Drosophila Syntrophins are involved in locomotion and regulation of synaptic morphology

Transcriptome analysis of Drosophila melanogaster laboratory strains of different geographical origin after long-term laboratory maintenance

Positive selection may be the main factor of the between-population divergence in gene expression. Expression profiles of two Drosophila melanogaster laboratory strains of different geographical origin and long-term laboratory maintenance were analyzed using microchip arrays encompassing probes for 18,500 transcripts. The Russian strain D18 and the North American strain Canton-S were compared. A set of 223 known or putative genes demonstrated significant changes in expression levels between these strains. Differentially expressed genes (DEG) were enriched in response to DDT (p = .0014), proteolysis (p = 2.285E-5), transmembrane transport (p = 1.03E-4), carbohydrate metabolic process (p = .0317), protein homotetramerization (p = .0444), and antibacterial humoral response (p = 425E-4). The expression in subset of genes from different categories was verified by qRT-PCR. Analysis of transcript abundance between Canton-S and D18 strains allowed to select several genes to estimate their participation in latitude adaptation. Expression of selected genes was analyzed in five D. melanogaster lines of different geographic origins by qRT-PCR, and we found two candidate genes that may be associated with latitude adaptation in adult flies-smp-30 and Cda9. Quite possible that several alleles of these genes may be important for insect survival in the environments of global warming. It is interesting that the number of genes involved in local adaptation demonstrates expression level appropriate to their geographical origin even after decades of laboratory maintenance.

Drosophila mutants of the autism candidate gene neurobeachin (rugose) exhibit neuro-developmental disorders, aberrant synaptic properties, altered locomotion, and impaired adult social behavior and activity patterns

Autism spectrum disorder (ASD) is a neurodevelopmental disorder in humans characterized by complex behavioral deficits, including intellectual disability, impaired social interactions, and hyperactivity. ASD exhibits a strong genetic component with underlying multigene interactions. Candidate gene studies have shown that the neurobeachin (NBEA) gene is disrupted in human patients with idiopathic autism ( Castermans et al., 2003 ). The NBEA gene spans the common fragile site FRA 13A and encodes a signal scaffold protein ( Savelyeva et al., 2006 ). In mice, NBEA has been shown to be involved in the trafficking and function of a specific subset of synaptic vesicles. ( Medrihan et al., 2009 ; Savelyeva et al., 2006 ). Rugose (rg) is the Drosophila homolog of the mammalian and human NBEA. Our previous genetic and molecular analyses have shown that rg encodes an A kinase anchor protein (DAKAP 550), which interacts with components of the epidermal growth factor receptor or EGFR and Notch-mediated signaling pathways, facilitating cross talk between these and other pathways ( Shamloula et al., 2002 ). We now present functional data from studies on the larval neuromuscular junction that reveal abnormal synaptic architecture and physiology. In addition, adult rg loss-of-function mutants exhibit defective social interactions, impaired habituation, aberrant locomotion, and hyperactivity. These results demonstrate that Drosophila NBEA (rg) mutants exhibit phenotypic characteristics reminiscent of human ASD and thus could serve as a genetic model for studying ASDs.

Identification of ter94, Drosophila VCP, as a strong modulator of motor neuron degeneration induced by knockdown of Caz, Drosophila FUS

In humans, mutations in the fused in sarcoma (FUS) gene have been identified in sporadic and familial forms of amyotrophic lateral sclerosis (ALS). Cabeza (Caz) is the Drosophila ortholog of human FUS. Previously, we established Drosophila models of ALS harboring Caz-knockdown. These flies develop locomotive deficits and anatomical defects in motoneurons (MNs) at neuromuscular junctions; these phenotypes indicate that loss of physiological FUS functions in the nucleus can cause MN degeneration similar to that seen in FUS-related ALS. Here, we aimed to explore molecules that affect these ALS-like phenotypes of our Drosophila models with eye-specific and neuron-specific Caz-knockdown. We examined several previously reported ALS-related genes and found genetic links between Caz and ter94, the Drosophila ortholog of human Valosin-containing protein (VCP). Genetic crossing the strongest loss-of-function allele of ter94 with Caz-knockdown strongly enhanced the rough-eye phenotype and the MN-degeneration phenotype caused by Caz-knockdown. Conversely, the overexpression of wild-type ter94 in the background of Caz-knockdown remarkably suppressed those phenotypes. Our data demonstrated that expression levels of Drosophila VCP ortholog dramatically modified the phenotypes caused by Caz-knockdown in either direction, exacerbation or remission. Our results indicate that therapeutic agents that up-regulate the function of human VCP could modify the pathogenic processes that lead to the degeneration of MNs in ALS.

Combining genome-wide methods to investigate the genetic complexity of courtship song variation in Drosophila melanogaster

Little is currently known about the genetic complexity of quantitative behavioral variation, the types of genes involved, or their effects on intermediate phenotypes. Here, we conduct a genome-wide association study of Drosophila melanogaster courtship song variation using 168 sequenced inbred lines, and fail to find highly significant associations. However, by combining these data with results from a well-powered Evolve and Resequence (E&R) study on the same trait, we provide statistical evidence that some power to associate genotype and phenotype is available. Genes that are significant in both analyses are enriched for expression in the nervous system, and affect neural development and synaptic growth when perturbed. Quantitative complementation at one of these loci, Syntrophin-like 1, supports a hypothesis that variation at this locus affects variation in the inter-pulse interval of courtship song. These results suggest that experimental evolution may provide an approach for genome-scale replication in Drosophila.

Dg-Dys-Syn1 signaling in Drosophila regulates the microRNA profile

Background

The Dystrophin Glycoprotein Complex (DGC) is at the center of significant inheritable diseases, such as muscular dystrophies that can be fatal and impair neuronal function in addition to muscle degeneration. Recent evidence has shown that it can control cellular homeostasis and work via Dystrophin signaling to regulate microRNA gene expression which implies that disease phenotypes hide an entourage of regulatory and homeostatic anomalies. Uncovering these hidden processes could shed new light on the importance of proper DGC function for an organism’s overall welfare and bring forth new ideas for treatments.

Results

To better understand a role for the DGC in these processes, we used the genetically advantageous Drosophila muscular dystrophy model to conduct a whole animal microarray screen. Since we have recently found that dystrophic symptoms can be caused by stress even in wild type animals and are enhanced in mutants, we screened stressed animals for microRNA misregulation as well. We were able to define microRNAs misregulated due to stress and/or dystrophy. Our results support the hypothesis that there is a Dystrophin and Dystroglycan dependent circuitry of processes linking stress response, dystrophic conditions and cellular signaling and that microRNAs play an important role in this network. Verification of a subset of our results was conducted via q-PCR and revealed that miR-956, miR-980 and miR-252 are regulated via a Dystroglycan-Dystrophin-Syntrophin dependent pathway.

Conclusions

The results presented in this study support the hypothesis that there is a Dystrophin and Dystroglycan dependent circuitry of processes that includes regulation of microRNAs. Dystrophin signaling has already been found to occur in mammalian musculature; however, our data reveals that this regulation is evolutionarily conserved and also present in at least neuronal tissues. Our data imply that Dystroglycan-Dystrophin-Syntrophin signaling through control of multiple microRNAs is involved in highly managed regulation of gene expression required to adapt cellular homeostasis that is compromised under stress and dystrophic conditions.