Getting DNA or RNA into cells can be a tricky business, and a variety of transfection reagents have been developed over the years to make the process easier. Lipid-based reagents are especially popular because they combine efficient transfection with relatively low toxicity.
When it comes to transfection, it pays to think small. Human cells range in volume from 20–40 µm3 (sperm cells) to as large as 4 million µm3 (mature egg cells, or oocytes). For several decades, transfection reagents have targeted this size range. However, breakthrough research involves leaving the “micro” realm and entering a world that was once the domain only of science fiction: nanotechnology. Continue reading
Ribonucleoprotein complex with Cas9, guide RNA and donor ssDNA. Copyright Promega Corporation.
With the advent of genome editing using CRISPR-Cas9, researchers have been excited by the possibilities of precisely placed edits in cellular DNA. Any double-stranded break in DNA like that induced by CRISPR-Cas9 is repaired by one of two pathways: Non-homologous end joining (NHEJ) or homology-directed repair (HDR). Using the NHEJ pathway results in short insertions or deletions (indels) at the break site, so the HDR pathway is preferred. However, the low efficiency of HDR recombination to insert exogenous sequences into the genome hampers its use. There have been many attempts at boosting HDR frequency, but the methods compromise cell growth and behave differently when used with various cell types and gene targets. The strategy employed by the authors of an article in Communications Biology
tethered the DNA donor template to Cas9 complexed with the ribonucleoprotein and guide RNA, increasing the local concentration of the donor template at the break site and enhancing homology-directed repair. Continue reading