ABSTRACT The evolutionarily conserved Glycogen Synthase Kinase 3β (GSK3β), a negative regulator of microtubules, is crucial for neuronal polarization, growth and migration during animal development. However, it remains unknown whether GSK3β regulates neuronal pruning, which is a regressive process. Here, we report that the Drosophila GSK3β homologue Shaggy (Sgg) is cell-autonomously required for dendrite pruning of ddaC sensory neurons during metamorphosis. Sgg is necessary and sufficient to promote microtubule depolymerization, turnover and disassembly in the dendrites. Although Sgg is not required for the minus-end-out microtubule orientation in dendrites, hyperactivated Sgg can disturb the dendritic microtubule orientation. Moreover, our pharmacological and genetic data suggest that Sgg is required to promote dendrite pruning at least partly via microtubule disassembly. We show that Sgg and Par-1 kinases act synergistically to promote microtubule disassembly and dendrite pruning. Thus, Sgg and Par-1 might converge on and phosphorylate a common downstream microtubule-associated protein(s) to disassemble microtubules and thereby facilitate dendrite pruning.
CTP synthase (CTPSyn) is an essential metabolic enzyme, synthesizing precursors required for nucleotides and phospholipids production. Previous studies have also shown that CTPSyn is elevated in various cancers. In many organisms, CTPSyn compartmentalizes into filaments called cytoophidia. In Drosophila melanogaster, only its isoform C (CTPSynIsoC) forms cytoophidia. In the fruit fly's testis, cytoophidia are normally seen in the transit amplification regions close to its apical tip, where the stem-cell niche is located, and development is at its most rapid. Here, we report that CTPSynIsoC overexpression causes the lengthening of cytoophidia throughout the entirety of the testicular body. A bulging apical tip is found in approximately 34% of males overexpressing CTPSynIsoC. Immunostaining shows that this bulged phenotype is most likely due to increased numbers of both germline cells and spermatocytes. Through a microRNA (miRNA) overexpression screen, we found that ectopic miR-975 concurrently increases both the expression levels of CTPSyn and the length of its cytoophidia. The bulging testes phenotype was also recovered at a penetration of approximately 20%. However, qPCR assays reveal that CTPSynIsoC and miR-975 overexpression each provokes a differential response in expression of a number of cancer-related genes, indicating that the shared CTPSyn upregulation seen in either case is likely the cause of observed testicular overgrowth. This study presents the first instance of consequences of miRNA-asserted regulation upon CTPSyn in D. melanogaster, and further reaffirms the enzyme's close ties to germline cells overgrowth.
Dietary composition affects food preference in animals. High sugar intake suppresses sweet sensation from insects to humans, but the molecular basis of this suppression is largely unknown. Here, we reveal that sugar intake in Drosophila induces the gut to express and secrete Hedgehog (Hh) into the circulation. We show that the midgut secreted Hh localize to taste sensilla and suppresses sweet sensation, perception, and preference. We further find that the midgut Hh inhibits Hh signalling in the sweet taste neurons. Our electrophysiology studies demonstrate that the midgut Hh signal also suppresses bitter taste and some odour responses, affecting overall food perception and preference. We further show that the level of sugar intake during a critical window early in life, sets the adult gut Hh expression and sugar perception. Our results together reveal a bottom-up feedback mechanism involving a "gut-taste neuron axis" that regulates food sensation and preference.
Abstract The mosquito Aedes aegypti (Ae. aegypti ) is the most notorious vector of illness-causing viruses such as Dengue, Chikugunya, and Zika. Although numerous genetic expression studies utilizing quantitative real-time PCR (qPCR) have been conducted with regards to Ae. aegypti , a panel of genes to be used suitably as references for the purpose of expression-level normalization within this epidemiologically important insect is presently lacking. Here, the usability of seven widely-utilized reference genes i.e. actin ( ACT ), eukaryotic elongation factor 1 alpha ( eEF1α ), alpha tubulin ( α - tubulin ), ribosomal proteins L8, L32 and S17 ( RPL8, RPL32 and RPS17 ), and glyceraldeyde 3-phosphate dehydrogenase ( GAPDH ) were investigated. Expression patterns of the reference genes were observed in sixteen pre-determined developmental stages and in cell culture. Gene stability was inferred from qPCR data through three freely available algorithms i.e. BestKeeper, geNorm, and NormFinder. The consensus rankings generated from stability values provided by these programs suggest a combination of at least two genes for normalization. ACT and RPS17 are the most dependably expressed reference genes and therefore, we propose an ACT/RPS17 combination for normalization in all Ae. aegypti derived samples. GAPDH performed least desirably, and is thus not a recommended reference gene. This study emphasizes the importance of validating reference genes in Ae. aegypti for qPCR based research.
Abstract Background Post-translational transport is a vital process which ensures that each protein reaches its site of function. Though most do so via an ordered ER-to-Golgi route, an increasing number of proteins are now shown to bypass this conventional secretory pathway. Results In the Drosophila olfactory sensory neurons (OSNs), odorant receptors (ORs) are trafficked from the ER towards the cilia. Here, we show that Or22a, a receptor of various esters and alcoholic compounds, reaches the cilia partially through unconventional means. Or22a frequently present as puncta at the somatic cell body exit and within the dendrite prior to the cilia base. These rarely coincide with markers of either the intermediary ER-Golgi-intermediate-compartment (ERGIC) or Golgi structures. ERGIC and Golgi also displayed axonal localization biases, a further indication that at least some measure of OR transport may occur independently of their involvement. Additionally, neither the loss of several COPII genes involved in anterograde trafficking nor ERGIC itself affected puncta formation or Or22a transport to the cilium. Instead, we observed the consistent colocalization of Or22a puncta with Grasp65, the sole Drosophila homolog of mammalian GRASP55/Grh1, a marker of the unconventional pathway. The numbers of both Or22a and Grasp65-positive puncta were furthermore increased upon nutritional starvation, a condition known to enhance Golgi-bypassing secretory activity. Conclusions Our results demonstrate an alternative route of Or22a transport, thus expanding the repertoire of unconventional secretion mechanisms in neurons.
To determine the prevalence of vitamin D deficiency (<37.5 nmol/L) among young adolescents in Malaysia and its association with demographic characteristics, anthropometric measures and physical activity.This is a cross-sectional study among Form 1 (year 7) students from 15 schools selected using a stratified random sampling design. Information regarding sociodemographic characteristics, clinical data and environmental factors was collected and blood samples were taken for total vitamin D. Descriptive and multivariable logistic regression was performed on the data.National secondary schools in Peninsular Malaysia.1361 students (mean age 12.9±0.3 years) (61.4% girls) completed the consent forms and participated in this study. Students with a chronic health condition and/or who could not understand the questionnaires due to lack of literacy were excluded.Vitamin D status was determined through measurement of sera 25-hydroxyvitamin D (25(OH)D). Body mass index (BMI) was classified according to International Obesity Task Force (IOTF) criteria. Self-reported physical activity levels were assessed using the validated Malay version of the Physical Activity Questionnaire for Older Children (PAQ-C).Deficiency in vitamin D was seen in 78.9% of the participants. The deficiency was significantly higher in girls (92.6%, p<0.001), Indian adolescents (88.6%, p<0.001) and urban-living adolescents (88.8%, p<0.001). Females (OR=8.98; 95% CI 6.48 to 12.45), adolescents with wider waist circumference (OR=2.64; 95% CI 1.65 to 4.25) and in urban areas had higher risks (OR=3.57; 95% CI 2.54 to 5.02) of being vitamin D deficient.The study shows a high prevalence of vitamin D deficiency among young adolescents. Main risk factors are gender, ethnicity, place of residence and obesity.
Abstract CTPsyn is a crucial metabolic enzyme which synthesizes CTP molecules through the de novo or salvage pathway. It has the extraordinary ability to compartmentalize into filaments termed cytoophidia. Although this property is retained amongst orthologues, and cytoophidia are therefore found across kingdoms, the mechanisms behind their formation remain unknown. Micro-RNAs (miRNAs) are single-stranded RNA with length of 20 – 22 nucleotides, capable of exerting mRNA silencing and degradation as a form of regulation. D. melanogaster itself has a high total gene count to miRNA gene number ratio, alluding to the possibility that CTPsyn may too come under the regulatory effects of these small RNAs. A thorough miRNA overexpression involving 123 UAS-miRNA lines, followed by staining of ovarian cytoophidia dme- egg chambers, revealed a small group of candidates which confer either a lengthening or truncating effect on the structure. Prime candidates are identified on the basis of consistency. MiR-975 and miR-1014 are both cytoophidia-elongating, whereas miR-190 and miR-932 are cytoophidia-shortening. Though target prediction shows that miR-975 and miR-932 do indeed have binding sites on CTPsyn mRNA, in vitro assays instead revealed that none of the four candidates may actually do so. This suggests that the effects asserted by overexpressed miRNAs indirectly reach CTPsyn and its cytoophidia through the actions of middling elements. In silico target prediction and qPCR quantification indicated that, at least for miR-932 and miR-1014, these undetermined elements may be players in fat metabolism. This is the first study to thoroughly investigate miRNAs in connection to CTPsyn expression and activity in any species. The findings presented could serve as a basis for further queries into not only the fundamental aspects of the enzyme’s regulation, but may uncover new facets of closely related pathways as well.
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