Biology subjects

Restrepo, L.

Publications and source records attributed to Restrepo, L..

3 recordsLinked to original sources

bioRxiv2022

Different olfactory neuron classes use distinct temporal and molecular programs to complete synaptic development

Developing neurons must meet core molecular, cellular, and temporal requirements to ensure the correct formation of synapses, resulting in functional circuits. However, because of the vast diversity in neuronal class and function, it is unclear whether or not all neurons use the same organizational mechanisms to form synaptic connections and achieve functional and morphological maturation. Moreover, it remains unknown if neurons united in a common goal and comprising the same sensory circuit develop on similar timescales and using identical molecular approaches to ensure the formation of the correct number of synapses. To begin to answer these questions, we took advantage of the Drosophila antennal lobe, a model olfactory circuit with remarkable genetic access and synapse-level resolution. Using tissue-specific genetic labeling of active zones, we performed a quantitative analysis of synapse formation in multiple classes of neurons throughout development and adulthood. We found that olfactory receptor neurons (ORNs), projection neurons (PNs), and local interneurons (LNs) each have unique time-courses of synaptic development, addition, and refinement, demonstrating that each class follows a distinct developmental program. This raised the possibility that these classes may also have distinct molecular requirements for synapse formation. We genetically altered neuronal activity in each neuronal subtype and observed differing effects on synapse number based on the neuronal class examined. Silencing neuronal activity in ORNs, PNs, and LNs impaired synaptic development but only in ORNs did enhancing neuronal activity influence synapse formation. ORNs and LNs demonstrated similar impairment of synaptic development with enhanced activity of a master kinase, GSK-3{beta}, suggesting that neuronal activity and GSK-3{beta} kinase activity function in a common pathway. ORNs also, however, demonstrated impaired synaptic development with GSK-3{beta} loss-of-function, suggesting additional activity-independent roles in development. Ultimately, our results suggest that the requirements for synaptic development are not uniform across all neuronal classes with considerable diversity existing in both their developmental timeframes and molecular requirements. These findings provide novel insights into the mechanisms of synaptic development and lay the foundation for future work determining their underlying etiologies.

neuroscience↗

bioRxiv2020

γ-secretase promotes postsynaptic maturation through the cleavage of a Wnt receptor

An emerging feature of neurodegenerative disease is synaptic dysfunction and loss, leading to the suggestion that mechanisms required for synaptic maturation may be linked to disease. Synaptic maturation requires the transmission of signals between nascent synaptic sites and the nucleus, but how these signals are generated is not well understood. We posit that proteolytic cleavage of receptors, which enables their translocation to the nucleus, may be a shared molecular mechanism between the events that promote synaptic maturation and those linked to later-onset disorders of the nervous system, including neurodegenerative disease. Here we show during synaptic development, that cleavage of synaptic maturation molecules requires {gamma}-secretase, a protein complex linked to Alzheimers Disease, a devastating neurodegenerative condition, is required for postsynaptic maturation. In the absence of {gamma}-secretase, Drosophila neuromuscular synapses fail to appropriately recruit postsynaptic scaffolding and cytoskeletal proteins, and mutant larvae display behavioral deficits. At the NMJ, {gamma}-secretase promotes synaptic maturation through the cleavage of the Wnt receptor Fz2, and the subsequent entry of its C-terminus into the nucleus. A developmental synaptic role for {gamma}-secretase is also conserved in both the Drosophila central nervous system and mammalian cortical neuron dendrites. Finally, we found that similar maturation defects are evident in fly models for ALS, Alzheimers, Huntingtons, and Parkinsons Diseases. The previously unknown, but conserved, role for {gamma}-secretase coupled with its well-known role in neurodegenerative disease suggest that neurodevelopmental defects may be common to diverse neurodegenerative disease models.

neuroscience↗

bioRxiv2019

Zinc finger RNA binding protein Zn72D regulates ADAR-mediated RNA editing in neurons

Adenosine-to-inosine RNA editing, catalyzed by ADAR enzymes, alters RNA sequences from those encoded by DNA. These editing events are dynamically regulated, but few trans regulators of ADARs are known in vivo. Here, we screen RNA binding proteins for roles in editing regulation using in vivo knockdown experiments in the Drosophila brain. We identify Zinc-Finger Protein at 72D (Zn72D) as a regulator of editing levels at a majority of editing sites in the brain. Zn72D both regulates ADAR protein levels and interacts with ADAR in an RNA-dependent fashion, and similar to ADAR, Zn72D is necessary to maintain proper neuromuscular junction architecture and motility in the fly. Furthermore, the mammalian homolog of Zn72D, Zfr, regulates editing in mouse primary neurons, demonstrating the conservation of this regulatory role. The broad and conserved regulation of ADAR editing by Zn72D in neurons represents a novel mechanism by which critically important editing events are sustained.

genetics↗