of the germline of P-element-carrying males. We show that both the recombination frequency and the incidence of "clustering" increase with the age of males carrying various P-element derivatives. The combination of end-deleted elements can lead to average recombination frequencies >50% with individual instances of 100% recombination. These elements also lowered the fertility of the carriers. We investigated these features by constructing an analytical and a computer simulation model of the course of events in the germline, incorporating the recently proposed hybrid element insertion (HEI) model of P-element activity. The model is able to predict extreme recombination levels, segregation ratio biases and lowered fertility through cell death in a single analysis.     

virilizer regulates Sex-lethal in the germline of Drosophila melanogaster

BACKGROUND AND PURPOSE: Advancing age is associated with declines in motor function; understanding age-related changes in the basal ganglia, therefore, is imperative for comprehension of such functional changes. The purpose of this study was to examine the age, sex, and hemispheric differences in volume of the caudate nucleus, the putamen, and the globus pallidus. METHODS: In a sample of 148 healthy right-handed adults (18-77 years old) with no evidence of age-related motor disorders, we estimated the volume of the head of the caudate nucleus, the putamen, and the globus pallidus from MR images. RESULTS: The analyses revealed bilateral age-related shrinkage of the head of the caudate nucleus and the putamen in both sexes. In men, the age-related shrinkage of the caudate was stronger on the left, whereas, in women, the opposite trend was evident. In both sexes, age-related shrinkage of the right putamen was greater than of its left counterpart. The mild bilateral age-related shrinkage of the globus pallidus was observed only in men. In both sexes, we observed significant rightward asymmetry in the putamen, significant leftward asymmetry in the caudate, and no asymmetry in the globus pallidus. CONCLUSIONS: Bilateral age-related shrinkage of the neostriatum is found in healthy adults. The shrinkage of the globus pallidus is less pronounced and may be restricted to men only.     

Formation of the male pronuclear lamina in Drosophila melanogaster

E. coli homologs of the signal recognition particle (SRP) and its receptor are essential for viability, but their role in protein export is unclear. To elucidate their function, we devised a genome-wide screen to identify genes that encode SRP substrates. Inhibition of the SRP pathway sharply blocked the membrane insertion of several polytopic inner membrane proteins (IMPs) that were predicted to be SRP substrates, but had a smaller effect on the insertion of other IMPs and no significant effect on preprotein translocation. Our results suggest that whereas most E. coli preproteins and some IMPs can utilize SRP-independent targeting pathways effectively, the structural features of a subset of IMPs have required the conservation of an SRP-based targeting machinery.     

The dynamics of neurogenic signalling underlying bristle development in Drosophila melanogaster

We have examined expression of the neurogenic gene, Delta (Dl), and the regulatory relationships between the Delta-Notch signalling pathway and the proneural gene, achaete, during microchaeta development in Drosophila. Delta is expressed in all microchaeta proneural cells and microchaeta sensory organ precursors (SOPs) and is expressed dynamically in SOP progeny. We find that Delta expression in microchaeta proneural cells is detected prior to the onset of achaete expression and arises normally in the absence of achaete/scute function, indicating that initial Delta expression in the notum is not dependent on proneural gene function. Activation of the Delta-Notch pathway results in loss of Delta protein accumulation, suggesting that Delta expression is regulated, in part, by Delta-Notch signalling activity. We find that Delta signalling is required for correct delineation of early proneural gene expression in developing nota. Within microchaeta proneural stripes, we demonstrate that Delta-Notch signalling prohibits adoption of the SOP fate by repressing expression of proneural genes.     

The determination of biogenic amines in four strains of the fruit fly Drosophila melanogaster

A range of biogenic amines were measured in the heads from four strains of Drosophila melanogaster. Quantitation was carried out using gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) with stable isotope dilution. The principal amines detected in the heads were dopamine, noradrenaline and 5 HT with small amounts of p- and m-tyramine; p-octopamine could not be detected in samples of 25 heads with a limit of detection of 10 pg per sample. In addition to conventional neurotransmitters or putative neurotransmitters the amines 5- and 6-hydroxydopamine were detected in the heads in substantial amounts.     

mei-W68 in Drosophila melanogaster encodes a Spo11 homolog: evidence that the mechanism for initiating meiotic recombination is conserved

Meiotic recombination requires the action of several gene products in both Saccharomyces cerevisiae and Drosophila melanogaster. Genetic studies in D. melanogaster have shown that the mei-W68 gene is required for all meiotic gene conversion and crossing-over. We cloned mei-W68 using a new genetic mapping method in which P elements are used to promote crossing-over at their insertion sites. This resulted in the high-resolution mapping of mei-W68 to a <18-kb region that contains a homolog of the S. cerevisiae spo11 gene. Molecular analysis of several mutants confirmed that mei-W68 encodes an spo11 homolog. Spo11 and MEI-W68 are members of a family of proteins similar to a novel type II topoisomerase. On the basis of this and other lines of evidence, Spo11 has been proposed to be the enzymatic activity that creates the double-strand breaks needed to initiate meiotic recombination. This raises the possibility that recombination in Drosophila is also initiated by double-strand breaks. Although these homologous genes are required absolutely for recombination in both species, their roles differ in other respects. In contrast to spo11, mei-W68 is not required for synaptonemal complex formation and does have a mitotic role.     

The gene fl(2)d is needed for the sex-specific splicing of transformer pre-mRNA but not for double-sex pre-mRNA in Drosophila melanogaster

In Drosophila melanogaster, regulation of the sex determination genes throughout development occurs by sex-specific splicing of their products. The first gene is Sex-lethal(Sxl). The downstream target of Sxl is the gene transformer (tra): the Sxl protein controls the female-specific splicing of the Tra pre-mRNA. The downstream target of the gene tra is the gene double-sex (dsx): the Tra protein of females, controls the female-specific splicing of the Dsx pre-mRNA. We have identified a gene, female-lethal-2-d fl(2) d, whose function is required for the female-specific splicing of Sxl pre-mRNA. In this report we analyze whether the gene fl(2)d is also required for the sex-specific splicing of both Tra and Dsx pre-mRNAs. We found that the Sxl protein is not sufficient for the female-specific splicing of Tra pre-mRNA, the fl(2)d function also being necessary. This gene, however, is not required for the female-specific splicing of Dsx pre-mRNA.