Inhibition of AKT Signaling Alters ßIV Spectrin Distribution at the AIS and Increases Neuronal Excitability.

The axon initial segment (AIS) is a highly regulated subcellular domain required for neuronal firing. Changes in the AIS protein composition and distribution are a form of structural plasticity, which powerfully regulates neuronal activity and may underlie several neuropsychiatric and neurodegenerative disorders. Despite its physiological and pathophysiological relevance, the signaling pathways mediating AIS protein distribution are still poorly studied. Here, we used confocal imaging and whole-cell patch clamp electrophysiology in primary hippocampal neurons to study how AIS protein composition and neuronal firing varied in response to selected kinase inhibitors targeting the AKT/GSK3 pathway, which has previously been shown to phosphorylate AIS proteins. Image-based features representing the cellular pattern distribution of the voltage-gated Na+ (Nav) channel, ankyrin G, ßIV spectrin, and the cell-adhesion molecule neurofascin were analyzed, revealing ßIV spectrin as the most sensitive AIS protein to AKT/GSK3 pathway inhibition. Within this pathway, inhibition of AKT by triciribine has the greatest effect on ßIV spectrin localization to the AIS and its subcellular distribution within neurons, a phenotype that Support Vector Machine classification was able to accurately distinguish from control. Treatment with triciribine also resulted in increased excitability in primary hippocampal neurons. Thus, perturbations to signaling mechanisms within the AKT pathway contribute to changes in ßIV spectrin distribution and neuronal firing that may be associated with neuropsychiatric and neurodegenerative disorders.

Examining the independent and joint effects of genomic and exposomic liabilities for schizophrenia across the psychosis spectrum.

AIMS: Psychosis spectrum disorder has a complex pathoetiology characterised by interacting environmental and genetic vulnerabilities. The present study aims to investigate the role of gene-environment interaction using aggregate scores of genetic (polygenic risk score for schizophrenia (PRS-SCZ)) and environment liability for schizophrenia (exposome score for schizophrenia (ES-SCZ)) across the psychosis continuum. METHODS: The sample consisted of 1699 patients, 1753 unaffected siblings, and 1542 healthy comparison participants. The Structured Interview for Schizotypy-Revised (SIS-R) was administered to analyse scores of total, positive, and negative schizotypy in siblings and healthy comparison participants. The PRS-SCZ was trained using the Psychiatric Genomics Consortiums results and the ES-SCZ was calculated guided by the approach validated in a previous report in the current data set. Regression models were applied to test the independent and joint effects of PRS-SCZ and ES-SCZ (adjusted for age, sex, and ancestry using 10 principal components). RESULTS: Both genetic and environmental vulnerability were associated with case-control status. Furthermore, there was evidence for additive interaction between binary modes of PRS-SCZ and ES-SCZ (above 75% of the control distribution) increasing the odds for schizophrenia spectrum diagnosis (relative excess risk due to interaction = 6.79, [95% confidential interval (CI) 3.32, 10.26], p < 0.001). Sensitivity analyses using continuous PRS-SCZ and ES-SCZ confirmed gene-environment interaction (relative excess risk due to interaction = 1.80 [95% CI 1.01, 3.32], p = 0.004). In siblings and healthy comparison participants, PRS-SCZ and ES-SCZ were associated with all SIS-R dimensions and evidence was found for an interaction between PRS-SCZ and ES-SCZ on the total (B = 0.006 [95% CI 0.003, 0.009], p < 0.001), positive (B = 0.006 [95% CI, 0.002, 0.009], p = 0.002), and negative (B = 0.006, [95% CI 0.004, 0.009], p < 0.001) schizotypy dimensions. CONCLUSIONS: The interplay between exposome load and schizophrenia genetic liability contributing to psychosis across the spectrum of expression provide further empirical support to the notion of aetiological continuity underlying an extended psychosis phenotype.

A new family with autosomal dominant porencephaly with a novel Col4A1 mutation. Are arachnoid cysts related to Col4A1 mutations?

Porencephaly is an extensively encountered condition in pediatric neurology practice and leads to serious morbidity with its complications. Important etiological factors are trauma, hemorrhage, infection and thrombophilic factors that may cause destruction in the developing brain. Col4A1 mutations were also shown in familial porencephaly cases. We describe two siblings with porencephaly, hemiparesis, epilepsy, atrophic kidney in one of the siblings and asymptomatic mothers with an arachnoid cyst. We performed Col4A1 gene mutation screening and detected a novel mutation in mother and both of the children. This family has some features previously undescribed in patients with mutations of Col4A1 gene like atrophic kidney in one sibling and arachnoid cyst in the mother. We discuss here the possible relationship between these abnormalities and the mutation.

Sphenoid sinus mucocele causing third nerve paralysis: CT and MR findings.

A 64-year-old woman presented with a 2 week history of ptosis and medial-gaze paralysis of her left eye. Computed tomography scanning of the paranasal sinuses revealed an expansile, homogeneous lesion with no contrast enhancement in the sphenoid sinus. The mass was hyperintense on all MR sequences and there was extension of the mass to the left cavernous sinus and optic canal. Operation revealed a large mucocele. Third nerve palsy disappeared 4 weeks after operation. Because the spread of mucoceles is variable, they may cause different symptoms. Radiological evaluation, especially computed tomography and magnetic resonance imaging, are useful in diagnosis of mucoceles and help to explain the clinical symptoms by showing the spread of the lesion.