Association analysis of ANK3 gene variants with schizophrenia in a northern Chinese Han population

The Node of Ranvier as an Interface for Axo-Glial Interactions: Perturbation of Axo-Glial Interactions in Various Neurological Disorders

The action potential conduction along the axon is highly dependent on the healthy interactions between the axon and myelin-producing glial cells. Myelin, which facilitates action potential, is the protective insulation around the axon formed by Schwann cells and oligodendrocytes in the peripheral (PNS) and central nervous system (CNS), respectively. Myelin is a continuous structure with intermittent gaps called nodes of Ranvier, which are the sites enriched with ion channels, transmembrane, scaffolding, and cytoskeletal proteins. Decades-long extensive research has identified a comprehensive proteome with strictly regularized localization at the node of Ranvier. Concurrently, axon-glia interactions at the node of Ranvier have gathered significant attention as the pathophysiological targets for various neurodegenerative disorders. Numerous studies have shown the alterations in the axon-glia interactions culminating in neurological diseases. In this review, we have provided an update on the molecular composition of the node of Ranvier. Further, we have discussed in detail the consequences of disruption of axon-glia interactions during the pathogenesis of various CNS and PNS disorders.

Ankyrin2 is essential for neuronal morphogenesis and long-term courtship memory in Drosophila

Dysregulation of HDAC4 expression and/or nucleocytoplasmic shuttling results in impaired neuronal morphogenesis and long-term memory in Drosophila melanogaster. A recent genetic screen for genes that interact in the same molecular pathway as HDAC4 identified the cytoskeletal adapter Ankyrin2 (Ank2). Here we sought to investigate the role of Ank2 in neuronal morphogenesis, learning and memory. We found that Ank2 is expressed widely throughout the Drosophila brain where it localizes predominantly to axon tracts. Pan-neuronal knockdown of Ank2 in the mushroom body, a region critical for memory formation, resulted in defects in axon morphogenesis. Similarly, reduction of Ank2 in lobular plate tangential neurons of the optic lobe disrupted dendritic branching and arborization. Conditional knockdown of Ank2 in the mushroom body of adult Drosophila significantly impaired long-term memory (LTM) of courtship suppression, and its expression was essential in the γ neurons of the mushroom body for normal LTM. In summary, we provide the first characterization of the expression pattern of Ank2 in the adult Drosophila brain and demonstrate that Ank2 is critical for morphogenesis of the mushroom body and for the molecular processes required in the adult brain for the formation of long-term memories.

Roles and mechanisms of ankyrin-G in neuropsychiatric disorders

Ankyrin proteins act as molecular scaffolds and play an essential role in regulating cellular functions. Recent evidence has implicated the ANK3 gene, encoding ankyrin-G, in bipolar disorder (BD), schizophrenia (SZ), and autism spectrum disorder (ASD). Within neurons, ankyrin-G plays an important role in localizing proteins to the axon initial segment and nodes of Ranvier or to the dendritic shaft and spines. In this review, we describe the expression patterns of ankyrin-G isoforms, which vary according to the stage of brain development, and consider their functional differences. Furthermore, we discuss how posttranslational modifications of ankyrin-G affect its protein expression, interactions, and subcellular localization. Understanding these mechanisms leads us to elucidate potential pathways of pathogenesis in neurodevelopmental and psychiatric disorders, including BD, SZ, and ASD, which are caused by rare pathogenic mutations or changes in the expression levels of ankyrin-G in the brain.

Mutations affecting the production, distribution, or function of the ankyrin-G protein may contribute to a variety of different neuropsychiatric disorders. Ankyrin-G is typically observed at the synapses between neurons, and contributes to intercellular adhesion and signaling along with other important functions. Peter Penzes and colleagues at Northwestern University, Chicago, USA, review the biology of this protein and identify potential mechanisms by which ankyrin-G mutations might impair healthy brain development. Mutations in the gene encoding this protein are strongly linked with bipolar disorder, but have also been tentatively connected to autism spectrum disorders and schizophrenia. The authors highlight physiologically important interactions with a diverse array of other brain proteins, which can in turn be modulated by various chemical modifications to ankyrin-G, and conclude that drugs that influence these modifications could have potential therapeutic value.

Ankyrins and neurological disease

Ankyrins are scaffolding proteins widely expressed throughout the nervous system. Ankyrins recruit diverse membrane proteins, including ion channels and cell adhesion molecules, into specialized subcellular membrane domains. These domains are stabilized by ankyrins interacting with the spectrin cytoskeleton. Ankyrin genes are highly associated with a number of neurological disorders, including Alzheimer's disease, schizophrenia, autism spectrum disorders, and bipolar disorder. Here, we discuss ankyrin function and their role in neurological disease. We propose mutations in ankyrins contribute to disease through two primary mechanisms: 1) altered neuronal excitability by disrupting ion channel clustering at key excitable domains, and 2) altered neuronal connectivity via impaired stabilization of membrane proteins.

DNA methylation signatures of adolescent victimization: analysis of a longitudinal monozygotic twin sample

Accumulating evidence suggests that individuals exposed to victimization at key developmental stages may have different epigenetic fingerprints compared to those exposed to no/minimal stressful events, however results are inconclusive. This study aimed to strengthen causal inference regarding the impact of adolescent victimization on the epigenome by controlling for genetic variation, age, gender, and shared environmental exposures. We conducted longitudinal epigenome-wide association analyses (EWAS) on DNA methylation (DNAm) profiles of 118 monozygotic (MZ) twin pairs from the Environmental Risk study with and without severe adolescent victimization generated using buccal DNA collected at ages 5, 10 and 18, and the Illumina EPIC array. Additionally, we performed cross-sectional EWAS on age-18 blood and buccal DNA from the same individuals to elucidate tissue-specific signatures of severe adolescent victimization. Our analyses identified 20 suggestive differentially methylated positions (DMPs) (P < 5e-05), with altered DNAm trajectories between ages 10–18 associated with severe adolescent victimization (∆Beta range = −5.5%−5.3%). Age-18 cross-sectional analyses revealed 72 blood (∆Beta range = −2.2%−3.4%) and 42 buccal (∆Beta range = −3.6%−4.6%) suggestive severe adolescent victimization-associated DMPs, with some evidence of convergent signals between these two tissue types. Downstream regional analysis identified significant differentially methylated regions (DMRs) in LGR6 and ANK3 (Šidák P = 5e-09 and 4.07e-06), and one upstream of CCL27 (Šidák P = 2.80e-06) in age-18 blood and buccal EWAS, respectively. Our study represents the first longitudinal MZ twin analysis of DNAm and severe adolescent victimization, providing initial evidence for altered DNA methylomic signatures in individuals exposed to adolescent victimization.

The role of genes affected by human evolution marker GNA13 in schizophrenia

Numerous variants associated with increased risk for SCZ have undergone positive selection and were associated with human brain development, but which brain regions and developmental stages were influenced by the positive selection for SCZ risk alleles are unclear. We analyzed SCZ using summary statistics from a genome-wide association study (GWAS) from the Psychiatric Genomics Consortium (PGC). Machine-learning scores were used to investigate two natural-selection scenarios: complete selection (loci where a selected allele has reached fixation) and incomplete selection (loci where a selected allele has not yet reached fixation). Based on the p value of single nucleotide polymorphisms (SNPs) with selection scores in the top 5%, we formed five subgroups: p < 0.0001, 0.001, 0.01, 0.05, or 0.1. We found that 48 and 29 genes (p < 0.0001) in complete and incomplete selection, respectively, were enrichedfor the transcriptionalco-expressionprofilein theprenatal dorsolateral prefrontal cortex (DFC), inferior parietal cortex (IPC), and ventrolateral prefrontal cortex (VFC). Core genes (GNA13, TBC1D19, and ZMYM4) involved in regulating early brain development were identified in these three brain regions. RNA sequencing for primary cortical neurons that were transfected Gna13 overexpressed lentivirus demonstrated that 135 gene expression levels changed in the Gna13 overexpressed groups compared with the controls. Gene-set analysis identified important associations among common variants of these 13 genes, which were associated with neurodevelopment and putamen volume [p = 0.031; family-wise error correction (FWEC)], SCZ (p = 0.022; FWEC). The study indicate that certain SCZ risk alleles were likely to undergo positive selection during human evolution due to their involvement in the development of prenatal DFC, IPC and VFC, and suggest that SCZ is related to abnormal neurodevelopment.