Messenger ribonucleic acid (mRNA) is the form of RNA that helps transfer genetic information from inside the cell nucleus to ribosomes in the cytoplasm. It acts as a template for making proteins and is synthesized from a DNA template during a process known as transcription. When mRNA dynamics are disrupted, pathological abnormalities – such as interrupted embryonic development and cell death – can occur.

Imaging mRNA in real time is no easy task and most techniques that have attempted to do this to date have failed. A team led by Shawn Chen of the National Institute of Biomedical Imaging and Bioengineering at the National Institutes of Health says that it has now designed a new nanocomplex containing multiple mRNA imaging probes that can retrieve spatial and temporal information from different mRNA sequences.

Gold nanoparticle core

“We used gold nanoparticles as the core of our nanocomplex,” explains team member Zhe Wang of the School of Life Sciences and Technology at Xidian University and the National Institutes of Health. “This core is functionalized with a dense layer of stable dithiol-modified DNA oligonucleotides hybridized with distinctive fluorophore-capped ‘reporter’ sequences.”

The fluorophore attached to the reporter sequences does not fluoresce when it is attached to the gold nanoparticle core (it is “quenched”), but it reactivates when it attaches to mRNA. The mRNA competitively hybridizes with the DNA oligonucleotides on the nanocomplex, and it is more attracted to this DNA than are the existing reporter genes.

Real-time imaging of mRNA

The technique allows for real-time imaging of mRNA without any artifacts, Chen tells “The nanocomplex is also very stable in the cell cytosol, is resistant to endonuclease enzymes that might otherwise break it down, and senses mRNA fast.”

By using the nanocomplex in conjunction with computer programme codes and imaging software, the researchers were able to follow how mRNA expresses itself during neural stem cell differentiation. This differentiation plays a crucial role in both the developing and adult nervous system. The technique might thus be used as a chemical screening platform for treating neurodegenerative diseases, such as Alzheimer’s and Parkinson’s, as well as brain trauma, explains Chen.

The team says that it is now busy improving its nanocomplex platform to explore small interfering RNA or micro RNA regulated neural stem cell differentiation and corresponding mRNA sequential expression imaging profiles. “We are also trying to optimize this system and adapt it to various cell types, to ultimately create a versatile nanocomplex for use in a host of basic biology studies and chemical screening in regenerative medicine,” says team member Zhongliang Wang, who works in China and the US.

The research is detailed in ACS Nano DOI: 10.1021/nn505047n.