Neuronal Receptors Research Articles

Epidermal maintenance of Langerhans cells relies on autophagy-regulated lipid metabolism

Macroautophagy (often-named autophagy), a catabolic process involving autophagy-related (Atg) genes, prevents the accumulation of harmful cytoplasmic components and mobilizes energy reserves in long-lived and self-renewing cells. Autophagy deficiency affects antigen presentation in conventional dendritic cells (DCs) without impacting their survival. However, previous studies did not address epidermal Langerhans cells (LCs). Here, we demonstrate that deletion of either Atg5 or Atg7 in LCs leads to their gradual depletion. ATG5-deficient LCs showed metabolic dysregulation and accumulated neutral lipids. Despite increased mitochondrial respiratory capacity, they were unable to process lipids, eventually leading them to ferroptosis. Finally, metabolically impaired LCs upregulated proinflammatory transcripts and showed decreased expression of neuronal interaction receptors. Altogether, autophagy represents a critical regulator of lipid storage and metabolism in LCs, allowing their maintenance in the epidermis.

Impaired oxytocin signalling in the central amygdala in rats with chronic heart failure

AbstractHeart failure (HF) patients suffer from cognitive decline and mood impairments, but the molecular signals and brain circuits underlying these effects remain elusive. The hypothalamic neuropeptide oxytocin (OT) is critically involved in regulating mood, and OTergic signalling in the central amygdala (CeA) is a key mechanism that controls emotional responses including anxiety‐like behaviours. Still, whether an altered OTergic signalling contributes to mood disorders in HF remains unknown. To address this, we used an ischaemic rat HF model, along with a highly multidisciplinary approach, to mechanistically study multiple levels of the hypothalamus‐to‐CeA OTergic circuit in male rats with HF. We aimed to test the hypothesis that sustained activation of the OT system following an infarct leads to depletion of OT content in this pathway, with subsequent changes in OT receptor expression and blunted modulation of local GABAergic circuits. We found that most of OTergic innervation of the CeA originated from the supraoptic nucleus (SON). While no differences in the numbers of SON→CeA OTergic neurons was observed between sham and HF rats, we observed a blunted content and release of OT from axonal terminals within the CeA. Moreover, we report downregulation of neuronal and astrocytic OT receptors, and impaired OTR‐driven GABAergic synaptic activity within the CeA microcircuit of HF rats. We provide the first evidence that male HF rats display perturbations in the hypothalamus‐to‐amygdala OTergic circuit, laying the foundation for future translational studies targeting either the OT system or GABAergic amygdalar microcircuit to ameliorate mood impairments in rats or patients with chronic HF. imageKey points Heart failure patients suffer from cognitive decline, depression and mood impairments, but the underlying mechanisms remain elusive. Acting within the central amygdala, the neuropeptide oxytocin regulates emotional responses, including anxiety‐like behaviours. However, whether changes in oxytocin signalling occurs during heart failure is unknown. In this study, we used an ischaemic rat heart failure model to mechanistically study multiple levels of the hypothalamus‐to‐amygdala oxytocinergic circuit in this disease. We report an overall blunted oxytocinergic signalling pathway in rats with heart failure, including blunted content and release of oxytocin from axonal terminals, downregulation of neuronal and astrocytic oxytocin receptors, and impaired oxytocin‐driven GABAergic synaptic activity within the central amygdala microcircuit of HF rats. These studies shed light on mechanisms that contribute to mood disorders in cardiovascular disease states and help to identify potential molecular targets for their improved treatment.

Modulation of Ca2+ oscillation following ischemia and nicotinic acetylcholine receptors in primary cortical neurons by high-throughput analysis

Modulation of Ca2+ oscillation following ischemia and nicotinic acetylcholine receptors in primary cortical neurons by high-throughput analysis

Bifurcation Enhances Temporal Information Encoding in the Olfactory Periphery

Living systems continually respond to signals from the surrounding environment. Survival requires that their responses adapt quickly and robustly to the changes in the environment. One particularly challenging example is olfactory navigation in turbulent plumes, where animals experience highly intermittent odor signals while odor concentration varies over many length- and timescales. Here, we show theoretically that olfactory receptor neurons (ORNs) can exploit proximity to a bifurcation point of their firing dynamics to reliably extract information about the timing and intensity of fluctuations in the odor signal, which have been shown to be critical for odor-guided navigation. Close to the bifurcation, the system is intrinsically invariant to signal variance, and information about the timing, duration, and intensity of odor fluctuations is transferred efficiently. Importantly, we find that proximity to the bifurcation is maintained by mean adaptation alone and therefore does not require any additional feedback mechanism or fine-tuning. Using a biophysical model with calcium-based feedback, we demonstrate that this mechanism can explain the measured adaptation characteristics of ORNs. Published by the American Physical Society 2024

CNSC-69. GLIOBLASTOMA-NETWORK CONNECTIVITY IS REGULATED THROUGH ALTERATIONS IN CHLORIDE HOMEOSTASIS AND GABAERGIC SIGNALING

Abstract The specific pathophysiological mechanisms underlying glioma-related epilepsy, which presents an unfavorable clinical course, are still not well explored. To identify the candidate pathways involved in glioblastoma-induced neuronal hyperexcitability, we used high-density electrode arrays in vivo in humans to record local field potentials from cortically projecting gliomas and identified hyperexcitable intratumoral regions with elevated functional connectivity to the brain. Single-cell RNA sequencing (13,730 cells analyzed) of the functionally connected intratumoral regions identified several circuit assembly and GABAergic signaling genes elevated in glioma-intrinsic neurons, including the sodium-potassium-chloride co-transporter 1 (NKCC1), which accumulates chloride in the cells. We hypothesized that the hyperexcitable behavior of glioma-intrinsic neurons in glioblastoma is mediated by elevated NKCC1 and chloride dysregulation and that inhibiting NKCC1 would reinforce the inhibitory action of GABA and rescue the neuronal hyperresponsive phenotype. Single-nucleus (sNuc-seq) sequencing was performed on neuron-glioblastoma co-cultures (54,000 cells analyzed) to determine NKCC1-facilitated GABAergic signaling in glioblastoma-mediated neuronal responses. Mechanistic and functional studies using perforated whole-cell patch-clamp recordings, multielectrode array, calcium, and chloride imaging for validating therapeutic vulnerabilities to NKCC1 silencing by shRNA knockdown and by the FDA-approved drug bumetanide were performed using in vitro and organotypic mouse slice culture models. sNuc-seq revealed an upregulation of neuronal NKCC1 and GABAA receptors when co-cultured with NKCC1-high-expressing glioblastoma cells, indicating the strong association between neuronal NKCC1 and GABAergic signaling. Electrophysiological analysis of glioblastoma-neuron co-cultures demonstrated increased network burst synchrony and a positive shift in the GABA reversal potential (EGABA). This increase was eliminated in the presence of NKCC1 inhibition using bumetanide and shRNA knockdown, which correlated with a significant decrease in intracellular neuronal chloride. Mechanistically, glioma NKCC1 downregulation significantly decreased GAP43-mediated tumor microtube (TMT) formation. Whether this reduced TMT formation also results in decreased chloride release by glioma cells, thereby altering neuronal chloride equilibrium, is currently under investigation. Collectively, these findings aim to identify a new mechanism of glioma-associated epilepsy, which may provide a novel approach to treatment.

Targeted deletion of olfactory receptors in D. melanogaster via CRISPR/Cas9-mediated LexA knock-in

The study of olfaction in Drosophila melanogaster has greatly benefited from genetic reagents such as olfactory receptor mutant lines and GAL4 reporter lines. The CRISPR/Cas9 gene-editing system has been increasingly used to create null receptor mutants or replace coding regions with GAL4 reporters. To further expand this toolkit for manipulating fly olfactory receptor neurons (ORNs), we generated null alleles for 11 different olfactory receptors by using CRISPR/Cas9 to knock in LexA drivers, including multiple lines for receptors which have thus far lacked knock-in mutants. The targeted neuronal types represent a broad range of antennal ORNs from all four morphological sensillum classes. Additionally, we confirmed their loss-of-function phenotypes, assessed receptor haploinsufficiency, and evaluated the specificity of the LexA knock-in drivers. These receptor mutant lines have been deposited at the Bloomington Drosophila Stock Center for use by the broader scientific community.

Prosaposin/Saposin Expression in the Developing Rat Olfactory and Vomeronasal Epithelia

Prosaposin is a glycoprotein widely conserved in vertebrates, and it acts as a precursor for saposins that accelerate hydrolysis in lysosomes or acts as a neurotrophic factor without being processed into saposins. Neurogenesis in the olfactory neuroepithelia, including the olfactory epithelium (OE) and the vomeronasal epithelium (VNE), is known to occur throughout an animal’s life, and mature olfactory neurons (ORNs) and vomeronasal receptor neurons (VRNs) have recently been revealed to express prosaposin in the adult olfactory organ. In this study, the expression of prosaposin in the rat olfactory organ during postnatal development was examined. In the OE, prosaposin immunoreactivity was observed in mature ORNs labeled using olfactory marker protein (OMP) from postnatal day (P) 0. Immature ORNs showed no prosaposin immunoreactivity throughout the examined period. In the VNE, OMP-positive VRNs were mainly observed in the basal region of the VNE on P10 and showed an adult-like distribution from P20. On the other hand, prosaposin immunoreactivity was observed in VRNs from P0, suggesting that not only mature VRNs but also immature VRNs express prosaposin. This study raises the possibility that prosaposin is required for the normal development of the olfactory organ and has different roles in the OE and the VNE.

Effects of NMDA glutamatergic receptors pharmacological stimulation of the ventral tegmental area on the memory deficits induced by maternal deprivation

Maternal deprivation (MD) is a potent stressor during early life and can lead to behavioral changes during adulthood. Several neurochemical mechanisms underlying MD-induced stress have been proposed; among them is the damage caused to dopaminergic neurons in the ventral tegmental area (VTA). We hypothesized that pharmacological stimulation of dopaminergic neurons in VTA by the infusion of an N-Methyl-D-Aspartate (NMDA) receptors agonist (used considering the wide distribution of these glutamatergic receptors in the VTA neurons) can reverse MD-induced memory deficits. Here, we demonstrated that MD affects male and female rats distinctly, with females being more resilient to early-life stress. Furthermore, NMDA pharmacological stimulation of the VTA promotes object recognition (OR) memory persistence in male and female non-MD rats. In males, infusion of NMDA into the VTA immediately after the learning session reverses recognition memory deficits related to MD. Although MD female rats have not shown deficits in OR memory consolidation, the NMDA infusion immediately after the learning session promotes memory persistence. We verified that MD leads to memory deficits in adult male rats, while the females are resilient to early life stress. Furthermore, NMDA pharmacological stimulation of dopaminergic VTA neurons reveals the dopaminergic modulation of OR memory in MD rats, even in females that did not exhibit memory deficits.

Pharmacological characterization of prostaglandin E2 EP2 and EP4 receptors in male rat locus coeruleus neurons ex vivo

The inflammatory mediator prostaglandin E2 (PGE2) binds to Gs-coupled EP2 and EP4 receptors. These receptors are located in the locus coeruleus (LC), the principal noradrenergic nucleus in the brain, but their functional role remains unknown. In this study, the PGE2 EP2 and EP4 receptors in LC cells from male rat brain slices were pharmacologically characterized by single-unit extracellular electrophysiology. The EP2 receptor agonists butaprost (0.01–10 μM) and treprostinil (0.03–10 µM) and the EP4 receptor agonists rivenprost (0.01 nM–1 µM) and TCS2510 (0.20 nM–2 µM) increased the firing rate of LC neurons in a concentration-dependent manner. The EP2 receptor antagonist PF-04418948 (10 nM) hindered the excitatory effect of butaprost and treprostinil while the EP4 receptor antagonist L-161,982 (30 and 300 nM) blocked the excitatory effect caused by rivenprost and TCS2510. The effects of butaprost and rivenprost were prevented by extracellular sodium replacement but were not modified by the protein kinase A (PKA) activator 8-Br-cAMP (1 mM) or the inhibitor H-89 (10 μM). However, the Gβγ subunit blocker gallein (20 μM) hindered the stimulatory effect of butaprost while the Gαs subunit inhibitor NF449 (10 µM) prevented that of rivenprost. Finally, rivenprost-induced stimulation (30 nM) was not occluded by butaprost (1 µM).In conclusion, activation of EP2 and EP4 receptors excites LC noradrenergic neurons through sodium-dependent currents via different G protein subunits in male rat brain slices. EP2 and EP4 in the LC may constitute pharmacological targets for the treatment of pain, fever, drug addiction, anxiety and neuroinflammatory diseases.

Activated microglia secretome and proinflammatory cytokines increase neuronal mu-opioid receptor signalling and expression

Due to its potential role in processes which rely on mu-opioid receptor function, investigating the relationship between Mu-Opioid receptors (MORs), neuroinflammation, and glial cells has gained momentum. Traditionally, MOR activation has been associated with immunosuppression, but recent findings suggest a more nuanced, bidirectional relationship with the immune system. To further investigate this relationship, herein, we investigated the role of the activated microglia secretome and proinflammatory cytokines in neuronal MOR expression and signalling. Our results show that both microglial secretome and specific cytokines increase neuronal MOR expression and enhance the [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO)-induced MOR activation. We also show that DAMGO-induced neuroinflammation increases neuronal MOR expression, activation, and regulation. Our findings suggest a feedback loop between microglial activation, cytokine release, and neuronal MOR dynamics. Future research should delve into the temporal dynamics and functional implications of this relationship, particularly concerning clinically relevant opioids like morphine and fentanyl and pain management.

Molecular signature underlying (R)-ketamine rapid antidepressant response on anhedonic-like behavior induced by sustained exposure to stress

Anhedonia induced by sustained stress exposure is a hallmark symptom of major depressive disorder (MDD) and in rodents, it can be accessed through the sucrose preference test (SPT). (R)-ketamine is a fast-acting antidepressant with less detrimental side effects and abuse liability compared to racemic ketamine. The present study combined high-throughput proteomics and network analysis to identify molecular mechanisms involved in chronic variable stress (CVS)-induced anhedonia and promising targets underlying (R)-ketamine rapid antidepressant response. Male Wistar rats were subjected to CVS for five weeks. Based on the SPT, animals were clustered into resilient or anhedonic-like (ANH) groups. ANH rats received a single dose of saline or (R)-ketamine (20 mg/kg, i.p.), which was proceeded by treatment response evaluation. After prefrontal cortex collection, proteomic analysis was performed to uncover the differentially expressed proteins (DEPs) related to both anhedonic-like behavior and pharmacological response. The behavioral assessment showed that the ANH animals had a significant decrease in SPT, and that (R)-ketamine responders showed a reversal of anhedonic-like behavior. On a molecular level, anhedonia-like behavior was associated with the downregulation of Neuronal Pentraxin Receptor (Nptxr) and Galectin−1 (Gal-1). These data reinforce a disruption in the inflammatory response, neurotransmitter receptor activity, and glutamatergic synapses in chronic stress-induced anhedonia. (R)-ketamine response-associated DEPs included novel potential targets involved in the modulation of oxidative stress, energetic metabolism, synaptogenesis, dendritic arborization, neuroinflammation, gene expression, and telomere length, converging to biological themes extensively documented in MDD physiopathology. Our data provide valuable insights into the molecular mechanisms underlying the response to (R)-ketamine and highlight these pathways as potential therapeutic targets for anhedonia. By addressing proteins involved in oxidative stress, energy metabolism, synaptogenesis, dendritic arborization, neuroinflammation, gene expression, and telomere length, we can target multiple key factors involved in the pathophysiology of MDD. Modulating these proteins could open avenues for novel therapeutic strategies and deepen our understanding of anhedonia, offering hope for improved outcomes in individuals facing this challenging condition. However, additional studies will be essential to validate these findings and further explore their therapeutic implications.

Monitoring Dopamine Release in a Rat Model with VTA Dopaminergic Neuron Receptor Manipulation

Monitoring Dopamine Release in a Rat Model with VTA Dopaminergic Neuron Receptor Manipulation

Monitoring Dopamine Release in a Rat Model with VTA Dopaminergic Neuron Receptor Manipulation

Monitoring Dopamine Release in a Rat Model with VTA Dopaminergic Neuron Receptor Manipulation

Leptin-activated hypothalamic BNC2 neurons acutely suppress food intake.

Leptin is an adipose tissue hormone that maintains homeostatic control of adipose tissue mass by regulating the activity of specific neural populations controlling appetite and metabolism1. Leptin regulates food intake by inhibiting orexigenic agouti-related protein (AGRP) neurons and activating anorexigenic pro-opiomelanocortin (POMC) neurons2. However, whereas AGRP neurons regulate food intake on a rapid time scale, acute activation of POMC neurons has only a minimal effect3-5. This has raised the possibility that there is a heretofore unidentified leptin-regulated neural population that rapidly suppresses appetite. Here we report the discovery of a new population of leptin-target neurons expressing basonuclin 2 (Bnc2) in the arcuate nucleus that acutely suppress appetite by directly inhibiting AGRP neurons. Opposite to the effect of AGRP activation, BNC2 neuronal activation elicited a place preference indicative of positive valence in hungry but not fed mice. The activity of BNC2 neurons is modulated by leptin, sensory food cues and nutritional status. Finally, deleting leptin receptors in BNC2 neurons caused marked hyperphagia and obesity, similar to that observed in a leptin receptor knockout in AGRP neurons. These data indicate that BNC2-expressing neurons are a key component of the neural circuit that maintains energy balance, thus filling an important gap in our understanding of the regulation of food intake and leptin action.

A nociceptive-nociplastic spectrum of myofascial orofacial pain: insights from neuronal ion channel studies

Myofascial orofacial pain, traditionally viewed as a nociceptive pain condition, also exhibits characteristics consistent with nociplastic pain—pain arising from altered nociception without clear evidence of tissue damage. Evidence supporting myofascial orofacial pain as nociplastic pain includes clinical observations of central sensitisation in patients, even in the absence of visible inflammation. Sensitisation is characterised by heightened responsiveness of nociceptive neurons to normal stimuli or activation by normally subthreshold stimuli, either in the peripheral or central nervous system. It is linked to maladaptive neuroplastic changes, including increased functional potentiation and altered expression of neuronal ion channels, receptors and neurotransmitters. This mini-review presents insights from existing evidence regarding altered nociception and its relation to changes in the expression of neuronal ion channels in myofascial orofacial pain. Increased expression of transient receptor potential (TRP) vanilloid 1 channels (TRPV1), TRPV4, TRP ankyrin 1 channels (TRPA1), Piezo2 channels, P2X3 purinergic receptors, N-Methyl-D-Aspartate (NMDA) receptors and voltage-gated calcium channels in the trigeminal ganglion of rodents has been observed in association with myofascial orofacial pain. This evidence highlights the role of neuronal ion channels in the pathophysiology of myofascial orofacial pain and supports the involvement of nociplastic mechanisms.

Characterization and Regulation of the Neonatal Growth Hormone Surge.

High neonatal growth hormone (GH) secretion has been described in several species. However, the neuroendocrine mechanisms behind this surge remain unknown. Thus, the pattern of postnatal GH secretion was investigated in mice and rats. Blood GH levels were very high on postnatal day (P)1 and progressively decreased until near zero by P17 in C57BL/6 mice without sex differences. This pattern was similar to that observed in rats, except that female rats showed higher GH levels on P1 than males. In comparison, follicle-stimulating hormone exhibited higher secretion in females during the first 3 weeks of life. Hypothalamic Sst mRNA and somatostatin neuroendocrine terminals in the median eminence were higher in P20/P21 mice than in newborns. Knockout mice for GH-releasing hormone (GHRH) receptor showed no GH surge, whereas knockdown mice for the Sst gene displayed increased neonatal GH peak. Leptin deficiency caused only minor effects on early-life GH secretion. GH receptor ablation in neurons or the entire body did not affect neonatal GH secretion, but the subsequent reduction in blood GH levels was attenuated or prevented by these genetic manipulations, respectively. This phenotype was also observed in knockout mice for the insulin-like growth factor-1 (IGF-1) receptor in GHRH neurons. Moreover, glucose-induced hyperglycemia overstimulated GH secretion in neonatal mice. In conclusion, GH surge in the first days of life is not regulated by negative feedback loops. However, neonatal GH secretion requires GHRH receptor, and is modulated by somatostatin and blood glucose levels, suggesting that this surge is controlled by hypothalamic-pituitary communication.

Cortical norepinephrine-astrocyte signaling critically mediates learned behavior.

Updating behavior based on feedback from the environment is a crucial means by which organisms learn and develop optimal behavioral strategies 1-3 . Norepinephrine (NE) release from the locus coeruleus (LC) has been shown to mediate learned behaviors 4-6 such that in a task with graded stimulus uncertainty and performance, a high level of NE released after an unexpected outcome causes improvement in subsequent behavior 7 . Yet, how the transient activity of LC-NE neurons, lasting tens of milliseconds, influences behavior several seconds later, is unclear. Here, we show that NE acts directly on cortical astrocytes via Adra1a adrenergic receptors to elicit sustained increases in intracellular calcium. Chemogenetic blockade of astrocytic calcium elevation prevents the improvement in behavioral performance. NE-activated calcium invokes purinergic pathways in cortical astrocytes that signal to neurons; pathway-specific astrocyte gene expression is altered in mice trained on the task, and blocking neuronal adenosine-sensitive A1 receptors also prevents post-reinforcement behavioral gain. Finally, blocking either astrocyte calcium dynamics or A1 receptors alters encoding of the task in prefrontal cortex neurons, preventing the post-reinforcement change in discriminability of rewarded and unrewarded stimuli underlying behavioral improvement. Together, these data demonstrate that astrocytes, rather than indirectly reflecting neuronal drive, play a direct, instrumental role in representing task-relevant information and signaling to neurons to mediate a fundamental component of learning in the brain.

Structure and sexual dimorphism of the first antennae in Penaeus vannamei, Boone, 1931

ABSTRACT This contribution is a histological and scanning electron microscopy study of major flagellar setae of antennules from the most cultured crustacean species, Penaeus vannamei. Antennule samples were collected from females and males of selected species and processed for histological as well as scanning electron microscopy (SEM) evaluation. The histological and SEM description of major setae from antennules, namely aesthetascs, plumose setae, and male spines are presented in detail. A unique sexually dimorphic structure, male spines on the inner (medial) flagella, is reported for the first time in a penaeid shrimp. These spines are robust structures, short and thick with non-permeable cuticle and no terminal pore, innervated by receptor neuron clusters. This histological organization suggests the spines are sensilla for mechanoreception, possibly involved in courtship mechanoreception, complementing chemosensory information from aesthetascs. Additionally, SEM observations of other antennule setae are presented, including asymmetric setae associated with aesthetascs.

Olfactory and gustatory chemical sensor systems in the African turquoise killifish: Insights from morphology.

Smell and taste are extensively studied in fish species as essential for finding food and selecting mates while avoiding toxic substances and predators. Depending on the evolutionary position and adaptation, a discrete variation in the morphology of these sense organs has been reported in numerous teleost species. Here, for the first time, we approach the phenotypic characterization of the olfactory epithelium and taste buds in the African turquoise killifish (Nothobranchius furzeri), a model organism known for its short lifespan and use in ageing research. Our observations indicate that the olfactory epithelium of N. furzeri is organized as a simple patch, lacking the complex folding into a rosette, with an average size of approximately 600µm in length, 300µm in width, and 70µm in thickness. Three main cytotypes, including olfactory receptor neurons (CalbindinD28K), supporting cells (β-tubulin IV), and basal cells (Ki67), were identified across the epithelium. Further, we determined the taste buds' distribution and quantification between anterior (skin, lips, oral cavity) and posterior (gills, pharynx, oesophagus) systems. We identified the key cytotypes by using immunohistochemical markers, i.e. CalbindinD28K, doublecortin, and neuropeptide Y (NPY) for gustatory receptor cells, glial fibrillary acidic protein (GFAP) for supporting cells, and Ki67, a marker of cellular proliferation for basal cells. Altogether, these results indicate that N. furzeri is a microsmatic species with unique taste and olfactory features and possesses a well-developed posterior taste system compared to the anterior. This study provides fundamental insights into the chemosensory biology of N. furzeri, facilitating future investigations into nutrient-sensing mechanisms and their roles in development, survival, and ageing.

MBL-1/Muscleblind regulates neuronal differentiation and controls the splicing of a terminal selector in Caenorhabditis elegans.

The muscleblind family of mRNA splicing regulators is conserved across species and regulates the development of muscles and the nervous system. However, how Muscleblind proteins regulate neuronal fate specification and neurite morphogenesis at the single-neuron level is not well understood. In this study, we found that the C. elegans Muscleblind/MBL-1 promotes axonal growth in the touch receptor neurons (TRNs) by regulating microtubule stability and polarity. Transcriptomic analysis identified dozens of MBL-1-controlled splicing events in genes related to neuronal differentiation or microtubule functions. Among the MBL-1 targets, the LIM-domain transcription factor mec-3 is the terminal selector for the TRN fate and induces the expression of many TRN terminal differentiation genes. MBL-1 promotes the splicing of the mec-3 long isoform, which is essential for TRN fate specification, and inhibits the short isoforms that have much weaker activities in activating downstream genes. MBL-1 promotes mec-3 splicing through three "YGCU(U/G)Y" motifs located in or downstream of the included exon, which is similar to the mechanisms used by mammalian Muscleblind and suggests a deeply conserved context-dependency of the splicing regulation. Interestingly, the expression of mbl-1 in the TRNs is dependent on the mec-3 long isoform, indicating a positive feedback loop between the splicing regulator and the terminal selector. Finally, through a forward genetic screen, we found that MBL-1 promotes neurite growth partly by inhibiting the DLK-1/p38 MAPK pathway. In summary, our study provides mechanistic understanding of the role of Muscleblind in regulating cell fate specification and neuronal morphogenesis.