Micromanipulation of single cells from tissue imprints is an alternative to laser-assisted microdissection

Exploring viral infection using single-cell sequencing

Single-cell sequencing (SCS) has emerged as a valuable tool to study cellular heterogeneity in diverse fields, including virology. By studying the viral and cellular genome and/or transcriptome, the dynamics of viral infection can be investigated at single cell level. Most studies have explored the impact of cell-to-cell variation on the viral life cycle from the point of view of the virus, by analyzing viral sequences, and from the point of view of the cell, mainly by analyzing the cellular host transcriptome. In this review, we will focus on recent studies that use single-cell sequencing to explore viral diversity and cell variability in response to viral replication.

Amplification of multiple genomic loci from single cells isolated by laser micro-dissection of tissues

BACKGROUND

Whole genome amplification (WGA) and laser assisted micro-dissection represent two recently developed technologies that can greatly advance biological and medical research. WGA allows the analysis of multiple genomic loci from a single genome and has been performed on single cells from cell suspensions and from enzymatically-digested tissues. Laser micro-dissection makes it possible to isolate specific single cells from heterogeneous tissues.

RESULTS

Here we applied for the first time WGA on laser micro-dissected single cells from stained tissue sections, and developed a protocol for sequentially performing the two procedures. The combined procedure allows correlating the cell's genome with its natural morphology and precise anatomical position. From each cell we amplified 122 genomic and mitochondrial loci. In cells obtained from fresh tissue sections, 64.5% of alleles successfully amplified to approximately 700000 copies each, and mitochondrial DNA was amplified successfully in all cells. Multiplex PCR amplification and analysis of cells from pre-stored sections yielded significantly poorer results. Sequencing and capillary electrophoresis of WGA products allowed detection of slippage mutations in microsatellites (MS), and point mutations in P53.

CONCLUSION

Comprehensive genomic analysis of single cells from stained tissue sections opens new research opportunities for cell lineage and depth analyses, genome-wide mutation surveys, and other single cell assays.

Numeric simulation of heat transfer and electrokinetic flow in an electroosmosis-based continuous flow PCR chip

Precise design and operational control of the polymerase chain reaction process is key to the performance of on-chip DNA analysis. This research is dedicated to understanding the fluid flow and heat transfer mechanisms occurring in continuous flow PCR chips from the engineering point of view. In this work, a 3-dimensional model was developed to simulate the electrical potential field, the flow field, and the temperature field in an electroosmosis-based continuous flow PCR chip. On the basis of the simultaneous solution to this model, the effects of the channel/chip size, the chip material, and the applied voltage difference on the temperature distribution and control are discussed in detail. The importance of each heat transfer mechanism for different situations is also discussed. It was found that if a larger chip thickness or a material with a lower heat conductivity was used, the temperature in the microfluidic PCR chip would decrease dramatically. The effects of the applied electrical field strength and flow velocity on the temperature distribution, however, are negligible for microchannels with a small cross-sectional area. With bigger channels, the flow direction will affect the temperature distribution in the channel because heat convection will dominate heat transfer.