Biology subjects

Meltzer, H.

Publications and source records attributed to Meltzer, H..

6 recordsLinked to original sources

bioRxiv2026

Branch-specific axon pruning induced by Dpr4/DIP-{Theta} transneuronal interactions

Neuronal remodeling is a conserved, late developmental mechanism to refine neural circuits. Although remodeling typically occurs with remarkable spatiotemporal precision, its underlying molecular mechanisms remain poorly understood. In the Drosophila mushroom body (MB) circuit, {gamma}-Kenyon cells ({gamma}-KCs) undergo stereotyped remodeling during metamorphosis, in which they prune their larval vertical and medial axonal branches and subsequently regrow a medial, adult-specific branch. Our previous transcriptional profiling of developing {gamma}-KCs revealed dynamic expression of Defective proboscis extension response (Dpr) proteins and their binding partners, Dpr-interacting proteins (DIPs), members of the Immunoglobulin (Ig) superfamily. Despite their established roles in neurodevelopment, how Dpr/DIPs function - given their lack of intracellular domains - remains unclear. Here, we show that overexpression of Dpr4 in developing {gamma}-KCs cell-autonomously inhibits axon pruning. Strikingly, this effect is branch-specific: the vertical axonal branch fails to prune, while the medial branch prunes normally. To our knowledge, this represents the first demonstration of branch-specific control of pruning in this system. Moreover, the adult medial branch regrows normally, indicating that pruning and regrowth are independently regulated at the level of individual branches. We demonstrate that this unique branch-specificity arises from trans-neuronal interactions between Dpr4 in {gamma}-KCs and DIP-{theta} in dopaminergic neurons that selectively innervate the vertical larval MB lobe. Furthermore, our findings suggest that this phenotype relies on an Ig2 domain of a Dpr family member, implying the involvement of a third binding partner. Leveraging this robust overexpression phenotype to probe downstream mechanisms, we find that loss of the transmembrane adhesion protein N-Cadherin suppresses the Dpr4-induced pruning defect. Together, our findings highlight the local impact of Dpr/DIP-mediated trans-neuronal interactions on the spatial regulation of remodeling, and provide genetic evidence implicating N-Cadherin as a potential downstream mediator of Dpr/DIP function within a developing neural circuit.

neuroscience↗

bioRxiv2025

Comparative developmental transcriptomics of Drosophila mushroom body neurons highlights the mevalonate pathway as a regulator of axon growth

The ability of neurons to extend axons is governed by tightly regulated genetic programs that vary across developmental stages and cell types. Understanding the molecular features that control axon growth potential is critical for uncovering how neural circuits form, mature, and respond to injury or disease. The Drosophila mushroom body (MB) offers a powerful model to dissect axon growth programs, as lineage-related Kenyon cells (KCs) undergo different developmental events under shared spatiotemporal conditions. During metamorphosis, {gamma}-KCs undergo axon pruning, followed by developmental regrowth at the same time-frame as /{beta}-KCs initiate axon growth - thus providing a unique opportunity to compare these distinct growth paradigms. We thus performed RNA-sequencing of /{beta}-and {gamma}-KCs during their initial growth and developmental regrowth, respectively, revealing dynamic transcriptional changes and identifying 300 shared genes upregulated during both growth states. A targeted loss-of-function screen revealed genes specifically required for either /{beta} initial growth, {gamma} regrowth, or both. Focusing on one such candidate, Pmvk, we found that it plays a crucial role in axon regrowth by acting within the mevalonate pathway. Notably, other enzymes in this pathway were also required, suggesting that the entire metabolic pathway is essential for supporting regrowth. Genetic mutant analyses and rescue exepriements suggest that Pmvk likely controls axon regrowth via Rheb, an effector of the TOR pathway, which we previously found to be required for regrowth. Our developmental transcriptomic atlas not only advances understanding of intrinsic axon growth programs, but also provides candidate genes and a valuable framework for future studies aimed at enhancing axon regeneration in the adult nervous system.

neuroscience↗

bioRxiv2024

A Drosophila screen of schizophrenia-related genes highlights the requirement of neural and glial matrix metalloproteinases for neuronal remodeling

Schizophrenia (SCZ) is a multifactorial neuropsychiatric disorder of complex and mostly unknown etiology, affected by genetic, developmental and environmental factors. Neuroanatomical abnormalities, such as loss of grey matter, are apparent prior to the onset of symptoms, suggesting neurodevelopmental origin. Indeed, it has been hypothesized, and recently experimentally supported, that SCZ is associated with dysregulation of developmental synaptic pruning. Here, we explore the molecular link between SCZ-associated genes and developmental neuronal remodeling. We focused on the Drosophila mushroom body (MB), which undergoes stereotypic remodeling during metamorphosis. We conducted a loss-of-function screen in which we knocked down, in either glia or neurons, Drosophila homologs of human genes that are associated with SCZ based on genomic studies (GWAS). Out of our positive hits, we focused on matrix metalloproteinases (MMPs), mostly known for their role in remodeling of the extracellular matrix. Our combinatorial loss-of-function experiments suggest that Drosophila MMPs, which are closely related to mammalian MMPs, are required in neurons and in glia for the pruning of MB axons. Our results shed new light on potential molecular players underlying neurodevelopmental defects in SCZ and highlight the advantage of genetically tractable model organisms in the study of human neurodevelopmental disorders.

neuroscience↗

bioRxiv2024

Cis inhibition of co-expressed DIPs and Dprs shapes neural development

In Drosophila, two interacting adhesion protein families, Dprs and DIPs, coordinate the assembly of neural networks. While intercellular DIP/Dpr interactions have been well characterized, DIPs and Dprs are often co-expressed within the same cells, raising the question as to whether they also interact in cis. We show, in cultured cells and in vivo, that DIP- and DIP-{delta} can interact in cis with their ligands, Dpr6/10 and Dpr12, respectively. When co-expressed in cis with their cognate partners, these Dprs regulate the extent of trans binding, presumably through competitive cis interactions. We demonstrate the neurodevelopmental effects of cis inhibition in fly motor neurons and in the mushroom body. We further show that a long disordered region of DIP- at the C-terminus is required for cis but not trans interactions, likely because it alleviates geometric constraints on cis binding. Thus, the balance between cis and trans interactions plays a role in controlling neural development.

biochemistry↗

bioRxiv2019

Transneuronal interactions facilitate axonal compartment formation

The mechanisms controlling wiring of neuronal networks are largely unknown. The stereotypic architecture of the Drosophila mushroom-body (MB) offers a unique system to study circuit assembly. The adult medial MB {gamma}-lobe is comprised of a long bundle of axons that wires with specific modulatory and output neurons in a tiled manner defining five distinct zones. We found that the immunoglobulin superfamily protein Dpr12 is cell-autonomously required in {gamma}-neurons for their developmental regrowth into the distal {gamma}4/5 zones, where both Dpr12 and its interacting protein, DIP-{delta}, are enriched. DIP-{delta} functions in a subset of dopaminergic neurons that wire with {gamma}-neurons within the {gamma}4/5 zone. During metamorphosis, these dopaminergic projections arrive to the {gamma}4/5 zone prior to {gamma}-axons, suggesting that {gamma}-axons extend through a prepatterned region. Thus, Dpr12/DIP-{delta} transneuronal interaction is required for {gamma}4/5 zone formation. Our study sheds light onto molecular and cellular mechanisms underlying circuit formation within subcellular resolution.

neuroscience↗

bioRxiv2018

Activation of dopamine receptor 2 (DRD2) prompts transcriptomic and metabolic plasticity in glioblastoma

Glioblastoma (GBM) is one of the most aggressive and lethal tumor types. Evidence continues to accrue indicating that the complex relationship between GBM and the brain microenvironment contributes to this malignant phenotype. However, the interaction between GBM and neurotransmitters, signaling molecules involved in neuronal communication, remains incompletely understood. Here we examined, in both sexes of humans and mice, how the monoamine dopamine influences GBM cells. We demonstrate that GBM cells express DRD2, with elevated expression in the glioma-initiating cell (GIC) population. Stimulation of DRD2 caused neuron-like depolarization exclusively in GICs. In addition, long-term activation of DRD2 heightened the sphere-forming capacity of GBM cells as well as tumor engraftment efficiency. Mechanistic investigation revealed that DRD2 signaling activates the hypoxia response and functionally alters metabolism. Finally, we found that GBM cells synthesize and secrete dopamine themselves, suggesting a potential autocrine mechanism. These results identify dopamine signaling as a potential therapeutic target in GBM and further highlight neurotransmitters as a key feature of the pro-tumor microenvironment.\n\nSignificance StatementThis work offers critical insight into the role of the neurotransmitter dopamine in the progression of GBM. We show that dopamine induces specific changes in the state of tumor cells, augmenting their growth and shifting them to a more stem-cell like state. Further, we show that dopamine can alter the metabolic behavior of GBM cells, increasing glycolysis. Finally, we show that GBM cells, including tumor samples from patients, can synthesize and secrete dopamine, suggesting an autocrine signaling process underlying these results. These results describe a novel connection between neurotransmitters and brain cancer, further highlighting the critical influence of the brain milieu on GBM.

cancer biology↗