Gaucher disease (GD) is the most common of the lysosomal storage disorders and is caused by defects in the GBA gene encoding glucocerebrosidase (GlcCerase). The accumulation of its substrate, glucocylceramide (GlcCer) is considered the main cause of GD. We found here that the expression of human mutated GlcCerase gene (hGBA) that is associated with neuronopathy in GD patients causes neurodevelopmental defects in Drosophila eyes. The data indicate that endoplasmic reticulum (ER) stress was elevated in Drosophila eye carrying mutated hGBAs by using of the ER stress markers dXBP1 and dBiP. We also found that Ambroxol, a potential pharmacological chaperone for mutated hGBAs, can alleviate the neuronopathic phenotype through reducing ER stress. We demonstrate a novel mechanism of neurodevelopmental defects mediated by ER stress through expression of mutants of human GBA gene in the eye of Drosophila.

Phototaxis has been described in many insects, which are often attracted to specific wavelengths of light. However, little is known about phototaxis in parasitoid insect species that are potentially useful for integrated pest management. In this study, we investigated the wavelength dependency of the phototactic behavior of the parasitoid fly Exorista japonica and its possible mechanism. Multiple-choice tests with six monochromatic stimuli revealed that the flies were specifically attracted to violet light peaking at 405 nm, which was unexpected because insects are generally attracted to ultraviolet or green light. We measured the spectral sensitivity of the compound eye, and found that the sensitivity peaked at 340 nm, as in other brachyceran flies. We used statistical modeling and optimization of the process parameters to predict the type of photoreceptor contributing to the violet preference. The analysis revealed that the wavelength preference could be explained by linear models of the quanta received by photoreceptors, including the R1-6 broadband receptors. The broadband receptors appear to contribute positively, whereas the R7-8 narrowband receptors contribute negatively to achieve the violet preference; i.e., spectral opponency might be involved.

Drosophila FMR1 mutants are models of human fragile X syndrome. They show a loss of locomotor activity rhythm and severe degradation of eclosion timing. We analyzed the circadian behavior of FMR1 mutants (dfmr1B55) in two genetic backgrounds, yellow white (yw) and Canton S (CS). The arrhythmic phenotype of circadian locomotor activity in constant darkness (DD) did not significantly change in either genetic background. Surprisingly, eclosion timing was completely restored by backcrossing dfmr1B55 with yw or CS flies. Morphological analysis of the small ventrally located lateral neurons of FMR1 mutants revealed that the dorsal-projection area was significantly larger in arrhythmic than rhythmic flies. In addition, dfmr1B55 mutants in both genetic backgrounds had a significantly lower evening peak in the light-dark (LD) cycle. These results indicate that lack of FMR1 does not affect eclosion timing, but alters locomotor activity patterns in both LD and DD conditions by affecting the arborization of small ventrally located lateral neurons. Thus, the FMR1 gene may regulate the circadian-related locomotor activity of Drosophila.

Double-time (dbt) is a casein kinase gene involved in cell survival, proliferation, and circadian rhythms in the fruit fly, Drosophila melanogaster. Genetic and biochemical studies have shown that dbt and its mammalian ortholog casein kinase I epsilon (hckI epsilon) regulate the circadian phosphorylation of period (per), thus controlling per subcellular localization and stability. Mutations in these kinases can shorten the circadian period in both mammals and Drosophila. Since similar activities in circadian clock have been described for these kinases, we investigated whether the expression of mammalian casein kinase I can replace the activity of dbt in flies. Global expression of the full-length dbt rescued lethality of the null mutant dbt revVIII and rescued flies showed normal locomotor activity rhythms. Global expression of dbt also restored the locomotor activity rhythm of the arrhythmic genotype, dbt ar/dbt revVIII. In contrast, global expression of hckI epsilon or hckI alpha did not rescue lethality or locomotor activity of dbt mutants. Furthermore dbt overexpression in wild-type clock cells had only a small effect on period length, whereas hckI epsilon expression in clock cells greatly lengthened period to ~30.5 hours and increased the number of arrhythmic flies. These results indicate that hckI epsilon cannot replace the activity of dbt in flies despite the high degree of similarity in primary sequence and kinase function. Moreover, expression of hck Iepsilon in flies appears to interfere with dbt activity. Thus, caution should be used in interpreting assays that measure activity of mammalian casein kinase mutants in Drosophila, or that employ vertebrate CKI in studies of dPER phosphorylations.

Stress-activated protein kinases such as p38 regulate the activity of transcription factor ATF-2. However, the physiological role of ATF-2, especially in the brain, is unknown. Here, we found that Drosophila melanogaster ATF-2 (dATF-2) is expressed in large ventral lateral neurons (l-LN v s) and also, to a much lesser extent, in small ventral lateral neurons, the pacemaker neurons. Only l-LN v s were stained with the antibody that specifically recognizes phosphorylated dATF-2, suggesting that dATF-2 is activated specifically in l-LN v s. The knockdown of dATF-2 in pacemaker neurons using RNA interference decreased sleep time, whereas the ectopic expression of dATF-2 increased sleep time. dATF-2 knockdown decreased the length of sleep bouts but not the number of bouts. The ATF-2 level also affected the sleep rebound after sleep deprivation and the arousal threshold. dATF-2 negatively regulated locomotor activity, although it did not affect the circadian locomotor rhythm. The degree of dATF-2 phosphorylation was greater in the morning than at night and was enhanced by forced locomotion via the dp38 pathway. Thus, dATF-2 is activated by the locomotor while it increases sleep, suggesting a role for dATF-2 as a regulator to connect sleep with locomotion.