Hsp70 affects memory formation and behaviorally relevant gene expression in Drosophila melanogaster.

Heat shock proteins, in particular Hsp70, play a central role in proteostasis in eukaryotic cells. Due to its chaperone properties, Hsp70 is involved in various processes after stress and under normal physiological conditions. In contrast to mammals and many Diptera species, inducible members of the Hsp70 family in Drosophila are constitutively synthesized at a low level and undergo dramatic induction after temperature elevation or other forms of stress. In the courtship suppression paradigm used in this study, Drosophila males that have been repeatedly rejected by mated females during courtship are less likely than naive males to court other females. Although numerous genes with known function were identified to play important roles in long-term memory, there is, to the best of our knowledge, no direct evidence implicating Hsp70 in this process. To elucidate a possible role of Hsp70 in memory formation, we used D. melanogaster strains containing different hsp70 copy numbers, including strains carrying a deletion of all six hsp70 genes. Our investigations exploring the memory of courtship rejection paradigm demonstrated that a low constitutive level of Hsp70 is apparently required for learning and the formation of short and long-term memories in males. The performed transcriptomic studies demonstrate that males with different hsp70 copy numbers differ significantly in the expression of a few definite groups of genes involved in mating, reproduction, and immunity in response to rejection. Specifically, our analysis reveals several major pathways that depend on the presence of hsp70 in the genome and participate in memory formation and consolidation, including the cAMP signaling cascade.

[Heat shock during the development of brain structures of Drosophila: the memory development in the l(1)ts403 mutant of Drosophila melanogaster]. / Teplovoi shok v period razvitiia tsentral'nykh struktur mozga drozofily: formirovanie pamiati u mutanta l(1)ts403 Drosophila melanogaster.

The structures and functions of many genes are homologous in Drosophila and humans. Therefore, studying pathological processes in Drosophila, in particular neurogenerative processes accompanied by progressive memory loss, helps to understand the ethiology of corresponding human disorders and to develop therapeutic strategies. It is believed that the development of neurogenerative diseases might result from alterations in the functioning of the heat shock/chaperone machinery. In view of this, we used Drosophila mutant l(1)ts403 with defective synthesis of heat shock proteins for studying learning and memory in a test of conditioned courtship suppression following a heat shock given at different developmental stages. High learning indices were registered immediately and 30 min after training both in the intact controls and in flies subjected to different developmental heat shocks. This indicated normal learning and memory acquisition in the mutant. At the same time, memory retention (3 h after training) suffered to different extent depending on the developmental stage. The remote effects of heat shock given during the formation of the mushroom bodies indicated the important role of this brain structure in the memory formation. The observed memory defects may result from alterations both in mRNA transport and in the functions of molecular chaperones in the l(1)ts403 mutant.

The ability of Drosophila mutants with defects in the central complex and mushroom bodies to learn and form memories.

One of the most important questions in the genetics of behavior is that of studies of the mechanisms of learning and memory. A convenient system for this is provided by Drosophila melanogaster, in which a whole series of mutations affecting the formation of different types of memory and learning have been obtained. The brain formations involved in these processes have been studied in parallel. Attention is currently focused on two main structures: the central complex and the mushroom bodies. These mediate the integration and storage of information accumulating during the process of learning. Mutants with defects in individual parts of the central complex and mushroom bodies have been obtained. Mutants simultaneously affecting the operation, development, or structure of the central part of the cerebral neural ganglion and the ability to learn and form memory traces are of particular interest. We have evaluated the learning ability of mutants with defects in the central complex (cexKS181 and ccbKS127) and mutants with defects in the mushroom bodies (mud1, mbm1, and cxbN71), using a method based on the conditioned reflex suppression of courtship. Memory defects were seen in cexKS181 and mud1 mutants.

[Learning ability and memory formation in the Drosophila mutants with defective central complex and mushroom bodies]. / Sposobnost' k obucheniiu i formirovaniiu pamiati u mutantov drosophily s defektami tsentral'nogo kompleksa i gribovidnykh tel.

Drosophila proved to be a very convenient model for genetic dissection of learning and memory in a number of experimental paradigms. A battery of mutations affecting either different subdomains of the central complex (CC) or of the mushroom bodies (MBs) enable the elucidation of the role of these central brain structures in different forms of learning and memory formation. We tested the CC mutants cexKS181 and ccbKS127 and MBs mutants mud1, mbm1 and cxbN71 for their ability for learning and memory formation in the conditioned courtship suppression paradigm. All the mutants were able to learn but demonstrated different memory defects. While the ccbKS127 mutant was normal in respect to memory formation, the cexKS181 mutant was defective in 30-min. and 3-hour memory; mud1 demonstrated a reduced 3-hour memory.

Identification of Drosophila mutant with memory defects after acquisition of conditioned reflex suppression of courtship.

Four lines were selected from a collection of 33 lines prepared by P insertion mutagenesis using a single-copy P-element system; the males of these four lines showed memory defects after acquisition of conditioned reflex suppression of courting. In two lines (P171 and P95), the dynamics of retention of the conditioned reflex in the repeated impregnated-female courting test were similar to those of known short-term memory mutants dnc and rut. In line P153, the dynamics were more reminiscent of the memory dynamics in a known medium-term memory mutant, amn. In line P124, the learning index was insignificant immediately after training was completed, which may indicate that this line was unable to acquire conditioned reflex suppression of courting. Determination of the positions of the P elements (P171: 48A-B; P153: 49B-C; P124: 67B-68A; P95: 77C-D) showed no correspondence with previously known mutations producing memory lesions.

[Isolation of memory-deficient Drosophila mutants in conditioned courtship suppression paradigm]. / Vyiavlenie mutantov drozofily, proiavliaiushchikh defekty pamiati posle vyrabotki uslovnoreflektornogo podavleniia ukhazhivaniia.

Among 33 mutant stocks of Drosophila melanogaster generated by means of P-insertional mutagenesis in the system with single P element, 4 stocks have been isolated as demonstrating deficient memory in the conditioned courtship suppression paradigm. Localization of the P insertions never coincided with that of previously known mutations affecting memory.

[Structural-functional chromosome organization in response to stress]. / Issledovanie strukturno-funktsional'noi organizatsii khromosom pri reaktsii na stress.

Published data and the results of experiments conducted at the Laboratory of Genetics of Higher Nervous Activity, Pavlov Institute of Physiology, on the effect of stress on chromosome structure and function are reviewed briefly. Experiments were performed on inbred rats selected for excitation threshold and mutant Drosophila with altered metabolism of secondary mediators.

Organization of the Drosophila genome in mutants with changes in second messenger metabolism and learning ability.

Mechanisms modifying the structural-functional organization of polytene chromosomes were studied in a Drosophila line in which the activating properties of calmodulin were altered and learning ability was increased, by treating mutants with homeopathic preparations which affect Ca2+ and F- ion metabolism. The results indicated a dominant role for Ca2+ ions and calmodulin in determining the chromocentric organization of the nucleus. F- ions, which stimulate the adenylate cyclase complex, were found not to have a role.

Study of the activity of head ganglion cells of larvae of the Drosophila ts-mutant with altered capacity for learning and increased activational properties of calmodulin.

The mitotic activity of cells of the head neural ganglion of Drosophila larvae of two genetic lines, the agts 3-mutant line, which possesses increased calmodulin activational properties and altered capacity for learning, and the wild type CS line, serving as a control, was studied. The value of the mitotic index, as a ratio of the number of dividing cells to their total number, was assessed. The mitotic index was calculated following the exposure of the larvae to a temperature of 37 degrees C for 30 min, and without exposure, at a temperature which was standard for the maintenance of Drosophila ts-mutants, 22 degrees C. A higher mitotic index was observed at 22 degrees C in the agts 3 line as compared with the CS line. Exposure to a temperature of 37 degrees C led to a sharp decrease in mitotic activity in both the lines investigated. The increase in mitotic index at 22 degrees C in the agts 3 line was presumptively related to an increase in the activational properties of calmodulin, which is characteristic for this line. Following preliminary treatment of the neural ganglia by the calmodulin inhibitor, trifluoperazine, at a concentration of 10(-3) M for 30 min, the difference between the mitotic index of the mutant and the control line disappeared due to its approximately three-fold decrease in the agts 3 line; this confirmed the hypothesis advanced and suggested an important role of calmodulin in the regulation of the mitotic activity of cells of the general ganglion of Drosophila larvae.

[The organizational characteristics of the Drosophila genome in mutants with altered second-messenger metabolism and with learning ability]. / Osobennosti organizatsii genoma drozofily u mutantov s izmenennym metabolizmom vtorichnykh posrednikov i sposobnosti k obucheniiu.

The data obtained on homeopathic correction of the Drosophila mutant strains with altered activation properties of calmodulin and increased ability for learning, suggest an important role of Ca ions calmodulin in formation of chromocentral organisation of the nucleus. No significant role of the F ions was revealed.

[The mitotic activity of the cells in the head neural ganglion in larvae of the Drosophila ts mutant with an altered capacity for learning and augmented calmodulin activation properties]. / Izuchenie mitoticheskoi aktivnosti kletok golovnogo nervnogo gangliia lichinok ts-mutanta drozofily s izmenennoi sposobnost'iu k obucheniiu i povyshennymi aktivatsionnymi svoistvami kal'modulina.

Mitotic activity of head neural ganglion cells of Drosophila melanogaster larvae from two genetic stocks was studied. The mutant stock agts3 with augmented activatory potentialities of calmodulin and modified capacity for learning was compared with the control wild type Canton-S stock. The mitotic index was defined as the ratio of the number of cells in the state of division to the total cell number. The mitotic index was calculated after 30-min incubation of the larvae at the temperature of 37 degrees C and without heating under normal conditions (22 degrees C). At 22 degrees C the mitotic index in agts3 was higher than in CS. Exposure to 37 degrees C led to a sharp decrease of mitotic activity in both stocks. Increased mitotic index in agts3 stocks at 22 degrees C was probably connected with augmented activatory potentialities of calmodulin. After preincubation of the neural ganglions with calmodulin inhibitor trifluoperazine (10(-3)M) for 30 minutes the difference between the mutant and control stocks in mitotic index disappeared due to its approximately 3-fold decrease in agts3 stock. The obtained results supported the proposed hypothesis and demonstrated importance of calmodulin as a regulator of mitotic activity of cells from the neural ganglion of Drosophila larvae.