Generation of amplified RNAs and cDNA libraries from single mammalian cells

Stem Cell Strategies to Evaluate Idiosyncratic Drug-induced Liver Injury

The host-dependent nature of idiosyncratic drug-induced liver injury (iDILI) suggests that rare genetic polymorphisms may contribute to the disease. Indeed, a few mutations in key genes have already been identified using conventional human genetics approaches. Over 50 commonly used drugs can precipitate iDILI, making this a substantial medical problem. Only recently have human induced pluripotent stem cells been used as a research tool to discover novel iDILI genes and to study the mechanisms of iDILI in vitro. Here we review the current state of stem cell use in the investigation of iDILI, with a special focus on genetics. In addition, the concerns and difficulties associated with genetics and animal model research are discussed. We then present the features of patient-specific pluripotent stem cells (which may be derived from iDILI patients themselves), and explain why these cells may be of great utility. A variety of recent approaches to produce hepatocyte-like cells from pluripotent cells and the associated advantages and limitations of such cells are discussed. Future directions for the use of stem cell science to investigate iDILI include novel ways to identify new iDILI genes, a consideration of epigenetic impacts on iDILI, and the development of new and improved strategies for the production of hepatocytes from human pluripotent cells.

Sequestration within nuclear chromocenters is not a requirement for silencing olfactory receptor transcription in a placode-derived cell line

Mouse olfaction depends on specialized olfactory sensory neurons (OSNs) that each express only one olfactory receptor protein from among a family of >1000 olfactory receptor (OR) genes encoded in the genome. To investigate epigenetic mechanisms underlying monogenic OR expression, we characterized the nuclear organization of OR loci in an olfactory placode-derived cell line (OP6) derived from a pre-neuronal cell along the OSN lineage. OR loci are significantly enriched within nuclear chromocenters in these cells as compared with control loci tested. However, we observe variability in chromocenter occupancy among different OR loci and from cell-to-cell, suggesting that these associations are transient or context dependent. The lamin B receptor (LBR), whose downregulation is necessary for aggregation of chromocenters and OR genes in mature OSNs, exhibits an unusual non-peripheral expression pattern in OP6 nuclei; upon further OP6 cell differentiation, LBR expression is lost and chromocenters begin to aggregate. However, neither undifferentiated nor differentiated OP6 cells sequester OR genes within the chromocenters, despite the establishment of monogenic OR expression in these cells. These results indicate that sequestration of competing OR loci is not a requirement for monogenic OR expression in OP6 cells, and could indicate that the initial establishment of monogenic OR expression during OSN differentiation in vivo occurs prior to recruitment of OR genes into chromocenters.

The current status of cDNA cloning

The cloning of cDNAs, copies of cellular RNA, is one of the classical technologies in molecular biology. Over the past 30 years cDNA cloning technologies have been improved to enable the cloning of large cDNA collections, which are fundamental to today's understanding of the utilization of genetic information. With the discovery of noncoding RNAs, additional new approaches to the cloning of short RNAs have been developed. However, with the realization that much larger portions of genomes are transcribed than anticipated from genome annotations, cDNA cloning faces new challenges to uncover rare transcripts and to make the corresponding cDNAs available for functional studies. This review provides an overview on the current status of cDNA cloning and possibilities for the discovery and characterization of new RNA families.