Dimensionality reduction simplifies synaptic partner matching in an olfactory circuit.

The distribution of postsynaptic partners in three-dimensional (3D) space presents complex choices for a navigating axon. Here, we discovered a dimensionality reduction principle in establishing the 3D glomerular map in the fly antennal lobe. Olfactory receptor neuron (ORN) axons first contact partner projection neuron (PN) dendrites at the 2D spherical surface of the antennal lobe during development, regardless of whether the adult glomeruli are at the surface or interior of the antennal lobe.

Molecular and cellular mechanisms of teneurin signaling in synaptic partner matching.

In developing brains, axons exhibit remarkable precision in selecting synaptic partners among many non-partner cells. Evolutionarily conserved teneurins are transmembrane proteins that instruct synaptic partner matching. However, how intracellular signaling pathways execute teneurins' functions is unclear.

Cdk8/CDK19 promotes mitochondrial fission through Drp1 phosphorylation and can phenotypically suppress pink1 deficiency in Drosophila.

Cdk8 in Drosophila is the orthologue of vertebrate CDK8 and CDK19. These proteins have been shown to modulate transcriptional control by RNA polymerase II. We found that neuronal loss of Cdk8 severely reduces fly lifespan and causes bang sensitivity.

The AMPK-like protein kinases Sik2 and Sik3 interact with Hipk and induce synergistic tumorigenesis in a cancer model.

Homeodomain-interacting protein kinases (Hipks) regulate cell proliferation, apoptosis, and tissue development. Overexpression of Hipk in causes tumorigenic phenotypes in larval imaginal discs. We find that depletion of Salt-inducible kinases Sik2 or Sik3 can suppress Hipk-induced overgrowth.

Origin of wiring specificity in an olfactory map revealed by neuron type-specific, time-lapse imaging of dendrite targeting.

How does wiring specificity of neural maps emerge during development? Formation of the adult olfactory glomerular map begins with the patterning of projection neuron (PN) dendrites at the early pupal stage. To better understand the origin of wiring specificity of this map, we created genetic tools to systematically characterize dendrite patterning across development at PN type-specific resolution. We find that PNs use lineage and birth order combinatorially to build the initial dendritic map.

Cellular bases of olfactory circuit assembly revealed by systematic time-lapse imaging.

Neural circuit assembly features simultaneous targeting of numerous neuronal processes from constituent neuron types, yet the dynamics is poorly understood. Here, we use the Drosophila olfactory circuit to investigate dynamic cellular processes by which olfactory receptor neurons (ORNs) target axons precisely to specific glomeruli in the ipsi- and contralateral antennal lobes. Time-lapse imaging of individual axons from 30 ORN types revealed a rich diversity in extension speed, innervation timing, and ipsilateral branch locations and identified that ipsilateral targeting occurs via stabilization of transient interstitial branches.

Metabolic reprogramming in cancer: mechanistic insights from Drosophila.

Cancer cells constantly reprogram their metabolism as the disease progresses. However, our understanding of the metabolic complexity of cancer remains incomplete. Extensive research in the fruit fly Drosophila has established numerous tumor models ranging from hyperplasia to neoplasia.

Hyperpolarized mitochondria accumulate in Hipk-overexpressing cells to drive tumor-like growth.

Both functional and dysfunctional mitochondria are known to underlie tumor progression. Here, we establish use of the proto-oncogene Homeodomain-interacting protein kinase (Hipk) as a new tool to address this paradox. We find that, in Hipk-overexpressing tumor-like cells, mitochondria accumulate and switch from fragmented to highly fused interconnected morphologies.

LRP6 lets Merlin go in times of nutrient scarcity.

Cells take advantage of cross-talk in signaling pathways to integrate diverse signals and produce coordinated responses. In this issue of EMBO Reports, Jeong et al discover that the Wnt co-receptor, low-density lipoprotein (LDL) receptor-related protein LRP6, negatively regulates Hippo signaling by serving as a binding sink to sequester and inhibit Merlin, an activator of Hippo signaling (Jeong et al, 2020). This regulation is nutrient-responsive, likely using LRP6 O-GlcNAcylation as a molecular switch.

High specificity and tight spatial restriction of self-biotinylation by DNA and RNA G-Quadruplexes complexed in vitro and in vivo with Heme.

Guanine-rich, single-stranded DNAs and RNAs that fold to G-quadruplexes (GQs) are able to complex tightly with heme and display strongly enhanced peroxidase activity. Phenolic compounds are particularly good substrates for these oxidative DNAzymes and ribozymes; we recently showed that the use of biotin-tyramide as substrate can lead to efficient GQ self-biotinylation. Such biotinylated GQs are amenable to polymerase chain reaction amplification and should be useful for a relatively non-perturbative investigation of GQs as well as GQ-heme complexes within living cells.

Homeodomain-interacting protein kinase (Hipk) plays roles in nervous system and muscle structure and function.

Homeodomain-interacting protein kinases (Hipks) have been previously associated with cell proliferation and cancer, however, their effects in the nervous system are less well understood. We have used Drosophila melanogaster to evaluate the effects of altered Hipk expression on the nervous system and muscle. Using genetic manipulation of Hipk expression we demonstrate that knockdown and over-expression of Hipk produces early adult lethality, possibly due to the effects on the nervous system and muscle involvement.

The nutrient sensor OGT regulates Hipk stability and tumorigenic-like activities in .

Environmental cues such as nutrients alter cellular behaviors by acting on a wide array of molecular sensors inside cells. Of emerging interest is the link observed between effects of dietary sugars on cancer proliferation. Here, we identify the requirements of hexosamine biosynthetic pathway (HBP) and GlcNAc transferase (OGT) for homeodomain-interacting protein kinase (Hipk)-induced growth abnormalities in response to a high sugar diet.

A positive feedback loop between Myc and aerobic glycolysis sustains tumor growth in a tumor model.

Cancer cells usually exhibit aberrant cell signaling and metabolic reprogramming. However, mechanisms of crosstalk between these processes remain elusive. Here, we show that in an in vivo tumor model expressing oncogenic Homeodomain-interacting protein kinase (Hipk), tumor cells display elevated aerobic glycolysis.

Homeodomain-interacting protein kinase promotes tumorigenesis and metastatic cell behavior.

Aberrations in signaling pathways that regulate tissue growth often lead to tumorigenesis. Homeodomain-interacting protein kinase (Hipk) family members are reported to have distinct and contradictory effects on cell proliferation and tissue growth. From these studies, it is clear that much remains to be learned about the roles of Hipk family protein kinases in proliferation and cell behavior.

Role of nuclear factor of activated T-cells 5 in regulating hypertonic-mediated secretin receptor expression in kidney collecting duct cells.

A growing body of evidence suggests that secretin (SCT) is an important element in the osmoregulatory pathway. It is interesting to note that both SCT and its receptor (SCTR) gene are activated upon hyperosmolality in the kidney. However, the precise molecular mechanisms underlying the induction of the SCTR gene expression in response to changes in osmolality have yet to be clarified.

β-Spectrin regulates the hippo signaling pathway and modulates the basal actin network.

Emerging evidence suggests functional regulation of the Hippo pathway by the actin cytoskeleton, although the detailed molecular mechanism remains incomplete. In a genetic screen, we identified a requirement for β-Spectrin in the posterior follicle cells for the oocyte repolarization process during Drosophila mid-oogenesis. β-spectrin mutations lead to loss of Hippo signaling activity in the follicle cells.