Dr Chantel Fitzsimmons

Circular RNAs (circRNAs) are a covalently closed subclass of non-coding RNA molecules formed by back splicing of linear precursor RNA. These molecules are relatively stable and particularly abundant in the mammalian brain and therefore may participate in neural development and function. With the emergence of circRNAs activity in gene regulation, these molecules have been implicated in several biological processes, including synaptic plasticity, and we therefore suspect they may have a role in neurobehavioral disorders. Here, we profile cortical circRNAs expression in 35 postmortem cortical gray matter (BA46) schizophrenia and a non-psychiatric comparison group, using circRNA enrichment sequencing. While more than 90,000 circRNAs species were identified in the dorsolateral prefrontal cortex (DLPFC), we observed lower complexity and substantial depletion in subjects with the disorder. Although circRNAs expression was independent of their host gene transcription, alternative splicing rates were lower in samples from cases compared to controls. Gene set analysis of differentially expressed circRNAs host genes revealed significant enrichment of neural functions and neurological disorders. Many of these depleted circRNAs are also predicted to sequester miRNAs that were shown previously to be increased in the disorder, potentially exacerbating the functional impact of their dysregulation through posttranscriptional gene silencing. While this is the first reported exploration of circRNAs in schizophrenia, there is significant potential for dysregulation more broadly in other major mental illnesses and behavioral disorders. Given their capacity for modulating miRNA function, circRNA may play a significant role in the pathophysiology of disease and even be targeted for therapeutic manipulation.

Background The single nucleotide polymorphism (SNP) rs1344706 [A > C] within intron 2 of the zinc finger protein 804A gene (ZNF804A) is associated with schizophrenia at the genome-wide level, but its function in relation to the development of psychotic disorders, including its influence on brain morphology remains unclear. Methods Using both univariate (voxel-based morphometry, VBM; cortical thickness) and multivariate (source-based morphometry, SBM) approaches, we examined the effects of variation of the rs1344706 polymorphism on grey matter integrity in 214 Caucasian schizophrenia cases and 94 Caucasian healthy individuals selected from the Australian Schizophrenia Research Bank. Results Neither univariate nor multivariate analyses showed any associations between indices of grey matter and rs1344706 variation in schizophrenia or healthy participants. This was revealed in the context of the typical pattern of decreased grey matter integrity in schizophrenia compared to healthy individuals, including: (1) large grey matter volume reductions in the orbitofrontal and anterior cingulate cortices and the left fusiform/inferior temporal gyri; (2) decreased cortical thickness in the left inferior temporal and fusiform gyri, the left orbitofrontal gyrus, as well as in the right pars opercularis/precentral gyrus; and (3) decreased covariation of grey matter concentration in frontal and limbic brain regions emerging from the SBM analyses. Conclusions Contrary to some ¿ but not all ¿ previous findings, this study of a large sample of schizophrenia cases and healthy controls reveals no evidence for association between grey matter alterations and variation in rs1344706 (ZNF804A). Differences in sample sizes and ethnicities may account for discrepant findings between the present and previous studies.

The low-density lipoprotein receptor-related protein (LRP) is a large multifunctional cell surface membrane receptor capable of binding over 50 ligands. These include molecules important in Alzheimer's disease such as the amyloid ß-protein precursor (AßPP), the ß-amyloid (Aß) peptide and apolipoprotein E (ApoE). Full length LRP consists of a 515 kDa extracellular ligand binding a-chain and an 85 kDa membrane spanning ß-chain. A soluble form of LRP (sLRP) present in human plasma retains the ability to bind ligands, including Aß. This soluble form is an ectodomain fragment generated from the membrane bound form of the receptor by proteolytic cleavage. Here we report data demonstrating that some commercial 'serum-free' supplements and 'serum-free' media contain unlisted sLRP immunoreactive species that may reflect the presence of undefined serum protein extracts in these 'serum-free' preparations. This has the potential to interfere with experimental results and interpretation in a range of cell culture studies involving LRP or any of its ligands and possibly also other serum proteins.