The effect of genetic environment on locus-specific instability of the yellow gene in Uman' population of Drosophila melanogaster

The effects of genotype of the laboratory strains, C(1)DX, ywf/Y, 23.5 MRF/CyL4, and C(1)DX,yf; pi2, on locus-specific instability in the yellow gene of the strains y(2-717, y(2-715), and y(2-700 ) from Uman' population of Drosophila melanogaster was studied. Crosses of the males from Uman'-derived lines with the C(1)DX, ywf/Y females yielded a cascade of derivatives, mostly consisting of y+ and y2 alleles, while their crosses with the 23.5 MRF/CyL4 and C(1)DX,yf; pi2 females mostly resulted in the appearance of y+ and y(1) derivatives. The genomes of laboratory strains used in the study contained the full-sized hobo elements, which could differ from one another relative to the structure of variable region and affinity to different DNA sequences.     

Functional properties of the pOV13 plasmid as a vector for DNA cloning in a broad spectrum of gram negative bacteria

The birepliconed plasmid pOV13 possesses all the properties of a vector for DNA cloning in a broad host range of bacterial cells. pOV13 is transfered by transformation and stably inherited by Escherichia coli, Brucella, Pseudomonas cells determining the resistance to streptomycin, tetrocycline and kanamycin in these bacteria. The plasmid pOV13 is a multicopy plasmid optimal in replication capacity (23kb). The plasmid carries single sites for some restriction endonucleases that are used for DNA cloning, including some restriction sites in antibiotic resistance genes. The examples of DNA cloning with the selection of recombinant clones by the insertional inactivation of kanamycin or tetracycline resistance and expression of the cloned DNAs are presented.     

The Reason for the Preservation of High Instability at the yellow Gene in Drosophila melanogaster Strains Isolated from the Natural Population of Uman' during the “Mode for Mutation”

Mobile genetic elements are responsible for most spontaneous mutations in Drosophila melanogaster. The discovered in the 1980s phenomenon of frequent change of the wild-type yellow phenotype for a mutant one, and vice-versa, in strains of D. melanogaster isolated from the Uman' natural population can be, according to our data, explained by repeated inversions and reinversions of the gene regulatory region located between the two copies of the hobo transposon. However, most molecular genetic events accompanying the process can occur without the phenotype change. After several generations, the strains, remaining phenotypically unchanged, can possess different molecular genetic properties with respect to yellow. Using genetically homogenous or isogenic strains for the genetic analysis or for production of the new plant cultivars or animal breeds, geneticists and breeders often face the problem of stability of the strains. In the present study, the mechanism underlying the generation of instability at the yellowlocus of D. melanogaster determined by the hobo-induced genome instability is described.     

Polymorphism of <Emphasis Type="Italic">yellow</Emphasis> locus in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> mutants from natural populations

We have studied the molecular characteristics of the yellow locus (y; 1–0.0), which determines the body color of phenotypically wild-type and mutant alleles isolated in different years from geographically distant populations of Drosophila melanogaster. According to the Southern blot, data restriction maps of the yellow locus of all examined strains differ from one another, as well as from Oregon stock. FISH analysis shows that, in the neighborhood of the yellow locus in the X chromosome, neither P nor hobo elements are found in y^1–775 stock, while only hobo is found in these region in y^1–859 and y^1–866 stocks, only the P element is found in y⁺sn⁸⁴⁹ stock, and both elements are found in y^1–719 stock. Thus, all yellow mutants studied are of independent origin. Locus yellow located on the end of X chromosome (region 1A5–8 on the cytologic map) carries significantly more transposon than retrotransposon induced mutations compared to the white locus (region 3C2). It is possible that, at the ends of Drosophila melanogaster chromosomes, transposons are more active than retrotransposons.     

Three-dimensional organization of telomeres in nuclei of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> salivary glands

3D-FISH method was employed to investigate the telomere topology in polytene nuclei of salivary glands in Drosophila melanogaster. The majority of telomeres in polytene nuclei of salivary glands in Drosophila strain y^2-717 is localized in the nuclear central area and have no contacts with nuclear membrane. In the females ectopic contacts between telomeres occur in frequency 25% higher than in males. HeT-A DNA in y^2-717alk3-2 strain, which is a derivative of the y^2-717 stain carrying an inversion between 1B and 13C bands, is found in the region 13 of X chromosome. The frequency of ectopic contacts of telomeres in y^2-717alk3-2 males is 10% higher than in the y^2-717 strain. The number of ectopic contacts can be differ significantly in independent experiments, possibly indicating the role of random factors in the contact formation.     

stathmin, a gene enriched in the amygdala, controls both learned and innate fear

Little is known about the molecular mechanisms of learned and innate fear. We have identified stathmin, an inhibitor of microtubule formation, as highly expressed in the lateral nucleus (LA) of the amygdala as well as in the thalamic and cortical structures that send information to the LA about the conditioned (learned fear) and unconditioned stimuli (innate fear). Whole-cell recordings from amygdala slices that are isolated from stathmin knockout mice show deficits in spike-timing-dependent long-term potentiation (LTP). The knockout mice also exhibit decreased memory in amygdala-dependent fear conditioning and fail to recognize danger in innately aversive environments. By contrast, these mice do not show deficits in the water maze, a spatial task dependent on the hippocampus, where stathmin is not normally expressed. We therefore conclude that stathmin is required for the induction of LTP in afferent inputs to the amygdala and is essential in regulating both innate and learned fear.     

Presynaptic BDNF required for a presynaptic but not postsynaptic component of LTP at hippocampal CA1-CA3 synapses

Brain-derived neurotrophic factor (BDNF) has been implicated in several forms of long-term potentiation (LTP) at different hippocampal synapses. Using two-photon imaging of FM 1-43, a fluorescent marker of synaptic vesicle cycling, we find that BDNF is selectively required for those forms of LTP at Schaffer collateral synapses that recruit a presynaptic component of expression. BDNF-dependent forms of LTP also require activation of L-type voltage-gated calcium channels. One form of LTP with presynaptic expression, theta burst LTP, is thought to be of particular behavioral importance. Using restricted genetic deletion to selectively disrupt BDNF production in either the entire forebrain (CA3 and CA1) or in only the postsynaptic CA1 neuron, we localize the source of BDNF required for LTP to presynaptic neurons. These results suggest that long-term synaptic plasticity has distinct presynaptic and postsynaptic modules. Release of BDNF from CA3 neurons is required to recruit the presynaptic, but not postsynaptic, module of plasticity.     

Heterosynaptic dopamine neurotransmission selects sets of corticostriatal terminals

Dopamine input to the striatum is required for voluntary motor movement, behavioral reinforcement, and responses to drugs of abuse. It is speculated that these functions are dependent on either excitatory or inhibitory modulation of corticostriatal synapses onto medium spiny neurons (MSNs). While dopamine modulates MSN excitability, a direct presynaptic effect on the corticostriatal input has not been clearly demonstrated. We combined optical monitoring of synaptic vesicle exocytosis from motor area corticostriatal afferents and electrochemical recordings of striatal dopamine release to directly measure effects of dopamine at the level of individual presynaptic terminals. Dopamine released by either electrical stimulation or amphetamine acted via D2 receptors to inhibit the activity of subsets of corticostriatal terminals. Optical and electrophysiological data suggest that heterosynaptic inhibition was enhanced by higher frequency stimulation and was selective for the least active terminals. Thus, dopamine, by filtering less active inputs, appears to reinforce specific sets of corticostriatal synaptic connections.