Biology subjects

Francis, M. M.

Publications and source records attributed to Francis, M. M..

4 recordsLinked to original sources

bioRxiv2025

Genome-wide analysis reveals pathways important for the development and maturation of excitatory synaptic connections to GABAergic neurons

A high degree of cell and circuit-specific regulation has presented challenges for efforts to precisely define molecular mechanisms controlling synapse formation and maturation. Here, we pursue an unbiased forward genetic approach to identify C. elegans genes involved in the formation and maturation of cholinergic synaptic connections with GABAergic motor neurons as indicated by the distribution of GFP-tagged postsynaptic acetylcholine receptors (AChR) on GABAergic dendrites. We identified mutations in 3 genes that identify key processes in synapse/circuit maturation. Mutation of the RUN domain (RPIP8, UNC-14, and NESCA) cargo adaptor gene unc-14 dramatically impacts overall GABAergic neuron morphology and dendritic spines. Mutation of the nicotinic acetylcholine alpha subunit gene unc-63 causes a failure in AChR assembly in GABAergic neurons but does not significantly alter dendritic spine structure or abundance. Finally, a mutation in the Liprin- synaptic scaffold gene syd-2 severely disrupts both dendritic spines and AChR localization. The identification of these three genes from our screen highlights how mechanisms for cargo trafficking, receptor assembly, and synapse structural organization each make distinct contributions to synapse assembly and circuit connectivity.

neuroscience↗

bioRxiv2025

Transcriptional responses to prolonged oxidative stress require cholinergic activation of G-protein-coupled receptor signaling

Organisms have evolved protective strategies that are geared toward limiting cellular damage and enhancing organismal survival in the face of environmental stresses, but how these protective mechanisms are coordinated remains unclear. Here, we define a requirement for neural activity in mobilizing the antioxidant defenses of the nematode Caenorhabditis elegans both during chronic oxidative stress and prior to its onset. We show that acetylcholine-deficient mutants are particularly vulnerable to chronic oxidative stress. We find that extended oxidative stress mobilizes a broad transcriptional response which is strongly dependent on both cholinergic signaling and activation of the muscarinic G-protein acetylcholine coupled receptor (mAChR) GAR-3. Gene enrichment analysis revealed a lack of upregulation of proteasomal proteolysis machinery in both cholinergic-deficient and gar-3 mAChR mutants, suggesting that muscarinic activation is critical for stress-responsive upregulation of protein degradation pathways. Further, we find that GAR-3 overexpression in cholinergic motor neurons prolongs survival during chronic oxidative stress. Our studies demonstrate neuronal modulation of antioxidant defenses through cholinergic activation of G protein-coupled receptor signaling pathways, defining new potential links between cholinergic signaling, oxidative damage, and neurodegenerative disease.

neuroscience↗

bioRxiv2022

Converging pathways direct synapse elimination through the homeodomain transcriptional regulator DVE-1

An important step in brain development is the remodeling of juvenile neural circuits to establish mature connectivity. The elimination of juvenile synapses is a critical step in this process; however, the molecular mechanisms directing synapse elimination activities and their timing are not fully understood. We identify here a conserved transcriptional regulator, DVE-1, that shares homology with mammalian special AT-rich sequence-binding (SATB) family members and directs the elimination of juvenile synaptic inputs onto remodeling C. elegans GABAergic neurons. Dorsally localized juvenile acetylcholine receptor clusters and apposing presynaptic sites are eliminated during maturation of wild type GABAergic neurons but persist into adulthood in dve-1 mutants. The persistence of juvenile synapses in dve-1 mutants does not impede synaptic growth during GABAergic remodeling and therefore produces heightened motor connectivity and a turning bias during movement. DVE-1 is localized to GABAergic nuclei prior to and during remodeling and DVE-1 nuclear localization is required for synapse elimination to proceed, consistent with DVE-1s function as a transcriptional regulator. Pathway analysis of DVE-1 targets and proteasome inhibitor experiments implicate transcriptional control of the ubiquitin-proteasome system in synapse elimination. Together, our findings demonstrate a new role for a SATB family member in the control of synapse elimination during circuit remodeling through transcriptional regulation of ubiquitin-proteasome signaling. Contributions SummaryKDA generated strains, transgenic lines, molecular constructs, confocal microscopy images and analysis, performed optogenetic behavioral experiments, photoconversion experiments, modencode ChIP-seq analysis and pathway analysis. SR performed all calcium imaging experiments/analysis and conducted single worm tracking. KB performed all Bortezomib inhibitor experiments and analysis. CL generated most vectors and constructs. JR assisted with generation of CRISPR/Cas9 generated strains. WA and MR assisted with aldicarb behavioral assay. DO assisted with EMS screen and isolation of dve-1 mutant. CB and MD aided in CloudMap bioinformatic analysis of the uf171 mutant. MMF and KDA designed and interpreted results of all experiments and wrote the manuscript.

neuroscience↗

bioRxiv2020

A conserved neuropeptide system links head and body motor circuits to enable adaptive behavior

Neuromodulators promote adaptive behaviors that are often complex and involve concerted activity changes across circuits that are often not physically connected. It is not well understood how neuromodulatory systems accomplish these tasks. Here we show that the C. elegans NLP-12 neuropeptide system shapes responses to food availability by modulating the activity of head and body wall motor neurons through alternate G-protein coupled receptor (GPCR) targets, CKR-1 and CKR-2. We show ckr-2 deletion reduces body bend depth during movement under basal conditions. We demonstrate CKR-1 is a functional NLP-12 receptor and define its expression in the nervous system. In contrast to basal locomotion, biased CKR-1 GPCR stimulation of head motor neurons promotes turning during local searching. Deletion of ckr-1 reduces head neuron activity and diminishes turning while specific ckr-1 overexpression or head neuron activation promote turning. Thus, our studies suggest locomotor responses to changing food availability are regulated through conditional NLP-12 stimulation of head or body wall motor circuits. Impact statementInvestigation of neuromodulatory control of ethologically conserved area-restricted food search behavior shows that NLP-12 stimulation of the head motor circuit promotes food searching through the previously uncharacterized CKR-1 GPCR.

neuroscience↗