Mechanism by which Rab5 promotes regeneration and functional recovery of zebrafish Mauthner axons

Rab5 is a GTPase protein that is involved in intracellular membrane trafficking. It functions by binding to various effector proteins and regulating cellular responses, including the formation of transport vesicles and their fusion with the cellular membrane. Rab5 has been reported to play an important role in the development of the zebrafish embryo;however, its role in axonal regeneration in the central nervous system remains unclear. In this study, we established a zebrafish Mauthner cell model of axonal injury using single-cell electroporation and two-photon axotomy techniques. We found that overexpression of Rab5 in single Mauthner cells promoted marked axonal regeneration and increased the number of intra-axonal transport vesicles. In contrast, treatment of zebrafish larvae with the Rab kinase inhibitor CID-1067700markedly inhibited axonal regeneration in Mauthner cells. We also found that Rab5 activated phosphatidylinositol 3-kinase(PI3K) during axonal repair of Mauthner cells and promoted the recovery of zebrafish locomotor function. Additionally, rapamycin, an inhibitor of the mechanistic target of rapamycin downstream of PI3K, markedly hindered axonal regeneration. These findings suggest that Rab5 promotes the axonal regeneration of injured zebrafish Mauthner cells by activating the PI3K signaling pathway.

Amplification of the miR-181c/d cluster is inversely correlated with PDCD4 expression in gastric cancer

miR-181c/d is dysregulated in gastric cancer(GC).We investigated the amplification and expression of miR-181c/d and its predicted target genes in GC.Amplification of miR-181c/d was quantified by genomic real-time PCR in GC and adjacent normal tissues,as well as the levels of mature miR-181c/d was performed by real-time PCR in the same tissues.The potential target genes of miR-181c/d were predicted using bioinformatics software.Expression of one potential target gene,PDCD4,was measured by semiquantitative RT-PCR,real-time PCR,and immunohistochemistry.Next,the relationship between miR181c/d expression and PDCD4 expression was analyzed.Results indicated that the amplification and expression of miR-181c/d were significantly higher in GC than in adjacent normal tissues(primary miR-181c/d,P\0.001;miR-181c,P=0.0344;miR-181d,P=0.0153),and there was a strong correlation between mature miR-181c/d and primary miR-181c/d.Thirty-two target genes were predicted,including PDCD4 which is a known tumor suppressor gene.Expression of PDCD4 was significantly down-regulated in GC as compared to adjacent normal tissues and was inversely correlated with miR-181c/d expression in GC(miR-181c and PDCD4:R=-0.496,P=0.008;miR-181d and PDCD4:R=-0.454,P=0.003).Therefore,miR-181c/d may play a pivotal role in the pathogenesis of GC by downregulating PDCD4 expression.