The central nervous system (CNS) has specific barriers that protect the brain from potential threats and tightly regulate molecular transport. Despite the critical functions of the CNS barriers, the mechanisms underlying their development and function are not well understood, and there are very limited experimental models for their study. Claudin 5 is a tight junction protein required for blood brain barrier (BBB) and, probably, choroid plexus (CP) structure and function in vertebrates. Here, we show that the gene claudin 5a is the zebrafish orthologue with high fidelity expression, in the BBB and CP barriers, that demonstrates the conservation of the BBB and CP between humans and zebrafish. Expression of claudin 5a correlates with developmental tightening of the BBB and is restricted to a subset of the brain vasculature clearly delineating the BBB. We show that claudin 5a-expressing cells of the CP are ciliated ependymal cells that drive fluid flow in the brain ventricles. Finally, we find that CP development precedes BBB development and that claudin 5a expression occurs simultaneously with angiogenesis. Thus, our novel transgenic zebrafish represents an ideal model to study CNS barrier development and function, critical in understanding the mechanisms underlying CNS barrier function in health and disease.

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Background: This study aimed to explore the biological activities of miR-330-3p in dextan sulphate sodium (DSS)induced ulcerative colitis and apoptosis and the direct target of miR-330-3p in this process. HT-29 cells and male C57BL/6 mice were used to examine the function of miR-330-3p in vitro and in vivo, respectively. Expression of miRNA and mRNA was measured using quantitative real time PCR (qRT-PCR). Western blotting was used to measure the change of protein expression. Flow cytometry was used to determine cell apoptosis and luciferase assay was used to confirm the direct target of miR-330-3p. Results: miR-330-3p expression was increased by DSS in both HT-29 cells and mice. Upregulation miR-330-3p induced cell apoptosis, mice weight loss and ulcerative colitis in vivo, which could prevent by suppression of miR-330-3p. Cell apoptosis related protein expression, cleaved caspase-3 and cleaved PARP was also inhibited by miR-330-3p overexpression and elevated by miR-330-3p inhibition both in vitro and in vivo. Luciferase assay confirmed that 3′ untranslated region (3′-UTR) of XBP1 is the directed target of miR-330-3p and Western blotting results have showed that protein expression of XBP1 was decreased by miR-330-3p mimics and increased by miR-330-3p inhibitor. Conclusion: miR-330-3p is upregulated by DSS in both HT-29 cells and mice and promoted ulcerative colitis and cell apoptosis by targeting of 3′-UTR of XBP1, which is a key component of ER stress. Inhibition of miR-330-3p prevent DSS-induced ulcerative colitis and cell apoptosis mediated by upregulation of XBP1 expression.

A transgenic zebrafish model for the in vivo study of the blood and choroid plexus brain barriers It is made available under a (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint . http://dx.doi.org/10.1101/180653 doi: bioRxiv preprint first

In vertebrate photoreceptors, opsins are highly concentrated in a morphologically distinct ciliary compartment known as the outer segment (OS). Opsin is synthesized in the cell body and transported to the OS at a remarkable rate of 100-1000 molecules per second. Opsin transport defects contribute to photoreceptor loss and blindness in human ciliopathies. Previous studies revealed that the opsin C-terminal tail, of 44 amino acids, is sufficient to mediate OS targeting in Xenopus photoreceptors. Here we show that although the Xenopus C-terminus retains this function in zebrafish, the homologous zebrafish sequence is not sufficient to target opsin to the OS. This functional difference is largely caused by a change of a single amino acid present in Xenopus, but not in other vertebrates examined. Furthermore, we find that sequences in the 3rd intracellular cytoplasmic loop (IC3) and adjacent regions of transmembrane helixes 6 and 7 are also necessary for opsin transport in zebrafish. Combined with the cytoplasmic tail, these sequences are sufficient to target opsin to the ciliary compartment.