Development of synthetic microRNA-214 showing enhanced cytotoxicity and RNase resistance for treatment of canine hemangiosarcoma.

MicroRNA-214 (miR-214), a pivotal tumour-suppressive miRNA, is downregulated in canine hemangiosarcoma (HSA) cells. Although these tumour-suppressive miRNAs are potential therapeutic agents, their clinical efficacy may be limited because of their vulnerability to RNase-rich microenvironments and low in vivo transfection rates. We developed synthetic miR-214s with enhanced cytotoxicity, RNase resistance and quantity of miR-214 in/on cells. These synthetic miR-214s were synthesized by various chemical modifications (such as 4'-aminoethyl-2'-fluoro, 2'-fluoro, 2'-O-methyl, phosphorothioate and oligospermine modifications) of the wild-type mature miR-214 sequences. Transfection of HSA cells with synthetic miR-214 (miR-214 5AE) demonstrated significant growth suppressive effect and induced the strongest apoptotic response. Synthetic miR-214s (miR-214 5AE, miR-214 10AE and miR-214 OS) were much more stable than mature miR-214s in foetal bovine serum. Similar to mature miR-214, 5AE and OS suppressed the expression level of COP1 in HSA cells. The quantity of synthetic miR-214s in/on cells was higher than that of mature miR-214. In conclusion, we developed a clinically applicable, synthetic miR-214 5AE that regulates the COP1 protein expression similar to that mediated by mature miR-214. Additionally, miR-214 5AE confers better cytotoxicity, nuclease resistance and transfection rate than mature miR-214. Thus, miR-214 5AE could potentially be a novel miRNA-based chemotherapeutic agent that could improve the prognosis of HSA. Its in vivo effects on canine HSA need to be examined in future.

Null mutation in PGAP1 impairing Gpi-anchor maturation in patients with intellectual disability and encephalopathy.

Many eukaryotic cell-surface proteins are anchored to the membrane via glycosylphosphatidylinositol (GPI). There are at least 26 genes involved in biosynthesis and remodeling of GPI anchors. Hypomorphic coding mutations in seven of these genes have been reported to cause decreased expression of GPI anchored proteins (GPI-APs) on the cell surface and to cause autosomal-recessive forms of intellectual disability (ARID). We performed homozygosity mapping and exome sequencing in a family with encephalopathy and non-specific ARID and identified a homozygous 3 bp deletion (p.Leu197del) in the GPI remodeling gene PGAP1. PGAP1 was not described in association with a human phenotype before. PGAP1 is a deacylase that removes an acyl-chain from the inositol of GPI anchors in the endoplasmic reticulum immediately after attachment of GPI to proteins. In silico prediction and molecular modeling strongly suggested a pathogenic effect of the identified deletion. The expression levels of GPI-APs on B lymphoblastoid cells derived from an affected person were normal. However, when those cells were incubated with phosphatidylinositol-specific phospholipase C (PI-PLC), GPI-APs were cleaved and released from B lymphoblastoid cells from healthy individuals whereas GPI-APs on the cells from the affected person were totally resistant. Transfection with wild type PGAP1 cDNA restored the PI-PLC sensitivity. These results indicate that GPI-APs were expressed with abnormal GPI structure due to a null mutation in the remodeling gene PGAP1. Our results add PGAP1 to the growing list of GPI abnormalities and indicate that not only the cell surface expression levels of GPI-APs but also the fine structure of GPI-anchors is important for the normal neurological development.

Both mammalian PIG-M and PIG-X are required for growth of GPI14-disrupted yeast.

GPI mannosyltransferase I (GPI-MT-I) transfers the first mannose to a GPI-anchor precursor, glucosamine-(acyl)phosphatidylinositol [GlcN-(acyl)PI]. Mammalian GPI-MT-I consists of two components, PIG-M and PIG-X, which are homologous to Gpi14p and Pbn1p in Saccharomyces cerevisiae, respectively. In the present study, we disrupted yeast GPI14 and analysed the phenotype of gpi14 yeast. The gpi14 haploid cells were inviable and accumulated GlcN-(acyl)PI. We cloned PIG-M homologues from human, Plasmodium falciparum (PfPIG-M) and Trypanosoma brucei (TbGPI14), and tested whether they could complement gpi14-disrupted yeast. None of them restored GPI-MT-I activity and cell growth in gpi14-disrupted yeast. However, gpi14-disrupted yeast cells with human PIG-M, but not with PfPIG-M or TbGPI14, grew slowly but significantly when they were supplemented with rat PIG-X. This suggests that the association of PIG-X and PIG-M for GPI-MT-I activity is not interchangeable between mammals and the other lower eukaryotes.