TIVA TAG: cell-penetrating peptide (CPP), FRET fluorophores (Cy3 and Cy5), photocleavable linker (PL), uracil (U), adenine (A)© GEORGE RETSECKNeighboring cells with the same morphology in the same tissue—neurons in the brain, for example—may be unique in their mRNA and protein-expression profiles. While cell individuality is increasingly appreciated, current whole-transcriptome techniques cannot analyze a single cell within a tissue without perturbing the cell’s neighbors or having to use fixed tissue samples.
Cleverly combining several molecular tools into a single, multitasking molecule, neurobiologist James Eberwine and chemist Ivan Dmochowski, both at the University of Pennsylvania, created the transcriptome in vivo analysis (TIVA) tag. It’s composed of a light-activated hairpin oligonucleotide that can enter a cell and capture its mRNA profile without contamination from neighboring cells. “The TIVA tag in its closed hairpin structure looks like a pocket knife with tools folded inside. Upon photoactivation, TIVA opens up and the RNA capture strand is revealed,” says Dmochowski.
Before opening the tag’s hairpin loop, fluorescence resonance energy transfer (FRET) between dyes attached to the RNA hairpin confirms the presence of the tag inside the cell. Because many cells in a tissue might take up tags, the trick to analyzing ...
