Single-cell RNA-seq reveals dynamic paracrine control of cellular variation.

High-throughput single-cell transcriptomics offers an unbiased approach for understanding the extent, basis and function of gene expression variation between seemingly identical cells. Here we sequence single-cell RNA-seq libraries prepared from over 1,700 primary mouse bone-marrow-derived dendritic cells spanning several experimental conditions. We find substantial variation between identically stimulated dendritic cells, in both the fraction of cells detectably expressing a given messenger RNA and the transcript's level within expressing cells. Distinct gene modules are characterized by different temporal heterogeneity profiles. In particular, a 'core' module of antiviral genes is expressed very early by a few 'precocious' cells in response to uniform stimulation with a pathogenic component, but is later activated in all cells. By stimulating cells individually in sealed microfluidic chambers, analysing dendritic cells from knockout mice, and modulating secretion and extracellular signalling, we show that this response is coordinated by interferon-mediated paracrine signalling from these precocious cells. Notably, preventing cell-to-cell communication also substantially reduces variability between cells in the expression of an early-induced 'peaked' inflammatory module, suggesting that paracrine signalling additionally represses part of the inflammatory program. Our study highlights the importance of cell-to-cell communication in controlling cellular heterogeneity and reveals general strategies that multicellular populations can use to establish complex dynamic responses.

Monitoring cognitive functioning: psychometric properties of the brief test of adult cognition by telephone.

Assessment of cognitive functioning is an important component of telephone surveys of health. Previous cognitive telephone batteries have been limited in scope with a primary focus on dementia screening. The Brief Test of Adult Cognition by Telephone (BTACT) assesses multiple dimensions central for effective functioning across adulthood: episodic memory, working memory, reasoning, verbal fluency, and executive function. The BTACT is the first instrument that includes measures of processing speed, reaction time, and task-switching/inhibitory control for use over the telephone. We administered the battery to a national sample (N = 4,268), age 32 to 84 years, from the study of Midlife in the United States (MIDUS) and examined age, education, and sex differences; reliability; and factor structure. We found good evidence for construct validity with a subsample tested in person. Implications of the findings are considered for efficient neuropsychological assessment and monitoring changes in cognitive aging, for clinical and research applications by telephone or in person.

Taking qPCR to a higher level: Analysis of CNV reveals the power of high throughput qPCR to enhance quantitative resolution.

This paper assesses the quantitative resolution of qPCR using copy number variation (CNV) as a paradigm. An error model is developed for real-time qPCR data showing how the precision of CNV determination varies with the number of replicates. Using samples with varying numbers of X chromosomes, experimental data demonstrates that real-time qPCR can readily distinguish four copes from five copies, which corresponds to a 1.25-fold difference in relative quantity. Digital PCR is considered as an alternative form of qPCR. For digital PCR, an error model is shown that relates the precision of CNV determination to the number of reaction chambers. The quantitative capability of digital PCR is illustrated with an experiment distinguishing four and five copies of the human gene MRGPRX1. For either real-time qPCR or digital PCR, practical application of these models to achieve enhanced quantitative resolution requires use of a high throughput PCR platform that can simultaneously perform thousands of reactions. Comparing the two methods, real-time qPCR has the advantage of throughput and digital PCR has the advantage of simplicity in terms of the assumptions made for data analysis.

Surgical management of ascending aortic disease.

Two cases of aortic pathology have been presented--namely, ascending aortic aneurysm and ascending aortic dissection. These entities are distinct, but can be superimposed. Surgical resection is the procedure of choice for both these entities, in contradistinction to descending aortic dissections. Although dealing with these entities can indeed be a humbling experience, lifesaving treatment can be delivered by a combination of a high index of suspicion, early diagnosis, and prompt surgical therapy.