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Gene expression in choroid plexus of Otx2 +/GFP mice. (A) Venn diagrams of the number of up-or down-regulated genes (p-adj < 0.05) to compare overlap between fourth ventricle (4th V ChP) changes in Otx2 +/GFP mice and in Cre-Tat icv-injected Otx2 lox/lox mice (Cre + Otx2 lox/lox ); (B) Ontology analysis of differentially regulated genes in Otx2 +/GFP mice.
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The choroid plexus is an important blood barrier that secretes cerebrospinal fluid, which essential for embryonic brain development and adult brain homeostasis. The OTX2 homeoprotein is a transcription factor that is critical for choroid plexus development and remains highly expressed in adult choroid plexus. Through RNA sequencing analyses of cons...
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... suggests that conditional knockdown of Otx2 leads to altered ChP barrier function and ChP signaling, and can impact immune responses. The constitutive heterozygote Otx2 +/GFP adult mice showed significant expression changes in 528 genes of the 4V ChP (p-adj < 0.05), which is comparatively less than for conditional Otx2 knockdown in the 4V ChP (Figure 2A). Given that fewer genes are deregulated in this constitutive model, this suggests that compensatory mechanisms for countering reduced OTX2 levels were activated during development. ...
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... that fewer genes are deregulated in this constitutive model, this suggests that compensatory mechanisms for countering reduced OTX2 levels were activated during development. The changes in gene expression were relatively balanced between upregulation (273 genes) and downregulation (255 genes), and ontology analysis revealed shared terms, including glycoprotein, signal, membrane-related, and secreted proteins ( Figure 2B). The upregulated genes are also enriched for cell adhesion and alternative splicing, while downregulated genes are enriched for trafficking and transport. ...
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... hypothesized that genes that were deregulated in both conditional and constitutive models could be either direct targets of OTX2 transcription regulation or targets of important OTX2-dependent pathways. Comparison of gene expression changes in 4V ChP of these two models revealed an overlap of more than 80 genes, in both the upregulated and downregulated repertoires ( Figure 2A). This represented about half of the identified expression changes in Otx2 +/GFP mice, but less than a third of the changes in the conditional model. ...
Citations
... Among the 292 DEGs, overlapping between MR1 and MR2 (Fig 3E), we detected a group of 13 genes consistently down-regulated in BLA of phasic compared to sustained responders but up-regulated in CeA during MR1 (Fig 3F and 3G). Notably, Ttr (encoding transthyretin) that had the largest log fold change (LFC) in all 3 conditions was accompanied by Otx2 (Orthodenticle Homeobox 2), which was previously shown to regulate Ttr expression [40]. Kcne2 (voltage-gated potassium channel accessory subunit 2), Kcnj13 (potassium inwardly rectifying channel), Aqp1 (aquaporin 1), Slc16a8 (lactate transporter), Slc4a5 (sodium bicarbonate cotransporter), Folr1 (folic acid receptor and 5-methyltetrahydrofolate transporter), Steap1 (six-transmembrane epithelial antigen of prostate), Tmem72 (transmembrane protein 72), and Ecrg4 (augurin) had the same expression pattern. ...
Trait anxiety is a major risk factor for stress-induced and anxiety disorders in humans. However, animal models accounting for the interindividual variability in stress vulnerability are largely lacking. Moreover, the pervasive bias of using mostly male animals in preclinical studies poorly reflects the increased prevalence of psychiatric disorders in women. Using the threat imminence continuum theory, we designed and validated an auditory aversive conditioning-based pipeline in both female and male mice. We operationalised trait anxiety by harnessing the naturally occurring variability of defensive freezing responses combined with a model-based clustering strategy. While sustained freezing during prolonged retrieval sessions was identified as an anxiety-endophenotype behavioral marker in both sexes, females were consistently associated with an increased freezing response. RNA-sequencing of CeA, BLA, ACC, and BNST revealed massive differences in phasic and sustained responders’ transcriptomes, correlating with transcriptomic signatures of psychiatric disorders, particularly post-traumatic stress disorder (PTSD). Moreover, we detected significant alterations in the excitation/inhibition balance of principal neurons in the lateral amygdala. These findings provide compelling evidence that trait anxiety in inbred mice can be leveraged to develop translationally relevant preclinical models to investigate mechanisms of stress susceptibility in a sex-specific manner.
... We then compared our zebrafish transcriptomic data with publicly available human, rat and mouse ChP data (SuppleFig.4 and Fig.2) Planques et al, 2021;Rodriguez-Lorenzo et al, 2020). We found 12,230 genes expressed in the ChP which were conserved across all 4 species, corresponding to 65-74 % of all protein coding genes ( Fig.2A and Supplementary Fig.4A, C, D). ...
... The human choroid plexus transcriptome data was obtained with GEO accession number GSE137619 (samples: SRR10134643-SRR10134648) (Rodriguez-Lorenzo et al., 2020). The mouse choroid plexus transcriptome data was obtained from GEO accession number GSE157386 (samples; SRR12576642-SRR12576645, SRR12576650-SRR12576653) (Planques et al., 2021). The zebrafish choroid plexus transcriptome data was obtained from this study. ...
The choroid plexus produces cerebrospinal fluid (CSF) by transport of electrolytes and water from the vasculature to the brain ventricles. The choroid plexus plays additional roles in brain development and homeostasis by secreting neurotrophic molecules, and by serving as a CSF-blood barrier and immune interface. Prior studies have identified transporters on the epithelial cells that transport water and ions into the ventricles and tight junctions involved in the CSF-blood barrier. Yet, how the choroid plexus epithelial cells maintain the brain ventricle system and control brain physiology remain unresolved. To provide novel insights into the physiological roles of the choroid plexus, we use juvenile and adult zebrafish as model systems. Upon histological and transcriptomic analyses, we first identified that the zebrafish choroid plexus is highly conserved with the mammalian choroid plexus and that it expresses all transporters necessary for CSF secretion. Using novel genetic lines, we also identified that the choroid plexus secretes proteins into the CSF. Next, we generated a transgenic line allowing us to ablate specifically the epithelial cells in the choroid plexus. Using the ablation system, we identified a reduction of the ventricular sizes, but no alterations of the CSF-blood barrier. Altogether, our findings identified that the zebrafish choroid plexus is evolutionarily conserved and critical for maintaining the size and homeostasis of the brain ventricles.
Graphical abstract
Highlights
The zebrafish choroid plexus has similar anatomical features with the mammalian choroid plexus.
The expression of choroid plexus transporters involved in CSF secretion is evolutionarily conserved across vertebrates.
Generation of a novel choroid plexus specific driver line shows that the choroid plexus epithelial cells secrete proteins into CSF.
Ablation of the choroid plexus decreases the size of the brain ventricles.
... This transport is experience-dependent. In addition, Otx2 is released from the choroid plexus epithelium into the cerebrospinal fluid and transferred into distant cerebral cortex areas (Spatazza et al., 2013;Planques et al., 2019;Planques et al., 2021). In summary, the transfer of Otx2 along visual structures seems disturbed. ...
Fast-spiking parvalbumin interneurons are critical for the function of mature cortical inhibitory circuits. Most of these neurons are enwrapped by a specialized extracellular matrix (ECM) structure called perineuronal net (PNN), which can regulate their synaptic input. In this study, we investigated the relationship between PNNs, parvalbumin interneurons, and synaptic distribution on these cells in the adult primary visual cortex (V1) of quadruple knockout mice deficient for the ECM molecules brevican, neurocan, tenascin-C, and tenascin-R. We used super-resolution structured illumination microscopy (SIM) to analyze PNN structure and associated synapses. In addition, we examined parvalbumin and calretinin interneuron populations. We observed a reduction in the number of PNN-enwrapped cells and clear disorganization of the PNN structure in the quadruple knockout V1. This was accompanied by an imbalance of inhibitory and excitatory synapses with a reduction of inhibitory and an increase of excitatory synaptic elements along the PNNs. Furthermore, the number of parvalbumin interneurons was reduced in the quadruple knockout, while calretinin interneurons, which do not wear PNNs, did not display differences in number. Interestingly, we found the transcription factor Otx2 homeoprotein positive cell population also reduced. Otx2 is crucial for parvalbumin interneuron and PNN maturation, and a positive feedback loop between these parameters has been described. Collectively, these data indicate an important role of brevican, neurocan, tenascin-C, and tenascin-R in regulating the interplay between PNNs, inhibitory interneurons, synaptic distribution, and Otx2 in the V1.
... Onset not specified, Adult expression in reference [54] TAT-Cre delivery Adult (5 days after single injection) [71][72][73][74] Page 3 of 15 Jang and Lehtinen Fluids and Barriers of the CNS (2022) 19:36 recombinase, the mT cassette is excised, enabling expression of the mG (GFP) cassette [35]. In this way, mT/mG mice crossed with FOXJ1-Cre transgenic mice reveal GFP-positive ChP epithelial cells ( Fig. 1) [24]. ...
... When TAT-Cre is delivered into adult ventricles, it is taken up by ChP epithelial cells. In Otx2 fl/fl mice, TAT-Cre results in ChP-Otx2 deletion, resulting in altered cortical plasticity and neurogenesis [71][72][73]. Similarly, TAT-Cre injection into adult App fl/fl mice induces App knockdown in ChP, with downstream consequences on adult neurogenesis [74]. ...
... Remarkably, when delivered I.C.V., conditional gene deletion in ChP epithelial cells can be obtained without disrupting the same gene's expression in nearby hippocampus [74]. AAV2/5-harboring Otx2 shRNA injected I.C.V. into adult mice can also be used for Otx2 knockdown in the ChP for at least three weeks following injection [73]. ChP-specific inhibition of miR-204 was achieved using AAV2/5 following adult mouse I.C.V. delivery [95]. ...
Choroid plexus (ChP) epithelial cells are crucial for the function of the blood-cerebrospinal fluid barrier (BCSFB) in the developing and mature brain. The ChP is considered the primary source and regulator of CSF, secreting many important factors that nourish the brain. It also performs CSF clearance functions including removing Amyloid beta and potassium. As such, the ChP is a promising target for gene and drug therapy for neurodevelopmental and neurological disorders in the central nervous system (CNS). This review describes the current successful and emerging experimental approaches for targeting ChP epithelial cells. We highlight methodological strategies to specifically target these cells for gain or loss of function in vivo. We cover both genetic models and viral gene delivery systems. Additionally, several lines of reporters to access the ChP epithelia are reviewed. Finally, we discuss exciting new approaches, such as chemical activation and transplantation of engineered ChP epithelial cells. We elaborate on fundamental functions of the ChP in secretion and clearance and outline experimental approaches paving the way to clinical applications.
... The distinct role of CPs in both the control and production of CSF suggests this structure regulates neural stem cell behaviourgiven their direct contact with CSF-and thereby neurogenesis and brain development [54,55]. Indeed, there is evidence that CP-CSF signalling via the OTX2 homeoprotein is involved in the modulation of developmental neurogenesis and anxiety related behaviour [2,[56][57][58][59][60][61][62]. The specific mechanisms by which the CPs modulate brain development both in terms of the CPs as well as specific aspects of their functions (e.g., transfer of blood-borne molecules or secretion of a particular molecule) needs to be investigated. ...
The choroid plexus (CP) is a delicate and highly vascularized structure in the brain comprised of a dense network of fenestrated capillary loops that help in the synthesis, secretion and circulation of cerebrospinal fluid (CSF). This unique neuroanatomical structure is comprised of arachnoid villi stemming from frond-like surface projections—that protrude into the lumen of the four cerebral ventricles—providing a key source of nutrients to the brain parenchyma in addition to serving as a ‘sink’ for central nervous system metabolic waste. In fact, the functions of the CP are often described as being analogous to those of the liver and kidney. Beyond forming a barrier/interface between the blood and CSF compartments, the CP has been identified as a modulator of leukocyte trafficking, inflammation, cognition, circadian rhythm and the gut brain-axis. In recent years, advances in molecular biology techniques and neuroimaging along with the use of sophisticated animal models have played an integral role in shaping our understanding of how the CP–CSF system changes in relation to the maturation of neural circuits during critical periods of brain development. In this article we provide an ontogenetic perspective of the CP and review the experimental evidence implicating this structure in the pathophysiology of neurodevelopmental and neuropsychiatric disorders.
OTX homeobox genes have been extensively studied for their role in development, especially in neuroectoderm formation. Recently, their expression has also been reported in adult physiological and pathological tissues, including retina, mammary and pituitary glands, sinonasal mucosa, in several types of cancer, and in response to inflammatory, ischemic, and hypoxic stimuli. Reactivation of OTX genes in adult tissues supports the notion of the evolutionary amplification of functions of genes by varying their temporal expression, with the selection of homeobox genes from the “toolbox” to drive or contribute to different processes at different stages of life. OTX involvement in pathologies points toward these genes as potential diagnostic and/or prognostic markers as well as possible therapeutic targets.
Elevated amyloid precursor protein (APP) expression in the choroid plexus suggests an important role for extracellular APP metabolites such as sAPPα in cerebrospinal fluid. Despite widespread App brain expression, we hypothesized that specifically targeting choroid plexus expression could alter animal physiology. Through various genetic and viral approaches in the adult mouse, we show that choroid plexus APP levels significantly impact proliferation in both subventricular zone and hippocampus dentate gyrus neurogenic niches. Given the role of Aβ peptides in Alzheimer disease pathogenesis, we also tested whether favoring the production of Aβ in choroid plexus could negatively affect niche functions. After AAV5-mediated long-term expression of human mutated APP specifically in the choroid plexus of adult wild-type mice, we observe reduced niche proliferation, reduced hippocampus APP expression, behavioral defects in reversal learning, and deficits in hippocampal long-term potentiation. Our findings highlight the unique role played by the choroid plexus in regulating brain function and suggest that targeting APP in choroid plexus may provide a means to improve hippocampus function and alleviate disease-related burdens.
