Long-term Neuronal Survival Research Articles

J147 treatment protects against traumatic brain injury by inhibiting neuronal endoplasmic reticulum stress potentially via the AMPK/SREBP-1 pathway

Endoplasmic reticulum (ER) stress is recognized as a crucial contributor to the progression of traumatic brain injury (TBI) and represents a potential target for therapeutic intervention. This study aimed to assess the potential of J147, a novel neurotrophic compound, in alleviating ER stress by modulating related signaling pathways, thereby promoting functional recovery in TBI. To this end, adult mice underwent controlled cortical impact (CCI) injury to induce TBI, followed by oral administration of J147 one-hour post-injury, with daily dosing for 3 to 7 days. Multiple behavioral assessments were conducted over 35 days, revealing a significant, dose-dependent improvement in neurofunctional recovery with J147 treatment. The neuropathological analysis demonstrated reduced acute neurodegeneration (observed at three days through FJC staining), enhanced long-term neuron survival (H&E and Nissl staining), and improved neuroplasticity (Golgi staining) at 35 days post-TBI. At the molecular level, TBIinduced AMP-activated protein kinase (AMPK) dephosphorylation, sterol regulatory element binding protein-1 (SREBP-1) activation, and upregulation of ER stress marker proteins, including phosphorylated eukaryotic initiation factor-2α (p-eIF2a), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP) in perilesional cortex neurons at three days post-injury. Notably, the J147 treatment significantly attenuated AMPK dephosphorylation, SERBP-1 activation, and expression of the ER stress markers. In summary, this study reveals the therapeutic promise of J147 in mitigating secondary brain damage associated with TBI and improving long-term functional recovery by modulating ER stress pathways.

Enhanced neuronal survival and BDNF elevation via long-term co-activation of galanin 2 (GALR2) and neuropeptide Y1 receptors (NPY1R): potential therapeutic targets for major depressive disorder

ABSTRACT Background Major Depressive Disorder (MDD) is a prevalent and debilitating condition, necessitating novel therapeutic strategies due to the limited efficacy and adverse effects of current treatments. We explored how galanin receptor 2 (GALR2) and Neuropeptide Y1 Receptor (NPYY1R) agonists, working together, can boost brain cell growth and increase antidepressant-like effects in rats. This suggests new ways to treat Major Depressive Disorder (MDD). Research Design and Methods In a controlled laboratory setting, adult naive Sprague-Dawley rats were administered directly into the brain’s ventricles, a method known as intracerebroventricular (ICV) administration, with GALR2 agonist (M1145), NPYY1R agonist, both, or in combination with a GALR2 antagonist (M871). Main outcome measures included long-term neuronal survival, differentiation, and behavioral. Results Co-administration of M1145 and NPYY1R agonist significantly enhanced neuronal survival and maturation in the ventral dentate gyrus, with a notable increase in Brain-Derived Neurotrophic Factor (BDNF) expression. This neurogenic effect was associated with an antidepressant-like effect, an outcome partially reversed by M871. Conclusions GALR2 and NPYY1R agonists jointly promote hippocampal neurogenesis and exert antidepressant-like effects in rats without adverse outcomes, highlighting their therapeutic potential for MDD. The study’s reliance on an animal model and intracerebroventricular delivery warrants further clinical exploration to confirm these promising results.

UDP-Glucose/P2Y14 Receptor Signaling Exacerbates Neuronal Apoptosis After Subarachnoid Hemorrhage in Rats.

Subarachnoid hemorrhage (SAH) is a severe subtype of stroke with poor outcomes. Abnormal glucose metabolism often occurs after SAH, but the strict control of blood glucose levels is not always beneficial. This study aimed to investigate the contribution of uridine diphosphate glucose (UDP-G), an intermediate of glucose/glycogen metabolism, and its receptor P2Y14 (P2Y purinoceptor 14) to SAH pathology and explored the potential targeted treatments in rats. A total of 218 Sprague-Dawley male rats were used. SAH was induced by endovascular perforation. Brain expressions of P2Y14, uridine diphosphate glucose (UDP-G), and its converting enzyme UGP2 (UDP-G pyrophosphorylase-2) were evaluated. Exogenous UDP-G or selective P2Y14 inhibitor was administered intranasally at 1 hour after SAH to explore their potential effects. Intranasal Ugp2 or P2ry14 siRNA was delivered 24 hours before SAH for mechanistic evaluation. Primary neuron culture and hemoglobin stimulation were used as in vitro model of SAH. Post-SAH evaluation included liquid chromatography-mass spectrometry measurement of brain endogenous UDP-G level, neurobehavioral assessments, Western blotting, immunohistochemistry, TUNEL staining, and Nissl staining. There was an acute elevation of endogenous brain UDP-G and UGP2 after SAH, and P2Y14 was expressed in neurons. Although P2Y14 inhibitor decreased neurological dysfunction, neuronal apoptosis, and proapoptotic molecules, exogenous UDP-G exacerbated these outcomes at 24 hours after SAH. Early inhibition of P2Y14 preserved long-term neuronal survival in the hippocampus, amygdala, and cortex with improved neurocognition and depressive-like behavior. In addition, in vivo knockdown of Ugp2- and P2ry14-reduced neurological deficits and proapoptotic molecules at 24 hours after SAH, and furthermore in vitro knockdown of P2ry14-reduced apoptosis in hemoglobin stimulated primary neuron. These findings suggest a detrimental role of brain UDP-G/P2Y14 signaling in SAH, as a part of glucose metabolic pathology at the tissue level. P2Y14 inhibitor 4-[4-(4-piperidinyl)phenyl]-7-[4-(trifluoromethyl)phenyl]-2-naphthalenecarboxylic acid hydrochloride may serve as a potential therapeutic target in treating patients with SAH.

FMRP Long-Range Transport and Degradation Are Mediated by Dynlrb1 in Sensory Neurons

The fragile X messenger ribonucleoprotein 1 (FMRP) is a multifunctional RNA-binding protein implicated in human neurodevelopmental and neurodegenerative disorders. FMRP mediates the localization and activity-dependent translation of its associated mRNAs through the formation of phase-separated condensates that are trafficked by microtubule-based motors in axons. Axonal transport and localized mRNA translation are critical processes for long-term neuronal survival and are closely linked to the pathogenesis of neurological diseases. FMRP dynein-mediated axonal trafficking is still largely unexplored but likely to constitute a key process underlying FMRP spatiotemporal translational regulation. Here, we show that dynein light chain roadblock 1 (Dynlrb1), a subunit of the dynein complex, is a critical regulator of FMRP function. In sensory axons, FMRP associates with endolysosomal organelles, likely through annexin A11, and is retrogradely trafficked by the dynein complex in a Dynlrb1-dependent manner. Moreover, Dynlrb1 silencing induced FMRP granule accumulation and repressed the translation of microtubule-associated protein 1b, one of its primary mRNA targets. Our findings suggest that Dynlrb1 regulates FMRP function through the control of its transport and targeted degradation.

Cdk12 maintains the integrity of adult axons by suppressing actin remodeling

The role of cyclin-dependent kinases (CDKs) that are ubiquitously expressed in the adult nervous system remains unclear. Cdk12 is enriched in terminally differentiated neurons where its conical role in the cell cycle progression is redundant. We find that in adult neurons Cdk12 acts a negative regulator of actin formation, mitochondrial dynamics and neuronal physiology. Cdk12 maintains the size of the axon at sites proximal to the cell body through the transcription of homeostatic enzymes in the 1-carbon by folate pathway which utilize the amino acid homocysteine. Loss of Cdk12 leads to elevated homocysteine and in turn leads to uncontrolled F-actin formation and axonal swelling. Actin remodeling further induces Drp1-dependent fission of mitochondria and the breakdown of axon-soma filtration barrier allowing soma restricted cargos to enter the axon. We demonstrate that Cdk12 is also an essential gene for long-term neuronal survival and loss of this gene causes age-dependent neurodegeneration. Hyperhomocysteinemia, actin changes, and mitochondrial fragmentation are associated with several neurodegenerative conditions such as Alzheimer’s disease and we provide a candidate molecular pathway to link together such pathological events.

Neural precursor cell delivery induces acute post-ischemic cerebroprotection, but fails to promote long-term stroke recovery in hyperlipidemic mice due to mechanisms that include pro-inflammatory responses associated with brain hemorrhages

BackgroundThe intravenous delivery of adult neural precursor cells (NPC) has shown promising results in enabling cerebroprotection, brain tissue remodeling, and neurological recovery in young, healthy stroke mice. However, the translation of cell-based therapies to clinical settings has encountered challenges. It remained unclear if adult NPCs could induce brain tissue remodeling and recovery in mice with hyperlipidemia, a prevalent vascular risk factor in stroke patients.MethodsMale mice on a normal (regular) diet or on cholesterol-rich Western diet were exposed to 30 min intraluminal middle cerebral artery occlusion (MCAO). Vehicle or 106 NPCs were intravenously administered immediately after reperfusion, at 3 day and 7 day post-MCAO. Neurological recovery was evaluated using the Clark score, Rotarod and tight rope tests over up to 56 days. Histochemistry and light sheet microscopy were used to examine ischemic injury and brain tissue remodeling. Immunological responses in peripheral blood and brain were analyzed through flow cytometry.ResultsNPC administration reduced infarct volume, blood–brain barrier permeability and the brain infiltration of neutrophils, monocytes, T cells and NK cells in the acute stroke phase in both normolipidemic and hyperlipidemic mice, but increased brain hemorrhage formation and neutrophil, monocyte and CD4+ and CD8+ T cell counts and activation in the blood of hyperlipidemic mice. While neurological deficits in hyperlipidemic mice were reduced by NPCs at 3 day post-MCAO, NPCs did not improve neurological deficits at later timepoints. Besides, NPCs did not influence microglia/macrophage abundance and activation (assessed by morphology analysis), astroglial scar formation, microvascular length or branching point density (evaluated using light sheet microscopy), long-term neuronal survival or brain atrophy in hyperlipidemic mice.ConclusionsIntravenously administered NPCs did not have persistent effects on post-ischemic neurological recovery and brain remodeling in hyperlipidemic mice. These findings highlight the necessity of rigorous investigations in vascular risk factor models to fully assess the long-term restorative effects of cell-based therapies. Without comprehensive studies in such models, the clinical potential of cell-based therapies cannot be definitely determined.

Environmental enrichment enhanced neurogenesis and behavioral recovery after stroke in aged rats.

Age is identified as a significant prognostic factor for poorer outcome after stroke. However, environmental enrichment (EE) has been reported to promote functional recovery after ischemic stroke. The purpose of this study was to investigate whether environmental enrichment was beneficial to ischemic stroke in aged rats. Aged rats were randomly assigned as control rats, rats subjected to cerebral ischemia, and rats with cerebral ischemia treated with EE for 30 days. Focal cortical ischemia was induced by intracranial injection of endothelin-1 (ET-1). EE housing began one day after focal ischemia and was maintained for the whole experimental period. We used immunofluorescence staining to analyze the neurogenesis in the subventricular zone (SVZ) and TdT-mediated dUTP-biotin nick-end labeling (TUNEL) assay to evaluate apoptosis. The expression of neuronal nuclei, glial fibrillary acidic protein (GFAP) and Iba-1 around the infarcted area were also measured by double immunohistochemistry. EE enhanced the proliferation of newborn neurons in the SVZ, as well as increased the long-term survival of newborn neurons. EE also exerted effects on inflammation after stroke. Furthermore, EE suppressed apoptosis and improved the motor functions after stroke in the aged rats. EE improved post-stroke recovery on the basis of enhancing neurogenesis in aged rats.

3D culture of the spinal cord with roots as an ex vivo model for comparative studies of motor and sensory nerve regeneration

Motor and sensory nerves exhibit tissue-specific structural and functional features. However, in vitro models designed to reflect tissue-specific differences between motor and sensory nerve regeneration have rarely been reported. Here, by embedding the spinal cord with roots (SCWR) in a 3D hydrogel environment, we compared the nerve regeneration processes between the ventral and dorsal roots. The 3D hydrogel environment induced an outward migration of neurons in the gray matter of the spinal cord, which allowed the long-term survival of motor neurons. Tuj1 immunofluorescence labeling confirmed the regeneration of neurites from both the ventral and dorsal roots. Next, we detected asymmetric ventral and dorsal root regeneration in response to nerve growth factor (NGF) and glial cell line–derived neurotrophic factor (GDNF), and we observed motor and sensory Schwann cell phenotypes in the regenerated ventral and dorsal roots, respectively. Moreover, based on the SCWR model, we identified a targeted effect of collagen VI on sensory nerve fasciculation and characterized the protein expression profiles correlating to motor/sensory-specific nerve regeneration. These results suggest that the SCWR model can serve as a valuable ex vivo model for comparative study of motor and sensory nerve regeneration and for pharmacodynamic evaluations.

Discoidin domain receptor regulates ensheathment, survival and caliber of peripheral axons.

Most invertebrate axons and small-caliber axons in mammalian peripheral nerves are unmyelinated but still ensheathed by glia. Here, we use Drosophila wrapping glia to study the development and function of non-myelinating axon ensheathment, which is poorly understood. Selective ablation of these glia from peripheral nerves severely impaired larval locomotor behavior. In an in vivo RNA interference screen to identify glial genes required for axon ensheathment, we identified the conserved receptor tyrosine kinase Discoidin domain receptor (Ddr). In larval peripheral nerves, loss of Ddr resulted in severely reduced ensheathment of axons and reduced axon caliber, and we found a strong dominant genetic interaction between Ddr and the type XV/XVIII collagen Multiplexin (Mp), suggesting that Ddr functions as a collagen receptor to drive axon wrapping. In adult nerves, loss of Ddr decreased long-term survival of sensory neurons and significantly reduced axon caliber without overtly affecting ensheathment. Our data establish essential roles for non-myelinating glia in nerve development, maintenance and function, and identify Ddr as a key regulator of axon-glia interactions during ensheathment and establishment of axon caliber.

Clonal Imaging of Mitochondria in the Dissected Fly Wing.

Mitochondria are essential for long-term neuronal function and survival. They are maintained in neurons, including long axonal stretches, through dynamic processes such as fission, fusion, biogenesis, and mitophagy. Here, we describe a protocol for the in-depth morphological analysis of individual mitochondria in axons in vivo. Most mitochondrial analysis of axons is currently performed in vitro with neurons in a developmental state. Therefore, an understanding of the axonal mitochondrial network during aging in fully differentiated neurons and the long-term consequence of gene knockout is often not developed. By using a clonal system paired with fluorescent genetically encoded markers in the Drosophila wing, we can visualize individual neurons (out of the whole bundle), including their long axons and the mitochondria that they contain, using confocal imaging. The clonal system also allows visualization of neurons with genetic perturbations that would otherwise be lethal if present in the whole organism, allowing investigators to bypass lethality. This protocol can further be adapted to measure the physiological and biochemical state of the mitochondria. Mitochondrial morphology and health in axons are tightly linked to aging, axon injury, and neurodegeneration; therefore, this method can be used to investigate mitochondrial dysfunction associated with novel genes or those linked to neurodegenerative disease and axonopathy.

Phosphodiesterase 10A deactivation induces long-term neurological recovery, Peri-infarct remodeling and pyramidal tract plasticity after transient focal cerebral ischemia in mice

The phosphodiesterase (PDE) superfamily comprises enzymes responsible for the cAMP and cGMP degradation to AMP and GMP. PDEs are abundant in the brain, where they are involved in several neuronal functions. High PDE10A abundance was previously observed in the striatum; however its consequences for stroke recovery were unknown. Herein, we evaluated the effects of PDE10A deactivation by TAK-063 (0.3 or 3 mg/kg, initiated 72 h post-stroke) in mice exposed to intraluminal middle cerebral artery occlusion. We found that PDE10A deactivation over up to eight weeks dose-dependently increased long-term neuronal survival, angiogenesis, and neurogenesis in the peri-infarct striatum, which represents the core of the middle cerebral artery territory, and reduced astroglial scar formation, whole brain atrophy and, more specifically, striatal atrophy. Functional motor-coordination recovery and the long-distance plasticity of pyramidal tract axons, which originate from the contralesional motor cortex and descend through the contralesional striatum to innervate the ipsilesional facial nucleus, were enhanced by PDE10A deactivation. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed a set of dopamine receptor-related and neuronal plasticity-related PDE10A targets, which were elevated (e.g., protein phosphatase-1 regulatory subunit 1B) or reduced (e.g., serine/threonine protein phosphatase 1α, β-synuclein, proteasome subunit α2) by PDE10A deactivation. Our results identify PDE10A as a therapeutic target that critically controls post-ischemic brain tissue remodeling and plasticity.

The long-term survival and functional maturation of human iNPC-derived neurons in the basal forebrain of cynomolgus monkeys

Abstract Human induced neural stem/progenitor cells (iNPCs) are a promising source of cells for stem cell-based therapy. The therapeutic potential of human iNPCs has been extensively tested in animal models, including both mouse and monkey models. However, the comprehensive characterization of grafted iNPCs in the brain of non-human primates has been lagged behind. In this study, we transplanted human iNPCs into the basal forebrain of adult cynomolgus monkeys. We found that grafted iNPCs predominantly differentiated into neurons that displayed long-term survival up to 12 months. Additionally, iNPC-derived human neurons gradually matured in term of morphology and subtype differentiation. More excitingly, we observed that human neurons displayed electrophysiological activities resembling those of mature neurons, indicating the acquisition of functional membrane properties. Collectively, this study systematically characterized human iNPCs in the brain of non-human primates, and will provide invaluable clues for developing safe and effective stem cell-based therapies for different brain disorders.

The Unconventional Growth Factors Cerebral Dopamine Neurotrophic Factor and Mesencephalic Astrocyte-Derived Neurotrophic Factor Promote Post-ischemic Neurological Recovery, Perilesional Brain Remodeling, and Lesion-Remote Axonal Plasticity.

Considerable efforts are currently made to develop strategies that boost endogenous recovery once a stroke has occurred. Owing to their restorative properties, neurotrophic factors are attractive candidates that capitalize on endogenous response mechanisms. Non-conventional growth factors cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF) promote neuronal survival and reduce neurological deficits in the acute phase of ischemic stroke in mice. Their effects on endogenous repair and recovery mechanisms in the stroke recovery phase were so far unknown. By intracerebroventricular delivery of CDNF or MANF starting 3days post-stroke (1µg/day for 28days via miniosmotic pumps), we show that delayed CDNF and MANF administration promoted functional neurological recovery assessed by a battery of behavioral tests, increased long-term neuronal survival, reduced delayed brain atrophy, glial scar formation, and, in case of CDNF but not MANF, increased endogenous neurogenesis in the perilesional brain tissue. Besides, CDNF and MANF administration increased long-distance outgrowth of terminal axons emanating from the contralesional pyramidal tract, which crossed the midline to innervate ipsilesional facial nucleus. This plasticity promoting effect was accompanied by downregulation of the axonal growth inhibitor versican and the guidance molecules ephrin B1 and B2 in the previously ischemic hemisphere at 14 dpi, which represents a sensitive time-point for axonal growth. CDNF and MANF reduced the expression of the proinflammatory cytokines IL1β and TNFα in both hemispheres. The effects of non-conventional growth factors in the ischemic brain should further be examined since they might help to identify targets for restorative stroke therapy.

Neural Crest‐Specific Elp1 Deletion Disrupts Trigeminal Ganglion Development in a Model of Familial Dysautonomia

Neurons in the trigeminal ganglion relay sensory information from the face and oral cavity to the brain. The trigeminal ganglion is unique in its complexity, containing a mixed population of modality‐specific (i.e., touch, pain) neurons derived from both neural crest and placodal precursors. The identity of trigeminal ganglion neurons is associated with the expression of Trk neurotrophin receptors, which are required for long‐term neuronal function and survival. Within sensory ganglia, nociceptive neurons that detect pain or temperature generally express TrkA, while mechanoreceptors responding to touch express TrkB or TrkC. However, the processes that guide the emergence and maintenance of distinct neuronal subpopulations in the trigeminal ganglion are poorly understood. We recently uncovered a role for Elongator complex protein 1 (Elp1) in the maintenance of TrkA‐expressing trigeminal ganglion nociceptors. Mutation of ELP1 causes Familial Dysautonomia (FD), a fatal neuropathy characterized, in part, by trigeminal sensory deficits, including impaired facial nociception. In a mouse model of FD, where Elp1 is deleted from neural crest derivatives (Elp1 CKO), we found that Elp1 is required for proper trigeminal nerve morphology. Moreover, loss of Elp1 reduces TrkA levels and enhances death of TrkA neurons during embryogenesis, explaining the facial sensory impairments experienced by FD patients. Given the targeted effects on TrkA neurons in Elp1 CKO, we hypothesized that most TrkA neurons in the trigeminal ganglion arise from the neural crest, while TrkB and TrkC neurons originate from placode cells. To address this, we first examined whether individual Trk receptors are co‐expressed with the transcription factor Six1, which has previously been used to identify placodal neurons in the trigeminal ganglion. We discovered that Six1 is expressed in waves, marking newly differentiated trigeminal ganglion neurons regardless of presumptive placode or neural crest origin. Without bona fide immunohistochemical lineage markers, a Wnt1‐Cre reporter mouse was used to identify neural crest (Wnt1‐Cre recombined) versus placode (not recombined) derivatives. In support of our hypothesis, we observed a majority of TrkA neurons in the trigeminal ganglion had previously undergone Cre recombination, indicating trigeminal ganglion nociceptors are largely neural crest‐derived. In contrast, most TrkB and TrkC neurons were not targeted for recombination, confirming trigeminal ganglion mechanoreceptors generally arise from placodes. Lastly, the majority of Six1‐expressing cells were, indeed, Wnt1‐Cre recombined once neural crest neuronal differentiation commenced in the trigeminal ganglion, confirming that Six1 is not exclusively expressed by placodal neurons at later stages. Future studies will expand upon this work by crossing the Wnt1‐Cre reporter with Elp1 CKO to evaluate how Elp1 regulates the development and interactions of neural crest versus placodal derivatives within the trigeminal ganglion. Together, these findings provide novel insight into the origin and maintenance of trigeminal ganglion neurons and enhance our understanding of the pathogenesis of FD and other sensory nerve disorders.

Aging entails distinct requirements for Rb at maintaining adult neurogenesis.

Cell cycle proteins play essential roles in regulating embryonic and adult neurogenesis in the mammalian brain. A key example is the Retinoblastoma protein (Rb) whose loss disrupts the whole neurogenic program during brain development, but only results in increased progenitor proliferation in the adult subventricular zone (SVZ) and compromised long-term neuronal survival in the adult olfactory bulb (OB). Whether this holds true of neurogenesis in the aged brain remains unknown. In this study, we find no evidence of irregular proliferation or early commitment defects in the mid-aged (12-month-old) and old-aged (20-month-old) SVZ following tamoxifen-inducible Rb knockout (Rb iKO) in mice. However, we highlight a striking defect in early maturation of Rb-deficient migrating neuroblasts along the rostral migratory stream (RMS), followed by massive decline in neuronal generation inside the aged OB. In the absence of Rb, we also show evidence of incomplete cell cycle re-entry (CCE) along with DNA damage in the young OB, while we find a similar trend towards CCE but no clear signs of DNA damage or neurodegenerative signatures (pTau or Synuclein accumulation) in the aged OB. However, such phenotype could be masked by the severe maturation defect reported above in addition to the natural decline in adult neurogenesis with age. Overall, we show that Rb is required to prevent CCE and DNA damage in adult-born OB neurons, hence maintain neuronal survival. Moreover, while loss of Rb alone is insufficient to trigger seeding of neurotoxic species, this study reveals age-dependent non-monotonic dynamics in regulating neurogenesis by Rb.

Post-ischemic protein restriction induces sustained neuroprotection, neurological recovery, brain remodeling, and gut microbiota rebalancing

BackgroundModerate dietary protein restriction confers neuroprotection when applied before ischemic stroke. How a moderately protein-reduced diet influences stroke recovery when administered after stroke, is a clinically relevant question. This question has not yet been investigated. MethodsMale C57BL6/J mice were exposed to transient intraluminal middle cerebral artery occlusion. Immediately after the stroke, mice were randomized to two normocaloric diets: a moderately protein-reduced diet containing 8% protein (PRD) or normal diet containing 20% protein (ND). Post-stroke neurological deficits were evaluated by a comprehensive test battery. Antioxidant and neuroinflammatory responses in the brain and liver were evaluated by Western blot and RTqPCR. Stroke-induced brain injury, microvascular integrity, glial responses, and neuroplasticity were assessed by immunohistochemistry. Fecal microbiota analysis was performed using 16S ribosomal RNA amplicon sequencing. ResultsWe show that PRD reduces brain infarct volume after three days and enhances neurological and, specifically, motor-coordination recovery over six weeks in stroke mice. The recovery-promoting effects of PRD were associated with increased antioxidant responses and reduced neuroinflammation. Histochemical studies revealed that PRD increased long-term neuronal survival, increased peri-infarct microvascular density, reduced microglia/macrophage accumulation, increased contralesional pyramidal tract plasticity, and reduced brain atrophy. Fecal microbiota analysis showed reduced bacterial richness and diversity in ischemic mice on ND starting at 7 dpi. PRD restored bacterial richness and diversity at these time points. ConclusionModerate dietary protein restriction initiated post-ischemic stroke induces neurological recovery, brain remodeling, and neuroplasticity in mice by mechanisms involving antiinflammation and, in the post-acute phase, commensal gut microbiota rebalancing.

A nod and a Wnk to axon branching and destruction

In this issue of Neuron, Izadifar etal. (2021) have identified a conserved molecule Wnk as a key regulator in both developmental axon branching and long-term survival of neurons, characterizing its interplay with axon destruction genes including Sarm. The discovery of Wnk will be important to our understanding of neurodevelopmental and neurodegenerative diseases.

Mitochondrial fission, integrity and completion of mitophagy require separable functions of Vps13D in Drosophila neurons.

A healthy population of mitochondria, maintained by proper fission, fusion, and degradation, is critical for the long-term survival and function of neurons. Here, our discovery of mitophagy intermediates in fission-impaired Drosophila neurons brings new perspective into the relationship between mitochondrial fission and mitophagy. Neurons lacking either the ataxia disease gene Vps13D or the dynamin related protein Drp1 contain enlarged mitochondria that are engaged with autophagy machinery and also lack matrix components. Reporter assays combined with genetic studies imply that mitophagy both initiates and is completed in Drp1 impaired neurons, but fails to complete in Vps13D impaired neurons, which accumulate compromised mitochondria within stalled mito-phagophores. Our findings imply that in fission-defective neurons, mitophagy becomes induced, and that the lipid channel containing protein Vps13D has separable functions in mitochondrial fission and phagophore elongation.

The transcription factor ZEB1 regulates stem cell self-renewal and cell fate in the adult hippocampus.

SummaryRadial glia-like (RGL) stem cells persist in the adult mammalian hippocampus, where they generate new neurons and astrocytes throughout life. The process of adult neurogenesis is well documented, but cell-autonomous factors regulating neuronal and astroglial differentiation are incompletely understood. Here, we evaluate the functions of the transcription factor zinc-finger E-box binding homeobox 1 (ZEB1) in adult hippocampal RGL cells using a conditional-inducible mouse model. We find that ZEB1 is necessary for self-renewal of active RGL cells. Genetic deletion of Zeb1 causes a shift toward symmetric cell division that consumes the RGL cell and generates pro-neuronal progenies, resulting in an increase of newborn neurons and a decrease of newly generated astrocytes. We identify ZEB1 as positive regulator of the ets-domain transcription factor ETV5 that is critical for asymmetric division.

Role of Calpain-1 in Neurogenesis.

While calpains have been implicated in neurogenesis for a long time, there is still little information regarding the specific contributions of various isoforms in this process. We took advantage of the availability of mutant mice with complete deletion of calpain-1 to analyze its contribution to neurogenesis. We first used the incorporation of BrdU in newly-generated cells in the subgranular zone of the dentate gyrus to determine the role of calpain-1 deletion in neuronal proliferation. Our results showed that the lack of calpain-1 decreased the rate of cell proliferation in adult hippocampus. As previously shown, it also decreased the long-term survival of newly-generated neurons. We also used data from previously reported RNA and miRNA sequencing analyses to identify differentially expressed genes in brain of calpain-1 knock-out mice related to cell division, cell migration, cell proliferation and cell survival. A number of differentially expressed genes were identified, which could play a significant role in the changes in neurogenesis in calpain-1 knock out mice. The results provide new information regarding the role of calpain-1 in neurogenesis and have implications for better understanding the pathologies associated with calpain-1 mutations in humans.