Molecuar Characteristics Of Bicc1in Mouse

Translational activation and repression play an important role in the spatial-temporal regulation of gene expression in the development of embryo. Bicaudal-C (Bic-C) gene was originally discovered in Drosophila melanogaster. The gene product of dBic-C is generally accepted as an RNA-binding molecule, which can modulate the expression of diverse genes at the post-transcriptional level. The homologues of Bicaudal-C in many other species (C.elegans, Xenopus, mouse, human, etc.) had also been found, the stucture were very conserved. Mouse Bic-C gene(Biccl) localized at C1region of Chromosome10. Currently, at least three Biccl mouse models (jcpk, bpk, and67Gso) have been reported. All the models exhibit the cystic phenotypes in kidney, liver, and pancreas and their phenotypes are very similar to human poly cystic kidney disease (such as ADPKD and ARPKD). However, the molecular and genetic relationships between Biccl and human polycystic kidney disease remain unknown. Using our previously produced anti-Bicc1antibodies (mBic-Np and mBic-Cp) and multiple ADPKD and ARPKD mutant mouse models, we investigated Biccl expression and distribution patterning during mouse embryogenesis and organogenesis and molecular relationship between Biccl and other human PKD causal genes, including polycystin-1/-2(PC1/PC2) and fibrocystin (FPC) whose mutations result in ADPKD and ARPKD. By immnohistochemistry (IHC) staining in wildtype mouse embryo (E12.5-E16.5), we found that expression of Biccl appears choroid plexus, cavitas nasi, heart, intestine, kidney, adrenal gland at E12.5; Biccl expresses in the lung at E13.5; while Bicc1starts to express in salivary gland, pituitary body and pancreas at15.5. Among Biccl-positive tissue and organs, gland-containing tissues exhibit very high Biccl expression. In mouse embryos, once Biccl is expressed, there is no significant Biccl expression change in the positive organs and tissues. Due to mutation of Biccl results in PKD phenotypes, we particularly examined Biccl distribution and localization in the mouse kidneys. By IHC staining, Biccl is seen to be highly expressed at the proximal convoluted tubules of the inner cortical and outer medullary regions. Costaining with an antibody against Ago-2which has been reported to be expressed at P-body of the cells, we found that Biccl colocalizes with Ago-2, suggesting that Biccl is P-body associated protein. Using our Pkdl, Pkd2and Pkhdl knockout mouse models, we performed biochemistry and IHC assays to determine if other human PKD causal gene products (PC1/2and FPC) also associate with Biccl. The results from IHC, quantatitive PCR and western analyses indicate that loss of PC2and FPC does not significantly alter expression of Biccl, but loss of PC1reduces Biccl expression in vitro and in vivo. This finding suggests that there is genetic links between PC1and Bicc1. In summary, our studies reveal the expressional patterning and distrubution of Biccl during embryogenesis and renal development. We also demonstrated that Biccl is subcellularly localized to P-body of the cells and discovered that Biccl genetically associates with PC1whose mutation causes human ADPKD. These finding provide new insights that Biccl plays functional roles in the pathogenesis of human polycystic kidney diseases.