NF-κB regulates neuronal ankyrin-G via a negative feedback loop

Tsc1 deletion in Purkinje neurons disrupts the axon initial segment, impairing excitability and cerebellar function

Loss-of-function mutations in tuberous sclerosis 1 (TSC1) are prevalent monogenic causes of autism spectrum disorder (ASD). Selective deletion of Tsc1 from mouse cerebellar Purkinje neurons has been shown to cause several ASD-linked behavioral impairments, which are linked to reduced Purkinje neuron repetitive firing rates. We used electrophysiology methods to investigate why Purkinje neuron-specific Tsc1 deletion (Tsc1mut/mut) impairs Purkinje neuron firing. These studies revealed a depolarized shift in action potential threshold voltage, an effect that we link to reduced expression of the fast-transient voltage-gated sodium (Nav) current in Tsc1mut/mut Purkinje neurons. The reduced Nav currents in these cells was associated with diminished secondary immunofluorescence from anti-pan Nav channel labeling at Purkinje neuron axon initial segments (AIS). Anti-ankyrinG immunofluorescence was also found to be significantly reduced at the AIS of Tsc1mut/mut Purkinje neurons, suggesting Tsc1 is necessary for the organization and functioning of the Purkinje neuron AIS. An analysis of the 1st and 2nd derivative of the action potential voltage-waveform supported this hypothesis, revealing spike initiation and propagation from the AIS of Tsc1mut/mut Purkinje neurons is impaired compared to age-matched control Purkinje neurons. Heterozygous Tsc1 deletion resulted in no significant changes in the firing properties of adult Purkinje neurons, and slight reductions in anti-pan Nav and anti-ankyrinG labeling at the Purkinje neuron AIS, revealing deficits in Purkinje neuron firing due to Tsc1 haploinsufficiency are delayed compared to age-matched Tsc1mut/mut Purkinje neurons. Together, these data reveal that the loss of Tsc1 impairs Purkinje neuron firing and membrane excitability through the dysregulation of proteins essential for AIS organization and function.

Tsc1 Deletion in Purkinje Neurons Disrupts the Axon Initial Segment, Impairing Excitability and Cerebellar Function

Loss-of-function mutations in tuberous sclerosis 1 (TSC1) are prevalent monogenic causes of autism spectrum disorder (ASD). Selective deletion of Tsc1 from mouse cerebellar Purkinje neurons has been shown to cause several ASD-linked behavioral impairments, which are linked to reduced Purkinje neuron repetitive firing rates. We used electrophysiology methods to investigate why Purkinje neuron-specific Tsc1 deletion (Tsc1 mut/mut ) impairs Purkinje neuron firing. These studies revealed a depolarized shift in action potential threshold voltage, an effect that we link to reduced expression of the fast-transient voltage-gated sodium (Nav) current in Tsc1 mut/mut Purkinje neurons. The reduced Nav currents in these cells was associated with diminished secondary immunofluorescence from anti-pan Nav channel labeling at Purkinje neuron axon initial segments (AIS). Interestingly, anti-ankyrinG immunofluorescence was also found to be significantly reduced at the AIS of Tsc1 mut/mut Purkinje neurons, suggesting Tsc1 is necessary for the organization and functioning of the Purkinje neuron AIS. An analysis of the 1st and 2nd derivative of the action potential voltage-waveform supported this hypothesis, revealing spike initiation and propagation from the AIS of Tsc1 mut/mut Purkinje neurons is impaired compared to age-matched control Purkinje neurons. Heterozygous Tsc1 deletion resulted in no significant changes in the firing properties of adult Purkinje neurons, and slight reductions in anti-pan Nav and anti-ankyrinG labeling at the Purkinje neuron AIS, revealing deficits in Purkinje neuron firing due to Tsc1 haploinsufficiency are delayed compared to age-matched Tsc1 mut/mut Purkinje neurons. Together, these data reveal the loss of Tsc1 impairs Purkinje neuron firing and membrane excitability through the dysregulation of proteins necessary for AIS organization and function.

Therapeutic strategies to recover ependymal barrier after inflammatory damage: relevance for recovering neurogenesis during development

The epithelium covering the surfaces of the cerebral ventricular system is known as the ependyma, and is essential for maintaining the physical and functional integrity of the central nervous system. Additionally, the ependyma plays an essential role in neurogenesis, neuroinflammatory modulation and neurodegenerative diseases. Ependyma barrier is severely affected by perinatal hemorrhages and infections that cross the blood brain barrier. The recovery and regeneration of ependyma after damage are key to stabilizing neuroinflammatory and neurodegenerative processes that are critical during early postnatal ages. Unfortunately, there are no effective therapies to regenerate this tissue in human patients. Here, the roles of the ependymal barrier in the context of neurogenesis and homeostasis are reviewed, and future research lines for development of actual therapeutic strategies are discussed.

Risk of migraine contributed by genetic polymorphisms of ANKDD1B gene: a case-control study based on Chinese Han population

Early studies have indicated that the risk of migraine is contributed by both genetic and environmental factors. We aimed to evaluate the association between the risk of migraine and genetic polymorphisms in the ANKDD1B gene in a large sample of Chinese Han populations. A total of 882 patients with MO and 1,784 age-matched controls were recruited. A list of 12 tag SNPs located within the ANKDD1B gene region was genotyped. Distributions of SNP genotypes and alleles between patients and controls were examined to investigate the associations between the risk of migraine and genetic polymorphisms. The GTEx database was used to examine the effects of the significant SNPs on gene expressions. A stop-gain SNP, rs34358, was discovered to be significantly related with the risk of migraine (χ² = 25.02, P = 5.66 × 10^-7). The A allele of this SNP was significantly associated with a decreased risk of migraine (OR [95% CI] = 0.73 [0.65-0.83]). A dose-dependent pattern was identified in the genotypic analyses. The OR with 95% confidence interval for genotype AA versus GG was 0.55 [0.42-0.72], while for AG versus GG it was 0.74 [0.62-0.88]. Further bioinformatics analysis showed multiple significant signals (20 out of 47) for the association between SNP rs34358 and gene expression levels of ANKDD1B. In conclusion, we have provided population-based evidence for the association between genetic polymorphisms of the ANKDD1B gene and the risk of migraine. A protein-truncating variant was significantly associated with a decreased risk of migraine in the samples recruited from the Chinese Han population.

Cellular Specificity of NF-κB Function in the Nervous System

Nuclear Factor Kappa B (NF-κB) is a ubiquitously expressed transcription factor with key functions in a wide array of biological systems. While the role of NF-κB in processes, such as host immunity and oncogenesis has been more clearly defined, an understanding of the basic functions of NF-κB in the nervous system has lagged behind. The vast cell-type heterogeneity within the central nervous system (CNS) and the interplay between cell-type specific roles of NF-κB contributes to the complexity of understanding NF-κB functions in the brain. In this review, we will focus on the emerging understanding of cell-autonomous regulation of NF-κB signaling as well as the non-cell-autonomous functional impacts of NF-κB activation in the mammalian nervous system. We will focus on recent work which is unlocking the pleiotropic roles of NF-κB in neurons and glial cells (including astrocytes and microglia). Normal physiology as well as disorders of the CNS in which NF-κB signaling has been implicated will be discussed with reference to the lens of cell-type specific responses.

Construction of an attenuated goatpox virus AV41 strain by deleting the TK gene and ORF8-18

Goatpox virus (GTPV) is prevalent in goats and is associated with high mortality. This virus causes fever, skin nodules, lesions in the respiratory and lymph node enlargement. Considering the safety risks and side effects of vaccination with attenuated live GPTV vaccine strain AV41, an attenuated goatpox virus (GTPV-TK-ORF), was constructed by deleting non-essential gene fragments without affecting replication and related to the virulence and immunomodulatory functions of the goatpox virus AV41 strain (GTPV-AV41) using homologous recombination and the Cre (Cyclization Recombination Enzyme)/Loxp system. The results of both in vivo and in vitro experiments demonstrated that GTPV-TK-ORF was safer than wild type GTPV-AV41, possessed satisfactory immunogenicity, and could protect goats from a virulent GTPV-AV40 infection. Moreover, the IFN-γ, GTPV-specific antibody, and neutralizing antibody levels in the GTPV-TK-ORF-immunized group were significantly higher than that in the normal saline control group following immunization (P < 0.01). Thus, GTPV-TK-ORF may be used as a potential novel vaccine and viral vector with good safety and immunogenicity.

A constitutively-active IKK-complex at the axon initial segment

BACKGROUND

Previous studies provided evidence for an accumulation of IκB-kinase (IKK) α/β at the axon initial segment (AIS), a neuronal compartment defined by ankyrin-G expression. Here we explored whether the presence of the IKK-complex at the AIS was associated with the activation of IKK signaling at this site.

METHODS AND RESULTS

Proximity-ligation assays (PLAs) using pan-IKKα/β, phospho-IKKα/β-specific as well as ankyrin-G specific antibodies validated their binding to proximal epitopes in the AIS, while antibodies to other phosphorylated signaling proteins showed no preference for the AIS. Small-hairpin mediated silencing of IKKβ significantly reduced anti-phospho-IKKα/β-immunoreactivities in the AIS. ank3 gene-deficient cerebellar Purkinje cells also exhibited no phosphorylated IKKα/β at the proximal region of their axons. Transient ankyrin-G overexpression in PC12 cells augmented NF-κB transactivation in an ankyrin-G death-domain dependent manner. Finally, small molecule inhibitors of IKK-activity, including Aspirin, inhibited the accumulation of activated IKK proteins in the AIS.

CONCLUSION

Our data suggest the existence of a constitutively-active IKK signaling complex in the AIS.