Perturbation of IIS/TOR signaling alters the landscape of sex-differential gene expression in Drosophila.

BACKGROUND: The core functions of the insulin/insulin-like signaling and target of rapamycin (IIS/TOR) pathway are nutrient sensing, energy homeostasis, growth, and regulation of stress responses. This pathway is also known to interact directly and indirectly with the sex determination regulatory hierarchy. The IIS/TOR pathway plays a role in directing sexually dimorphic traits, including dimorphism of growth, metabolism, stress and behavior. Previous studies of sexually dimorphic gene expression in the adult head, which includes both nervous system and endocrine tissues, have revealed variation in sex-differential expression, depending in part on genotype and environment. To understand the degree to which the environmentally responsive insulin signaling pathway contributes to sexual dimorphism of gene expression, we examined the effect of perturbation of the pathway on gene expression in male and female Drosophila heads. RESULTS: Our data reveal a large effect of insulin signaling on gene expression, with greater than 50% of genes examined changing expression. Males and females have a shared gene expression response to knock-down of InR function, with significant enrichment for pathways involved in metabolism. Perturbation of insulin signaling has a greater impact on gene expression in males, with more genes changing expression and with gene expression differences of larger magnitude. Primarily as a consequence of the response in males, we find that reduced insulin signaling results in a striking increase in sex-differential expression. This includes sex-differences in expression of immune, defense and stress response genes, genes involved in modulating reproductive behavior, genes linking insulin signaling and ageing, and in the insulin signaling pathway itself. CONCLUSIONS: Our results demonstrate that perturbation of insulin signaling results in thousands of genes displaying sex differences in expression that are not differentially expressed in control conditions. Thus, insulin signaling may play a role in variability of somatic, sex-differential expression. The finding that perturbation of the IIS/TOR pathway results in an altered landscape of sex-differential expression suggests a role of insulin signaling in the physiological underpinnings of trade-offs, sexual conflict and sex differences in expression variability.

Investigation of Drosophila fruitless neurons that express Dpr/DIP cell adhesion molecules.

Drosophila reproductive behaviors are directed by fruitless neurons. A reanalysis of genomic studies shows that genes encoding dpr and DIP immunoglobulin superfamily (IgSF) members are expressed in fru P1 neurons. We find that each fru P1 and dpr/DIP (fru P1 ∩ dpr/DIP) overlapping expression pattern is similar in both sexes, but there are dimorphisms in neuronal morphology and cell number. Behavioral studies of fru P1 ∩ dpr/DIP perturbation genotypes indicate that the mushroom body functions together with the lateral protocerebral complex to direct courtship behavior. A single-cell RNA-seq analysis of fru P1 neurons shows that many DIPs have high expression in a small set of neurons, whereas the dprs are often expressed in a larger set of neurons at intermediate levels, with a myriad of dpr/DIP expression combinations. Functionally, we find that perturbations of sex hierarchy genes and of DIP-ε change the sex-specific morphologies of fru P1 ∩ DIP-α neurons.

An Examination of Dynamic Gene Expression Changes in the Mouse Brain During Pregnancy and the Postpartum Period.

The developmental transition to motherhood requires gene expression changes that alter the brain to drive the female to perform maternal behaviors. We broadly examined the global transcriptional response in the mouse maternal brain, by examining four brain regions: hypothalamus, hippocampus, neocortex, and cerebellum, in virgin females, two pregnancy time points, and three postpartum time points. We find that overall there are hundreds of differentially expressed genes, but each brain region and time point shows a unique molecular signature, with only 49 genes differentially expressed in all four regions. Interestingly, a set of "early-response genes" is repressed in all brain regions during pregnancy and postpartum stages. Several genes previously implicated in underlying postpartum depression change expression. This study serves as an atlas of gene expression changes in the maternal brain, with the results demonstrating that pregnancy, parturition, and postpartum maternal experience substantially impact diverse brain regions.

C. elegans EIF-3.K promotes programmed cell death through CED-3 caspase.

Programmed cell death (apoptosis) is essential for the development and homeostasis of metazoans. The central step in the execution of programmed cell death is the activation of caspases. In C. elegans, the core cell death regulators EGL-1(a BH3 domain-containing protein), CED-9 (Bcl-2), and CED-4 (Apaf-1) act in an inhibitory cascade to activate the CED-3 caspase. Here we have identified an additional component eif-3.K (eukaryotic translation initiation factor 3 subunit k) that acts upstream of ced-3 to promote programmed cell death. The loss of eif-3.K reduced cell deaths in both somatic and germ cells, whereas the overexpression of eif-3.K resulted in a slight but significant increase in cell death. Using a cell-specific promoter, we show that eif-3.K promotes cell death in a cell-autonomous manner. In addition, the loss of eif-3.K significantly suppressed cell death-induced through the overexpression of ced-4, but not ced-3, indicating a distinct requirement for eif-3.K in apoptosis. Reciprocally, a loss of ced-3 suppressed cell death induced by the overexpression of eif-3.K. These results indicate that eif-3.K requires ced-3 to promote programmed cell death and that eif-3.K acts upstream of ced-3 to promote this process. The EIF-3.K protein is ubiquitously expressed in embryos and larvae and localizes to the cytoplasm. A structure-function analysis revealed that the 61 amino acid long WH domain of EIF-3.K, potentially involved in protein-DNA/RNA interactions, is both necessary and sufficient for the cell death-promoting activity of EIF-3.K. Because human eIF3k was able to partially substitute for C. elegans eif-3.K in the promotion of cell death, this WH domain-dependent EIF-3.K-mediated cell death process has potentially been conserved throughout evolution.

Latent membrane protein 1 of Epstein-Barr virus regulates death-associated protein kinase 1 in lymphoblastoid cell line.

The Epstein-Barr virus (EBV) infects and transforms primary B cells into lymphoblastoid cell lines (LCLs). We observed death-associated protein kinase 1 (DAPK1) upregulation in B cells following EBV infection and high DAPK1 levels in LCLs. DAPK1 participates in several apoptosis-inducing pathways, yet DAPK1 expression increased during B cell transformation. Data from LMP1 overexpression in LCLs and HeLa cells and from knocked down LMP1 in LCLs suggest LMP1 regulation of DAPK1 expression. We observed NF-κB signaling in DAPK1 upregulation by LMP1 with CTAR deletion mutants failing to induce DAPK1 expression and with Bay11 blocking DAPK1 expression. DAPK1 is inactive in LCLs due to insufficient stimuli, and is not regulated by Ser308 phosphorylation. However, DAPK1 in LCLs is functional, as evidenced by its quick mediation of cell death following UV or H(2)O(2) exposure, and increased survival among LCLs knocked down with DAPK. DAPK roles in EBV-infected B cells remain to be identified.