Biology subjects

Rui Liu

Publications and source records attributed to Rui Liu.

3 recordsLinked to original sources

bioRxiv2016

Assessing the measurement transfer function of single-cell RNA sequencing

Recently, measurement of RNA at single cell resolution has yielded surprising insights. Methods for single-cell RNA sequencing (scRNA-seq) have received considerable attention, but the broad reliability of single cell methods and the factors governing their performance are still poorly known. Here, we conducted a large-scale control experiment to assess the transfer function of three scRNA-seq methods and factors modulating the function. All three methods detected greater than 70% of the expected number of genes and had a 50% probability of detecting genes with abundance greater than 2 to 4 molecules. Despite the small number of molecules, sequencing depth significantly affected gene detection. While biases in detection and quantification were qualitatively similar across methods, the degree of bias differed, consistent with differences in molecular protocol. Measurement reliability increased with expression level for all methods and we conservatively estimate the measurement transfer functions to be linear above ~5-10 molecules. Based on these extensive control studies, we propose that RNA-seq of single cells has come of age, yielding quantitative biological information.

Genomics↗

bioRxiv2016

PARAQUAT TOLERANCE3 is an E3 ligase and acts as a negative regulator of oxidative stress response

Oxidative damage could be caused in plant cells when biotic and abiotic stresses are imposed. While the response to oxidative stress is well studied, little is known about how the activated response is switched off when oxidative stress is diminished. By studying Arabidopsis mutant paraquat tolerance3, we identified the genetic locus PARAQUAT TOLERANCE3 (PQT3) as a major negative regulator of oxidative stress tolerance. PQT3, encoding an E3 ligase, is rapidly down-regulated by oxidative stress. PQT3 has E3 ubiquitin ligase activity in ubiquitination assay. Subsequently, we identified PRMT4b as a PQT3-interacting protein. By histone methylation, PRMT4b may regulate the expression of APX1 and GPX1, encoding two key enzymes against oxidative stress. Moreover, PQT3 is able to recognize PRMT4b for targeted degradation via 26S proteasome. Therefore, we have identified PQT3 as an E3 ligase that acts as a negative regulator of activated response to oxidative stress.

Plant Biology↗

bioRxiv2015

Characterizing transcriptional heterogeneity through pathway and gene set overdispersion analysis

Single-cell transcriptome measurements are being applied at rapidly increasing scales to study cellular repertoires underpinning functions of complex tissues and organs, including mammalian brains. The transcriptional state of each cell, however, reflects a variety of biological factors, including persistent cell-type specific regulatory configurations, transient processes such as cell cycle, local metabolic demands, and extracellular signals. Depending on the biological setting, all such aspects of transcriptional heterogeneity can be of potential interest, but detecting complex heterogeneity structure from inherently uncertain single-cell data presents analytical challenges. We developed PAGODA to resolve multiple, potentially overlapping aspects of transcriptional heterogeneity by identifying known pathways or novel gene sets that show significant excess of coordinated variability among the measured cells. We demonstrate that PAGODA effectively recovers the subpopulations and their corresponding functional characteristics in a variety of single-cell samples, and use it to characterize transcriptional diversity of neuronal progenitors in the developing mouse cortex.

Genomics↗