Lotun, A;Li, D;Xu, H;Su, Q;Tuncer, S;Sanmiguel, J;Mooney, M;Baer, CE;Ulbrich, R;Eyles, SJ;Strittmatter, L;Hayward, LJ;Gessler, DJ;Gao, G;
PMID: 37149081 | DOI: 10.1016/j.pneurobio.2023.102460
Myelinating oligodendrocytes are essential for neuronal communication and homeostasis of the central nervous system (CNS). One of the most abundant molecules in the mammalian CNS is N-acetylaspartate (NAA), which is catabolized into L-aspartate and acetate by the enzyme aspartoacylase (ASPA) in oligodendrocytes. The resulting acetate moiety is thought to contribute to myelin lipid synthesis. In addition, affected NAA metabolism has been implicated in several neurological disorders, including leukodystrophies and demyelinating diseases such as multiple sclerosis. Genetic disruption of ASPA function causes Canavan disease, which is hallmarked by increased NAA levels, myelin and neuronal loss, large vacuole formation in the CNS, and early death in childhood. Although NAA's direct role in the CNS is inconclusive, in peripheral adipose tissue, NAA-derived acetate has been found to modify histones, a mechanism known to be involved in epigenetic regulation of cell differentiation. We hypothesize that a lack of cellular differentiation in the brain contributes to the disruption of myelination and neurodegeneration in diseases with altered NAA metabolism, such as Canavan disease. Our study demonstrates that loss of functional Aspa in mice disrupts myelination and shifts the transcriptional expression of neuronal and oligodendrocyte markers towards less differentiated stages in a spatiotemporal manner. Upon re-expression of ASPA, these oligodendrocyte and neuronal lineage markers are either improved or normalized, suggesting that NAA breakdown by Aspa plays an essential role in the maturation of neurons and oligodendrocytes. Also, this effect of ASPA re-expression is blunted in old mice, potentially due to limited ability of neuronal, rather than oligodendrocyte, recovery.
Cotellessa, L;Marelli, F;Duminuco, P;Adamo, M;Papadakis, GE;Bartoloni, L;Sato, N;Lang-Muritano, M;Troendle, A;Dhillo, WS;Morelli, A;Guarnieri, G;Pitteloud, N;Persani, L;Bonomi, M;Giacobini, P;Vezzoli, V;
PMID: 36729644 | DOI: 10.1172/jci.insight.161998
In vertebrate species, fertility is controlled by gonadotropin-releasing hormone (GnRH) neurons. GnRH cells arise outside the central nervous system, in the developing olfactory pit, and migrate along olfactory/vomeronasal/terminal nerve axons into the forebrain during embryonic development. Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are rare genetic disorders characterized by infertility and they are associated with defects in GnRH neuron migration and/or altered GnRH secretion and signaling.Here, we documented the expression of Jagged 1/Notch signaling pathway in GnRH neurons and along the GnRH neuron migratory route both in zebrafish embryos and in human fetuses. Genetic knock-down of the zebrafish ortholog of JAG1 (jag1b) resulted in altered GnRH migration and olfactory axonal projections to the olfactory bulbs.Next-generation sequencing was performed in 467 CHH unrelated probands leading to the identification of heterozygous rare variants in JAG1. Functional in vitro validation of JAG1 mutants revealed that 7 out of the 9 studied variants exhibit reduced protein levels and altered subcellular localization.Altogether our data provide compelling evidence that Jag1/Notch signaling plays a prominent role in the development of GnRH neurons and we propose that JAG1 insufficiency may contribute to the pathogenesis of CHH in humans.
Ling KK, Jackson M, Alkam D, Liu D, Allaire N, Sun C, Kiaei M, McCampbell A, Rigo F.
PMID: 29518482 | DOI: 10.1016/j.nbd.2018.03.002
Amyotrophic lateral sclerosis (ALS) is a fatal adult onset motor neuron disease characterized by progressive denervation and subsequent motor impairment. EphA4, a negative regulator of axonal growth, was recently identified as a genetic modifier in fish and rodent models of ALS. To evaluate the therapeutic potential of EphA4 for ALS, we examined the effect of CNS-directed EphA4 reduction in preclinical mouse models of ALS, and assessed if the levels of EPHA4 mRNA in blood correlate with disease onset and progression in human ALS patients. We developed antisense oligonucleotides (ASOs) to specifically reduce the expression of EphA4 in the central nervous system (CNS) of adult mice. Intracerebroventricular administration of an Epha4-ASO in wild-type mice inhibited Epha4 mRNA and protein in the brain and spinal cord, and promoted re-innervation and functional recovery after sciatic nerve crush. In contrast, lowering of EphA4 in the CNS of two mouse models of ALS (SOD1G93A and PFN1G118V) did not improve their motor function or survival. Furthermore, the level of EPHA4 mRNA in human blood correlated weakly with age of disease onset, and it was not a significant predictor of disease progression as measured by ALS Functional Rating Scores (ALSFRS). Our data demonstrates that lowering EphA4 in the adult CNS may not be a stand-alone viable strategy for treating ALS.
Liu, QR;Zhu, M;Zhang, P;Mazucanti, CH;Huang, NS;Lang, DL;Chen, Q;Auluck, P;Marenco, S;O'Connell, JF;Ferrucci, L;Chia, CW;Egan, JM;
PMID: 34649926 | DOI: 10.2337/db21-0198
Human insulin (INS) gene diverged from the ancestral genes of invertebrate and mammalian species millions of years ago. We previously found that mouse insulin gene (Ins2) isoforms are expressed in brain choroid plexus (ChP) epithelium cells where insulin secretion is regulated by serotonin and not by glucose. We further compared human INS isoform expression in postmortem ChP and islets of Langerhans. We uncovered novel INS upstream open reading frame (uORF) isoforms and their protein products. In addition, we found a novel alternatively spliced isoform that translates to a 74-amino acid (AA) proinsulin containing a shorter 19-AA C-peptide sequence, herein designated Cα-peptide. The middle portion of the conventional C-peptide contains β-sheet (GQVEL) and hairpin (GGGPG) motifs that are not present in Cα-peptide. Islet amyloid polypeptide (IAPP) is not expressed in ChP and its amyloid formation was inhibited in vitro by Cα-peptide more efficiently than by C-peptide. Of clinical relevance, the ratio of the 74-AA proinsulin to proconvertase processed Cα-peptide was significantly increased in islets from type 2 diabetes mellitus (T2DM) autopsy donors. Intriguingly, 100 years after the discovery of insulin we found that INS isoforms are present in ChP from insulin-deficient autopsy donors.
Forrest, SL;Lee, S;Nassir, N;Martinez-Valbuena, I;Sackmann, V;Li, J;Ahmed, A;Tartaglia, MC;Ittner, LM;Lang, AE;Uddin, M;Kovacs, GG;
PMID: 37354322 | DOI: 10.1007/s00401-023-02604-x
Microtubule-associated protein tau (MAPT) aggregates in neurons, astrocytes and oligodendrocytes in a number of neurodegenerative diseases, including progressive supranuclear palsy (PSP). Tau is a target of therapy and the strategy includes either the elimination of pathological tau aggregates or reducing MAPT expression, and thus the amount of tau protein made to prevent its aggregation. Disease-associated tau affects brain regions in a sequential manner that includes cell-to-cell spreading. Involvement of glial cells that show tau aggregates is interpreted as glial cells taking up misfolded tau assuming that glial cells do not express enough MAPT. Although studies have evaluated MAPT expression in human brain tissue homogenates, it is not clear whether MAPT expression is compromised in cells accumulating pathological tau. To address these perplexing aspects of disease pathogenesis, this study used RNAscope combined with immunofluorescence (AT8), and single-nuclear(sn) RNAseq to systematically map and quantify MAPT expression dynamics across different cell types and brain regions in controls (n = 3) and evaluated whether tau cytopathology affects MAPT expression in PSP (n = 3). MAPT transcripts were detected in neurons, astrocytes and oligodendrocytes, and varied between brain regions and within each cell type, and were preserved in all cell types with tau aggregates in PSP. These results propose a complex scenario in all cell types, where, in addition to the ingested misfolded tau, the preserved cellular MAPT expression provides a pool for local protein production that can (1) be phosphorylated and aggregated, or (2) feed the seeding of ingested misfolded tau by providing physiological tau, both accentuating the pathological process. Since tau cytopathology does not compromise MAPT gene expression in PSP, a complete loss of tau protein expression as an early pathogenic component is less likely. These observations provide rationale for a dual approach to therapy by decreasing cellular MAPT expression and targeting removal of misfolded tau.
Pook C, Ahrens JM, Clagett-Dame M
PMID: 32081718 | DOI: 10.1016/j.gep.2020.119099
Neuron navigator 2 (NAV2, RAINB1, POMFIL2, HELAD1, unc53H2) is essential for nervous system development. In the present study the spatial distribution of Nav2 transcript in mouse CNS during embryonic, postnatal and adult life is examined. Because multiple NAV2 proteins are predicted based on alternate promoter usage and RNA splicing, in situ hybridization was performed using probes designed to the 5' and 3' ends of the Nav2 transcript, and PCR products using primer sets spanning the length of the mRNA were also examined by real time PCR (qPCR). These studies support full-length Nav2 transcript as the predominant form in the wild-type mouse CNS. The developing cortex, hippocampus, thalamus, olfactory bulb, and granule cells (GC) within the cerebellum show the highest expression, with a similar staining pattern using either the 5'Nav2 or 3'Nav2 probe. Nav2 is expressed in GC precursors migrating over the cerebellar primordium as well as in the postmitotic premigratory cells of the external granule cell layer (EGL). It is expressed in the cornu ammonis (CA) and dentate gyrus (DG) throughout hippocampal development. In situ hybridization was combined with immunohistochemistry for Ki67, CTIP2 and Nissl staining to follow Nav2 transcript location during cortical development, where it is observed in neuroepithelial cells exiting the germinal compartments, as well as later in the cortical plate (CP) and developing cortical layers. The highest levels of Nav2 in all brain regions studied are observed in late gestation and early postnatal life which coincides with times when neurons are migrating and differentiating. A hypomorphic mouse that lacks the full-length transcript but expresses shorter transcript shows little staining in the CNS with either probe set except at the base of the cerebellum, where a shorter Nav2 transcript is detected. Using dual fluorescent probe in situ hybridization studies, these cells are identified as oligodendrocytes and are detected using both Olig1 and the 3'Nav2 probe. The identification of full-length Nav2 as the primary transcript in numerous brain regions suggests NAV2 could play a role in CNS development beyond that of its well-established role in the cerebellum
Serafini, RA;Frere, JJ;Zimering, J;Giosan, IM;Pryce, KD;Golynker, I;Panis, M;Ruiz, A;tenOever, BR;Zachariou, V;
PMID: 37159520 | DOI: 10.1126/scisignal.ade4984
Although largely confined to the airways, SARS-CoV-2 infection has been associated with sensory abnormalities that manifest in both acute and chronic phenotypes. To gain insight on the molecular basis of these sensory abnormalities, we used the golden hamster model to characterize and compare the effects of infection with SARS-CoV-2 and influenza A virus (IAV) on the sensory nervous system. We detected SARS-CoV-2 transcripts but no infectious material in the cervical and thoracic spinal cord and dorsal root ganglia (DRGs) within the first 24 hours of intranasal virus infection. SARS-CoV-2-infected hamsters exhibited mechanical hypersensitivity that was milder but prolonged compared with that observed in IAV-infected hamsters. RNA sequencing analysis of thoracic DRGs 1 to 4 days after infection suggested perturbations in predominantly neuronal signaling in SARS-CoV-2-infected animals as opposed to type I interferon signaling in IAV-infected animals. Later, 31 days after infection, a neuropathic transcriptome emerged in thoracic DRGs from SARS-CoV-2-infected animals, which coincided with SARS-CoV-2-specific mechanical hypersensitivity. These data revealed potential targets for pain management, including the RNA binding protein ILF3, which was validated in murine pain models. This work elucidates transcriptomic signatures in the DRGs triggered by SARS-CoV-2 that may underlie both short- and long-term sensory abnormalities.
Stein LM, Lhamo R, Cao A, Workinger J, Tinsley I, Doyle RP, Grill HJ, Hermann GE, Rogers RC, Hayes MR
PMID: 32152264 | DOI: 10.1038/s41398-020-0767-0
Previous studies identify a role for hypothalamic glia in energy balance regulation; however, a narrow hypothalamic focus provides an incomplete understanding of how glia throughout the brain respond to and regulate energy homeostasis. We examined the responses of glia in the dorsal vagal complex (DVC) to the adipokine leptin and high fat diet-induced obesity. DVC astrocytes functionally express the leptin receptor; in vivo pharmacological studies suggest that DVC astrocytes partly mediate the anorectic effects of leptin in lean but not diet-induced obese rats. Ex vivo calcium imaging indicated that these changes were related to a lower proportion of leptin-responsive cells in the DVC of obese versus lean animals. Finally, we investigated DVC microglia and astroglia responses to leptin and energy balance dysregulation in vivo: obesity decreased DVC astrogliosis, whereas the absence of leptin signaling in Zucker rats was associated with extensive astrogliosis in the DVC and decreased hypothalamic micro- and astrogliosis. These data uncover a novel functional heterogeneity of astrocytes in different brain nuclei of relevance to leptin signaling and energy balance regulation
Qian, X;DeGennaro, EM;Talukdar, M;Akula, SK;Lai, A;Shao, DD;Gonzalez, D;Marciano, JH;Smith, RS;Hylton, NK;Yang, E;Bazan, JF;Barrett, L;Yeh, RC;Hill, RS;Beck, SG;Otani, A;Angad, J;Mitani, T;Posey, JE;Pehlivan, D;Calame, D;Aydin, H;Yesilbas, O;Parks, KC;Argilli, E;England, E;Im, K;Taranath, A;Scott, HS;Barnett, CP;Arts, P;Sherr, EH;Lupski, JR;Walsh, CA;
PMID: 36228617 | DOI: 10.1016/j.devcel.2022.09.011
Kinesins are canonical molecular motors but can also function as modulators of intracellular signaling. KIF26A, an unconventional kinesin that lacks motor activity, inhibits growth-factor-receptor-bound protein 2 (GRB2)- and focal adhesion kinase (FAK)-dependent signal transduction, but its functions in the brain have not been characterized. We report a patient cohort with biallelic loss-of-function variants in KIF26A, exhibiting a spectrum of congenital brain malformations. In the developing brain, KIF26A is preferentially expressed during early- and mid-gestation in excitatory neurons. Combining mice and human iPSC-derived organoid models, we discovered that loss of KIF26A causes excitatory neuron-specific defects in radial migration, localization, dendritic and axonal growth, and apoptosis, offering a convincing explanation of the disease etiology in patients. Single-cell RNA sequencing in KIF26A knockout organoids revealed transcriptional changes in MAPK, MYC, and E2F pathways. Our findings illustrate the pathogenesis of KIF26A loss-of-function variants and identify the surprising versatility of this non-motor kinesin.
Zhu H, Meissner LE, Byrnes C, Tuymetova G, Tifft CJ, Proia RL
PMID: 32179479 | DOI: 10.1016/j.isci.2020.100957
The SUSD4 (Sushi domain-containing protein 4) gene encodes a complement inhibitor that is frequently deleted in 1q41q42 microdeletion syndrome, a multisystem congenital disorder that includes neurodevelopmental abnormalities. To understand SUSD4's role in the mammalian nervous system, we analyzed Susd4 knockout (KO) mice. Susd4 KO mice exhibited significant defects in motor performance and significantly higher levels of anxiety-like behaviors. Susd4 KO brain had abnormal "hairy" basket cells surrounding Purkinje neurons within the cerebellum and significantly reduced dendritic spine density in hippocampal pyramidal neurons. Neurons and oligodendrocyte lineage cells of wild-type mice were found to express Susd4 mRNA. Protein expression of the complement component C1q was increased in the brains of Susd4 KO mice. Our data indicate that SUSD4 plays an important role in neuronal functions, possibly via the complement pathway, and that SUSD4 deletion may contribute to the nervous system abnormalities in patients with 1q41q42 deletions
Nuclear isoform of FGF13 regulates post-natal neurogenesis in the hippocampus through an epigenomic mechanism
Yang, QQ;Zhai, YQ;Wang, HF;Cai, YC;Ma, XY;Yin, YQ;Li, YD;Zhou, GM;Zhang, X;Hu, G;Zhou, JW;
PMID: 34010636 | DOI: 10.1016/j.celrep.2021.109127
The hippocampus is one of two niches in the mammalian brain with persistent neurogenesis into adulthood. The neurogenic capacity of hippocampal neural stem cells (NSCs) declines with age, but the molecular mechanisms of this process remain unknown. In this study, we find that fibroblast growth factor 13 (FGF13) is essential for the post-natal neurogenesis in mouse hippocampus, and FGF13 deficiency impairs learning and memory. In particular, we find that FGF13A, the nuclear isoform of FGF13, is involved in the maintenance of NSCs and the suppression of neuronal differentiation during post-natal hippocampal development. Furthermore, we find that FGF13A interacts with ARID1B, a unit of Brahma-associated factor chromatin remodeling complex, and suppresses the expression of neuron differentiation-associated genes through chromatin modification. Our results suggest that FGF13A is an important regulator for maintaining the self-renewal and neurogenic capacity of NSCs in post-natal hippocampus, revealing an epigenomic regulatory function of FGFs in neurogenesis.
Sodium leak channel contributes to neuronal sensitization in neuropathic pain
Zhang, D;Zhao, W;Liu, J;Ou, M;Liang, P;Li, J;Chen, Y;Liao, D;Bai, S;Shen, J;Chen, X;Huang, H;Zhou, C;
PMID: 33766679 | DOI: 10.1016/j.pneurobio.2021.102041
Neuropathic pain affects up to 10% of the total population and no specific target is ideal for therapeutic need. The sodium leak channel (NALCN), a non-selective cation channel, mediates the background Na+ leak conductance and controls neuronal excitability and rhythmic behaviors. Here, we show that increases of NALCN expression and function in dorsal root ganglion (DRG) and dorsal spinal cord contribute to chronic constriction injury (CCI)-induced neuropathic pain in rodents. NALCN current and neuronal excitability in acutely isolated DRG neurons and spinal cord slices of rats were increased after CCI which were decreased to normal levels by NALCN-siRNA. Accordingly, pain-related symptoms were significantly alleviated by NALCN-siRNA-mediated NALCN knockdown and completely prevented by NALCN-shRNA-mediated NALCN knockdown in rats or by conditional NALCN knockout in mice. Our results indicate that increases in NALCN expression and function contribute to CCI-induced neuronal sensitization; therefore, NALCN may be a novel molecular target for control of neuropathic pain.
