AKAP12 regulates the blood-brain barrier permeability by modulating the tight junction in zebrafish

Abstract

The Blood-Brain Barrier(BBB) has a crucial role in maintaining central nervous system(CNS) environments and protecting the CNS from pathogens and other harmful substances. The tight junction is the major component of maintaining the permeability of the BBB and is established with tight junction proteins between endothelial cells. Previous study reported that zebrafish(Danio rerio) also has the BBB and it starts to develop 3 days post fertilization(dpf). AKAP12 is a scaffolding protein and it has various roles in regulating cell migration, involving the BBB formation and suppressing tumors. To investigate whether the AKAP12 regulates the BBB development in zebrafish, expression of AKAP12 was knock-downed in zebrafish embryos by morpholinos injection. The AKAP12 knockdown zebrafish has shown hemorrhage in head region(3dpf). In addition, fluorescent dye was injected into common cardinal vein, which also has shown leakage in brain micro-vessels. Therefore, it was assumed that AKAP12 could be involved in the expression and distribution of tight junction proteins (Claudin-5, ZO-1). To identify this suggestion, the expression of tight junction proteins was examined in the mRNA and protein level. As a result, it has shown that mRNA expression of both Claudin-5 and ZO-1 was not changed but protein expression was decreased. Taken together, it was suggested that AKAP12 is involved in regulating the BBB permeability by modulating the expressions of tight junction proteins in zebrafish.